Telephone Projects

for the

Evil Genius

Evil Genius Series

Bike, Scooter, and Chopper Projects for the Evil Genius Bionics for the Evil Genius: 25 Build-It-Yourself Projects Electronic Circuits for the Evil Genius: 57 Lessons with Projects Electronic Gadgets for the Evil Genius: 28 Build-It-Yourself Projects Electronic Games for the Evil Genius

Electronic Sensors for the Evil Genius: 54 Electrifying Projects 50 Awesome Auto Projects for the Evil Genius

50 Model Rocket Projects for the Evil Genius

51 High-Tech Practical Jokes for the Evil Genius

Fuel Cell Projects for the Evil Genius

Mechatronics for the Evil Genius: 25 Build-It-Yourself Projects MORE Electronic Gadgets for the Evil Genius: 40 NEW Build-It-Yourself Projects 101 Outer Space Projects for the Evil Genius

101 Spy Gadgets for the Evil Genius

123 PIC® Microcontroller Experiments for the Evil Genius 123 Robotics Experiments for the Evil Genius

PC Mods for the Evil Genius

Programming Video Games for the Evil Genius

Solar Energy Projects for the Evil Genius

Telephone Projects for the Evil Genius

22 Radio and Receiver Projects for the Evil Genius 25 Home Automation Projects for the Evil Genius

Telephone Projects

for the

Evil Genius

TOM PETRUZZELLIS

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DOI: 10.1036/0071548440

This book is dedicated to my first grandson Giovanni.

May he dream big dreams and see them realized.

Wishing him a long, interesting, and enjoyable life!

About the Author

Tom Petruzzellis is an electronics engineer with 30 years’ experience, currently working with the geophysical field equipment department at the State University of New York-Binghamton. He has written extensively for industry publications such as Electronics Now and Modern Electronics, and is the author of numerous McGraw-Hill bestsellers, including Electronics Sensors for the Evil Genius.

vi

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For more information about this title, click here

Contents

Introduction

xi

Phone Line-in-Use Relay

131

Controller

Acknowledgments

xiv

Single Phone Line Status Light

134

Two-Line Phone Status Indicator

137

1 Telephone History

1

Smart Phone Light

141

2 How the Telephone Works

6

Telephone Line Vigilant

145

3 Identifying Electronic Components

13

15 Telephone and Phone Line Testers

150

Simple Telephone Line Tester

151

4 Reading Schematics

20

Off-Line Telephone Tester

153

5 Electronic Parts Installation

28

Telephone Line Tester

157

and Soldering

Telephone Line Simulator

159

6 Telephone Privacy Guard

39

16 FM Telephone Transmitter

166

7 Modem Protector

42

17 Telephone Project

173

8 Telephone Amplifiers and Projects

46

18 Talking/Musical Telephone Ringer

187

Magnetic Phone Pickup

47

19 Telephone Tollsaver

195

Direct Connect

52

20 Infinity Bug/Transmitter Project

204

9 Phone Recorder Switch Project

55

21 Radio Phone Patch

213

10 Telephone Conferencer Unit

61

22 Telephone Phone Intercom

221

11 The Frustrator

67

23 Speaker-Phone Project

231

12 Hold Circuits and Projects

75

Telephone Hold and Line-in-Use

78

24 Telephone Scrambler

241

Basic Music-on-Hold

80

25 Telephone Tattletale

251

Universal Hold Circuit

84

Automatic Music-on-Hold

89

26 DTMF Telephone Controller

261

Project

13 Telephone Ringer Projects

98

Silent Cellular Phone Ringer

100

27 The BASIC STAMP Microcontroller

275

Remote Telephone Ringer

105

28 DTMF Touch-Tone Generator/Decoder 282

Telephone Ring Detector

111

Display

Wireless Telephone Ringer

117

29 Caller-ID/Blocker Project

294

Telephone Ring Generator

126

30 Page-Alert

311

14 Phone Line Status Circuits and

121

Alarm Switch/Sensor Module

321

Projects

Temperature/Voltage Level

323

Phone In-Use Indicator

124

Module

Cut Phone Line Detector

128

vii

31 Tele-Alert Project

328

Appendix: Electronic Parts Suppliers

364

Motion Module

339

Index

367

Listen-in Module

344

32 Remote Temperature Monitor

348

Contents

viii

Introduction

Since its inception in 1876, the telephone has

This book will appeal to both electronics neophytes

captured the imagination of people around the

and seasoned circuit builders of all ages.

world. From its simple origins, the telephone has

Once you open up this book you will realize that

evolved from the humble device it once was to the

the common telephone and telephone lines can be

modern cell phone or satellite phone. The

used in a variety of ways to support many different

telephone has fundamentally and instantaneously

types of projects that you perhaps never knew

changed the human race’s ability to communicate

existed. You will explore the basics of the

over long distances. Today, not only can we

telephone, and learn how to build an electronic

communicate via the human voice but we can

telephone and a telephone modem/line protector,

rapidly send scientific and health data, pictures,

as well as remote ringer circuits, line use

and information between any two people or

indicators, a telephone intercom, speaker-phone, a

organizations on earth in just a few seconds by

telephone transmitter, and a telephone listening

picking up the phone and dialing the party at the

device, just to name a few projects.

other end. The development of the telephone has

The book is broken down into 32 chapters.

progressed at such a rapid rate in the last 50 years

Chapter 1 discusses a bit of telephone history,

alone that it is truly amazing what can be done

while Chapter 2 describes how a conventional

with the telephone in our modern lives;

telephone functions. Chapter 3 shows readers how

and it is now mostly taken for granted.

to identify components; this chapter is particularly

Our new book titled Telephone Projects for the

useful for newcomers to electronics or for younger

Evil Genius is a fun and informative project book readers. Chapter 4 delves into reading schematics,

which we hope will spark your imagination and

and you will learn the difference between a

creative abilities. If you are interested in learning schematic and a pictorial diagram, as well as

about the history of the telephone, and how a

how components are connected and work with

telephone operates, or if you want to know how a

one another. Next, Chapter 5 shows the reader

telephone remote control functions and how to

how to install components on circuit boards and

remotely control things around your home or

how to solder. Every electronic hobbyist should

office, or perhaps, if you would like to know how

know how to solder well before attempting

to build a remote telephone listening device, then

electronic projects.

you will definitely want to read on.

Chapter 6 begins the actual project section of the

This telephone project book was written for the

book and presents a device called the privacy guard.

general electronics enthusiast as well as for

The privacy guard prevents other persons around

telephone enthusiasts and experimenters alike.

the house from listening to your telephone calls.

ix

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You will notice that we begin with easier projects

Chapter 15 covers telephone and telephone line

and escalate to more advanced projects as we go

testers, from the simple phone device tester to

along. Next, Chapter 7 illustrates how to build a

phone line tester and a phone line simulator. Next

fax/modem/answering machine protector which

we move on to some intermediate telephone

can save your phone devices from voltage or

projects, such as the automatic telephone

lightning spikes and strikes. In Chapter 8 we

transmitter project in Chapter 16, which will

present two different types of telephone

automatically broadcast a two-way phone

amplifiers. One amplifier is a direct connect

conversation over to an FM radio, using phone-line

device which will allow you to amplify the

power. Chapter 17 shows the reader how to build a

telephone conversation for a group, or for

complete modern electronic telephone.

hard-of-hearing elders. The direct amplifier could

Chapter 18 features a fun voice/music

also be used to amplify a telephone ring remotely.

telephone ringer, which you can program to

The second amplifier uses a phone suction cup

announce the phone ringing in your own favorite

with a wireless connection to the phone to amplify

way. The tollsaver in Chapter 19 is a phone

a phone conversation.

dialer project which can be used to call a local

Chapter 9 illustrates an automatic phone

access phone number for saving money or can be

recorder switch device which will start and stop a

used for an older person to immediately call a

tape or voice recorder, in order to record phone

loved one.

conversations around your home or office. Moving

Chapter 20 presents the infinity bug, which can

on, in Chapter 10, we take a look at a phone

be placed on a phone line you wish to monitor.

conferencer circuit which will combine two phone

When called silently, the bug will allow you to

line conversations. Chapter 11 depicts a device

listen-in to a remote site for as long as you like.

called the frustrator, which will make annoying

If you operate a CB or ham radio setup,

people go away and never call back!

then you will be interested in building the radio/

Next we present four chapters which cover

telephone phone patch described in Chapter 21.

themes of circuits and projects. Chapter 12

This circuit will allow you to interface your radio

illustrates four telephone hold circuits from simple

equipment with the telephone line. The phone

manual on-hold and music-on-hold circuits to

patch will permit a person on the phone to talk

touch-tone-controlled hold circuits and an

to a person on the radio.

automatic music-on-hold project.

The phone intercom in Chapter 22 will turn the

Chapter 13 discusses telephone ringer circuits. We

telephones in your home into an intercom system

start first with a silent cell phone ringer circuit and throughout your whole house. The main intercom

then remote ringer circuits, both wired and wireless

controller is attached to the phone line and power,

types. Our final circuit is a ring generator circuit

while an alert module is placed at each phone to

which could be used for intercoms or phone testing.

form a complete intercom system using your in-

Chapter 14 presents phone status circuits and

house phone wiring.

projects, from in-use detector, to cut phone line

Chapter 23 presents a speaker-phone project

detector; then we move on to single and dual line

which will allow you to carry on a phone

status monitors. We also present a smart phone

conversation without using your handset, thus

light which turns on a room light when the phone

freeing up your hands for more important tasks.

rings so you can take a note or move around the

The speaker-phone project will also permit a group

room for a period of time; and finally a phone line

of people to converse on the phone with a person

monitor circuit, called the phone line vigilant.

at a distance.

Introduction

x

Introduction

Have you ever wanted your phone conversation

The Page-Alert project in Chapter 30 forms a

to remain private from possible nosy friends,

small local alarm system which pages you in the

family, or coworkers? Then you will appreciate

event of an alarm condition. You can create your

the phone scrambler project in Chapter 24, which

own multi-sensor alarm to monitor your home or

will keep your conversations unintelligible.

office and let the page-alert call you to report an

The tattletale project illustrated in Chapter 25

alarm condition.

was designed to remotely monitor alarm conditions

The Tele-Alert project in Chapter 31 will

and report to you via a remote phone call. You will

permit you to monitor your home or office with

be able to monitor a remote room or cottage while

alarm sensors and report an alarm condition to

you are away from home or the office.

your cell phone.

Chapter 26 will show you how to build a DTMF

Finally, Chapter 32 presents a dial-up temperature

remote phone controller. With this project you can

alarm system, which will allow you to monitor the

dial your home phone and remotely control devices

remote temperature of your vacation home or cabin

such as lights, fans, and air-conditioners.

in the comfort of your own home. If your creative

interest has been aroused, you may want to expand

Our next projects feature the use of a small

the system to monitor other devices.

microcontroller called the BASIC STAMP 2.

Telephone Projects for the Evil Genius will

In the remaining projects you will program the

open up a whole new area for electronics project

controller to perform specific telephone controls.

building fun, projects that both you and your

Chapter 27 is an introduction to the BASIC

family will find useful and enjoy, and which you

STAMP 2 controller. This chapter illustrates various

can build at a fraction of the cost of similar

types of BASIC STAMP 2 controllers and how

commercial products. A number of projects in this

they work; next we will move on to actual

book are not commercially available and will never

microcomputer projects using the BASIC

be available to the general consumer, but with this

STAMP 2.

book you will be able to create any number of

Chapter 28 will show you how to build a

telephone related projects that will save you time

touch-tone generator, as well as a touch-tone

and money as well. Take your time and enjoy the

decoder/display unit which will display a phone

book; you may even find a project that you cannot

number that was dialed on a phone line or on a

live without!

radio frequency, e.g., via ham radio.

We hope you will find the projects educational

Chapter 29 presents a caller-ID project which

and interesting and that you will want to build

will display the phone number of persons calling

one of these projects to enhance the telephone

you, so you can decide if you want to answer the

system in your home or office. Have fun and

phone or not.

be safe!

xi

Acknowledgments

A book is a complex entity and requires the help

Larry Steckler/Poptronix

of many people to see it through to completion.

Ken Gracey/Parallax, Inc

I would like to thank the following people in

Thomson Publications

making this book possible. First I would like to

thank senior editor Judy Bass, her assistant

Arthur Seymour/Elenco Electronics

Rebecca Behrens and all the folks at McGraw-Hill

Ramsey Electronics

Professional who had a part in making this book

Cengage Learning

possible. I would like to also like to thank the

Frank Montegari/Glolab, Inc

following people and companies listed below, who

had a part in bringing this book to completion. Our

Bill Bowden

hope is that the book will encourage readers to

Dave Johnson

build the projects and that it might help inspire

Anthony Caristi

young electronic enthusiasts to enter the fields of

Tom Engdahl

engineering and electronics.

Colin Mitchell/Talking Electronics

Rebecca Lowery/Vellemen, Inc

xii

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Telephone Projects

for the

Evil Genius

xiii

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Chapter 1

Telephone History

Telephone comes from the Greek word “tele,” meaning

He sent charges nearly 300 feet over brass wire and

from afar, and phone, meaning voice or voiced sound.

moistened thread. An electrostatic generator powered

Generally, a telephone is any device which conveys

his experiments, one charge at a time.

sound over a distance. Talking produces acoustic

In 1800, Alessandro Volta produced the first battery.

pressure. A telephone reproduces sound by

A major development, Volta’s battery provided

electrical means.

sustained low-powered electric current at high cost.

The dictionary defines the telephone as “an apparatus Chemically based, as all batteries are, the battery

for reproducing sound, especially that of the voice,

improved quickly and became the electrical source for at a great distance, by means of electricity; consisting further experimenting. But while batteries got more

of transmitting and receiving instruments connected by reliable, they still could not produce the power needed a line or wire which conveys the electric current.”

to work machinery.

Electricity operates the telephone and it carries

Then in 1820 Danish physicist Christian Oersted

your voice.

demonstrated electromagnetism, the critical idea needed Telephone history begins, perhaps, at the start of

to develop electrical power and to communicate. In a

human history. Man has always wanted to communicate

famous experiment at his University of Copenhagen

from afar. People have used smoke signals, mirrors,

classroom, Oersted pushed a compass under a live

jungle drums, carrier pigeons, and semaphores to get a electric wire. This caused its needle to turn from

message from one point to another. But a phone was

pointing north, as if acted on by a larger magnet.

something new. A real telephone could not be invented Oersted discovered that an electric current creates a until the electrical age began. The electrical principles magnetic field.

required to build a telephone were known in 1831 but it Around 1821, Michael Faraday reversed Oersted’s

was not until 1854 that Bourseul suggested transmitting experiment. He got a weak current to flow in a wire

speech electrically. And it was not until 22 years later revolving around a permanent magnet. In other words,

in 1876 that the idea became a reality. Telephone

a magnetic field caused or induced an electric current to development did not proceed in an organized line like flow in a nearby wire. In so doing, Faraday had built the powered flight, with one inventor after another working world’s first electric generator. Mechanical energy could to realize a common goal, rather, it was a series of often now be converted to electrical energy. Faraday worked disconnected events, mostly electrical, some accidental, through different electrical problems in the next 10 years, that made the telephone possible.

eventually publishing his results on induction in 1831.

Probably no means of communication has

Then in 1830 the great American scientist Professor

revolutionized the daily lives of ordinary people more Joseph Henry transmitted the first practical electrical than the telephone. The actual history of the telephone signal. A short time before, Henry had invented the first was long and arduous with many twists and turns and is efficient electromagnet. He also concluded similar

a subject of complex dispute to this day.

thoughts about induction before Faraday but he did not The actual telephone was built upon the work of

publish them first. Henry’s place in electrical history many people who preceded Alexander Graham Bell.

however, has always been secure, in particular for

In 1729, English chemist Stephen Gray is believed to be showing that electromagnetism could do more than create the first person to transmit electricity over a wire.

current or pick up heavy weights—it could communicate.

1

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In 1837, Samuel Morse invented the first workable

In the 1870s, two inventors, Elisha Gray and

telegraph, applied for its patent in 1838, and was finally Alexander Graham Bell, both independently designed

granted it in 1848. Joseph Henry helped Morse build a devices that could transmit speech electrically, the

telegraph relay or repeater that allowed long distance device destined to be called the telephone. Both men

operation. The telegraph later helped unite the country rushed their respective designs to the patent office

and eventually the world. In 1832, he heard of Faraday’s within hours of each other; Alexander Graham Bell

recently published work on inductance, and at the same patented his telephone first. Elisha Gray and Alexander time was given an electromagnet to ponder over. An

Graham Bell entered into a famous legal battle over the idea came to him and Morse quickly worked out details invention of the telephone, which Bell eventually won.

for his telegraph. His system used a key or switch, to The principle of the telephone was uncovered in

make or break the electrical circuit, a battery to produce 1874, but it was the unique combination of electricity power, a single line joining one telegraph station to and voice that led to Bell’s actual invention of the

another, and an electromagnetic receiver or sounder that telephone in 1876. Bell’s original telephone is shown in upon being turned on and off produced a clicking noise.

Figure 1-1. Convincing Bell’s partners, Gardiner Greene He completed the package by devising the Morse code

Hubbard, a prominent lawyer from Boston, and Thomas

system of dots and dashes. A quick key tap broke the

Sanders, a leather merchant with capital from Salem,

circuit momentarily, transmitting a short pulse to a

about the potential for voice transmittal was not an easy distant sounder, interpreted by an operator as a dot.

task, and they often threatened to pull Bell’s funding.

A lengthier break produced a dash. Telegraphy was not Nonetheless, agreement was finally reached and the trio accepted initially but eventually it became big business.

received U.S. Patent No. 174,465, issued on March 3,

In the early 1870s the world still did not have a

1876, for “Improvements in Telegraphy,” which is now

working telephone. Inventors focused on telegraph

considered to be the most valuable patent ever issued.

improvements since the telegraph itself already had a Bell’s experiments with his assistant Thomas Watson

proven market. Developing a telephone, on the other

finally proved successful on March 10, 1876, when the hand, had no immediate market, if one at all. Elisha

Gray, Alexander Graham Bell, as well as others such

as Antonio Meucci, and Philip Reis trying to develop

a multiplexing telegraph—a device to send several

messages over one wire at once. Such an instrument

would greatly increase traffic without the telegraph

company having to build more lines. As it turned out, for both men, the desire to invent one thing turned into a race to invent something altogether different.

The telegraph and telephone are both wire-based

electrical systems, and Alexander Graham Bell’s success with the telephone came as a direct result of his attempts to improve the telegraph. When Bell began experimenting with electrical signals, the telegraph had been an

established means of communication for some 30 years.

Bell developed new and original ideas but did so by

building on older ideas and developments. He

succeeded specifically because he understood acoustics, the study of sound, and something about electricity.

Other inventors knew electricity well but little of

acoustics. The telephone is a shared accomplishment

among many pioneers, therefore, although the credit and rewards were not shared equally.

Chapter One: Telephone History

Figure 1-1

Bell’s first telephone instrument

2

Chapter One: Telephone History

first complete sentence was transmitted: “Watson, come inventor and was still in use in some telephone offices here; I want you.”

well over 100 years later. Almon Strowger was issued

Bell considered his invention’s greatest advantage over a patent on March 11, 1891, for the first automatic

every other form of electrical apparatus to be the fact that telephone exchange. The first exchange using the

it could be used by anyone, as “all other telegraphic Strowger switch was opened in La Porte, Indiana, in

machines produce signals which require to be translated 1892 and initially subscribers had a button on their

by experts, and such instruments are therefore extremely telephone to produce the required number of pulses

limited in their application, but the telephone actually by tapping.

speaks, and for this reason it can be utilized for nearly Strowger installed his automatic exchanges in the

every purpose for which speech is employed.”

United States and Europe. In 1924, the Bell Telephone Bell was nearly beaten to the patent office by Elisha System decided that using operators was not the way to Gray, who had independently developed a very similar

go, and they licensed Strowger’s technology.

invention. Gray arrived just hours after Bell at the Patent An associate of Strowger invented the rotary dial in

Office, filing a “caveat,” a confidential report of an 1896 and this replaced the button. In 1943, Philadelphia invention that was not yet perfected. Western Electric, was the last major area to give up dual service (rotary co-founded by Gray, became one of the Bell System’s

and button).

major competitors. Western Union was another major

In 1879, telephone subscribers began to be designated competitor, already having established itself as a

by numbers rather than names—as a result of an

communications provider with the telegraph system.

epidemic of measles. A doctor from Lowell,

In 1877, construction of the first regular telephone

Massachusetts, concerned about the inability of

line from Boston to Somerville, Massachusetts, was

replacement exchange operators to put calls through

completed, a distance of three miles. Commercial

because they would not be familiar with the names

telephone service began in the United States in 1877.

associated with all the jacks on the switchboards,

The workable exchange, developed in 1878, enabled

suggested the alpha-numeric system of identifying

calls to be switched among any number of subscribers

customers by a two-letter and five-digit system.

rather than requiring direct lines. Exchanges were

Long-distance telephone service was established and

handled manually, first by boys, then by the now-

grew in the 1880s using metallic circuits. The commonfamous women operators.

battery system, developed by Hammond V. Hayes

By the end of 1880, there were 47,900 telephones in

in 1888, permitted a central battery to supply all

the United States. The following year telephone service telephones on an exchange with power, rather than

between Boston and Providence had been established.

relying upon each unit’s own troublesome battery.

Service between New York and Chicago started in

A young inventor, Dr. Lee De Forest, began work in

1892, and between New York and Boston in 1894.

1906 on applying what was known as an “Audion,” a

Transcontinental service by overhead wire was not

three-element vacuum tube, which could amplify radio

inaugurated until 1915. The first switchboard was set up waves. He recognized the potential for installing

in Boston in 1877. On January 17, 1882, Leroy Firman

Audions, which became the major component in what

received the first patent for a telephone switchboard.

would be called repeaters on telephone lines, in order to The first regular telephone exchange was established

amplify the sound waves at mid-points along the wires.

in New Haven in 1878. Early telephones were leased in The Bell System bought the rights to De Forest’s

pairs to subscribers. The subscriber was required to put patents in 1913. Long-distance telephone service was

up his own line to connect with another.

constructed on the New York to San Francisco circuit

In 1889, Almon B. Strowger, a Kansas City

using loading coils and repeaters.

undertaker, invented a switch that could connect one

American Telephone and Telegraph (AT&T) took

line to any of 100 lines by using relays and sliders.

control of the Western Union Telegraph Company in a

This step by step switch used to receive the dial pulses

“hostile takeover,” in 1911, having purchased the Western became known as “The Strowger Switch” after its

Union stocks through a subsidiary. The two eventually 3

merged, sharing financial data and telephone lines.

major improvement in service as they were less likely to By 1918, ten million Bell System telephones were

be interrupted by other electrical interference.

in service.

Microwave tube radio transmission was used for long-

The next major improvement to the automatic

distance telephony in 1947. The transistor, a key to

switching of large numbers of calls was made possible modern electronics, was invented at Bell Labs in 1947.

in 1921, using “phantom circuits,” which allowed three A team consisting of William Schockley, Walter

telephone conversations to be conducted on two pairs of Brattain, and John Bardeen demonstrated the “transistor wires. The “French” phone, with the transmitter and

effect,” using a germanium crystal that they had set up receiver in a single handset, was developed by the

in contact with two wires two-thousandths of an inch

Bell System around 1904, but was not released on a

apart. The development of the transistor not only made widespread basis because it cost more than the desk

possible the advances to telephony but miniaturization sets. They ultimately became available to subscribers of the transistor led to the development of small

in 1927. The first transatlantic service, from New York personal computer and laptops that we use today.

to London, became operational in 1927. Research in

On August, 17, 1951, the first transcontinental

electronic telephone exchanges began in 1936 in

microwave system began operating. One hundred and

Bell Labs, and was ultimately perfected in the 1960s

seven relay stations spaced about 30 miles apart formed with its Electronic Switching System (ESS).

a link from New York to San Francisco. It cost the Bell In 1938, the Bell System introduced crossbar

System $40,000,000; a milestone in their development

switching to the central office. The first No. 1 crossbar of radio relay begun in 1947 between New York and

was placed into service at the central office in Brooklyn, Boston. In 1954, over 400 microwave stations were

New York on February 13. AT&T improved on work

scattered across the country. By 1958, microwave carrier done by the brilliant Swedish engineer Gotthilf

made up 13,000,000 miles of telephone circuits or one Ansgarius Betulander. They even sent a team to Sweden quarter of the nation’s long distance lines. Six hundred to look at his crossbar switch. Western Electric’s models conversations or two television programs could be sent earned a worldwide reputation for ruggedness and

at once over these radio routes.

flexibility. Installed by the hundreds in medium to large Years of development led up to 1956 when the first

cities, crossbar technology advanced in development

transatlantic telephone cable system started carrying and popularity until 1978, when over 28 million

calls; this is an interesting story in itself. Two coaxial Bell System lines were connected to one.

cables about 20 miles apart carried 36 two-way circuits.

In the mid-1940s, the first mobile wireless phone

Nearly 50 sophisticated repeaters were spaced from 10

services appeared in the United States. These services to 40 miles along the way. Each vacuum tube repeater

used one tower in each metropolitan area. Since the

contained 5,000 parts and cost almost $100,000. On the technology was very expensive and the market small,

first day this system took 588 calls, 75% more than the one tower could handle all the phone calls. However,

previous 10 days’ average with AT&T’s transatlantic demand for mobile phone services began to grow, and

radio-telephone service.

technology improved so that phones could be smaller

The 1960s began a dizzying age of projects,

and less expensive. Engineers anticipated these trends, improvements, and introductions. In 1961, the Bell

and in the 1960s began researching and developing what System along with the help of the U.S. government

is now today’s cellular phone service.

started work on a classic cold war project, finally

The Bell System benefited greatly from U.S. defense

completed in 1965. It was the first coast to coast atomic spending during World War II in its laboratories.

bomb blast resistant cable network system.

Wartime experiments, innovations, and inventions

The six major transcontinental cables were evenly

brought Bell to the forefront of telecommunications in distributed from the southern United States to the

the post-war era. The first commercial mobile telephone northern states. The trunk lines were about six inches in service was put in service in 1946, linking moving

diameter with 22 coax cables and control and alarm

vehicles to telephone networks by radio. The same year wires within the major trunk cable. The telephone

Chapter One: Telephone History brought transmission via coaxial cables, resulting in a network also consisted of north–south links which were 4

Chapter One: Telephone History

accomplished with microwave radio links

coordinates to represent sound. T1 quickly became the interconnecting with the six major truck cables.

backbone of long distance toll service and then the

The original trunk line cables were later replaced with primary handler of local transmission between central half-inch diameter fiber optical cables. Over 950 buried offices. The T1 system handles calls throughout the

concrete repeater stations were constructed, and

telephone system to this day.

stretched along the 19 state route were 11 manned test In 1965, the first commercial communications satellite centers, buried 50 feet below ground, complete with air was launched, providing 240 two-way telephone

filtration, living quarters and food and water, for up circuits. The year 1965 also marked the debut of the

to a month of operation.

No. 1ESS, the Bell System’s first central office

The original repeater sites—every 20 miles along the

computerized switch. The product of at least 10 years of transcontinental cables were highly disguised

planning, 4,000 man years of research and development, earthquake proof underground bunkers which could

as well as $500 million dollars in costs, the first

maintain communications in the event of a nuclear war Electronic Switching System was installed in

or so it was believed. It was believed that a small

Succasunna, NJ. Built by Western Electric, the 1ESS

crew could man each repeater site with food and fuel

used 160,000 diodes, 55,000 transistors, and 226,000

enough to power a jet engine turbine for a month of

resistors. These and other components were mounted on operation. Special air filter/scrubbers were installed in thousands of circuit boards. Not a true digital switch, each location to allow the crew to be self contained in the 1ESS did feature Stored Program Control, a fancy

the event of a nuclear attack. AT&T contracted with Bell System name for memory, enabling all sorts of new many different companies which flew bi-weekly over

features like speed dialing and call forwarding.

the main transcontinental cables by overhead

Progress in miniaturization in the last 20 to 30 years helicopter flights to monitor any activity or digging has been astonishing. Few people realize that today’s near the cables.

palm-sized phones originated from the “bag” or

In 1963, the first modern touch-tone phone was

“briefcase phones” of the early and mid-1980s. This

introduced, the Western Electric 1500. It had only

miniaturization of the modern cell phones would not

10 buttons. Limited service tests had started in 1959.

have been possible without the cellular architecture, Also in 1963 digital carrier techniques were introduced.

which uses low power cell phone towers or base station Previous multiplexing schemes used analog

to hand-off calls between cell phone towers. The

transmission, carrying different channels separated by regularly spaced “cell” tower concept has permitted the frequency, much like those used by cable television.

rapid proliferation of the small pocket cell phone, since Transmission One, or T1, by comparison, reduced

the pocket phone can utilize a low power, small size, analog voice traffic to a series of electrical plots, binary stable UHF transmitter and receiver.

5

Chapter 2

How the Telephone Works

The telephone is so ubiquitous and transparent in our When your telephone is in on-hook state the “TIP” is

modern world that most often we take it for granted, yet at about 0 V, while “RING” is about −48 V with respect most people really do not understand how the telephone to earth ground. When you go off hook, and current is works. In this chapter we will take a closer look at the drawn, TIP goes negative and RING goes positive

telephone and its individual components as well as how (I mean less negative). A typical off-hook condition is the telephone companies’ Central Office (CO)

TIP at about −20 V and ring at about −28 V. This means equipment controls our home telephone.

that there is about 8 V voltage between the wires going A telephone uses an electric current to convey sound

to telephone in normal operation condition. The

information from your home to that of a friend. When

DC-resistance of typical telephone equipment is in

the two of you are talking on the telephone, the

200–300 ohm range and current flowing through the

telephone company is sending a steady electric current telephone is in 20–50 mA range.

through your telephones from the telephone company’s

The −48-V voltage was selected because it was

central office battery system. The two telephones, yours enough to get through kilometers of thin telephone

and your friend’s, are sharing this steady current. But as wire and still low enough to be safe (electrical safety you talk into your telephone’s microphone, the current regulations in many countries consider DC voltages

that your telephone draws from the telephone company

lower than 50 V to be safe low voltage circuits).

fluctuates up and down. These fluctuations are directly A voltage of 48 V is also easy to generate from normal related to the air pressure fluctuations that are the sound lead acid batteries (4 × 12 -V car battery in series).

of your voice at the microphone.

Batteries are needed in telephone central to make sure Because the telephones are sharing the total current, that it operates also when mains voltage is cut and

any change in the current through your telephone causes they also give very stable output voltage which is

a change in the current through your friend’s telephone.

needed for reliable operation of all the circuit in the Thus as you talk, the current through your friend’s

central office. Typically, the CO actually runs off the telephone fluctuates. A speaker or earphone in that

battery chargers, with the batteries in parallel getting a telephone’s handset responds to these current

floating charge.

fluctuations by compressing and rarefying the air. The The line feeding voltage was selected to be

resulting air pressure fluctuations reproduce the sound negative to make the electrochemical reactions on the of your voice. Although the nature of telephones and the wet telephone wiring to be less harmful. When the

circuits connecting them have changed radically in the wires are at negative potential compared to the

past few decades, the telephone system still functions in ground the metal ions go from the ground to the wire, a manner that at least simulates this behavior.

replacing a situation where positive voltage would

The current which powers your telephone is

cause metal from the wire to leave, causing quick

generated from the 48 -V battery in the central office.

corrosion.

The 48 -V voltage is sent to the telephone line through Some countries use other voltages in typically the

some resistors and indicators (typically there are 2,000

36 to 60 V range. PBXs may use as low as 24 V and

to 4,000 ohms in series with the 48-V power source).

can possibly use positive feeding voltage instead of

The old ordinary offices had about 400 ohm line relay the negative one used in normal telephone network.

coils in series with the line.

Positive voltage is more commonly used in many

6

Copyright © 2009 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Chapter Two: How the Telephone Works

electronics circuits, so it is easier to generate;

Dialing

electrolysis in telecommunications wiring is not a

problem in typical environments inside office

There are two types of dials in use around the world: buildings.

pulse dialing and tone dialing. The most common one is Ordinary telephones utilize only two wires, which

called pulse dialing (also called loop disconnect or

carry both speaker and microphone signals. This is

rotary dialing). Pulse dialing is the oldest form of

called full duplex operation in single wire pair.

dialing—it has been with us since the 1920s. Pulse

Full-Duplex is a term used to describe a

dialing is traditionally accomplished with a rotary dial, communications channel which is capable of both

which is a speed governed wheel with a cam that opens receiving and sending information simultaneously.

and closes a switch in series with your phone and the line. It works by actually disconnecting or “hanging up”

The signal path between two telephones, involving a

the telephone at specific intervals. The mostly used

call other than a local one, requires amplification using standard is one disconnect per digit (so if you dial a a 4-wire circuit. The cost and cabling required ruled out

“1,” your telephone is “disconnected” once and if you the idea of running a 4-wire circuit out to the

dial “2” your telephone is “disconnected” twice and for subscribers’ premises from the local exchange and an

zero the line is “disconnected” ten times) but there are alternative solution had to be found. Hence, the 4-wire also other systems used in some countries.

trunk circuits were converted to 2-wire local cabling, using a device called a “hybrid.” The hybrid device can Tone dialing is a more modern dialing method and is

send and receive audio signals at the same time; it is usually named Touch-tone, Dual Tone Multi-Frequency

accomplished by designing the system so that there

(DTMF) or Multi-Frequency (MF) in Europe. Touch-

is a well-balanced circuit in both ends of the wire

tone is fast and less prone to error than pulse dialing.

which are capable or separating incoming audio from

Bell Labs developed DTMF in order to have a dialing

outgoing signal. This function is done by telephone

system that could travel across microwave links and

hybrid circuit contained in the network interface

work rapidly with computer controlled exchanges.

of the telephone.

Touch-tone can therefore send signals around the

world via the telephone lines, and can be used to

A standard plain old telephone system or POTS

control phone answering machines and computers

telephone line has a bandwidth of 3 kHz. A normal

(this is used in many automatic telephone services

POTS line can transfer the frequencies between 400 Hz which you operate using your telephone keypad).

and 3.4 kHz. The frequency response is limited by the Each transmitted digit consists of two separate audio telephone transmission system.

tones that are mixed together (the four vertical

columns on the keypad are known as the high group

Telephone signaling

and the four horizontal rows as the low group).

Standard DTMF dials will produce a tone as long as a

Ringing

key is depressed. No matter how long you press, the

tone will be decoded as the appropriate digit. The

When someone places a call to you, the CO is notified shortest duration in which a digit can be sent and

and the switch gear sends an AC ringing signal which

decoded is about 100 milliseconds (ms).

will ring the bell in your telephone. Most of the world uses frequencies in 20 to 40 Hz range and voltage in the 50 to 150 V range. The ringer is built so that it will not Other telephone signals

pass any DC current when it is connected to telephone line (traditionally there has been a capacitor in series The telephone CO can send any different types of

with the bell coil). So only the AC ring signal can go signals to the caller telling the status of a telephone call.

though the bell and make it ring. The bell circuit is Those signals are typically audio tones generated by the either designed so that it has high impedance in audio CO. Typical kinds of tones are dialing tone (typically frequencies or it is disconnected from the line when

constant tone of around 400 Hz), calling tone (tone

phone is picked off hook.

telling that the telephone at the other end is ringing) 7

Telephone components

Switch hook

A “switch hook” is a manual control switch mechanism

that answers and hangs up a call on a telephone. When you place the handset in the telephone cradle, it depresses the switch hook’s button and hangs up (puts the phone

“on hook”). When the phone is lifted from the cradle the switch hook is activated and the phone goes “off hook”

and you will then get a dial tone.

The switch hook has two basic states: an “on-hook”

state and an “off-hook” state. When the phone is on

Figure 2-1

Model 500C telephone

hook, both its microphone and speaker are disabled,

as well as the network, while the bell is connected to the telephone line and awaits the ringing voltage when the or busy tone (usually like quickly on and off switched phone is called. In the off-hook state, that is, when dialing tone). The exact tones used vary from country the phone is lifted from the cradle, the microphone and to country.

speaker are connected together through the network

device and the bell is disconnected from the line. You In the United States, the standard black telephone,

will now hear a dial tone and you will be able to place which was provided by the Bell Telephone system for

or dial your call.

many years to the general public, was the classic

black standard model 500C shown in Figure 2-1.

The schematic or wiring diagram for the model 500C is Network device

shown in Figure 2-2; it included the switch-hook, the network device or hybrid, the microphone, the speaker, The standard telephone has a circuit called a voice

the bell, and the dial.

network or telephone hybrid, which connects the

NEON LAMP

RINGER

HOOK SWITCH

NETWORK

HANDSET

DIAL

(S-W)

F

(BL)

N/C

(S-G)

BR

(G)

TIP (+)

d

L1

Pulse

GN

(S-R)

(W)

(S-BK)

R

(W)

g Breaks

(y)

last

G

(W)

N/O

RCVR

GRD

(BL)

(W)

SPK

Lamp

(BK)

(R)

Off

Normal

K

1000 Ω

B

(BK)

(S)

(S-R)

XMTR

MIC

27 K

2500 Ω

A

(R)

L2

RING (−)

(S)

b

Chapter Two: How the Telephone Works Figure 2-2 Telephone schematic 8

Chapter Two: How the Telephone Works

microphone and speaker to the telephone line

8 TUV, 9 WXY, and 0 Operator. A curved device

(see telephone schematic). Network interface circuitry called a finger stop sits above the dial at the 4 o’clock is designed so that it sends only the current changes position.

the other telephone causes to the speaker. The current changes that the telephone’s own microphone

Microphone

generates are not sent to the speaker. All this is

accomplished using quite ingenious transformer

A basic telephone consists of a microphone, a speaker, circuitry. In theory the hybrid circuit can separate all and a simple electronic network that improves the

incoming audio from the audio sent out at the same time behavior of the telephone. It also has a system for

if all the impedances in the circuitry (hybrids on both dialing and a bell to announce an incoming call.

ends and the wire impedance in between) are well

Modern telephones often contain sophisticated

matched. Unfortunately, the hybrid is by its very nature electronic devices, such as audio amplifiers, radio

a “leaky” device. As voice signals pass from the 4-wire transmitters and receivers, lights, and audio recorders, to the 2-wire portion of the network, the higher energy but the basic concepts are still the same. When you talk level in the 4-wire section is also reflected back on into the microphone, it changes the amount of current itself, creating the echoed speech. Because the circuit flowing through the telephone. In older telephones, the does not work perfectly and you can still hear some of microphone contains a small canister of carbon granules your own voice in the speaker, this is called side-tone or between two metal sheets; see Figure 2-4.

feedback, which is actually a desired effect if the

volume level is kept low.

Since carbon conducts electricity somewhat, the

microphone is a resistor. Current from one metal sheet flows to the other sheet over a circuitous path through Rotary dial

the granules. The more tightly packed the carbon

granules, the more they touch one another and the more The common rotary dial was 3′′ in diameter,

direct the current path becomes. Compression causes

and had 10 finger holes that were cut through

the carbon microphone’s electric resistance to decrease.

its outer perimeter, as seen in Figure 2-3.

Expansion causes it to increase. As you talk into the The dial is mounted via a shaft extending from inside microphone, the air pressure fluctuations in your voice the telephone or mounting and sits above a faceplate.

alternately compress and expand the granules and make In North America, traditional dials had letter codes

the resistance of the microphone fluctuate up and down.

displayed with the numbers under the finger holes:

Because the microphone is connected between the two

1, 2 ABC, 3 DEF, 4 GHI, 5 JKL, 6 MNO, 7 PRS,

telephone wires, this fluctuating resistance causes a Front contact

Back

contact

Button

To current

source

Carbon

Diaphragm

block

Figure 2-3

Rotary dial

Figure 2-4

Telephone microphone

9

fluctuating current to flow through the telephone. Since Telephone speaker

all of the telephones in the parallel circuit share the same current, talking into the microphone of one

When the current through the telephone changes, the

telephone changes the currents flowing through each of telephone’s speaker or earphone creates sound. The

the other telephones. Carbon microphones have poor

speaker is a device that converts an electric current into frequency response and bad signal-to-noise ratios and pressure fluctuations in the air. A conventional speaker they are only suitable for telephones and such

pushes and pulls on the air with a paper or plastic

communication applications.

membrane, usually in the form of a cone; see Figure 2-5.

The cone is driven in and out by the electric current In more modern telephones, more sophisticated

through the telephone.

electronic microphones and amplifiers have replaced the carbon microphone. There are literally dozens of types This sound generation process requires a conversion

of microphones but the most popular one for telephones of electric power into mechanical power. The speaker or is the electret microphone. An electret is a thin

earphone unit performs this conversion using

insulating film that has charges permanently trapped in electromagnets. The speaker contains a permanent

its surfaces. One surface is positively charged and the magnet that is fixed to the back of the speaker so that it other surface is negatively charged—the film is

is immobile. It also has a mobile coil of wire that

electrically polarized. Although this charge separation becomes a magnet when current flows through it.

slowly disappears, it takes hundreds or even thousands The permanent magnet and the coil are arranged

of years to vanish. In an electret microphone, the

so that they attract one another if current flows in one electret film is drawn taut like the head of a drum and is direction through the coil and repel one another if the suspended just above a metal surface. As you talk into current is reversed. When an alternating current flows the microphone, pressure fluctuations in the air distort back and forth through the coil, the coil is alternately the electret film up and down, and it moves toward and attracted to the permanent magnet and repelled from it.

away from the metal surface below it. Charges in the

The speaker coil is attached to the speaker cone so that metal surface experience fluctuating forces as the

the two move together. The cone is loosely supported

polarized electret moves back and forth. As a result of by the speaker’s frame only at its periphery. The coil these forces, current flows alternately toward and away and cone have very little mass so that they accelerate from the metal surface through a wire that touches it.

in and out very easily. Their main resistance to motion is the air itself. As the cone moves out, it compresses In principle, talking into your own telephone

the air in front of it and as it moves in, it rarefies the microphone should cause the speaker of your telephone air in front of it. When it moves in and out rapidly, to reproduce your voice, too. However, this effect is undesirable because it would affect your speech. If you were to hear the full audio signal from your voice

through your own speaker, you would think you were

talking too loudly and you would unconsciously

start to talk more softly. The sound you hear in your Permanent

Speaker

cone

telephone speaker when you talk into your telephone

magnet

Coil

microphone is called side-tone. Each telephone

contains a balancing network that reduces side-tone.

Motion

This network is usually a simple collection of

electronic components that detects audio signals

created by the telephone’s microphone and keeps

them from causing current changes in the telephone’s

speaker. The balancing network reduces the extent

Current

to which audio signals from your microphone affect

your speaker so that you are not fooled into talking

Chapter Two: How the Telephone Works too quietly.

Figure 2-5

Telephone earphone

10

Chapter Two: How the Telephone Works

it produces sound. The speaker does a good job of

Situated between the two poles is an iron clapper. The converting an electric current representing sound into clapper is magnetized by a small permanent magnet

actual sound. The compressions and rarefactions of the attached to its base so that it is attracted toward north air that it produces are very closely related to the

poles and repelled by south poles. The electromagnet

current fluctuations passing through it.

attracts the clapper first toward one pole and then

toward the other. The clapper swings back and forth

between the poles as the current reverses and its end The bell

strikes two metal bells in the process. The bells ring.

The two bells are usually tuned to an octave interval.

When your telephone is not in use, it is “on-hook.”

That means that the high-pitched bell rings at twice the When the handset is placed back into the cradle it

frequency of the low-pitched bell, giving the telephone electrically disconnects the microphone and the speaker its characteristic sound.

from the two telephone wires. When the phone is

on-hook it connects the bell equivalent ringer unit

Most modern telephones have replaced the bell with

across the telephone phone line. The bell is a device that an electronic ringer unit. They use the ring current to responds to an alternating current sent through the two power a tone-generating circuit and an amplifier, and telephone wires by the telephone company when a call

produce the electronic sound with a speaker.

is coming in. While the voltage on the telephone wires during a conversation is low and safe, the voltages used to drive current through the bell are large enough to How a cell phone works

give you a mild shock if you touch both wires while the bell is ringing.

Inside your cell phone, there is a compact speaker, a A real telephone bell uses this alternating current to microphone, a keyboard, a display screen, and a

energize an electromagnet (see Figure 2-6).

powerful circuit board with microprocessors that make each phone a miniature computer, along with a stable

One end of the electromagnet becomes a north pole

UHF transmitter and receiver pair. When connected to a and the other a south pole. Each time the current

wireless network, this technological wonder allows you reverses, so do the poles of the electromagnet.

to make phone calls or exchange data with other phones and computers around the world. The cell phone

components operate so efficiently that a lightweight

Low

High

battery can power your phone for days.

A cell phone is really a radio—a very sophisticated

Bell

Bell

computer and versatile radio. Because these radios

connect into a digital network, cell phones offer much more than the ability to call any telephone anywhere in the world; modern cell phones can access the Internet Permanent

and data services world wide.

magnet

Wireless networks operate on a type of grid network

N

S

that divides cities or regions into smaller cells. One cell might cover a few city blocks or up to 250 square miles.

Every cell uses a set of radio frequencies or channels to provide service in its specific area. The power of these radios is controlled in order to limit the signal’s

geographic range. Because of this, the same frequencies can be re-used in nearby cells. So, many people can

hold conversations simultaneously in different cells

throughout the city or region, even though they are on Figure 2-6

Ringer diagram

the same channel.

11

When you turn on your cell phone, it searches for a

just like a computer. These small packets of data

signal to confirm that service is available. Then the are relayed through wireless networks to the receiving phone transmits certain identification numbers, so the phone. On the other end, the conversion process

network can verify your customer information, such as is reversed and the person you are calling hears

your wireless provider and phone number.

your voice.

If you are calling from a cell phone to a wired phone, The key to the successful modern cell phone

your call travels through a nearby wireless antenna and system is the wireless network that senses when your

is switched by your wireless carrier to the traditional signal is getting weaker and hands over your call to an land-line phone system. The call then becomes like any antenna with a stronger signal. Using smaller cells

other phone call and is directed over the traditional enables your phone to use less power and keep a clear phone network, and to the person you are calling. If you signal as you move. Even when you are not talking,

are calling another cell phone, your call may go through your cell phone communicates with the wireless

the land-line network to the recipient’s wireless carrier, antenna nearest to you. So it is ready to connect your or it might be routed within the wireless network to the call at any time.

cell site nearest the person you called, but if you are If you travel outside your home area and make a call, calling someone further away, your call will be routed another wireless carrier may provide service for your to a long distance switching center, which relays the cell phone. That provider sends a signal back to your call across the country or around the world through

home network, so you can send and receive calls as you fiber-optic cables.

travel. This is called roaming. Roaming is key to mobile Most cell phones use digital technology, which

communications, as wireless providers cooperate to

converts your voice into binary digits or zeros and ones, provide callers service wherever they go.

Chapter Two: How the Telephone Works

12

Chapter 3

Identifying Electronic Components

Electronic circuits are comprised of electronic

(red) band will represent the digit (1), the digit (0) components such as resistors and capacitors, diodes,

with a multiplier value of (00) or one thousand, so that semiconductors and LEDs. Each component has a

the resistor will have a value of 1 K or 1,000 ohms.

specific purpose that it accomplishes in a particular There are a number of different styles and sizes of

circuit. In order to understand and construct electronic resistor. Small resistors can be carbon, thin film, or circuits it is necessary to be familiar with the different metal. Larger resistors are made to dissipate more

types of components, and how they are used. You

power and they generally have an element wound

should also know how to read resistor and capacitor

from wire.

color codes, and recognize physical components and

A Potentiometer or (pot) is basically a variable

their representative diagrams and pin-outs. You will also resistor. It generally has three terminals and it is fitted want to know the difference between a schematic and a with a rotary control shaft that varies the resistance as pictorial diagram. First, we will discuss the actual

it is rotated. A metal wiping contact rests against a components and their functions and then move on to

circular carbon or wire-wound resistance track. As the reading schematics. Then we will help you to learn how wiper arms move about the circular resistance, the

to insert the components into the circuit board. In the resistance to the output terminals changes.

next chapter we will discuss how to solder the

Potentiometers are commonly used as volume controls

components to the circuit board.

in amplifiers and radio receivers.

The diagrams shown in Figures 3-1 to 3-3 illustrate

A Trimpot is a special type of potentiometer which

many of the electronic components that we will be

while variable, is intended to be adjusted once or only using in the projects presented in this book.

occasionally. For this reason a control shaft is not

provided but a small slot is provided in the center of the Types of resistors

control arm. Trimpots are generally used on printed

circuit boards.

Resistors are used to regulate the amount of current

A light dependent resistor (LDR) is a special type of flowing in a circuit. The higher the resistor’s value or resistor that varies its resistance value according to the resistance, the less current flows, and conversely a

amount of light falling on it. When it is in the dark, an lower resistor value will permit more current to flow in LDR will typically have a very high resistance, i.e., a circuit. Resistors are measured in ohms (Ω) and are millions of ohms. When light falls on the LDR the

identified by color bands on the resistor body. The first resistance drops to a few hundred ohms.

band at one end is the resistor’s first digit, the second color band is the resistor’s second digit and the third band is the resistor’s multiplier value. A fourth color Types of capacitors

band on a resistor represents the resistor’s tolerance value. A silver band denotes a 10% tolerance resistor, Capacitors block DC current while allowing varying

while a gold band notes a 5% resistor tolerance. No

or AC current signals to pass. They are commonly used fourth band denotes that a resistor has a 20% tolerance.

for coupling signals from part of a circuit to another As an example, a resistor with a (brown) (black) and

part of a circuit; they are also used in timing circuits.

13

Copyright © 2009 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Polyester

Resistor

capacitor

(Greencap)

MKT polyester

capacitor

Potentiometer

Ceramic

capacitor

Trimpot

Electrolytic

or

capacitor

+

−

+

−

Light dependent

resistor (LDR)

Variable and

trimmer capacitors

Variables

Trimmer

Figure 3-1

Electronic components I

Chapter Three: Identifying Electronic Components

14

Chapter Three: Identifying Electronic Components

LED display

NPN transistor

(PN100, BC548)

C

B

E

PNP transistor

(PN200, BC558)

FET—Junction type

C

D

G

B

S

N-Channel

E

MOSFET—Power type

Power transistor

D

(NPN OR PNP)

G

(Same symbols

S

as above)

N-Channel

D

Silicon diode

G

S

A

K

P-Channel

A

Integrated circuit

K

(IC)

(ICs have many symbols,

Light emitting

usually depicting their

diode (LED)

function or circuit use)

A

A

K

3-Terminal

regulator

K

Zener diode

+

+

Figure 3-2

Electronic components II

15

Heatsink

Wire & cable

(No circuit symbol)

Electret

microphone

+

Loudspeakers

Inductors

(Coils)

Ferrite

slug

Former

Coil of

wire

Ferrite

Air cored

cored

Pins for

connection

Relay

Iron cored

to pc board

Transformer

Winding

connection

leads

Switch – Slider

(Iron cored)

Iron core

SPDT

DPDT

Figure 3-3

Chapter Three: Identifying Electronic Components

Electronic components III

16

Chapter Three: Identifying Electronic Components

There are a number of different types of capacitor as a few tens of picofarads (pF) and a few hundreds of

described below:

microfarads for larger variable capacitors.

■

Polyester capacitors use polyester plastic film as

their insulating dielectric. Some polyester

Diodes

capacitors are called greencaps since they are

coated with a green or brown color coating on the

A diode is a semiconductor device which can pass

outside of the component. Their values are specified

current in one direction only. In order for current to flow, in microfarads (μF), or nanofarads (nF), or picofarads the anode (A) must be positive with respect to the

(pF) and range from 1 nF up to about 10 μF. These

cathode (K). In this condition, the diode is said to be types of capacitors do not have polarity markings

forward biased and a voltage drop of about .6 V

and can be installed in either direction.

appears across its terminals. If the anode is less than .6 V

■

MKT capacitors are another type of capacitor, but

positive with respect to the cathode, negligible current they are rectangular or (block) in shape and are

will flow and the diode behaves as an open circuit.

usually yellow in color. One of the major

advantages of these capacitors is a more

Types of transistors

standardized lead spacing, making them more

useful for PC board projects. Their components can

Transistors are semiconductor devices that can either be generally be substituted for polyester types.

used as electronic switches or to amplify signals. They

■

Ceramic capacitors use a tiny disk of ceramic or

have three leads, called the collector, base, and emitter.

porcelain material in their construction for a

A small current flowing between base and emitter

dielectric and they range in value from 1 pF up to

(junction) causes a much larger current to flow between 2.2 μF. Those with values above 1 nF are often

the emitter and collector (junction). There are two basic made with multiple layers of metal electrodes and

types of transistors: PNP and NPN styles.

dielectric, to allow higher capacitance values in

A Field Effect Transistor or FET is a different type of smaller bodies. Their capacitors are usually called

transistor, which usually still has three terminals but

“multilayer monolithics” and are distinguished from

works in a different way. Here the control element is the lower value disc ceramic types. Ceramic capacitors

“gate” rather than the base, and it is the gate voltage are often used in Rf radio circuits and filter circuits.

which controls the current flowing in the “channel”

■

Electrolytic capacitors use very thin film of metal

between the other terminals—the “source” and the

oxide as their dielectric, which allows them to

“drain.” Like ordinary transistors FETs can be used

provide a large amount of capacitance in a very

either as electronic switches or amplifiers; they also small volume. They range in value from 100 nF up

come in P-channel and N-channel types, and are

to hundreds and thousands of microfarads (μF).

available in small signal types as well as power FETs.

They are commonly used to filter power supply

Power transistors are usually larger than the smaller circuits, coupling audio circuits, and in timing

signal type transistors. Power transistors are capable of circuits. Electrolytic capacitors have polarity and

handling larger currents and voltages. Often metal tabs must be installed with respect to these polarity

and heat sinks are used to remove excess heat from the markings. The capacitor will have either a white or

part. These devices are usually bolted to the chassis and black band denoting polarity with a plus (+) or

are used for amplifying RF or audio energy.

minus (−) marking next to the color band.

■

Variable capacitors are used in circuits for (trimming) or adjustment, i.e., for setting a frequency. A variable Integrated Circuits

capacitor has one set of fixed plates and one set of

plates which can be moved by turning a knob. The

Integrated circuits or ICs contain in one package all or dielectric between the plates is usually a thin plastic most of the components necessary for a particular circuit film. Most variable capacitors have low values up to

function. Integrated circuits contain as few as 10 transistors 17

or many millions of transistors, plus many resistors, diodes increase its inductance. Inductance is the ability to store and other components. There are many shapes, styles, and energy in a magnetic field. Many coils are wound on a sizes of integrated circuits; in this book we will use the former of insulating material, which may also have

dual-in-line style IC either 8, 14, or 16 pin devices.

connection pins to act as the coils’ terminals. The former Three-terminal regulators are special types of

may also be internally threaded to accept a small core or integrated circuits, which supply a regulated, or constant

“slug” of ferrite, which can be adjusted in position

and accurate, voltage from their output regardless (within relative to the coil itself to vary the coil inductance.

limits) of the voltage applied to their input. They are most A transformer consists of a number of coils or

often used in power supplies. Most regulators are

windings or wire wound on a common former, which is

designed to give specific output voltages, so that an also inside a core of iron alloy, ferrite, or other magnetic

“LM7805” regulator provides a 5-V output, but some

material. When an alternating current is passed through IC regulators can provide adjustable output based on an one of the windings (primary), it produces an

external potentiometer which can vary the output voltage.

alternating magnetic field in the core and this in turn induces AC voltages in the other (secondary) windings.

The voltages produced in the other winding depends

Heat sinks

on the number of turns in those windings, compared

with the turns in the primary winding. If a secondary Many electronic components generate heat when they

winding has fewer turns than the primary, it will

are operating. Generally, heat sinks are used on

produce a lower voltage, and be called a step-down

semiconductors such as transistors to remove heat.

transformer. If the secondary winding has more

Overheating can damage a particular component or the

windings than the primary then the transformer will

entire circuit. The heat sink cools the transistor and produce a higher voltage and it will be a step-up

ensures a long circuit life by removing the excess heat transformer. Transformers can be used to change the

from the circuit area.

voltage levels of AC power and they are available in

many different sizes and power-handling capabilities.

Light-emitting diodes

A light-emitting diode or LED, is a special diode which Microphones

has a plastic translucent body (usually clear, red, yellow, green, or blue in color) and a small semiconductor

A microphone converts audible sound waves into

element which emits light when the diode passes a

electrical signals which can then be amplified.

small current. Unlike an incandescent lamp, an LED

In an electret microphone, the sound waves vibrate a

does not need to get hot to produce light. LEDs must

circular diaphragm made from very thin plastic material always be forward biased to operate. Special LEDs can containing a permanent charge. Metal films coated on

also produce infrared light.

each side form a capacitor, which produces a very small LED displays consist of a number of LEDs together

AC voltage when the diaphragm vibrates. All electret

in a single package. The most common type has seven

microphones also contain FET which amplifies the very elongated LEDs arranged in an “8” pattern. By

small AC signals. To power an FET amplifier the

choosing which combinations of LEDs are lit, any

microphone must be supplied with a small DC voltage.

number of digits from “0” through “9”can be displayed.

Most of these “7-segment” displays also contain another Loudspeakers

small round LED which is used as a decimal point.

A loudspeaker converts electrical signals into sound

Types of inductors

waves that we can hear. It has two terminals which go to a voice coil, attached to a circular cone made of

An inductor or “coil” is basically a length of wire, wound either cardboard or thin plastic. When electrical signals Chapter Three: Identifying Electronic Components into a cylindrical spiral (or layers of spirals) in order to are applied to the voice coil, this creates a varying 18

Chapter Three: Identifying Electronic Components

magnetic field from a permanent magnet at the back of oxidize or tarnish in the presence of air. A thin metal the speaker. As a result the cone vibrates in sympathy alloy coating is often applied to the copper wire; usually with the applied signal to produce sound waves.

an alloy of tin or lead is used.

Single or multi-strand wire is covered in colored PVC

Relays

plastic insulation and is used quite often in electronic applications to connect circuits or components together.

Many electronic components are not capable of

This wire is often called a “hook-up”wire. On a circuit switching higher currents or voltages so a device called diagram, a solid dot indicates that the wires or PC

a relay is used. A relay has a coil which forms an

board tracks are connected together or joined, while a electromagnet, attracting a steel “armature,” which itself

“loop-over” indicates that they are not joined and must pushes on one or more sets of switching contacts. When be insulated. A number of insulated wires enclosed in a current is passed through the coil to energize it, the outer jackets are called electrical cables. Some electrical moving contacts disconnect from one set of contacts to cables can have many insulated wires in them.

another, and when the coil is de-energized the contacts go back to their original position. In most cases a relay Semiconductor substitution

needs a diode across the coil to prevent damage to the semiconductor driving the coil.

Often, when building an electronic circuit, it is difficult or impossible to find or locate the original transistor Switches

or integrated circuit. There are a number of circuits featured in this book which feature transistors, SCRs A switch is a device with one or more sets of switching and UJT and FETs that are specified but cannot be

contacts, which are used to control the flow of current found in this country. Where possible, many of these

in a circuit. The switch allows the contacts to be

foreign components are converted to substitute values, controlled by a physical actuator of some kind, such as either with a direct replacement or close substitution.

a press-button toggle lever, rotary, or knob. As the name Many foreign parts can be easily converted directly to a denotes, this type of switch has an actuator bar which commonly used transistor or component. Occasionally

slides back and forth between the various contact

an outdated component has no direct common

positions. In a single-pole, double throw (SPDT) slider replacement, so the closest specifications of that

switch, a moving contact links the center contact to

component are attempted.

either of the two end contacts. In contrast a double-pole, In some instances we have specified replacement

double throw (DPDT) slider switch has two of these

components with substitution components from the

sets of contacts, with their moving contacts operating in NTE brand or replacements. Most of the components

tandem when the slider is actuated.

for the project used in this book are quite common and easily located or substituted without difficulty.

Wire

When substituting components in the circuit, make

sure that the pin-outs match the original components.

A wire is simply a length of metal conductor, usually Sometimes, for example, a transistor may have a bottom made from copper since its conductivity is good, which view drawing, while the substituted value may have a

means its resistance is low. When there is a risk of a drawing with a top view. Also be sure to check the

wire touching another wire and causing a short, the

pin-outs of the original components versus the

copper wire is insulated or covered with a plastic

replacement. As an example, some transistors will have coating which acts as an insulating material. Plain

EBC versus ECB pin-outs, so be sure to look closely at copper wire is not usually used since it will quickly possible differences which may occur.

19

Chapter 4

Reading Schematics

Before we take a look at some electronics schematics, If a volt signal is applied to the input end of R1 the it is important that you understand the relationship

22 K ohm resistor, the current through the whole circuit between voltage and current and resistance. This

would be I = V/R = 1/22,033 or .000,045,386,4 amps or relationship is called Ohm’s Law and it is the backbone about .05 milliamps. Voltage dividers are used to reduce of simple electronics formulas for electronics. In its or step down voltages or signal levels to voltage

simplest form it is shown as the equation V= I ∗ R,

converter circuits, amplifiers, etc. Voltage dividers are which says voltage (V) is equal to current (I) multiplied often set up using resistor ratios or 1,000:1, 100:1, or by resistance (R). Voltage is represented as electromotive 10:1, for example a 10 to 1 resistor divider would have force where V is used instead of E. Current represented a 10 ohms and a 1 ohm resistor for R1 and R2 values.

as (I) is in amperes or amps; in typical electronic circuits The introduction of the operational amplifier or

milliamps may be used, and this is shown as 1/1,000 or Op-Amp in the late 1960s and early 1970s transformed

an ampere. One milliamp = .001 amp, abbreviated as

the electronics industry like no device before it.

mA or ma. The three most important Ohm’s Law

Op-Amps began life as large integrated amplifier

equations are V= I ∗ R; I = V/R; and R= V/I.

modules, some measuring up to 3′′ in length. Early

The most used Ohm’s Law power equation is shown as

Op-Amps were large and noisy but nonetheless a

P = I ∗ V, where P is power in watts or wattage, which monumental development in electronics. The Op-Amp

is equal to the current of a circuit multiplied by the permitted a simple building block approach to electronic voltage in the circuit. Thus a voltage of 100 V

circuit design. Early Op-Amps were primarily used for multiplied by a current consumption of two amps of

pre-amps and instrumentation amplifiers. As Op-Amp

current would equate to a power consumption of

quality progressed and their sizes and power

200 watts.

consumption reduced over time, Op-Amps were used in

The diagram shown in Figure 4-1 depicts a very

all types of electronic circuit designs. Op-Amps are now common circuit called a voltage divider.

utilized in audio amplifiers, filter design, oscillators, The basic voltage divider consists of two resistors,

comparators, regulators, etc. Since Op-Amps are now

usually connected in series as shown. The total

found in most all electronic circuits, we will spend

resistance is simply the sum of the two. In this example, some time identifying different Op-Amp configurations it would be 22 K ohms plus 33 ohms = 22,033 ohms.

and applications.

Integrated circuits (ICs) are used throughout much

of modern electronics, so understanding how they are

represented is important. ICs generally contain many

R1

individual circuits or components, and are shown

Input

Output

schematically as functional blocks. Op-amps can

22 K

be configured in many different ways, including

R2

non-inverting amplifiers.

33 Ω

The ubiquitous operational amplifier or Op-Amp is

shown in the diagram of Figure 4-2 as a triangle with a plus (+) and minus (−) input and a single output at the Figure 4-1

Voltage divider circuit

point of the triangle.

20

Copyright © 2009 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Chapter Four: Reading Schematics

R1

R2

R5

R6

R7

Input

+V

−V

+V

7

R4

2

−

6

U1

+V

Output

3

+

4

R3

−

R1

R2

R3

V

+V

7

2

−

R6

R7

6

U1

R4

Output

3

+

4

−V

R5

Input

−V

Figure 4-2

Inverting Op-Amp amplifier

Figure 4-3

Non-inverting Op-Amp amplifier

This type of Op-Amp configuration is called an

the output. Notice that in this configuration the signal inverting input amplifier circuit, since the input is fed input is applied to the plus (+) input of the Op-Amp.

through the minus (−) input of the Op-Amp. Note that

The balance and trim capability is performed via the

the signal input is applied through the input resistor at bias network formed by resistors R4 through R7, which R1. Also notice that a second resistor R2 is shown from connect to both the plus and minus power supply.

the minus input across to the output of the Op-Amp.

The circuit shown in Figure 4-4 depicts a basic

Resistor R2 is called the feedback resistor. The plus (+) differential Op-Amp instrumentation amplifier.

input of the Op-Amp is shown connected to a resistor

In this circuit, notice that there are two separate inputs network used to balance the input through a bias control and they are referenced against ground connection, which at resistor R4. Both plus and minus voltage sources are is separate from the inputs. This type of circuit is used in connected to the bias network.

high gain instrument amplifiers, when you wish to keep Simulate driving a current through the inverting input common modes noise from reaching the Op-Amp.

by placing a 1 volt on the input at R1 and assume that This configuration is commonly used for high input

the right end has 0 volts on it. The current will be

impedance sensor inputs, where low leads may be used

I = V/R = 1/1 K = 1 ma. The voltage output will try to and low noise is required. Note the balance or trim for counter this by driving a current of the opposite

Op-Amp is provided through the resistor network

polarity through the feedback resistor into the inverting composed of R4 through R7, which allows bias from

input. The required voltage to do that will be

both the plus and minus power sources.

V= −(I ∗ R) = −(1 ma ∗ 10 K) = −10 V. Thus we get a

voltage to current conversion, a current to voltage

Input 1

10 K

10 K

conversion, a polarity inversion and, most importantly, R1

R2

amplification. G = −(Feedback Resistor/Input Resistor)

+V

In this example, it is shown as Gain or G = −(R2/R1).

7

2

−

This inverting input Op-Amp configuration is

6

U1

Output

GND

3

commonly used in modern amplifiers and filters, etc.

+

4

GND

Op-amps generally require both plus (+) and minus (−)

−V

−V

voltages for operation; this allows a voltage swing either 10 K

10 K

10 K

side of zero.

10 K

Input 2

R3

R4

R6

R7

The diagram illustrated in Figure 4-3 shows a

R5

10 Ω

+V

non-inverting Op-Amp configuration.

This configuration is used when you wish to maintain

the same phase or polarity from the input, through to Figure 4-4

Differential Op-Amp amplifier

21

+9 V

The duty cycle is set up through resistors to produce R2

a symmetrical square-wave output.

1 K

As you can see from these examples, the Op-Amp

U1

is a very powerful electronic building block tool for 7 +V

2

LED

Input

−

greatly simplifying the design of electronic circuits.

6

Lm339

3

We have only covered a small number of Op-Amp

R1

+

−V

4

applications. Op-Amps are also used for filters, power 50 K

regulators, integrators, voltage to current and current to voltage convertors. For more information on Linear

Op-Amps theory and applications look for the IC

Op-Amp Cookbook by Walter Jung or point your

Figure 4-5

Differential Op-Amp comparator

browser to w1.859.telia.com/∼u85920178/begin/

opamp00.htm for a discussion on Operational Basics by Figure 4-5 illustrates how an Op-Amp can be used as

Harry Lythall.

a comparator to trigger an LED when a certain voltage The above examples illustrate linear Op-Amps, and

threshold is reached. In this configuration, the plus (+) they represent nearly a half of the spectrum of

input of the Op-Amp is connected to a 50 K

integrated circuits. On the other side of the spectrum of potentiometer which is connected between the plus

integrated circuits are the digital integrated circuits 9-V source and ground.

which generally contain multiple digital gates, switches, Note in this configuration, only a single voltage is

and memory functions all in one package. One of the

required. The minus (−) input lead of the Op-Amp is

more common digital integrated circuits is the Quad

connected to the voltage source you wish to monitor. In 2-input AND gate, shown in Figure 4-7.

operation, you would apply a voltage to the minus input This diagram illustrates a fourteen pin 74LS08 Quad

pin of the Op-Amp and adjust the R1, so the LED is not 2-input AND gate, and its truth table. The 74LS08

lit. Raising the voltage at the input would now offset the contains four AND gates. The inputs to the first AND

comparator and its trip point and the LED would

gate are at 1A and 1B represented by pins 1 and 2,

become lit.

while the output is at pin3. The second AND gate has

Op-Amps can also be used in oscillators and function

inputs 2A and 2B on pins 4 and 5 with its output on

generators as shown in Figure 4-6.

pin 6. The common ground connection is shown on pin 7, while 5-volt power is supplied to pin 14. The third AND

In this circuit the Lm339 comparator Op-Amp is used

gate has its inputs at 3A and 3B, on pins 9 and 10, with to generate a square-wave signal. A resistor and the

its output on pin8. The 4th AND gate shown as 4A and

capacitor at C1 form a timing network which is used to 4B are on pins 12 and 13, with its output on pin 11. The establish the frequency of the square-wave generator.

truth table or function table for the 74LS08 describes the input vs. the output condition for each of the gates.

47 K

R5

If inputs 1A and 1B are HIGH then the resulting output at 100 K

1Y will be HIGH. If input 1A is LOW and input at 1B is 100 K

R1

R4

either HIGH or LOW, then the output at 1Y will be LOW.

U1

If input 1B is LOW and input 1A is either HIGH or LOW

5

3

+

7

Lm339

the output at 1Y will be LOW once again.

4

Output

100 K

R2

−

12

In working with electronic circuits, you will come

100 K

across many schematics as well as pictorial diagrams.

R3

C1

Schematics are the electronic representations on paper

.1 μF

of an electronics circuit. A pictorial diagram is a

generally a physical layout diagram of the same circuit.

In electronics work you will come across both types of Chapter Four: Reading Schematics Figure 4-6 Square-wave Op-Amp oscillator diagrams; they look quite different but they are really 22

Chapter Four: Reading Schematics

74LS08

1

14

1A

+VCC

Function table

1B

4B

Inputs

1Y

4A

Output

A

B

T

2A

4Y

H

H

H

2B

3B

L

X

L

2Y

3A

X

L

L

GND

3Y

7

8

Figure 4-7

Quad 2-input AND gate

the same circuit shown differently. Experience in

to the second amplifier stage at Q2. Resistor R10 is

looking and comparing these two types of diagrams will used to bias the second stage amplifier stage. Capacitor help you enormously in your electronics projects.

C7 is used to connect the output of transistor Q2 to the final amplifier stage or to the input of a transmitter, The diagram shown in Figure 4-8 illustrates a

at J2. Note the ground bus or common connection for

schematic of a two transistor audio amplifier circuit.

ground at the bottom of the circuit, and the power bus The input jack at J1 is coupled to an input capacitor connection at the top of the schematic diagram.

at C1. Capacitor C1 couples the microphone of input

The pictorial diagram shown in Figure 4-9 serves to

source to the amplifier. It acts as a coupling device as illustrate the same two transistor amplifier circuits well as a blocking device which can keep any constant shown in Figure 4-8. Both diagrams are electrically the DC component or voltage from reaching the input of

same, but look quite different. The pictorial diagram the amplifier. The resistors R1 and R2 form the input shows how the circuit would look, and how it may look impedance and frequency response characteristics of the wired and laid out in a chassis box. Compare the two

input to the amplifier. The NPN Transistor at Q1 forms diagrams so that you can see and understand how they

the first stage of amplification of the amplifier. Resistors differ from each other.

R4 and R5 form the bias or voltage supply for Q1. The output of the first amplifier stage at Q1 is connected to An Op-Amp audio amplifier is shown schematically

capacitor C3, which is used to couple the first amplifier in Figure 4-10.

stage to the next amplifier stage. Capacitor C3 is next The input to the amplifier is shown at input jack at J1.

fed to variable resistor R6, which acts as the systems Resistor R1 serves to control the input signal or current volume control. Capacitor C5 couples the audio signal flowing into the amplifier circuit. Resistor R1

+12 V

R5

C4

R2

+

R8

R10

J1

+

J2

R4

Q2

+

C3

Input

C1

Output

Q1

+

C7

+

R6

R1

C5

+

+

C6

C2

R7 R9

Figure 4-8

Transistor amplifier schematic diagram

23

Output

Q1

+ C3

J1

Q2

C1

+

C7

+

R2

+ C5

R6

Input

+

R1

C2

R4

R3

R9

+

R7

+

C6

R10

R8

C4

R5

+12 V

Figure 4-9

Transistor amplifier pictorial diagram

establishes the input impedance to the amplifier circuit.

amplifier. Resistor R3, represents a variable resistor R1 is next fed to the .1-mF capacitor at C1. Capacitor which is as a volume control for the amplifier. The

C1 is used to block low frequency signals and couple

center tap on the variable resistor is fed to resistor R4, the input to the next stage as well as keep any constant which is used to couple the first stage of the amplifier to DC voltage from the guitar away from the input to the the second stage. Resistors R4 and R5 establish the gain Op-Amps. The low frequencies to be blocked are

of the second amplification stage. This gain stage forms dependent upon resistors R1 and R2. The triangle

the real muscle of the amplifier. The output of the

symbol shown at U1 represents the first Op-Amp

second Op-Amp at pin 6 is fed directly to a speaker

amplifier in the circuit. The Op-Amp has two inputs, an through resistor R7, which is used to protect the output inverting input and a non-inverting input. The input

of the amplifier as well as protecting the speaker from signal from resistor R2 is fed to the non-inverting input too much current.

of the Op-Amp. The connection from the input to the

The diagram shown in Figure 4-11 depicts the same

output pin of the Op-Amp forms the feedback network

audio amplifier circuit but it is now shown pictorially which generally determines the gain of the amplifier. In instead of schematically.

this example, there is no resistor but a direct connection between the input and the output. The direct connection The pictorial diagram shows the circuit as it might

from the input to the output of the amplifier establishes appear physically in its enclosure of circuit board. The a unity gain, or no change in the signal input. The

diagram looks quite different but it is really the same purpose of the first stage in this example is to reduce circuit drawn slightly differently. You will need to

the amount of current the guitar must supply to the

recognize and become familiar with the differences

+12 V

2

7

R5

−

6

JT

C1

U1

3

+12 V

+

4

R4

2

7

R3

−

6

R7

U2

R1

3

R2

+

4

−12 V

SPK

−12 V

R6

Chapter Four: Reading Schematics Figure 4-10 Op-Amp amplifier schematic diagram 24

Chapter Four: Reading Schematics

+12 V

R5

1 0

8

1 0

8

R4

2

U2

7

J1

C1

U1

2

7

3

6

3

6

4

5

4

5

R7

R1

R2

R3

−12 V

Figure 4-11

Op-Amp amplifier pictorial diagram

between these types of drawings. The best way to

resistor body. This is the first color code, which

familiarize yourself with schematics and pictorial

represents the first digit; the second color band

diagrams is to see and compare a number of them over

depicts the second digit, while the third band is the time. Once you get some practice it will become second resistor multiplier value. The fourth color band

nature to you. There are a number of good books on

represents the resistor tolerance value. If there is no how to read schematics, which cover the topic in

fourth band then the resistor has a 20% tolerance,

more depth.

if the fourth band is silver, then the resistor has a 10%

Before we discuss installing electronic components to tolerance value, and if the fourth band is gold then the printed circuit boards, we will take a few minutes to resistor has a 5% tolerance value. Therefore, if you

discuss the resistor and capacitor codes which are used have a resistor with the first band having a brown

to help identify these components. Table 4-1 lists the color, the second band with a black color and a third resistor color code information.

band with a red color, then this resistor would have a value of 1 K or 1,000 ohms.

Resistors will generally have at least three or four

color bands which help identify the resistor values.

Capacitor types are quite varied; there are ceramic,

The color band will start from one edge of the

mylar, electrolytic, polyester, paper, tantalum, mica, Table 4-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

No color

20%

25

polyproplene, etc. When installing the small non-

an abbreviated code was devised to mark the capacitor polarized capacitors such as the ceramic or mylar types, using a three-digit code to save space as shown. If you you will need to refer to the capacitor chart in Table 4-2, refer to the chart you will notice that a code marking of which illustrates the three-digit capacitor code values.

(104) would denote a small capacitor with a value of

Most large capacitors, such as electrolytic types, will

.1 mF (microfarads) or 100 nF (nanofarads) value. Once have their actual value printed on the body of the

you understand how these component codes work, you

capacitor. Often some small capacitors are just too small can easily identify the resistors and capacitors and

to have their actual capacitor values printed on them, so proceed to mount them on the printed circuit board.

Table 4-2

Three-digit capacitor codes

pF

nF

m F

CODE

pF

nF

m F

CODE

1.0

1R0

3,900

3.9

.0039

392

1.2

1R2

4,700

4.7

.0047

472

1.5

1R5

5,600

5.6

.0056

562

1.8

1R8

6,800

6.8

.0068

682

2.2

2R2

8,200

8.2

.0082

822

2.7

2R7

10,000

10

.01

103

3.3

3R3

12,000

12

.012

123

3.9

3R9

15,000

15

.015

153

4.7

4R7

18,000

18

.018

183

5.6

5R6

22,000

22

.022

223

6.8

6R8

27,000

27

.027

273

8.2

8R2

33,000

33

.033

333

10

100

39,000

39

.039

393

12

120

47,000

47

.047

473

15

150

56,000

56

.056

563

18

180

68,000

68

.068

683

22

220

82,000

82

.082

823

27

270

100,000

100

.1

104

33

330

120,000

120

.12

124

39

390

150,000

150

.15

154

47

470

180,000

180

.18

184

56

560

220,000

220

.22

224

68

680

270,000

270

.27

274

82

820

330,000

330

.33

334

100

.0001

101

390,000

390

.39

394

120

.00012

121

470,000

470

.47

474

150

.00015

151

560,000

560

.56

564

180

.00018

181

680,000

680

.68

684

220

.00022

221

820,000

820

.82

824

270

.00027

271

1,000

1

105

Chapter Four: Reading Schematics 330

.00033

331

1,500

1.5

155

26

Chapter Four: Reading Schematics

Table 4-2—cont’d

Three-digit capacitor codes

pF

nF

m F

CODE

pF

nF

m F

CODE

390

.00039

391

2,200

2.2

225

470

.00047

471

2,700

2.7

275

560

.00056

561

3,300

3.3

335

680

.00068

681

4,700

4.7

475

820

.00082

821

6.8

685

1,000

1.0

.001

102

10

106

1,200

1.2

.0012

122

22

226

1,500

1.5

.0015

152

33

336

1,800

1.8

.0018

182

47

476

2,200

2.2

.0022

222

68

686

2,700

2.7

.0027

272

100

107

3,300

3.3

.0033

332

157

157

Code = 2 significant digits of the capacitor value + number of zeros to follow 10 pF = 100

For values below 10 pF, use “R” in place of decimal e.g. 8.2 pF = 8R2

100 pF = 101

1,000 pF = 102

22,000 pF = 223

330,000 pF = 334

1 μF = 105

27

Chapter 5

Electronic Parts Installation

and Soldering

Before we begin constructing our telephone projects, you Once the capacitor leads are prepared, the

will need to understand how to prepare the electronic capacitor can be installed on to the circuit board.

components before installing them onto the circuit board.

The diagram shown in Figure 5-3 illustrates how to

First, you will need to know how to “dress” or prepare prepare diode leads before mounting them to the

resistor leads, which is shown in Figure 5-1.

PB board.

Resistor leads are first bent to fit the PC board

component holes, then the resistor is mounted to the

circuit board. Figure 5-2 depicts how capacitor leads are bent to fit the PC board holes.

Tips of long

nose pliers

Tips of long

Finger

nose pliers

tip

(a)

Grip leads with pliers near body

and bend out or in by 45°

Resistor

Bend lead

body

down by 90°

Grip leads with pliers near body

(a)

and bend down free ends

Tips of long

nose pliers

12.5 mm

Leads bent down and parallel,

(b)

spaced to match board holes

(b)

Grip now about 2 mm down and

bend down by 45°, parallel again

PC

board

Copper

tracks

(c)

Leads passed through PC board

holes, bent and soldered to pads

(c)

Both leads cranked in (or out)

(d)

Excess leads trimmed off

if necessary to match PC board

with sidecutters

hole spacing

Figure 5-1

Preparing resistor leads

Figure 5-2

Dressing capacitor leads

28

Copyright © 2009 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Chapter Five: Installation and Soldering

Tips of long

Finger

nose pliers

tip

PN100

PN100

PN100

Diode

A

K

Bend lead

down by 90°

body

(a)

(b)

(c)

Grip leads with pliers near body

(a)

Grip outer lead

Grip about 2 mm down

Both leads cranked

and bend down free ends

near body and

and bend down by 45°, to match 2.5 mm PC

bend out by 45°

parallel again

board hole spacing

Figure 5-4

Dressing transistor leads

12.5 mm

Leads bent down and parallel,

Soldering joins two pieces of metal, such as electrical (b)

spaced to match board holes

wires, by melting them together with another metal to form a strong, chemical bond. Done correctly, it unites the metals so that electrically they act as one piece of metal. Soldering is not just gluing metals together.

Soldering is tricky and intimidating in practice, but easy (c)

Leads passed through PC board

holes, bent and soldered to pads

to understand in theory. Basic supplies include a

soldering iron, which is a prong of metal that heats to a specific temperature through electricity, like a regular iron. The solder, or soldering wire, often an alloy of (d)

Excess leads trimmed off

aluminum and lead, needs a lower melting point than the with sidecutters

metal you are joining. Finally, you need a cleaning resin Figure 5-3

Preparing diode leads

called flux that ensures the joining pieces are incredibly clean. Flux removes all the oxides on the surface of the metal that would interfere with the molecular bonding, Finally, Figure 5-4 depicts transistor lead preparation, allowing the solder to flow into the joint smoothly. You while Figure 5-5 shows how integrated circuit leads are also need two things to solder together.

prepared for installation.

The first step in soldering is cleaning the surfaces, initially with sandpaper or steel wool and then by

Learning how to solder

Everyone working in electronics needs to know

Pin 1 dimple

how to solder well. Before you begin working on

8

4

a circuit, carefully read this chapter on soldering.

1

7

8

In this section you will learn how to make good

14

16

End notch

1

solder joints when soldering point-to-point wiring

1

connections as well as for PC board soldering

connections.

Roll in this direction

to bend pins inwards

In all electronics work the wiring connections must

be absolutely secure. A loose connection in a radio

Body of

results in noise, scratching sounds, or no sound at all.

dil IC

In a TV, poor connections can disrupt the sound or

picture. The safe operation of airplanes and the lives of Bench or flat surface

astronauts in flight depend on secure electronics

connections.

Figure 5-5

Preparing IC leads

29

melting flux onto the parts. Sometimes, flux is part of If the solder is deformed while it is in the plastic state, the alloy of the soldering wire, in an easy to use

the deformation remains when the solder freezes into

mixture. Then, the pieces are both heated above the

the solid state. Any stress or motion applied to “plastic melting point of the solder (but below their own

solder” causes a poor solder joint.

melting point) with the soldering iron. When touched

The 60/40 solder has the best wetting qualities.

to the joint, this precise heating causes the solder to Wetting is the ability to spread rapidly and bond

“flow” to the place of highest temperature and makes

materials uniformly. This solder also has a low melting a chemical bond. The solder should not drip or blob,

point. These factors make it the most commonly used

but spread smoothly, coating the entire joint.

solder in electronics.

When the solder cools, you should have a clean,

sturdy connection.

Some connections that carry high current cannot be

made with ordinary tin–lead solder because the heat

Many people use soldering in their field, from

generated by the current would melt the solder.

electrical engineering and plumbing to jewelry and

Automotive starter brushes and transmitter tank

crafts. In a delicate procedure, a special material

circuits are two examples. Silver-bearing solders have called solder, flows over two pre-heated pieces and

higher melting points, and so prevent this problem.

attaches them through a process similar to welding or High-temperature silver alloys become liquid in the

brazing. Various metals can be soldered together, such 1100 to l200°F range, and a silver–manganese

as gold and sterling silver in jewelry, brass in watches (85–15) alloy requires almost 1800°F.

and clocks, copper in water pipes, or iron in leaded

glass stained windows. All these metals have

Because silver dissolves easily in tin, tin bearing

different melting points, and therefore use different solders can leach silver plating from components. This solder. Some “soft” solder, with a low melting point, problem can be greatly reduced by partially saturating is perfect for wiring a circuit board. Other “hard”

the tin in the solder with silver or by eliminating the tin.

solder, such as for making a bracelet, needs a torch

Tin-silver or tin-lead-silver alloys become liquid at rather than a soldering iron to get a hot enough

temperatures from 430°F for 96.5–3.5 (tin-silver), to temperature. Electrical engineers and hobbyists

588°F for 1.0–97.5–1.5 (tin–lead–silver). A 15.0–80.0–5.0

alike can benefit from learning the art and science

alloy of lead–indium–silver melts at 314°F.

of soldering.

Never use acid-core solder for electrical work.

It should be used only for plumbing or chassis work.

Solder

For circuit construction, use only fluxes or solder-flux combinations that are labeled for electronic soldering.

The best solder for electronics work is 60/40 rosin-core The resin or the acid is a flux. Flux removes oxide by solder. It is made of 60% tin and 40% lead. This

suspending it in solution and floating it to the top. Flux mixture melts at a lower temperature than either lead or is not a cleaning agent! Always clean the work before tin alone. It makes soldering easy and provides good

soldering. Flux is not part of a soldered connection—

connections. The rosin keeps the joint clean as it is it merely aids the soldering process. After soldering, being soldered. The heat of the iron often causes a

remove any remaining flux. Resin flux can be removed

tarnish or oxide to form on the surface. The rosin

with isopropyl or denatured alcohol. A cotton swab is a dissolves the tarnish to make the solder cling tightly.

good tool for applying the alcohol and scrubbing the

Solders have different melting points, depending on the excess flux away. Commercial flux-removal sprays are

ratio of tin to lead. Tin melts at 450°F and lead at

available at most electronic part distributors.

621°F. Solder made from 63% tin and 37% lead melts

at 361°F, the lowest melting point for a tin and lead mixture. Called 63-37 (or eutectic), this type of solder The soldering iron

also provides the most rapid solid-to-liquid transition and the best stress resistance. Solders made with different Soldering is used in nearly every phase of electronic Chapter Five: Installation and Soldering lead/tin ratios have a plastic state at some temperatures.

construction so you will need soldering tools. A soldering 30

Chapter Five: Installation and Soldering

tool must be hot enough to do the job and

If a copper tip becomes pitted, file it smooth and

sufficiently lightweight for agility and comfort.

bright and then tin it immediately with solder. Modern A temperature controlled iron works well, although

soldering iron tips are nickel or iron clad and should not the cost is not justified for occasional projects. Get an be filed. The secret of good soldering is to use the right iron with a small conical or chisel tip. Soldering is not amount of heat. Many people who have not soldered

like gluing; solder does more than bind metal together before use too little heat, dabbing at the joint to be and provide an electrically conductive path between

soldered, and making little solder blobs that cause

them. Soldered metals and the solder combine to

unintended short circuits. Always use caution when

form an alloy.

soldering. A hot soldering iron can burn your hand

badly or ruin a tabletop. It is a good idea to buy or You may need an assortment of soldering irons to

make a soldering iron holder.

do a wide variety of soldering tasks. They range in

size from a small 25-W iron for delicate printed-

circuit work to larger 100- to 300-W sizes used to

Soldering station

solder large surfaces. If you could only afford a single soldering tool when initially setting up your

Often when building or repairing a circuit, your

electronics workbench, then an inexpensive to

soldering iron is kept switched on for unnecessarily long moderately priced pencil-type soldering iron with

periods, consuming energy and allowing the soldering

between 25- and 40-W capacity is best for PC board

iron tip to burn, and develop a buildup of oxide. By

electronics work. A 100-watt soldering gun is overkill using this soldering-iron temperature controller, you will for printed-circuit work, since it often gets too hot, avoid destroying sensitive components when soldering.

cooking solder into a brittle mess or damaging small

Buying a lower wattage iron may solve some of the

parts of a circuit. Soldering guns are best used for

problems, but new problems arise when you want to

point-to-point soldering jobs, for large mass soldering solder some heavy-duty component, setting the stage

joints, or large components. Small “pencil” butane

for creating a “cold” connection. If you have ever tried torches are also available, with optional soldering-iron to troubleshoot some instrument in which a cold solder tips. A small butane torch is available from the

joint was at the root of the problem, you know how

Solder-It Company. Butane soldering irons are ideal

difficult such defects are to locate. Therefore, the best for field service problems and will allow you to

way to satisfy all your needs is to buy a temperature solder where there is no 110-V power source. This

controlled electronics workbench.

company also sells a soldering kit that contains paste solders (in syringes) for electronics, pot metal and

A soldering station usually consists of a temperature plumbing. See the Appendix for the address

controlled soldering iron with an adjustable heat or

information.

temperature control and a soldering iron holder and

cleaning pad. If you are serious about your electronics Keep soldering tools in good condition by keeping

hobby or if you have been involved with electronics

the tips well tinned with solder. Do not run them at

building and repair for any length of time you will

full temperature for long periods when not in use.

eventually want to invest in a soldering station. There After each period of use, remove the tip and clean off are real low-cost soldering stations for hobbyists, for any scale that may have accumulated. Clean an

under $30, but it makes more sense to purchase a

oxidized tip by dipping the hot tip in Sal ammoniac

moderately-priced soldering station such as the quality (ammonium chloride) and then wiping it clean with a

Weller series. A typical soldering station is shown in rag. Sal ammoniac is somewhat corrosive, so if you

Figure 5-6.

do not wipe the tip thoroughly, it can contaminate

electronic soldering. You can also purchase a small

jar of Tip Tinner, a soldering iron tip dresser from

Soldering gun

your local RadioShack store. Place the tip of the

soldering into the Tip Tinner after every few

An electronics workbench would be incomplete without

solder joints.

a soldering gun. Soldering guns are useful for soldering 31

therefore a poor or noisy splice. Soldering wires to

binding post connections should be performed with a

soldering gun to ensure proper heating to the

connection. Most larger connectors should be soldered or pre-tinned using a soldering gun for even solder flow.

Preparing the soldering iron

If your iron is new, read the instructions about preparing it for use. If there are no instructions, follow this procedure. It should be hot enough to melt solder

applied quickly to its tip (half a second when dry,

instantly when wet with solder). Apply a little solder directly to the tip so that the surface is shiny. This process is called “tinning” the tool. The solder coating helps conduct heat from the tip to the solder joint. When soldering, bring the soldering tip in contact with one Figure 5-6

Temperature controlled soldering station

side of the solder joint. If you can place the tip on the underside of the joint, do so. With the tool below the large components to terminal strips, or splicing wires joint, convection helps transfer heat to the joint. Place together, or when putting connectors on coax cable.

the solder against the joint directly opposite the

There are many instances where more heat is needed

soldering tool. It should melt within a second for

than a soldering iron can supply. For example, a large normal PC connections, within two seconds for most

connector mass cannot be heated with a small soldering other connections. If it takes longer to melt, there is iron, so you would never be able to tin a connector with not enough heat for the job at hand. Keep the tool

a small wattage soldering iron. A soldering gun is a

against the joint until the solder flows freely

heavy-duty soldering device which does in fact look like throughout the joint. When it flows freely, solder tends a gun. Numerous tips are available for a soldering gun to form concave shapes between the conductors. With

and they are easily replaceable using two small nuts on insufficient heat solder does not flow freely; it forms the side arm of the soldering gun. Soldering guns are convex shapes, or blobs. Once the solder shape

available in two main heat ranges. Most soldering guns changes from convex to concave, remove the tool from

have a two-step “trigger” switch which enables you to the joint. Let the joint cool without movement at room select two heat ranges for different soldering jobs.

temperature. It usually takes no more than a few

The most common soldering gun provides a 100-W

seconds. If the joint is moved before it is cool, it may setting when the trigger switch is pressed to its first take on a dull, satin look that is characteristic of a setting. As the trigger switch is advanced to the next

“cold” solder joint. Reheat cold joints until the solder step, the soldering gun will provide 150 W when

flows freely and hold them still until cool. When the more heat is needed. A larger or heavy-duty soldering iron is set aside, or if it loses its shiny appearance, gun is also available, but a little harder to locate is the wipe away any dirt with a wet cloth or sponge. If it

200- to 250-W solder gun. The first trigger switch

remains dull after cleaning, tin it again.

position provides 200 W, while the second switch

Overheating a transistor or diode while soldering can position provides the 250-W heat setting. When

cause permanent damage. Use a small heat sink when

splicing wires together either using the “Western Union”

you solder transistors, diodes, or components with

or parallel splice or the end splice, a soldering gun plastic parts that can melt. Grip the component lead

should be used, especially if the wire gauge is below size with a pair of pliers up close to the unit so that the heat 22 ga. Otherwise the solder may not melt properly and is conducted away. You will need to be careful, since Chapter Five: Installation and Soldering the connections may reflect a “cold” solder joint and it is easy to damage delicate component leads.

32

Chapter Five: Installation and Soldering

A small alligator clip also makes a good heat sink to the solder melting point is about right for mounting

dissipate from the component.

components on PC boards. Also, use solder that is sized Mechanical stress can damage components, too.

appropriately for the job. As the cross section of the Mount components so there is no appreciable

solder decreases, so does the amount of heat required to mechanical strain on the leads.

melt it. Diameters from 0.025 to 0.040′′ are good for nearly all circuit wiring.

Always use a good quality multi-core solder.

Preparing work for soldering

A standard 60% tin–40% lead alloy solder with cores of non-corrosive flux will be found easiest to use. The flux If you use old junk parts, be sure to completely clean all contained in the longitudinal cores of multi-core solder is wires or surfaces before applying solder. Remove all

a chemical designed to clean the surfaces to be joined of enamel, dirt, scale, or oxidation by sanding or scraping deposited oxides, and to exclude air during the soldering the parts down to bare metal. Use fine sandpaper or

process, which would otherwise prevent these metals

emery paper to clean flat surfaces or wire. (Note, no coming together. Consequently, do not expect to be able amount of cleaning will allow you to solder to aluminum.

to complete a joint by using the application of the tip of When making a connection to a sheet of aluminum, you

the iron loaded with molten solder alone, as this usually must connect the wire by a solder lug or a screw.)

will not work. Having said that, there is a process called When preparing wires, remove the insulation with

tinning where conductors are first coated in fresh, new wire strippers or a pocket knife. If using a knife, do not solder prior to joining by a hot iron. Solder comes in cut straight into the insulation; you might nick the wire gauges like wire. The two most common types of solder and weaken it. Instead, hold the knife as if you were are 18 ga, used for general work, and the thinner 22 ga, sharpening a pencil, taking care not to nick the wire as used for fine work on printed circuit boards.

you remove the insulation. For enameled wire, use the A well-soldered joint depends on:

back of the knife blade to scrape the wire until it is 1.

Soldering with a clean, well-tinned tip

clean and bright. Next, tin the clean end of the wire.

Now, hold the heated soldering-iron tip against the

2.

Cleaning the wires or parts to be soldered

under surface of the wire and place the end of the rosin-3.

Making a good mechanical joint before soldering

core solder against the upper surface. As the solder

4.

Allowing the joint to get hot enough before

melts, it flows on the clean end of the wire. Hold the applying solder

hot tip of the soldering iron against the under surface of the tinned wire and remove the excess solder by letting 5.

Allowing the solder to set before handling or

it flow down on the tip. When properly tinned, the

moving soldered parts.

exposed surface of the wire should be covered with a

thin, even coating of solder.

Making a good mechanical joint

Unless you are creating a temporary joint, the next step How to solder

is to make a good mechanical connection between the

parts to be soldered. For instance, wrap the wire

The two key factors in quality soldering are time and carefully and tightly around a soldering terminal or

temperature. Generally, rapid heating is desired,

soldering lug, as shown in Figure 5-7.

although most unsuccessful solder jobs fail because

insufficient heat has been applied. Be careful; if heat is Bend wire and make connections with long-nosed

applied too long, the components or PC board can be

pliers. When connecting two wires together, make a

damaged, the flux may be used up, and surface oxidation tight splice before soldering. Once you have made a

can become a problem. The soldering-iron tips should be good mechanical contact, you are ready for the actual hot enough to readily melt the solder without burning, soldering.

charring, or discoloring components, PC boards,

The next step is to apply the soldering iron to

or wires. Usually, a tip temperature about 100°F above the connection, soldering the connection as shown.

33

Figure 5-7

Proper technique for soldering leads to lugs

Figure 5-8

Bad solder technique leads to lugs

In soldering a wire splice, hold the iron below the splice appearance, not pitted or grainy. If it does have a

and apply solder to the top of the splice. If the tip of the pitted, granular appearance as seen in Figure 5-8,

iron has a bit of melted solder on the side held against reheat the joint, scrape off the solder, and clean the the splice, heat is transferred more readily to the splice connection.

and the soldering is done more easily. Don’t try to

solder by applying solder to the joint and then pressing Then start over again. After the solder is well set,

down on it with the iron. Be sure not to disturb the

pull on the wire to see if it is a good, tight connection.

soldered joint until the solder has set. It may take a If you find that you made a poor soldering job do not few seconds for the solder to set, depending upon the get upset, be thankful you found it and do it over again.

amount of solder used in making the joint. Now take a A quick reference solder checklist is shown in the

good look at the joint. It should have a shiny, smooth listing in Table 5-1.

Table 5-1

Soldering checklist

1.

Prepare the joint. Clean all surfaces and conductors thoroughly with fine steel wool. First, clean the circuit traces, then clean the component leads.

2.

Prepare the soldering iron or gun. The soldering device should be hot enough to melt solder applied to the tip. Apply a small amount of solder directly to the tip, so that the surface is shiny.

3.

Place the tip in contact with one side of the joint; if possible place the tip below the joint.

4.

Place the solder against the joint directly opposite the soldering tool. The solder should melt within two seconds; if it takes longer use a larger iron.

5.

Keep the soldering tool against the joint until the solder flows freely throughout the joint. When it flows freely the joint should form a concave shape; insufficient heat will form a convex shape.

6.

Let the joint cool without any movement; the joint should cool and set up within a few seconds. If the joint is moved before it cools the joint will look dull instead of shiny and you will likely have a cold solder joint. Re-heat the joint and begin anew.

7.

Once the iron is set aside, or if it loses its shiny appearance, wipe away any dirt with a wet cloth or sponge. When the iron is Chapter Five: Installation and Soldering

clean the tip should look clean and shiny. After cleaning the tip apply some solder.

34

Chapter Five: Installation and Soldering

It is important to use the right amount of solder, both Soldering printed circuit boards

on the iron and on the joint. Too little solder on the iron will result in poor heat transfer to the joint, too much Most electronic devices use one or more printed circuit and you will suffer from the solder forming strings as (PC) boards. A PC board is a thin sheet of fiberglass or the iron is removed, causing splashes and bridges to

phenolic resin that has a pattern of foil conductors

other contacts. Too little solder applied to the joint will

“printed” on it. You insert component leads into holes in give the joint a half-finished appearance: a good bond the board and solder the leads to the foil pattern. This where the soldering iron has been, and no solder at all method of assembly is widely used and you will

on the other part of the joint.

probably encounter it if you choose to build from a kit.

The hard, cold solder on a properly made joint should Printed circuit boards make assembly easy. First, insert have a smooth shiny appearance and if the wire is

component leads through the correct holes in the circuit pulled it should not pull out of the joint. In a properly board. Mount parts tightly against the circuit board

made joint the solder will bond the components very

unless otherwise directed. After inserting a lead into the strongly indeed, since the process of soldering is similar board, bend it slightly outward to hold the part in place.

to brazing, and to a lesser degree welding, in that the When the iron is hot, apply some solder to the

solder actually forms a molecular bond with the

flattened working end at the end of the bit, and wipe it surfaces of the joint. Remember it is much more

on a piece of damp cloth or sponge so that the solder difficult to correct a poorly made joint than it is to make forms a thin film on the bit. This is tinning the bit.

the joint properly in the first place. Anyone can learn to solder, it just takes practice.

Melt a little more solder on to the tip of the soldering iron, and put the tip so it contacts both parts of the joint.

The diagram in Figure 5-9 shows how to solder a

It is the molten solder on the tip of the iron that allows component lead to a PC board pad.

the heat to flow quickly from the iron into both parts of The tip of the soldering iron heats both the lead and the joint. If the iron has the right amount of solder on it the copper pad, so the end of the solder wire melts when and is positioned correctly, then the two parts to be joined it is pushed into the contact. The diagram illustrated in will reach the solder’s melting temperature in a couple of Figure 5-10 show how a good solder joint is obtained.

seconds. Now apply the end of the solder to the point Notice that it has a smooth and shiny “fillet” of

where both parts of the joint and the soldering iron are all solder metal, bonding all around to both the component touching one another. The solder will melt immediately lead and the copper pad of the PC board. This joint

and flow around all the parts that are at, or over, the provides a reliable electrical connection.

melting part temperature. After a few seconds, remove the iron from the joint. Make sure that no parts of the joint move after the soldering iron is removed until the Heated tip of

Resin-cored

solder is completely hard. This can take quite a few

soldering iron

solder wire

seconds with large joints. If the joint is disturbed during this cooling period it may become seriously weakened.

Push into

joint

The most important point in soldering is that both

parts of the joint to be made must be at the same

Copper track

temperature. The solder will flow evenly and make a

and pad

good electrical and mechanical joint only if both parts of the joint are at an equal high temperature. Even

though it appears that there is a metal to metal contact Printed circuit

in a joint to be made, very often there exists a film of board

oxide on the surface that insulates the two parts. For this Component lead

reason it is no good applying the soldering iron tip to Component body

one half of the joint only and expecting this to heat the other half of the joint as well.

Figure 5-9

Proper application of soldering iron to joint

35

Smooth, shiny

Solder forming

Copper track

solder ‘fillet’

Copper track

‘blob’ on lead

and pad

(all around

and pad

(but not bonded at all

the lead)

to the PC board pad)

PC board

PC board

Component lead

Component lead

Figure 5-10

Proper PC board soldering

Figure 5-12

Bad PC board solder joint II

Try to make the solder joint as quickly as possible

For projects that use one or more integrated circuits, because the longer you take, the higher the risk that the with their leads closely spaced pins, you may find it component itself and the printed circuit board pad and easier to use a finer gauge solder, i.e. less than 1 mm track will overheat and be damaged. But don’t work so in diameter. This reduces the risk of applying too much quickly that you cannot make a good solder joint.

solder to each joint, and accidentally forming “bridges”

Having to solder the joint over again always increases between pads to PC “tracks.”

the risk of applying too much heat to the PCB.

The finished connection should be smooth and bright.

As the solder solidifies, take a careful look at the joint Reheat any cloudy or grainy-looking connections. Finally, you have made, to make sure there is a smooth and fairly clip off the excess wire length, as shown in Figure 5-13.

shiny metal “fillet” around it. This should be broadly Occasionally a solder “bridge” will form between two

concave in shape, showing that the solder has formed a adjacent foil conductors. You must remove these bridges, good bond to both metal surfaces. If it has a rough and otherwise a short circuit will exist between the two

dull surface or just forms a “ball” on the component

conductors. Remove a solder bridge by heating the

lead, or a “volcano” on the PCB pad with the lead

bridge and quickly wiping away the melted solder with emerging from the crater, you have a “dry joint.” If your a soft cloth. Often you will find a hole on the board solder joint looks like the picture shown in Figure 5-11, you will have to resolder the joint over again.

Figure 5-12 shows another type of dry solder joint

which would have to be resoldered. These types of

“dry” solder joints if now redone will cause the circuit to be unreliable and intermittent.

Solder forming

Copper track

‘volcano’ around lead

and pad

(but not really

bonding to it)

PC board

Component lead

Figure 5-13

Cutting excess components leads from

Chapter Five: Installation and Soldering Figure 5-11 Bad PC board solder joint I PC board

36

Chapter Five: Installation and Soldering

plugged by solder from a previous connection. Clear the on the device to suck the solder into the chamber of

hole by heating the solder while pushing a component

the desoldering tool.

lead through the hole from the other side of the board.

Good soldering is a skill that is learnt by practice.

Desoldering station

How to unsolder

A desoldering station is a very useful addition to an electronics workshop or workbench but in most cases,

In order to remove components, you need to learn the

they just cost too much for most hobbyists.

art of desoldering. You might accidentally make a

desoldering stations are often used in production

wrong connection or have to move a component that

environments or as re-work stations, when production

you put in an incorrect location. Take great care while changes warrant changes to many circuit boards in

unsoldering to avoid breaking or destroying good parts.

production. Some repair shops use desoldering stations The leads on components such as resistors or

to remove components quickly and efficiently.

transistors and the lugs on other parts may sometimes Another useful desoldering tool is one made

break off when you are unsoldering a good, tight joint.

specifically for removing integrated circuits. The

To avoid heat damage, you must use as much care in

specially designed desoldering tip is made the same size unsoldering delicate parts as you do in soldering them.

as the integrated circuit, so that all IC pins can be There are three basic ways of unsoldering. The first

desoldered at once. This tool is often combined with a method is to heat the joint and “flick” the wet solder vacuum suction device to remove the solder as all the off. The second method is to use a metal wick or braid IC pins are heated. The IC desoldering tips are made

to remove the melted solder. This braid is available at in various sizes: there are 8-pin, 14-pin, and 16-pin most electronics parts stores; use commercially made

versions, which are used to uniformly desolder all IC

wicking material (braid). Place the braid against the pins quickly and evenly, so as not to destroy the circuit joint that you want to unsolder. Use the heated

board. The specialized soldering tips are often used in soldering iron to gently press the braid against the

conjunction with vacuum systems to remove the solder

joint. As the solder melts, it is pulled into the braid.

at the same time.

By repeating this process, you can remove virtually all Remember these things when unsoldering:

the solder from the joint. Then reheat the joint and lift off the component leads.

1.

Be sure there is a little melted solder on the tip of your iron so that the joint will heat quickly.

Another useful tool is an air-suction solder remover.

Most electronics parts stores have these devices. Before 2.

Work quickly and carefully to avoid heat damage to

using a desolder squeeze bulb, use your soldering iron parts. Use long-nosed pliers to hold the leads of

to heat the joint you want to unsolder until the solder components just as you did while soldering.

melts. Then squeeze the bulb to create a vacuum inside.

3.

When loosening a wire lead, be careful not to bend

Touch the tip of the bulb against the melted solder.

the lug or tie point to which it is attached. Use

Release the bulb to suck up the molten solder. Repeat pieces of wire or some old radio parts and wire.

the process until you have removed most of the solder Practice until you can solder joints that are smooth, from the joint. Then reheat the joint and gently pry off shiny, and tight. Then practice unsoldering

the wires. This third method is easy, and is the preferred connections until you are satisfied that you can do

method, since it is fast and clean. You can use a vacuum them quickly and without breaking wires or lugs.

device to suck up molten solder. There are many new

styles of solder vacuum devices on the market that are much better than the older squeeze bulb types. The new Caring for your soldering iron

vacuum desoldering tools are about 8 to 12′′ long

with a hollow teflon tip. You draw the vacuum with a

To get the best service from your soldering iron, keep push handle and set it. As you reheat the solder around it cleaned and well tinned. Keep a damp cloth on the

the component to be removed, you push a button

bench as you work. Before soldering a connection,

37

wipe the tip of the iron across the cloth, then touch fumes can cause you to get dizzy or light-headed.

some fresh solder to the tip. The tip will eventually This is dangerous because you could fall down and

become worn or pitted. You can repair minor wear by

possibly hurt yourself in the process. Many people

filing the tip back into shape. Be sure to tin the tip who are highly allergic are also allergic to the

immediately after filing it. If the tip is badly worn or smell of solder fumes. Solder fumes can cause

pitted, replace it. Replacement tips can be found at

sensitive people to get sinus infections from

most electronics parts stores. Remember that oxidation smelling solder fumes. So ventilating solder

develops more rapidly when the iron is hot. Therefore, fumes is important.

do not keep the iron heated for long periods unless you There a few different ways to handle this problem.

are using it. Do not try to cool an iron rapidly with ice One method is to purchase a small fan unit housed with or water. If you do, the heating element may be

a carbon filter which sucks the solder fumes into the damaged and need to be replaced or water might get

carbon filter to eliminate them. This is the simplest into the barrel and cause rust. Take care of your

method of reducing or eliminating solder fumes from

soldering iron and it will give you many years of

the immediate area. If there is a window near your

useful service.

soldering area, be sure to open it to reduce the exposure Remember, soldering equipment gets hot! Be careful.

to solder fumes. Another method of reducing or

Treat a soldering burn as you would any other. Handling eliminating solder fumes is to buy or build a solder

lead or breathing soldering fumes is also hazardous.

smoke removal system. You can purchase one of

Observe these precautions to protect yourself and

these systems but they tend to be quite expensive.

others!

You can create you own solder smoke removal system

by locating or purchasing an 8–10′ piece of 2′′ diameter Ventilation

flexible hose, similar to your vacuum cleaner hose. At the solder station end of the hose, you can affix the hose Properly ventilate the work area where you will be

to a wooden stand in front of your work area. The other soldering. If you can smell fumes, you are breathing

end of the hose is funneled into a small square “muffin”

them. Often when building a new circuit or repairing

type fan placed near a window. Be sure to wash your

a “vintage” circuit you may be soldering continuously hands after soldering, especially before handling food, for a few hours at a time. This can mean you will be

since solder contains lead; also try to minimize direct breathing solder fumes for many hours and the

contact with flux and flux solvents.

Chapter Five: Installation and Soldering

38

Chapter 6

Telephone Privacy Guard

The circuit is simple to build, it only consumes a small Parts list

current from the phone line, and only consists of two components as shown in the circuit diagram.

Telephone Privacy Guard

The circuit can be built on a small circuit board

Q1

BR100 DIAC

or on a small piece of prototype board in just a few

semiconductor

minutes. The Privacy Guard circuit not only prevents

Q2

2N6073A TRIAC

others from listening-in on your telephone call,

semiconductor

but it also prevents others from interrupting modem

communication between your computer and a distant

Misc

PC board, wire,

computer or server.

connectors, etc.

The Telephone Privacy Guard is designed to prevent

telephone calls from being heard by other telephones in Circuit description

the same subscriber telephone line in your home or

office. When one telephone is picked up, the circuit

The basic idea of the Privacy Guard circuit is to sense prevents other telephones that may be picked up from

the voltage in the telephone line when the telephone is listening in on your conversation, since this circuit picked up. If that voltage is higher than about 30 V

“starves” the other phones on the line from obtaining (normal on-hook voltage is about 48 V) then the circuit telephone line current. The Privacy Guard circuit is

lets the telephone work normally. If the voltage is lower installed between telephone line and telephone as shown than 30 V it prevents the current from going from the in Figure 6-1.

telephone line to telephone (normally the voltage in line You need to install a Privacy Guard circuit in each

is about 6–10 V when one telephone is off-hook). The

telephone on the same subscriber line in order for the circuit is designed so that is passes the ring voltage to system to work properly. The Privacy Guard circuit can all telephones without problems.

be installed inside each telephone base unit, or it could The circuit is a very simple circuit built from one

be installed in a small plastic box next to each phone.

DIAC and one TRIAC. When a telephone headset is

picked up, it prevents any operating current from

flowing thorough the TRIAC. The triggering of the

O

2N6073A

TRIAC is accomplished through DIAC at Q1, which

Q2

TRIAC

will trigger the TRIAC if there is more than about

M1

G

M2

Tip

Tip

30 V present at the circuit. The TRIAC leads at

M1 and M2 are connected in series with the telephone

Telephone

DIAC

Phone

TIP line wires. When TRIAC Q2 starts to conduct,

Q1

line

BR100

instrument

it will conduct as long as there is any current flowing through it. So TRIAC Q2 conducts until the telephone

Ring

Ring

handset is put on-hook (call has ended).

Figure 6-1

Privacy group pictorial. Courtesy of

The circuit is very similar to the operation of

Tom Engdahl

commercial adapters. But remember that this adapter

39

Copyright © 2009 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Phone set

if your are going to build the Privacy Guard circuits on Tip

Ring

small printed circuit boards, or small perf-boards, or proto-boards available from RadioShack. Once you

have decided which route you are going to take, and

2N6073A

DIAC

TRIAC

you proceed to construct the Privacy Guard circuits,

Q1

Q2 M2

remember that you will need to build one for each phone BR100

in your home or office. Go ahead and locate both the

G

M1

DIAC and the TRAIC. Note that the DIAC only has two

leads, while the TRIAC has three leads. The DIAC has

no polarity; however, the TRIAC does. The TRIAC has

Tip

Ring

Telephone

an M1 and an M2 lead and a gate lead, as shown in both line

the schematic and pictorial diagrams. Go ahead and

Figure 6-2

Privacy guard schematic. Courtesy of

install the DIAC and TRIAC in their respective locations Tom Engdahl

on the PC, then take your end-cutters and cut the excess component leads flush to the edge of the circuit board.

After a short break, we will inspect the circuit board is not the type approved for connection to the public for any “cold” solder joints or possible “short” circuits.

telephone network. The component values used in the

Pick up the circuit board with the foil side facing

prototype could be replaced with similar types of

upwards toward you. Carefully inspect the circuit board components, such that a TRIAC with nearly any

against the parts placement diagram and the schematic type which will handle at least 200 V can be

to make sure that the proper component was inserted in triggered easily and keeps on conducting at currents

the correct PC hole. It is possible that you may have as low as 15 mA.

inserted a semiconductor backwards.

The drawing in Figure 6-2 represents a pictorial

Once this preliminary inspection is over, you can

diagram of the major components used in the prototype inspect the circuit board for any possible cold solder unit and how it is connected between the telephone line joints or short circuits. Take a careful look at each of and the telephone unit.

the PC solder joints; they should all look clean and

shiny. If any of the solder joints look dull, dark, or Circuit assembly

blobby, then you unsolder the joint, remove the solder and then resolder the joint all over again. Next, examine Before we begin building the Telephone Privacy Guard

the PC board for any short circuits. Short circuits can be project, let us first find a clean, well lit worktable or caused from two circuit traces touching each other due workbench. Next we will gather a small 20–30 W pencil to a stray component lead that stuck to the PC board

tipped soldering iron, a length of 60/40 tin–lead solder, from solder residue or from solder blobs bridging the a small canister of “Tip Tinner,” available at your local solder traces. Once you have fully examined the circuit RadioShack store, along with a few small hand tools.

board, you can reconnect the circuit board back to the Try and locate small flat blade and small Phillips

phone line and try out the phone transmitter once again.

screwdrivers. A pair of needle nose pliers, a pair of Once the inspection has been completed, you can

tweezers along with a magnifying glass, and a pair of move on to installing the circuit in each of the telephone end-cutters and we will begin constructing the project.

locations in your home or office. You may wish to

Now locate your schematic diagram and parts layout

install a Privacy Guard circuit inside of each telephone diagram along with all of the components to build the base or you could elect to place each Privacy Guard

project. Once all the components are in front of you, circuit inside a small plastic box with a phone jack at you can check them off against the project parts list to both ends, so that you could plug a telephone set in on make sure you are ready to start.

one connector and then place short telephone extension So, finally we are ready to begin assembling the

cable between the Privacy Guard and the telephone line.

Chapter Six: Telephone Privacy Guard project, so let’s get started! First, you will need to decide If the Privacy Guard is placed inside your telephone

40

Chapter Six: Telephone Privacy Guard

base then you will likely want to mount a 4-position

line or from a cell phone. Pick up one of the

terminal strip on each PC board to facilitate connecting home phones and talk over the phone. Now have

the phone wire inside the phone base to the Privacy

a second person pick up an extension phone in

Guard circuit. After wiring the telephone Privacy Guard your home or office. Once a second extension

circuits in or at each telephone then you are ready to phone is picked up, they should not be able to hear

test out the system.

your conversation with the remote phone or cell

phone. If the extension phone does hear the

Testing the privacy guard

conversation, then you may have wired the

Privacy Guard incorrectly. In that event you may

Testing the Privacy Guard circuit is simple. Have

want to carefully re-inspect each Privacy Guard

someone call your home phone from a remote phone

circuit for an error.

41

Chapter 7

Modem Protector

When a telephone handset is “on the hook” there

Parts list

are 48 V DC across the two wires designated “tip”

and “ring.” The green tip wire is at ground potential, Modem/fax Protector

or zero volts, and the red ring wire is at negative

SVP1, SVP2

gas surge

48 V. Approximately 21 to 35 mA of current flow

arrestors 250 V

in this condition. When the handset is picked up

CG

the line voltage drops to 6 V DC. The 20- or

¯230L (C.P. Claire

or equiv)

30-Hz telephone-ringing signal can be from about

100 V to about 120 V AC. It is superimposed

D1, D2, D3, D4

1N5386B

across the normal 48-V DC signal. That “ringing”

Zener diodes –

voltage determines the voltage ratings of the

180 V, 5 W

protective devices.

Misc

1N5386B Zener

diodes - 180 V,

5 W

Protect your modem and fax machine or answering

machine against errant transients with this easy to

build circuit. Shield your modem, fax, or answering

machine against harmful transients arriving over the

phone line by building this fast-acting Modem/fax

Protector, shown in Figure 7-1. Then you will be able to relax when electric storms bear down on your home

or office.

It is an easy, inexpensive project, and low-cost

insurance for your expensive telephone-dependent

equipment. Even people who plug their computers and

entertainment electronics into power-line surge

protectors (and would not dream of leaving them

unprotected) are likely to forget about protecting

modems, faxes, and answering machines from

transients arriving over the phone line. Then comes the first thunderstorm of the season. Before they remember to do anything about it, the innards of that equipment could disappear in a puff of smoke. You could, of

course, disconnect your telephone gadgets with a

switch when they are not in use. But will you

remember to do it in time? Needless to say, the switch won’t help much if the devices are running when the

lightning starts to flash.

Figure 7-1

Modem/fax protector

42

Copyright © 2009 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Chapter Seven: Modem Protector

disk becomes a matrix of conductive zinc-oxide grains Telephone protection

separated by highly resistive boundaries. This property gives them a symmetrical electrical characteristic

Although the effects of lightning are well known, many similar to the SVP (or two back-to-back Zener diodes).

people believe that only a direct strike on a nearby

However, the MOV’s breakdown time is too slow to

phone or power line will cause damage. However, most

protect connected electronics against the fastest voltage damage to electronic equipment is caused by voltages

spikes caused by lightning. As a result, faster Zener induced in those conductors by direct strikes elsewhere.

diodes and Sl/Pb have been combined in our

Harmful voltages can be caused by strikes as far away Modem/fax Protector.

as 15 miles! Telephone circuits generally have resistive elements in each wire to protect the telephone handsets Circuit details

from transient spikes in excess of about 500 V.

However, this rather crude passive protection is

The Modem/fax Protector is shown schematically in

inadequate for protecting more vulnerable electronics.

Figure 7-2. It has a typical response time of about

Spark-Gap tubes or surge voltage protectors (SVP)

l0 ns—fast enough to protect your equipment against

have been used for many years to protect electronic

the speediest voltage spikes. Zener diodes

circuits from man-made and natural surges arriving over D1 and D2 are connected back-to-back in parallel

either power or phone lines. They provide low

with surge voltage protector SVP1 between the ring

resistance paths for excessive voltage transients but and the PC board earth ground connection. Similarly,

appear open to normal voltages. The devices are

Zener diodes D3 and D4 are connected in parallel

hermetically sealed gas discharge tubes. Typically made with SVP2 between the tip wire and the PC board

of ceramic with properly spaced electrodes, they are

earth ground. The SVPs are rated for a nominal

filled with a rare gas.

DC voltage of 230 V with breakdown voltage from

The main purpose of the SVP is to provide a

195 to 265 V DC. The Zener diodes break down at

conductive path for unwanted and excessive transients, l80 V DC within about l0 ns, to protect the telephone thereby preventing the transient energy and associated circuits from the fastest initial voltage spikes, and voltages from damaging equipment and components and

then the SVPs ionize to ground the over current.

harming people. They are designed to switch current at Note that the circuit has no batteries; all it really a pre-established breakdown voltage.

needs to protect your equipment is an effective

ground.

The breakdown voltage causes the internal gas to

ionize and change from a non-conducting to a

Circuit assembly

conducting state, thus permitting an arc to form and

short the connected wires to ground. During conduction, Before we begin building the Modem/fax Protector,

the SVP can momentarily carry high currents. After the first you will need to locate a clean, well-lit worktable voltage transient has been discharged, the gas de-ionizes and the SVP is ready for another voltage transient. The SVP is bipolar and has a symmetrical characteristic. In Ring

the restored or extinguished condition, it causes very Red

D1

little loss because of its high impedance. This

N1

characteristic contrasts with those of transient

D2

Phone

Phone

absorbtion Zener diodes and metal-oxide varistors that modem

line

fax

exhibit leakage. However, both of those devices have

D3

N2

faster response times than SVPs.

D4

Tip

The metal-oxide varistor (MOV or SIOV) has also

Green

been said to protect electronics connected to telephone lines. It is made from finely powdered zinc oxide mixed Figure 7-2

Phone-modem-fax-answering machine

with binders and pressed into a disk. After firing, the protector

43

or workbench. Next we will gather a small 25–30 W

Short circuits can be caused from two circuit traces

pencil tipped soldering iron, a length of 60/40 tin–lead touching each other due to a stray component lead that solder, and a small canister of “Tip Tinner,” available at stuck to the PC board from solder residue or from

your local RadioShack store; “Tip Tinner” is used to

solder blobs bridging the solder traces. Once you have condition the soldering tip between solder joints. You fully examined the circuit board, you can now connect drive the soldering tip into the compound and it cleans the circuit board between the phone line and the item and prepares the soldering tip. Next grab a few small that you wish to protect. The Modem/fax Protector itself hand tools, try and locate small flat blade and Phillips does have a certain polarity in that the gas surge

screwdrivers. A pair of needle nose pliers, a pair of protectors are placed on the phone line side of the

tweezers along with a magnifying glass and a pair of

overall hookup, and the Zener diode side of the circuit end-cutters and we will begin constructing the project.

is connected to the modem, fax, or answering machine.

Now locate your schematic diagram and parts layout

Obtain a small modular plastic phone jack cover with

diagram along with all of the components needed to build an included jack. The jack should have a short section the project. Once all the components are in front of you can of 4-wire telephone cable attached. Cut off the black check them off against the project parts list to make sure and yellow wires and connect the red ring and green tip you are ready to start building the project. The prototype wire pigtails within the box. Cut a bottom plate from a Modem/fax Protector was built on a small, square

sheet of phenolic or other suitable thin but rigid

PC board measuring 11⁄2′′ per side. However,

insulating material slightly larger (about 1⁄16′′) than the point-to-point wiring techniques can also be used.

outer dimensions of the jack box. Carefully mark the

The Modem/fax Protector is quite easily constructed

location on the cover plate for a hole to accommodate using four Zener diodes and two gas surge arrestors.

the central screw so that it is opposite the hole in the The gas surge arrestors are small cylindrical tubes with jack box, and drill a hole of the same diameter through a lead at both ends. The gas surge arrestors do not have the cover.

polarity and so they can be installed in either direction on the PC board. Place the gas surge arrestors in their Determine a suitable length for the 4-wire telephone

proper locations on the circuit board and solder them in cable between your telephone outlet or junction box and place. Once soldered in place, trim the excess lead

the Modem/fax Protector and attach a plug to one end of lengths with a pair of end-cutters. Cut the excess leads that cable. Carefully form a hole in the side wall of the flush to the edge of the circuit board.

jack box, making it large enough to permit the bare end of the telephone cable to be pulled through a distance of The Modem/fax Protector project contains four Zener

3 to 4′′. Clamp the cable with a plastic cable tie.

diodes at D1 through D4. These diodes also have

polarity, which must be observed if the circuit is going Strip the cable jacket back to about 1⁄8 inch from the to work correctly. You will notice that each diode will cable tie, select out the red ring wire and green tip wire have a black or white colored band at one edge of the and strip their ends. Next, cut off the yellow and black diode’s body. The colored band represents the diode’s wires close to the cable tie. Then strip the ends of the cathode lead. Check your schematic and parts layout

red and green wires from the jack. Solder both red and diagram when installing these diodes on the circuit

green wires to the circuit board. Cut a short length of board. Place all four Zener diodes on the circuit board insulated l4 or l6 AWG wire, strip both ends, and solder and solder them in place on the PC board. Then cut the one end to the ground pad on the PC board.

excess components lead with your end-cutter.

Apply four drops of silicone RTV adhesive to the

Take a short break and inspect the circuit board for any inside as shown, align the hole in the circuit board over possible “cold” solder joints or “short” circuits. Take a the hole in the jack box, and bed the board down in the careful look at each of the PC solder joints, they should adhesive. Allow sufficient time for the adhesive to set all look clean and shiny. If any of the solder joints look up before proceeding. Determine a suitable length for a dull, dark or blobby, then you unsolder the joint, remove l4 to l6 AWG solid copper ground wire based on the

the solder and then resolder the joint all over again.

proximity of your telephone apparatus to a suitable

Chapter Seven: Modem Protector Next, examine the PC board for any short circuits.

location for a ground rod (to be discussed later).

44

Chapter Seven: Modem Protector

Form a loop in one end of the heavy ground wire to

a window opening or a hole drilled through the wall.

accommodate the central screw in the Modem/fax

Suitable grounding rods with wire connecting clamps

Protector. Then insert the loop in the ground wire, jack are available from electronics supply stores. The next box, and circuit board. Tightly wrap the bare copper end best grounding method is to connect the 14 to l6 AWG

of the ground wire on the circuit board several times wire to a cold-water pipe.

around the central screw to complete the ground

connection. Then apply solder to the outside of the turns.

Plug your modem, fax, or answering machine into the

Troubleshooting

jack, and plug the length of cable into your telephone wall outlet. The ring and tip wires of the telephone line If your Modem/fax Protector does not appear to

must remain consistent throughout. The tip lead must be function correctly or it shorts out the phone line, then positive with respect to the ring lead.

you will need to disconnect the circuit from the phone line and carefully inspect the circuit board. It is likely After making sure that all connections have been

that you made a soldering or parts placement mistake

made correctly apply a thin layer of adhesive to the rim during construction. Pick up the circuit board with the of the jack box, assemble the cover over the screw and foil side facing upwards toward you. Carefully inspect clamp it in position with a washer and two nuts.

the circuit board against the parts placement diagram and the schematic to make sure that the proper

Good grounding

component was inserted in the correct PC hole. You

may have placed the wrong end at a particular location; The necessity for a good ground in protective circuits or you may have inserted a Zener diode backwards.

cannot be overstated; a bad ground is no ground at all!

Once you have corrected the problem, reconnect the

The most effective ground is achieved with a metal rod, Modem/fax Protector between your modem and the

preferably copper, at least four feet long, and driven into phone line. The Modem/fax Protector should give you

moist soil. Connect the ground rod to the Modem/fax

many years of trouble-free service. You may want to

Protector with # 18 gauge insulated wire. The Modem

build a couple of the Modem/fax Protectors for other

Protector can be connected to the ground strap through devices around your home or office.

45

Chapter 8

Telephone Amplifiers and Projects

Kit available from:

Parts list

www.electronickits.com

Magnetic Phone

Telephone Amplifier

Amplifier I

II—Direct Connect

R1, R7

270 K,1⁄ W,

R1, R2, R3

10 K ohm,

4

1

5% resistor

⁄ W, 5% resistor

4

R4, R5

1 K ohm,

R2, R4, R5, R6

1

⁄ W, 5% resistor

10 K,1⁄ W,5% resistor

4

4

R6

10 ohm

R3

100 K 1⁄ W,

4

5% resistor

R7

3.3 K, 1⁄ W,

4

5% resistor

R8

10 K Trimpot

R8

560 ohm, 1⁄ W,

C1, C9

100 μF, 35 V

4

5% resistor

electrolytic capacitor

R9

10 K potentiometer

C3, C10

220 pF, 35 V

(PC mount)

ceramic capacitor

C1, C2

22 nF MKM,

C2

4.7 μF, 35 V MPE

35 V

capacitor

C3

18 nF (183) or MKM,

C4, C5, C7

100 nF,

35 V

35 V [104]

C4, C5

47 nF (473)

C6, C8

10 μF, 35 volt

or MKM

electrolytic capacitor

C6

100 nF, 35 V

U1

LM358 IC

C7

1 μF, 35 V

U2

LM386 IC

electrolytic

J1

audio jack

capacitor

M1

mini magnetic

C8

47 μF, 35 V

telephone suction

electrolytic capacitor

pickup coil

C9

100 μF, 35 V

SPKR

8 ohm mini speaker

electrolytic capacitor

Misc

IC socket,

C10

470 μF, 35 V

PC board, battery

electrolytic

clip, wire, terminal

capacitor

block, etc

D1, D2

1N4148 silicon

CK601 Amplifier kit

diode

46

Copyright © 2009 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Chapter Eight: Telephone Amplifiers and Projects

D3, D4

1N4000 silicon

from RadioShack with an 1⁄8′′ plug. A plug at

diode

the opposite end of the pickup’s line cord connects into T1

600 to 600 ohm mini

the amplifier circuit. The design is low cost and there matching transformer

is no direct electrical connection to the phone

(PC type)

system, so it is completely isolated. This telephone

amplifier could also be used to amplify the bell

SPKR

8 ohm mini speaker

ringer as a remote ringer to notify you of an incoming or headphone

phone call.

Misc

IC socket, PC

board, hookup wire,

etc

Circuit description

PWR supply

7–9 V or 9

to 12 V DC “wall

The telephone pickup is really a magnetic field

wart” power supply

fluctuation detector. It picks up the oscillating magnetic field from the receiver of your telephone when someone K4900 Amplifier kit is

is speaking to you. But it will also collect any other available from:

oscillating magnetic fields which happen to be floating Velleman Kits

around in the air, for example, low- and high-frequency noise from your TV set or computer monitor, or the

characteristic mains hum from power lines. High-

Project 1: Telephone

frequency filters have been built into the circuit to reduce some of this unwanted noise.

amplifier I—Magnetic

The telephone amplifier circuit shown in Figure 8-1

phone pickup

consists of two high gain pre-amplifier stages in the Lm358 followed by a power amplifier to drive the speaker.

It is often very convenient for other people in the

The ICs are low cost and easily available. Both pre-

room to listen to both sides of a phone conversation.

amplifiers in the Lm358 are biased to half the supply The telephone amplifier is ideal for older people who voltage by R4 and R5. This allows maximum voltage

are hard of hearing. This circuit will allow them to

swing at the outputs before hitting either supply rail.

better hear the phone conversation. A specially

C6 bypasses any AC signal to ground, stabilizing the

designed magnetic telephone pickup with a suction cup DC bias voltage. R3 is necessary to couple the DC bias attaches onto the earpiece of your phone, available

voltage to IC1:B while also providing a high impedance C4

C3

C10

+

R1

R4

U2

B1

C1

R7

U1:B

8

6

C5

R6

6 1 8

−

7

2

C7

5

1

3

C9

+

−

3

5

+

C2

4

+

J1

R3

U1:A

24 7

R8

+C6

R2

R5

C8

SPK

Figure 8-1

Magnetic-pickup telephone amplifier. Courtesy of DIY Electronics 47

to the input signal. The RC feedback circuit on both

a small can of Tip Tinner from your local RadioShack

pre-amps will, like any RC circuit, have a cut-off

store. Tip Tinner is used to clean and prep the soldering frequency. Or to think of it another way, the capacitance tip. You will also want to locate some small tools such starts to act as a short circuit as the frequency increases as a pair of small end cutters, a few small screwdrivers, and the gain decreases. The cut-off frequency is given and a small Exacto type knife. Heat up your soldering by the formula: f = 1/(6.28 × RC). This gives a cut-off iron and place all the project parts in front of you, along frequency of 2.7 kHz, which has the effect of limiting with your printed circuit board. When building

the amount of high frequency noise, or “hiss.” This high electronic circuit boards with integrated circuits it is a frequency roll-off does not greatly affect voice

good idea to install IC sockets on the PC board. In the frequency signals since voice frequency is nominally in event of an IC failure it is then a simple matter to

the range 300 Hz to 3.0 kHz.

simply remove the defective IC and just install a new The output of the second pre-amp is fed to the power

one. Integrated circuit sockets are inexpensive as well as amplifier stage via C7 and R8. Capacitor C7 removes

a good insurance policy.

any DC component from the amplified signal while

Place your single-sided PC board in front of you

R8 acts as a volume control. The Lm386 is very easy to along with the schematic and any parts layout diagrams.

use and requires a minimum of external components.

Next, place all of the parts in front of you and create a C8 provides filtering and bypassing for the internal bias check-off list to make sure you have all the components network. C9 removes any DC component from the

you will need for this project. It is usually a good idea output signal. The gain of the Lm386 may be set

to begin installing the lowest profile components such according to the combination of resistors and capacitors as resistors first. Now, locate Tables 8-1 and 8-2, and across pins 1 and 8. If no components are placed

place them in front of you. Table 8-1 illustrates the between pins 1 and 8 the overall gain would be 20.

resistor code chart and how to read resistors, while

Table 8-2 illustrates the capacitor code chart which will Circuit Assembly

aid you in constructing the project.

Refer now to Table 8-1, which introduces the resistor Locate a clean, well-lit worktable or workbench, a small color chart; this will help you identify resistors. Each pencil tip soldering iron, some 60/40 tin–lead solder and resistor will have either three or four color bands, which Table 8-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

Chapter Eight: Telephone Amplifiers and Projects

No color

20%

48

Chapter Eight: Telephone Amplifiers and Projects

begin at one end of the resistor’s body. The first colored Go ahead and locate where resistor R1 goes on

band represents the resistor’s first digit, while the the PC and install it; next solder it in place on the second color represents the second digit of the resistor’s PC board, and then with a pair of end-cutters trim

value. The third colored band represents the resistor’s the excess component leads flush to the edge of the

multiplier value, and the fourth color band represents circuit board. Next locate the remaining resistors and the resistor’s tolerance value. If there is no fourth install them in their respective locations on the main colored band then the resistor has a 20% tolerance

controller PC board. Solder the resistors to the board, value. If the resistor’s fourth band is silver then the and remember to cut the extra lead with your

resistor has a 10% tolerance value and if the fourth band end-cutter.

is gold then the resistor’s tolerance value will be 5%.

Now, let us begin installing the capacitors. Capacitors Finally, we are ready to begin assembling the project, will usually have their actual values printed on them.

so let’s get started. The prototype was constructed on a Often small capacitors will not have enough room for

single-sided printed circuit board or PCB. With your PC

the entire value to be printed so they will have a three board in front of you, we can now begin populating the digit code (see Table 8-2). Let us begin with C4, C5 and circuit board. We are going to place and solder the

C7, these are 100 nF capacitors, which may be

lowest height components first—the resistors and the

marked (104). Go ahead and place them in their

diodes. First locate resistor R1. Resistor R1 has a value respective locations on the PC board. Next locate

of 270 K ohms and is a 5% tolerance type. Now take a

C3 and C10, these are 220 pF capacitors, which may be look for a resistor whose first color band is red, violet, marked (221) Install these capacitors in their proper yellow, and gold. From the chart you will notice that red locations and solder them in place on the PC board.

is represented by the digit (2), the second color band is Next, take your end-cutters and trim the excess capacitor violet, which is represented by (7). Notice that the

leads flush to the edge of the PC board. The remaining third color is yellow and the multiplier is (10,000), so capacitors are all electrolytic types and will have a (2) (7) × 10,000 = 270,000 or 270 K ohms.

plus or minus marking at one end of the capacitor.

Table 8-2

Three-digit capacitor codes

pF

nF

m F

CODE

pF

nF

m F

CODE

1.0

1R0

3,900

3.9

.0039

392

1.2

1R2

4,700

4.7

.0047

472

1.5

1R5

5,600

5.6

.0056

562

1.8

1R8

6,800

6.8

.0068

682

2.2

2R2

8,200

8.2

.0082

822

2.7

2R7

10,000

10

.01

103

3.3

3R3

12,000

12

.012

123

3.9

3R9

15,000

15

.015

153

4.7

4R7

18,000

18

.018

183

5.6

5R6

22,000

22

.022

223

6.8

6R8

27,000

27

.027

273

8.2

8R2

33,000

33

.033

333

10

100

39,000

39

.039

393

12

120

47,000

47

.047

473

15

150

56,000

56

.056

563

18

180

68,000

68

.068

683

22

220

82,000

82

.082

823

(Continued)

49

Table 8-2—cont’d

Three-digit capacitor codes

pF

nF

m F

CODE

pF

nF

m F

CODE

27

270

100,000

100

.1

104

33

330

120,000

120

.12

124

39

390

150,000

150

.15

154

47

470

180,000

180

.18

184

56

560

220,000

220

.22

224

68

680

270,000

270

.27

274

82

820

330,000

330

.33

334

100

.0001

101

390,000

390

.39

394

120

.00012

121

470,000

470

.47

474

150

.00015

151

560,000

560

.56

564

180

.00018

181

680,000

680

.68

684

220

.00022

221

820,000

820

.82

824

270

.00027

271

1,000

1

105

330

.00033

331

1,500

1.5

155

390

.00039

391

2,200

2.2

225

470

.00047

471

2,700

2.7

275

560

.00056

561

3,300

3.3

335

680

.00068

681

4,700

4.7

475

820

.00082

821

6.8

685

1,000

1.0

.001

102

10

106

1,200

1.2

.0012

122

22

226

1,500

1.5

.0015

152

33

336

1,800

1.8

.0018

182

47

476

2,200

2.2

.0022

222

68

686

2,700

2.7

.0027

272

100

107

3,300

3.3

.0033

332

157

157

Code = 2 significant digits of the capacitor value + number of zeros to follow 10 pF = 100

For values below 10 pF, use “R” in place of decimal e.g. 8.2 pF = 8R2

100 pF = 101

1,000 pF = 102

22,000 pF = 223

330,000 pF = 334

1 μF = 105

The capacitors have polarity, and this must be observed Once you have installed all of the electrolytic

in order for the circuit to operate correctly. When

capacitors you can solder them in place on the circuit installing the electrolytic capacitors pay close attention board. Remember to trim the excess leads; use your

to the marking and install them correctly, referring to end-cutter to trim the leads flush to the edge of the Chapter Eight: Telephone Amplifiers and Projects both the schematic and parts layout diagrams.

circuit board.

50

Chapter Eight: Telephone Amplifiers and Projects

Locate the potentiometer R8, a 10 K trim-pot and

holder at the bottom of the chassis box. Finally, install install it on the circuit board and then solder it in place.

an 1⁄8′′ phone jack for the telephone pickup coil on the The Telephone Amplifier circuit contains two

front panel of the chassis box. When finished, apply

integrated circuits (ICs). ICs are often static sensitive, power to the circuit and plug in your telephone pickup so they must be handled with care. Use a grounded

coil and you will be ready to listen to a phone

anti-static wriststrap and stay seated in one location conversation.

when handling the integrated circuits. Take out a cheap Your telephone amplifier is now ready to serve you.

insurance policy by installing IC sockets for each of the Simply plug the telephone pickup into the 1⁄8′′ phone jack ICs. In the event of a possible circuit failure, it is much on the front panel, apply power to the circuit, and you easier to simply unplug a defective IC than trying to are ready to amplify any phone conversation. Your older unsolder 14 or 16 pins from a PC board without

relatives will be quite pleased to use this device, as now damaging the board. Integrated circuits have to be

they can hear the phone conversations loud and clear.

installed correctly if the circuit is going to work

The direct phone amplifier is also good in a party or properly. IC packages will have some sort of markings group conversation when a number of people wish to

which will help you orient them on the PC board.

contribute to the conversation.

An IC will have either a small indented circle, a cutout, When using the telephone amplifier, be sure to keep

or notch at the top end of the IC package. Pin 1 of the the speaker away from the telephone handset to prevent IC will be just to the left of the notch, or cutout.

any feedback. The pickup will be affected by strong

Refer to the manufacturer’s pin-out diagram, as well as magnetic fields—mains wiring, a computer monitor, and the schematic when installing these parts. If you doubt TV set. Low roll-off filters (to reduce the 50-Hz hum) your ability to correctly orient the ICs, seek the help of a could have been included in the circuit just as the high knowledgeable electronics enthusiast. Go ahead and

roll-off filters have been.

install the two IC sockets in their respective locations on If the telephone amplifier does not work

the printed circuit board.

immediately, it is likely that you inserted a component Now is a good time to take a short rest and when we

incorrectly or you have made some poor solder joints.

come back, we will inspect the circuit board for any

First you will need to inspect the PC board for possible

“cold” solder joints and any “shorts.” Pick up the

cold solder joints and short circuits. Pick up the PC board circuit board with the foil side facing upwards toward with the foil side facing upwards and facing you.

you. Examine the circuit board carefully, looking for Carefully inspect the solder joints, which should look any solder joins that look dark or blobby. If you see a smooth, clean, and bright. If any of the solder joints look solder joint that looks bad, use a desoldering tool and dull, dark, or blobby, then you should remove the solder remove the solder and then resolder the joint all over with a solder sucker or a solder wick and then resolder again. Also inspect the foil side of the board for any the joint all over again. Now we will inspect the

short circuits which may be caused by stray or cut

PC board for possible shortcircuits. Shortcircuits can be component leads, as they can often cause a bridge

caused by small solder blobs bridging the circuit traces or across the circuit traces.

from cut component leads which can often stick to the Once you have finished building the amplifier circuit, circuit board once they have been cut. A sticky residue you can install it in a small plastic or metal chassis box from solder will often trap component leads across the or enclosure. Install the integrated circuits into their circuit traces. Look carefully for any bridging wires respective sockets, paying close attention to the proper across circuit traces.

orientation of the IC in its socket. Mount the printed Now reapply power to the circuit and check to see

circuit board in the center of the chassis box using

if the amplifier is working; if not you may want to

1⁄4′′ plastic standoffs. You will most likely want

check the circuit board to make sure that you have not to install a power on-off switch on the front of the

installed a particular component at the wrong location.

enclosure. A 2- to 3′′ speaker can be mounted at the

Next, check the polarity of the capacitors, with respect top of the enclosure, but be sure to drill holes for the to its installation, and finally check to make sure that sound to exit the enclosure box. Install a plastic battery the integrated circuits have been installed correctly.

51

for group gatherings without the inconvenience and

interruption of vox operated speaker-phones.

This telephone amplifier also features line level

output designed to be connected to the auxillary input of any standard audio mixer or amplifier. This makes it perfect for radio stations, home broadcasters, and larger applications that need to connect their phone line into their systems. It features a standard isolation

transformer input for zero loading of the phone line.

Speaker output is a half watt into 8 ohms. Line output is 0 dB (.775 Vrms). The circuit runs on 7–10 VAC or

9–12 VDC at 150 mA. Board measures 2.5 × 2.1 inches.

Designed to be built into existing equipment, but the Figure 8-2

Telephone amplifier board. Courtesy of

amplifier can also be used as a stand-alone amplifier by Velleman Kits

placing the circuit in a small enclosure. (Group listen is great, no speaker-phone interruptions, yet everyone in my office can hear!)

Project 2: Telephone

amplifier II—Direct connect

Circuit description

The second telephone amplifier in this project is a Direct The telephone amplifier schematic is depicted in

Connect audio amplifier, as shown in Figure 8-2.

Figure 8-3. The amplifier circuit is connected directly The circuit features high performance and small size, to the telephone line through the resistor and diode

with both speaker and line outputs. The circuit is not network formed by resistors R1 and R2 placed across

really a speaker-phone, but a high performance isolated the phone line. Resistors R1 and R2 are placed in series input amplifier that connects directly to a telephone line.

with two capacitors and fed to resistor R4. Two silicon Unlike many types of amplifiers, this one provides both diodes are placed back-to-back across the input to the speaker output and line output. Speaker output is perfect isolation transformer at T1. Transformer T1 is a 600 to for “group listen” applications with standard telephones 600 ohm isolation/matching transformer. The secondary R8

D3

VA

D4

VB

A

C10

Tip

R1

GND

T

+V

e

l

C1

C3

T1

R3

e

p

C6

C8

h

6

1

o

3

n

8

C9

+

C4

5

e

R4

D1

D2

R9

2

U1

− 7

l

R6

4

R7

L

i

C2

SPK

n

R

e

R2

C5

R5

Line out

C7

Ring

GND

GND

B

Chapter Eight: Telephone Amplifiers and Projects Figure 8-3 Telephone amplifier-direct connect. Courtesy of Velleman Kits 52

Chapter Eight: Telephone Amplifiers and Projects

of the transformer is then fed to coupling capacitor C3

three or four color bands, which begin at one end of the and then on to resistor R3. Components C3, R3, and

resistor body. See the resistor color code value chart C4 ahead of the potentiometer at R9 form an input

shown in Table 8-1. The first resistor is the first number filter. The input from the network is next fed to the value, followed by the second number or code value.

potentiometer which is used to adjust the input signal to The third color band is the multiplier band, which is the IC amplifier chip, at U1. The output of the op-amp usually 20, 10 or 5%. If the resistor has no fourth color at pin is coupled to the output network formed by C5

band then the resistor has a 20% value. If the fourth and R6. The output coupling capacitor at C9 is fed to color band is silver then the resistor has a 10% value or the resistor divider network and the speaker. The

tolerance, and if the fourth color band is gold then the resistor network consists of resistors R5 and R7. This resistor has a 5% tolerance value. Let us go ahead and resistor network provides a line output. The line output begin installing the resistors. R1, R2, and R3 are all is provided in the event that you wish to couple the

10 K ohm or 10,000 ohm resistors. Since resistors

telephone amplifier to a tape recorder or to a mixer

have no polarity, you can install them in any direction circuit. Small radio station broadcasters may wish to in their proper locating holes (see the layout diagram).

feed the telephone amplifier into a mixer which is then Next locate and install R4 and R5 the 1 K ohm resistors, coupled to the transmitter’s audio input stage as a form followed by R6 and R7. Once all the resistors have been of manual phone patch of sorts. The amplifier circuit is placed in their proper locations, you can solder them in powered via diodes D3 and D4, which are fed from the

place on the PC board. Take your small end-cutters and telephone input connections through resistor R8 and

trim the excess component leads from the circuit board.

C10. The telephone amplifier circuit was constructed

Now, let us begin installing the capacitors. Capacitors on a small glass epoxy circuit board for reliable

will have usually have their actual values printed on operation.

them. Often small capacitors will not have enough room for the entire value to be printed so they will have a Circuit assembly

three digit code (see Table 8-2). Let us begin with C1

and C2, these are 22 nF or 22 nanofarad capacitors. Go Locate a clean, well-lit worktable or workbench, a small ahead and place them in their respective locations on pencil tip soldering iron, some 60/40 tin–lead solder and the PC board. Next locate C3, an 18 nF capacitor and

small can of Tip Tinner from your local RadioShack

then locate capacitors C4 and C5 which are both 47 nF

store. Tip Tinner is used to clean and prep the soldering types. Finally locate C6, a 100 nF capacitor and then tip. You will also want to locate some small tools such solder all of these capacitors to the circuit board. Now, as a pair of small end cutters, a few small screwdrivers, we will identify and install the electrolytic capacitors.

and a small Exacto type knife. Heat up your soldering Capacitors C7 through C10 are all electrolytic types and iron and place all the project parts in front of you, along will have a plus or minus marking at one end of the

with your printed circuit board. When building

capacitor. The capacitors have polarity, and this must be electronic circuit boards with integrated circuits it is a observed in order for the circuit to operate correctly.

good idea to install IC sockets on the PC board. In the When installing the electrolytic capacitors pay close event of an IC failure it is then a simple matter to

attention to the marking and install them correctly,

simply remove the defective IC and just install a new referring to both the schematic and parts layout

one. Integrated circuit sockets are inexpensive as well as diagrams. Once you have installed all of the electrolytic a good insurance policy.

capacitors you can solder them in place on the circuit board. Remember to trim the excess leads, use your

Place the your single-sided PC board in front of you, end-cutter to trim the leads flush to the edge of the along with the schematic and any parts layout diagrams.

circuit board.

Next, place all of the parts in front of you and create a check-off list to make sure you have all the components The phone line amplifier circuit uses four silicon diodes you will need for this project. It is usually a good idea located at D1, D2, D3, and D4. Diodes have polarity, so to begin installing the lowest profile components such when installing them be sure to observe the correct polarity.

as resistors first. Resistors are color coded, and have Diodes will usually have a black or white band

53

at one end of the diode body. The colored band

joint that looks bad, use a desoldering tool and remove specifies the cathode end of the diode. Observe the

the solder and then resolder the joint all over again.

proper orientation using your schematic and parts

Also inspect the foil side of the board for any short layout diagrams.

circuits which may be caused by stray or cut component Locate the potentiometer RV1 and install it on the

leads,as they can often create a bridge across the circuit circuit board and then solder it in place. Finally locate traces. Once you are satisfied that the circuit board the isolation or matching transformer, this 600 to

looks good you can attach two wires from the phone

600 ohm transformer will have both a primary and

line to the input of the phone line amplifier circuit at the secondary winding. You will want to make sure that

locations marked A and B.

you use the outside windings and not the center tap

Your Direct Connection telephone amplifier is now

windings, if your particular transformer has them.

ready to serve you. When the phone is on-the-hook the The matching transformer is installed between diode

amplifier will be silent, but once the phone is picked D1 and D2 and capacitor C3. Finally, use some wire

up, you will be ready to hear the conversation and

to connect the speaker to the terminal block output.

amplify it so others in the room can hear the phone

Now is a good time to take a short rest and when we

conversation out loud. Your older relatives will be

come back, we will inspect the circuit board for any

quite pleased to use this device, so now they can

coldsolder joints and any shorts. Pick up the circuit hear the phone conversation loud and clear. The

board with the foil side facing upwards toward you.

direct phone amplifier is also good in a party or

Examine the circuit board carefully, looking for any

group conversation when a number of people wish

solder joins that look dark or blobby. If you see a solder to contribute to the conversation.

Chapter Eight: Telephone Amplifiers and Projects

54

Chapter 9

Phone Recorder Switch Project

Kit available from

Parts list

www.electronickits.com

Ever want to tape that annoying or obscene phone call?

Phone Record Switch

Want to find out who is making those long distance

R1

220 ohm, 1⁄ W,

4

calls from your phone? Or how about taping that call

5% resistor

just to remember what was said? Many times we wish

R2

22 K ohm, 1⁄ W,

to remember exactly what was said during a phone

4

5% resistor

conversation. Whether it is directions to grandma’s

house or repair instructions for some other

R3, R4, R5

10 Megohm,

1

manufacturer’s electronic kits, the Phone Recorder

⁄ W, 5% resistor

4

Switch will become your “silent secretary,” recording R6

1 Megohm trim¯pot

calls for future playback. The Phone Recorder Switch

C1, C2

100 nF,

works in conjunction with a small tape recorder to

200 V mylar

record both sides of your phone conversation. When the capacitors (104)

phone is picked up from the switch-hook the Phone

D1, D2, D3

1N4148

Recorder Switch activates your small tape recorder to silicon diode

begin recording the phone conversation (see Figure 9-1).

Typical uses for the Phone Recorder Switch may include D4, D5, D6

1N4148

recording directions to a particular location, verifying silicon diode

calls made from or to your telephone, taping annoying or D7

10 V zener diode

obscene calls, or to record the detail of a business call D8

1N4004 silicon diode

you do not want to forget.

Q1

BC548 transistor or

This project serves well as an introduction to your

equivalent

telephone system and the tape recorder as well as the Q2

VN10 K N

more basic operation of transistors, FETs as switches,

¯channel

DMOSFET

S1

DPDT switch – PCB -

mount

J1

1

⁄′′ microphone plug

8

- plug into recorder

(specific to recorder)

J2

subminiature plug -

REMOTE control

Misc

PC board, wire,

hardware, enclosure

Model CK208 - Automatic

Phone Record Switch

Figure 9-1

Automatic telephone recording switch

55

Copyright © 2009 by The McGraw-Hill Companies, Inc. Click here for terms of use.

and diode operation. This circuit should work on

is high the base of the BC548 is pulled high so the

virtually all phone systems. The “Hands Off” or

transistor is turned “on.” This pulls the gate of the FET

automatic recorder switch project provides clean,

down to less than 1 V, which then shuts off the FET.

clear audio quality, and ease of assembly of this

Note that N-channel enhancement FETs need drain bias

build-it-yourself telephone recorder.

positive and a positive gate to turn on. When the line Note that your tape recorder must have both a

voltage falls (that is, the hand-set is picked up) the microphone or MIC socket and a REMOTE jack on it

BC548 must turn off; adjust the trim-pot if it does not.

so that this project can plug into the recorder and

So the FET gate potential rises to the 10 volts set by the control it. Cheaper tape recorders tend to omit these Zener diode. This turns the FET on to high efficiency external jacks and sockets, which are needed for this conduction mode. Different recorders may have

type of project. This circuit is designed to work for the different polarities in their REMOTE sockets. To allow newer 1.5-V and 3-V tape recorders as well as the usual for this a PCB mounted switch has been added to the

6-V or 12-V ones.

board which will reverse the polarity of the REMOTE

just by switching it.

Circuit description

Circuit assembly

The Phone Recorder Switch circuit shown in Figure 9-2

is divided into two main parts and these can be easily Before we begin building the Telephone Record Switch, seen in the diagram.

let’s first find a clean, well-lit worktable or workbench.

On the left are the connections to each telephone

Next we will gather a small 25–30 W pencil tipped

line and to the microphone or MIC socket of the tape

soldering iron, a length of 60/40 tin–lead solder, and a recorder. The diode and capacitors ensure that no DC

small canister of Tip Tinner, available at your local voltages pass through to the input of the MIC while the RadioShack store; Tip Tinner is used to condition the RC network clips large transients. On the right is the soldering tip between solder joints. You drive the

circuit which detects when the handset has been lifted soldering tip into the compound and it cleans and

and which then turns on the FET. The trim pot adjusts prepares the soldering tip. Next grab a few small hand the voltage level of this circuit. The voltage of the tools, and try and locate small flat blade and Phillips normal telephone line is between 40 and 60 V

screwdrivers. A pair of needle-nose pliers, a pair of (depending on country and telephone system).

tweezers along with a magnifying glass, and a pair of When you pick up the handset of the telephone the

end-cutters and we will begin constructing the project.

voltage falls to between 6 and 12 V. It is this drop in Now locate your schematic diagram and parts layout

voltage which is used to control the tape recorder

diagram along with all of the components needed to

through the REMOTE connector. When the line voltage

build the project. Once all the components are in front R4

Phone line

C1

Q2

R3

D7

R5

D

To remote

recorder jack

R1

To

P1

D3

D5

G

S

S1

MIC

Q1

P2

jack

D1 D2

R2

D4

D6

D8

R6

DPDT switch

C2

PC mount

Phone line

Chapter Nine: Phone Recorder Switch Project Figure 9-2 Auto telephone switch for tape recording. Courtesy of DIY Electronics 56

Chapter Nine: Phone Recorder Switch Project

of you, you can check them off against the project parts and the diodes. First locate our first resistor R1.

list to make sure you are ready to start building the Resistor R1 has a value of 220 ohms and is a

project. Now, locate Tables 9-1 and 9-2, and place them 5% tolerance type. Now take a look for a resistor

in front of you. Table 9-1 illustrates the resistor code whose first color band is red, red, brown, and gold.

chart and how to read resistors, while Table 9-2

From the chart you will notice that red is represented by illustrates the capacitor code chart which will aid you in the digit (2), and again the second band is red, which is constructing the project.

represented by (2). Notice that the third color is brown Refer now to the resistor color code chart shown in

and the multiplier is (10), so (2) (2) × 10 = 220 ohms.

Table 9-1, which will help you identify the project

Go ahead and place resistor R1 in its respective location resistors. Note that each resistor will have either three or on the PC board. Now solder the resistor to the circuit four color bands, which begin at one end of the

board and then use a pair of end-cutters to trim the

resistor’s body. The first colored band represents the excess component leads, flush to the edge of the circuit resistor’s first digit, while the second color represents board. Now locate and install the remaining resistors on the second digit of the resistor’s value. The third colored to the circuit board. Solder the resistors in place and band represents the resistor’s multiplier value, and the remember to trim the excess lead lengths.

fourth color band represents the resistor’s tolerance Note that capacitors generally come from two major

value. If there is no fourth colored band then the resistor groups or types. Non-polar types, such as the ones in has a 20% tolerance value. If the resistor’s fourth band this project, have no polarity and can be placed in

is silver then the resistor has a 10% tolerance value and either direction on the circuit board. The other type of if the fourth band is gold then the resistor’s tolerance capacitors are called polarized types; these capacitors value will be 5%.

have polarity and have to be inserted on the board,

We are now ready to begin assembling the project, so

with respect to their polarity marking, in order for the let’s get started. The prototype project was constructed circuit to operate correctly. On these types of

on a single-sided printed circuit board or PCB. With

capacitors, you will observe that the components

your PC board in front of you, we can now begin

actually have a plus or minus marking or a black or

populating the circuit board. We are going to place and white band with a plus or minus marking on the body

solder the lowest height components first, the resistors of the capacitors.

Table 9-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

No color

20%

57

Next refer to Table 9-2, this chart helps to determine Now locate the capacitors from the component pile

value of small capacitors.

and try and locate capacitor C1, which should be

Many capacitors are quite small in physical size.

marked with a (104); this capacitor has a 100 nF value.

Therefore, manufacturers have devised a three-digit

Let us go ahead install C1 on the circuit board and then code which can be placed on the capacitor instead of the solder it in place on the circuit board. Now take your actual value. The code occupies a much smaller space

end-cutters and cut the excess component leads flush to on the capacitor and can usually fit nicely on the

the edge of the circuit board. Once you have installed capacitor body, but without the chart the builder would C1, you can move on to installing the remaining

have a difficult time determining the capacitor’s value.

capacitors.

Table 9-2

Three-digit capacitor codes

pF

nF

m F

CODE

pF

nF

m F

CODE

1.0

1R0

3,900

3.9

.0039

392

1.2

1R2

4,700

4.7

.0047

472

1.5

1R5

5,600

5.6

.0056

562

1.8

1R8

6,800

6.8

.0068

682

2.2

2R2

8,200

8.2

.0082

822

2.7

2R7

10,000

10

.01

103

3.3

3R3

12,000

12

.012

123

3.9

3R9

15,000

15

.015

153

4.7

4R7

18,000

18

.018

183

5.6

5R6

22,000

22

.022

223

6.8

6R8

27,000

27

.027

273

8.2

8R2

33,000

33

.033

333

10

100

39,000

39

.039

393

12

120

47,000

47

.047

473

15

150

56,000

56

.056

563

18

180

68,000

68

.068

683

22

220

82,000

82

.082

823

27

270

100,000

100

.1

104

33

330

120,000

120

.12

124

39

390

150,000

150

.15

154

47

470

180,000

180

.18

184

56

560

220,000

220

.22

224

68

680

270,000

270

.27

274

82

820

330,000

330

.33

334

100

.0001

101

390,000

390

.39

394

120

.00012

121

470,000

470

.47

474

150

.00015

151

560,000

560

.56

564

180

.00018

181

680,000

680

.68

684

220

.00022

221

820,000

820

.82

824

270

.00027

271

1,000

1

105

Chapter Nine: Phone Recorder Switch Project 330

.00033

331

1,500

1.5

155

58

Chapter Nine: Phone Recorder Switch Project

Table 9-2—cont’d

Three-digit capacitor codes

pF

nF

m F

CODE

pF

nF

m F

CODE

390

.00039

391

2,200

2.2

225

470

.00047

471

2,700

2.7

275

560

.00056

561

3,300

3.3

335

680

.00068

681

4,700

4.7

475

820

.00082

821

6.8

685

1,000

1.0

.001

102

10

106

1,200

1.2

.0012

122

22

226

1,500

1.5

.0015

152

33

336

1,800

1.8

.0018

182

47

476

2,200

2.2

.0022

222

68

686

2,700

2.7

.0027

272

100

107

3,300

3.3

.0033

332

157

157

Code = 2 significant digits of the capacitor value + number of zeros to follow 10 pF = 100

For values below 10 pF, use “R” in place of decimal e.g. 8.2 pF = 8R2

100 pF = 101

1,000 pF = 102

22,000 pF = 223

330,000 pF = 334

1 μF = 105

This project contains seven silicon diodes at D1

lines represent the Collector and the Emitter. The

through D7. These diodes also have polarity which must diagonal lead with the arrow on it is the Emitter lead, be observed if the circuit is going to work correctly. You and this should help you install the transistor onto the will notice that each diode will have a black or white circuit board correctly. The FET also has three leads colored band at one edge of the diode’s body. The

but they are labeled differently, as seen in the

colored band represents the diode’s cathode lead. Check schematic.There is a Gate lead, a Drain lead, and a

your schematic and parts layout diagram when

Source lead, see pin-out diagram. Be sure not to mix up installing these diodes on the circuit board. Note that the VN10K FET with the BC548; make sure you can

D7 is a 10 V Zener diode, while D1 through D6 are

identify these correctly before installation. Go ahead 1N4148 diodes, and D8 is a 1N4004 silicon diode.

and install the transistor and the FET on the PC board Place all the diodes on the circuit board and solder them and solder them in place, then follow up by cutting the in place on the PC board. Then cut the excess

excess component leads.

component leads with your end-cutters.

Next, go ahead and mount the DPDT PC mounted

The Telephone Recorder Switch circuit also utilizes

switch on the circuit board. Now, cut it into two lengths one transistor at Q1 and an N-Channel DMOSFET

of 10′′ audio cable; these are used to make the

at Q2. Transistors generally have three leads, a Base connections to the telephone line and to the tape

lead, a Collector lead, and an Emitter lead. Refer to the recorder. Connect one end of each length of wire into schematic and you will notice that there will be two

the PCB at the places marked TO REMOTE, and MIC.

diagonal leads pointing to a vertical line. The vertical Connect the following connectors to the other ends of line is the transistor’s Base lead and the two diagonal the wires: to the free end of the TO REMOTE wire

59

attach the 2.5-mm diameter plug. (This plug

is the smaller of the two plugs. It plugs into the

Troubleshooting

REMOTE socket of the tape recorder; to the free

end of the MIC wire attach the 3.5-mm diameter

If your Telephone Recorder Switch does not appear to

plug. (This plug is the bigger of the two plugs

function correctly, you will need to disconnect the circuit supplied.) It plugs into the MIC socket of the tape

from the phone line and carefully inspect the circuit recorder. Use the alligator clip cable for the

board. It is likely that you made a soldering or parts TO EACH LINE pads. Cut the cable in half. Attach

placement mistake during construction. Pick up the circuit each half into the pads. Each clip goes onto one of the board with its foil side facing upwards toward you.

two telephone lines coming into your house. Note that Carefully inspect the circuit board against the parts this Phone Recorder Switch is attached in parallel with placement diagram and the schematic to make sure that the phone line. If you find you have four lines going to the proper component was inserted in the correct PC hole.

your phone then the two lines you want will either be You may have placed the wrong resistor at a particular the outer two (most likely) or the inner two. You will location. You may have inserted a diode backwards.

have to experiment.

Once this preliminary inspection is over, you can

When the project is completed place the phone record

inspect the circuit board for any possible cold solder switch and your tape recorder next to the phone. Plug joints or short circuits. Take a careful look at each of the the two sockets (MIC and REMOTE) into the recorder.

PC solder joints, they should all look clean and shiny.

Attach one alligator clip to each phone line (you may If any of the solder joints look dull, dark, or blobby, have to remove some plastic or covering from the phone then you unsolder the joint, remove the solder

line cables to get a good electrical connection.) Put in a and then resolder the joint all over again. Next,

cassette tape and push “play.” Provided the project has examine the PC board for any short circuits. Short

been assembled together correctly, either of two things circuits can be caused by two circuit traces touching will happen: the tape in the recorder will start to play or each other due to a stray component lead that stuck to it will not.

the PC board from solder residue or from solder blobs If it does not play then pick up the phone handset.

bridging the solder traces. Once you have fully

If the tape now starts to play then the Kit is working.

examined the circuit board, you can reconnect the

Put the handset down, depress the play and record

circuit board back to the phone line and try out the

buttons and the tape will now record when the handset phone transmitter once again.

is raised. If the tape plays then either of two things U.S. residents should note that it is illegal to tape needs adjustment: Move the position of the trim-pot

someone’s telephone conversation without informing all across its range of positions and see if this stops the parties that the conversation is being taped. So

playing. If it does, then lift the handset to see if the remember, when you pick up the phone and say hello,

playing starts. It should. The kit is ready for use.

also inform the caller the conversation is being recorded.

If adjustment of the trim-pot does nothing then the

Remember that this project is not a toy. You may need to REMOTE switch needs to be switched to the other

consult local regulations to provide you with the

position. Do this and repeat the steps as outlined above.

information necessary to use the Telephone Recorder

The kit should now work.

Switch’s capabilities in accordance with the law.

Chapter Nine: Phone Recorder Switch Project

60

Chapter 10

Telephone Conferencer Unit

Parts list

Telephone Conferencer

Circuit

R1

10 K ohm, 1⁄

W,

4

5% resistor

R2

100 ohm, 1⁄

W,

4

5% resistor

C1, C2

10 μF, 50 V

Figure 10-1

Conferencer circuit

electrolytic capacitor

they will want to charge you a monthly tariff whether C3

10 μF, 15 V

you use it or not. If you build the Conferencer shown in electrolytic capacitor

Figure 10-1, you can add conference call capability to Q1

2N3904 NPN silicon

your telephone and you won’t have to pay for its use.

transistor

Ma Bell will not even know that you have it, since it has S1, S2

DPST toggle

no effect on telephone performance, except to allow

switch

simultaneous communications between your two

T1

telephone coupling

telephone lines and two others.

transformer (Microtran

The Conferencer can be built at very low cost,

T2100 or equiv.)

making it a valuable addition to your telephone.

Misc

PC board, wire,

It requires no external power source for its operation connectors, enclosure,

and is always ready for use whenever you are. The

etc.

only requirement for making use of the Conferencer is to have two independent telephone lines available at

Today it is common for many people to have more than

a single location in your home or business.

one phone line coming into the house. Usually the

second line is called a “teen-age telephone” and is

provided by the telephone company at a specially

Circuit details

reduced rate. While the second telephone allows young people to talk on the telephone for hours at a time

In order to connect two independent telephone lines

without tying up the first telephone, there is an

together without disturbing the DC conditions on either additional benefit which can be derived by taking

line, a transformer must be used. This is the heart of the advantage of the fact that two independent telephone

circuit which allows audio information on one line to be lines are available. This is the conference call, which impressed on another line with no DC connection

has been available to commercial businesses for years.

between them. T1 is a telephone line coupling

Of course, the telephone company would be glad to

transformer, which has been designed for telephone line equip your telephone for conference call capability, but use. As shown in the schematic diagram of the

61

Copyright © 2009 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Note that only one telephone is required when

+

C1

T1

using the Conferencer. If that telephone is equipped for

+

Tip

Touch Tone dialing, it will be possible to dial telephone numbers to either line as required. If only rotary dialing Telephone

Telephone

S1

line #1

set

is available and it is desirable to dial a number

on line number #2, then a second telephone can be

Ring

connected across that line for dialing purposes only.

−

This is shown on the schematic diagram as an optional Tip

+

telephone set.

+

C2

R1

Once all the components are in front of you, you can

Optional

check them off against the project parts list to make Telephone

Q1

line #2

phone set S2

sure you are ready to start building the project. Now,

+

C3

locate Tables 10-1 and 10-2, and place them in front of R2

Ring

you. Table 10-1 illustrates the resistor code chart and

−

how to read resistors, while Table 10-2 illustrates the capacitor code chart, which will aide you in

Figure 10-2

Telephone conferencer. Courtesy of

constructing the project.

Thomson Corp

Refer now to the resistor color code chart shown in

Conferencer, Figure 10-2, each telephone line is

Table 10-1, which will assist you in identifying the

connected to the windings of T1 through coupling

project resistors. Note that each resistor will have either capacitors.

three or four color bands, which begin at one end of the Telephone line number #1 is connected across one

resistor’s body. The first colored band represents the winding of the transformer through S1 and electrolytic resistor’s first digit, while the second color represents capacitor C1. The capacitor prevents any DC from

the second digit of the resistor’s value. The third colored flowing through the transformer winding, while

band represents the resistor’s multiplier value, and the coupling the audio frequency information appearing

fourth color band represents the resistor’s tolerance across the telephone line to the transformer winding.

value. If there is no fourth colored band then the resistor The DC isolation provided by C1 ensures that the

has a 20% tolerance value. If the resistor’s fourth band normal DC conditions of the telephone line are not

is silver then the resistor has a 10% tolerance value and disturbed. In a similar manner, telephone line number if the fourth band is gold then the resistor’s tolerance two is connected to the second winding of the

value will be 5%.

transformer. Each telephone line can be independently Finally we are ready to begin assembling the project, controlled through the action of S1 and S2, which have so let’s get started. The prototype project was constructed been provided to allow connection and disconnection of on a single-sided printed circuit board or PCB. With your each telephone line as required.

PC board in front of you, we can now begin populating An additional circuit has been included, in the second the circuit board. We are going to place and solder the telephone line circuit. This is a DC holding circuit

lowest height components first, the resistors and the which provides the proper DC characteristic to hold

diodes. First locate our first resistor R1. Resistor R1 has a telephone line number two in operation even though no value of 10,000 ohms and is a 5% tolerance type. Now

telephone on that line is present. The circuit composed take a look for a resistor whose first color band is brown, of R1, R2, C3, and Q1 acts like a resistance to DC, and black, orange, and gold. From the chart you will notice as a high impedance to audio signals. The high

that brown is represented by the digit (1), the second impedance of the circuit is provided by C3, which

color band is black, which is represented by (0). Notice prevents any audio signals from appearing at the base that the third color is orange and the multiplier is (1,000), of Q1. Thus, any audio voltage appearing across the

so (1) (0) × 1,000 = 10,000 or 10 K ohms.

telephone line number #2 will not cause a

Go ahead and locate where resistor R1 goes on the

Chapter Ten: Telephone Conferencer Unit corresponding current in Q1.

PC and install it, next solder it in place on the PC board, 62

Chapter Ten: Telephone Conferencer Unit

Table 10-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

No color

20%

and then with a pair of end-cutters trim the excess

Capacitors must be installed properly with respect to component leads flush to the edge of the circuit board.

polarity in order for the circuit to work properly. Failure Next locate the remaining resistors and install them in to install electrolytic capacitors correctly could cause their respective locations on the PC board. Solder the damage to the capacitor as well as to other components resistors to the board, and remember to cut the excess in the circuit when power is first applied. Once you

lead lengths with your end-cutters.

have installed these components, you can move on to

Note that capacitors generally come from two

installing the remaining capacitors.

major groups or types. Non-polar types, such as the

ones in this project, which have no polarity, can be

Construction

placed in either direction on the circuit board. The

other type of capacitors are called polarized types,

The single-sided printed circuit board for the Conferencer these capacitors have polarity and have to be inserted circuit measures 2 × 3′′. This size is based on using the on the board with respect to their polarity marking in transformer specified in the parts list. For this application order for the circuit to operate correctly. On these

you can use any audio coupling transformer which is

types of capacitors, you will observe that the

rated at about 900 ohms both primary and secondary,

components actually have a plus or minus marking or

over the frequency range of about 300 to 3,000 Hz. Be a black or white band with a plus or minus marking on sure to allow extra room on the printed circuit board for the body of the capacitors.

the substitute transformer, if necessary.

Next refer to Table 10-2. This chart helps to

Pay careful attention when inserting Q1 into the board determine value of small capacitors. Many capacitors

so that the three leads are placed in the proper holes. The are quite small in physical size. Therefore,

transistor’s emitter lead connects to resistor R2, while the manufacturers have devised a three-digit code

base lead is connected between the junction of R1 and C3.

which can be placed on the capacitor instead of the

The transistor’s collector lead is connected to the plus end actual value. The code occupies a much smaller

of capacitor C2. Both capacitors C1 and C2, which are space on the capacitor and can usually fit nicely on

polarized components, must be installed correctly with the capacitor body, but without the chart the builder respect to the polarity markings. If these capacitors are would have a difficult time determining the

inadvertently placed in the board incorrectly, the

capacitor’s value.

telephone line DC conditions will be disturbed.

63

Table 10-2

Three-digit capacitor codes

pF

nF

m F

CODE

pF

nF

m F

CODE

1.0

1R0

3,900

3.9

.0039

392

1.2

1R2

4,700

4.7

.0047

472

1.5

1R5

5,600

5.6

.0056

562

1.8

1R8

6,800

6.8

.0068

682

2.2

2R2

8,200

8.2

.0082

822

2.7

2R7

10,000

10

.01

103

3.3

3R3

12,000

12

.012

123

3.9

3R9

15,000

15

.015

153

4.7

4R7

18,000

18

.018

183

5.6

5R6

22,000

22

.022

223

6.8

6R8

27,000

27

.027

273

8.2

8R2

33,000

33

.033

333

10

100

39,000

39

.039

393

12

120

47,000

47

.047

473

15

150

56,000

56

.056

563

18

180

68,000

68

.068

683

22

220

82,000

82

.082

823

27

270

100,000

100

.1

104

33

330

120,000

120

.12

124

39

390

150,000

150

.15

154

47

470

180,000

180

.18

184

56

560

220,000

220

.22

224

68

680

270,000

270

.27

274

82

820

330,000

330

.33

334

100

.0001

101

390,000

390

.39

394

120

.00012

121

470,000

470

.47

474

150

.00015

151

560,000

560

.56

564

180

.00018

181

680,000

680

.68

684

220

.00022

221

820,000

820

.82

824

270

.00027

271

1,000

1

105

330

.00033

331

1,500

1.5

155

390

.00039

391

2,200

2.2

225

470

.00047

471

2,700

2.7

275

560

.00056

561

3,300

3.3

335

680

.00068

681

4,700

4.7

475

820

.00082

821

6.8

685

1,000

1.0

.001

102

10

106

1,200

1.2

.0012

122

22

226

1,500

1.5

.0015

152

33

336

1,800

1.8

.0018

182

47

476

Chapter Ten: Telephone Conferencer Unit

64

Chapter Ten: Telephone Conferencer Unit

Table 10-2—cont’d

Three-digit capacitor codes

pF

nF

m F

CODE

pF

nF

m F

CODE

2,200

2.2

.0022

222

68

686

2,700

2.7

.0027

272

100

107

3,300

3.3

.0033

332

157

157

Code = 2 significant digits of the capacitor value + number of zeros to follow 10 pF = 100

For values below 10 pF, use “R” in place of decimal e.g. 8.2 pF = 8R2

100 pF = 101

1,000 pF = 102

22,000 pF = 223

330,000 pF = 334

1 μF = 105

There is no provision to mount S1 and S2 on the

solder joints look dull, dark, or blobby, then you should printed circuit board. The placement of these switches is remove the solder with a solder sucker or a solder wick left as an option for the builder. You may want to place and then re-solder the joint all over again. Now we will the entire circuit within the confines of a telephone set if inspect the PC board for possible short circuits. Short there is room, or you may want to house the Conferencer circuits can be caused from small solder blobs bridging in a small cabinet to be located next to the telephone.

the circuit traces or from cut component leads which

When making connections to the telephone line, be sure can often stick to the circuit board once they have been to follow correct procedure and use the standard four cut. A sticky residue from solder will often trap

prong telephone plugs or the new modular connectors,

component leads across the circuit traces. Look

available from many electronics parts suppliers. These carefully for any bridging wires across circuit traces.

connectors allow easy connection to and disconnection Once the inspection is complete, we can move on to

from the telephone line, which is an important factor installing the circuit board into an aluminum enclosure.

should the unit ever require servicing.

Locate a suitable enclosure to house the circuit board When making connections between the printed circuit

within the enclosure. Arrange the circuit board and the and the telephone lines it will be necessary to observe transformer on the bottom of the chassis box. Now, locate the polarity of the telephone line. Use a DC voltmeter to four 1/ ′′

4

standoffs, and mount the PC board between the

determine the polarity of each line before wiring the standoffs and the bottom of the chassis box. If you

telephone plugs. You must maintain correct polarity

selected a convention relay you will have to mount it on when connecting a Touch Tone telephone to the line and the chassis and wire it to the PC board. If you could not it is suggested that you follow the original wiring of the locate the small transformers specified, you will have to telephone set after it is disconnected to install the mount the transformers to the base of the chassis box and switch S1. Bear in mind that an optional telephone set wire it to the circuit board. You could install two terminal connected across line number #2 is necessary only if

strips to allow the two phone line connections to exit the you do not have Touch Tone dialing, and you wish to

rear of the chassis box. The two toggle switches can be dial numbers on line number two.

mounted on the front of the chassis box.

Once the Conferencer circuit board has been

completed, take a short break and then we will inspect Conferencer operation

the PC board for possible cold solder joints and short circuits. Pick up the PC board with the foil side facing You will be able to make and receive calls on either

upwards facing you. Carefully inspect the solder joints, telephone line by closing the appropriate switch and

they should look smooth, clean, and bright. If any of the using the telephone set connected across line number #1.

65

If you wish to initiate a conference call, use the following be able to carry on a three-way conversation. Finally, procedure: First, close S1 and make a call on line

when using only rotary dial telephones, perform step two number #1. When you have established contact with party by dialing the second number from the optional telephone number one, ask him or her to hold while you contact

set connected across line No. #2 before S2 is closed.

party number two. Next, close S2, and dial the second Once the number is dialed, you can close S2 and hang

number from the telephone set connected across telephone up telephone set number two and carry on the conference line number #1. When the second party answers, you will call in the normal manner.

Chapter Ten: Telephone Conferencer Unit

66

Chapter 11

The Frustrator

C2, C5

.01 μF, 10 V

Parts list

ceramic capacitor

C3, C10

6.8 μF, 10 V

The Frustrator

electrolytic capacitor

R1

22 ohms, 1⁄ W,

4

C6

10 μF, 10 V

5% resistor

electrolytic capacitor

R2

150 K ohms, 1⁄ W,

4

C8

100 μF, 10 V

5% resistor

electrolytic capacitor

R3

1 megohm, 1⁄ W,

4

C11

1,000 μF, 10 V

5% resistor

electrolytic capacitor

R4

47 K ohms, 1⁄ W,

4

D1, D2, D3, D4

1N2069

5% resistor

silicon diode

R5

2.2 K ohms, 1⁄ W,

4

D5

1N5953A – 150 V

5% resistor

Zener diode

R6

100 K ohms, 1⁄ W,

4

D6, D7, D8, D9

1N2069

5% resistor

silicon diode

R7

2.7 megohm, 1⁄ W,

4

D10, D11, D12,

1N2069

5% resistor

silicon diode

R8, R9

330 ohm, 1⁄ W,

4

D13, D14

1N2069 silicon

5% resistor

diode

R10

4.7 K ohms, 1⁄ W,

4

Q1

MPS A42 NPN

5% resistor

transistor

R11, R12

2.2 K ohms,

Q2

2N3904 NPN

1

⁄ W, 5% resistor

4

transistor

R13

10 K ohms, 1⁄ W,

4

Q3

2N3906 PNP

5% resistor

transistor

R14

47 K ohms, 1⁄ W,

4

U1, U4

LM555CN timer IC

5% resistor

U2

CD4001B Quad 2¯input

R15, R17

100 K ohms, 1⁄ W,

4

NOR gate IC

5% resistor

U3

CD4017B decade

R16

22 K ohms, 1⁄ w,

4

Johnson counter IC

5% resistor

U5

LM386 audio IC

C1, C4, C7, C9

.1 μF,

200 V ceramic

LED 1

red LED

capacitor

SPKR

4–8 ohm speaker

67

Copyright © 2009 by The McGraw-Hill Companies, Inc. Click here for terms of use.

T1

transformer

Otherwise the Frustrator will disconnect automatically.

115Pri/6¯V s @

The Frustrator can be left connected to your phone line 300 mA

at all times, and will not interfere in any way with

F1

1

⁄

normal telephone operation. You always have the option 2¯amp fast blow

fuse

of answering your telephone before or after the

Frustrator does, and you can carry on a normal

Misc

PC board, IC

conversation. The Frustrator is automatically

sockets, connectors,

disconnected from your received call after 30 s, and

hardware, wire,

resets itself to receive the next call each time you

enclosure, etc.

or it answers the phone.

Have you been annoyed by unwanted telephone calls,

especially at dinnertime, from people trying to sell you this or that? Is there ever a time when you just do not How it works

want to answer the phone, but worry that you might

miss an important or urgent message? If so, the

There are four sections to the circuit, each with a

telephone Frustrator, shown in Figure 11-1, is for you.

specific task. Refer to the schematic in Figure 11-2.

It is called the Frustrator because that is exactly what The integrated circuit at U1 is an LM555 timer chip

it will do to anyone who dials your number and does

connected as a monostable (one-shot) multi-vibrator and not know the secret to get through to you. It will answer detects the presence of the ringing signal (90 V rms, the call, on whatever ring you select, and the caller will 20 Hz) on the telephone line. Each time the ringing

hear nothing but silence. After about 30 seconds or so signal appears, U1 is triggered and its output (pin 3) he or she will be automatically disconnected. Repeated goes positive for a period of 3 s. In this way the

attempts to get your number will result in the same

20 Hz high-voltage ringing signal with an on/off time thing, and your unwanted caller will go away very

of 2 s and 4 s is converted to a digital pulse train of frustrated. It appears that your telephone or telephone 3 s on and 3 s off. This pulse train is used to clock line is defective.

decade Johnson counter U3, which counts from zero

However, if your caller knows the secret, all he or she to whatever ring you have selected for the Frustrator needs to do is talk into the mouthpiece and identify him to answer your telephone.

or herself. Even pressing any button (or a series of

When the circuit is at rest, U3 is reset to a zero count buttons in a predetermined code) on a Touch Tone

by a positive pulse fed to pin 15 from either the last phone will alert you that a friend or relative is calling.

time the Frustrator answered the phone or the phone

The Frustrator will connect an amplifier and speaker to was used in the normal way. As a result pin 3 of U3, the the phone line and let you hear voice and Touch Tone

decoded output for zero count, is positive (logic 1) and signals. You do not even have to go near your phone.

all other outputs are zero. Now, when the phone rings, At this point, if you so desire, you have about

each ring causes U3 to advance one count. Thus, the

30 s to pick up the receiver and answer the call.

first ring causes pin 2 of U3 to go positive, the second Chapter Eleven: The Frustrator Figure 11-1 Frustrator circuit. Courtesy of Cengage Learning 68

Chapter Eleven: The Frustrator

Jumper

D14

R4

1

3

C4

L1

R6

R3

R5

see text 4

R7

R8

Tip

D5

R9

D2

2

4

8 3

4

8

R1

3 D13

b

c

Phone

D1

2

3 2 4 7 10 1 5 6 9 11

line

R2

U1

2

7

16

R10

e

C1

5

7

14

U2:a

5

6

D3

Ring

13

Q1

6

15

8

D4

D6

D4

1

+

1

+

L2

C2

C3

C5

C6

e

Q3

U5

R13

D7

b

C8

c

3

6

11

R12

5 +

7

c

C7

SPK

14 U2:d

Q2

4

2

F1

D8

R14

12

e

b

R11

T1

D10

13

P1

D9

4

U2:c

U2:b

8

R15

10

D11

5

6

D12

+

+

9

R17

C9

C11

R16

C10

Figure 11-2

The Frustrator. Courtesy of Cengage Learning

ring causes pin 4 to go positive, and so on. When the pin you have selected goes positive the pulse is inverted Circuit assembly

by U2:a, differentiated, and fed to the trigger input of U4, another LM555 one-shot, multi-vibrator. U4 has a

Before we begin building the Frustrator, you will

timing cycle of about 30 s. The positive output at

first need to find a clean, well-lit worktable or

pin 3 of this chip is used to forward bias Q1 and

workbench. Next we will gather a small 25–30 W

switch it on. The resulting current through R9 and D14, pencil tipped soldering iron, a length of 60/40 tin/lead provided by the phone line, alerts the caller at the

solder, and a small canister of Tip Tinner, available at other end to hear a click, thus stopping the ring

your local RadioShack store. Tip Tinner is used to

answering the phone. Thirty seconds later U4 pin 3 goes condition the soldering tip between solder joints. You to zero, disconnecting the caller unless you have picked drive the soldering tip into the compound and it cleans up the phone.

and prepares the soldering tip. Next grab a few small The positive output voltage of U4 is also used as a

hand tools, try and locate small flat blade and Phillips drive signal to switch on Q2 and Q3, thus applying

screwdrivers. A pair of needle-nose pliers, a pair of B+ voltage to pin 6 of power amplifier U5.

tweezers along with a magnifying glass, and a pair of This amplifies the signals on the telephone line only end-cutters and we will begin constructing the project.

during the “on” time of U4, and lets you hear what is Now locate your schematic diagram and parts layout

going on even though you are not near your telephone.

diagram along with all of the components needed to build At all other times U5 is not powered, and the

the project. Once all the components are in front of you loudspeaker is silent.

can check them off again the project parts list to make sure you are ready to start building the project. The Digital logic fed to U1:c or U2:b is used to reset

Frustrator can be constructed on a small printed circuit U3 back to zero count after the Frustrator has done its board or even a perf-board, since layout is not critical.

job. U1:c detects when your telephone receiver is

lifted off the hook, and U2:b detects when U4 has

Locate Tables 11-1 and 11-2, and place them in front

automatically set to receive the next call. An LED

of you. Table 11-1 illustrates the resistor code chart and connected to the output of U4 alerts you to the status how to read resistors, while Table 11-2 illustrates the of the circuit at all times. When the Frustrator is on capacitor code chart, which will aid you in constructing standby, waiting for a call, the LED will be lighted.

the project.

During the 30-s call-answering sequence the LED

Refer now to the resistor color code chart shown

will be extinguished.

in Table 11-1, which will help you to identify the

69

Table 11-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

No color

20%

Table 11-2

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

1.0

1R0

3,900

3.9

.0039

392

1.2

1R2

4,700

4.7

.0047

472

1.5

1R5

5,600

5.6

.0056

562

1.8

1R8

6,800

6.8

.0068

682

2.2

2R2

8,200

8.2

.0082

822

2.7

2R7

10,000

10

.01

103

3.3

3R3

12,000

12

.012

123

3.9

3R9

15,000

15

.015

153

4.7

4R7

18,000

18

.018

183

5.6

5R6

22,000

22

.022

223

6.8

6R8

27,000

27

.027

273

8.2

8R2

33,000

33

.033

333

10

100

39,000

39

.039

393

12

120

47,000

47

.047

473

15

150

56,000

56

.056

563

18

180

68,000

68

.068

683

22

220

82,000

82

.082

823

27

270

100,000

100

.1

104

33

330

120,000

120

.12

124

39

390

150,000

150

.15

154

47

470

180,000

180

.18

184

Chapter Eleven: The Frustrator 56

560

220,000

220

.22

224

70

Chapter Eleven: The Frustrator

Table 11-2—cont’d

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

68

680

270,000

270

.27

274

82

820

330,000

330

.33

334

100

.0001

101

390,000

390

.39

394

120

.00012

121

470,000

470

.47

474

150

.00015

151

560,000

560

.56

564

180

.00018

181

680,000

680

.68

684

220

.00022

221

820,000

820

.82

824

270

.00027

271

1,000

1

105

330

.00033

331

1,500

1.5

155

390

.00039

391

2,200

2.2

225

470

.00047

471

2,700

2.7

275

560

.00056

561

3,300

3.3

335

680

.00068

681

4,700

4.7

475

820

.00082

821

6.8

685

1,000

1.0

.001

102

10

106

1,200

1.2

.0012

122

22

226

1,500

1.5

.0015

152

33

336

1,800

1.8

.0018

182

47

476

2,200

2.2

.0022

222

68

686

2,700

2.7

.0027

272

100

107

3,300

3.3

.0033

332

157

157

Code = 2 significant digits of the capacitor value + number of zeros to follow 10 pF = 100

For values below 10 pF, use “R” in place of decimal e.g. 8.2 pF = 8R2

100 pF = 101

1,000 pF = 102

22,000 pF = 223

330,000 pF = 334

1 μF = 105

project resistors. Note that each resistor will have either Finally we are ready to begin assembling the project, three or four color bands, which begin at one end of the so let’s get started. The prototype project was

resistor’s body. The first colored band represents the constructed on a single-sided printed circuit board or resistor’s first digit, while the second color represents PCB. With your PC board in front of you, we can now

the second digit of the resistor’s value. The third colored begin populating the circuit board. We are going to

band represents the resistor’s multiplier value, and the place and solder the lowest height components first, the fourth color band represents the resistor’s tolerance resistors and diodes. First locate our first resistor R1.

value. If there is no fourth colored band then the resistor Resistor R1 has a value of 22 ohms and is a 1⁄2-W

has a 20% tolerance value. If the resistor’s fourth band 5% tolerance type. Now take a look for a resistor whose is silver then the resistor has a 10% tolerance value and first color band is red, red, black, and gold. From the if the fourth band is gold then the resistor’s tolerance chart you will notice that red is represented by the

value will be 5%.

digit (2), and again the second band is red, which is 71

represented by (2). Notice that the third color is black positions on the PC board, then solder them in place.

and the multiplier is (0), so (2) (2) × 1 = 22 ohms. Install Next trim the excess component leads flush to the edge resistor R1 in its respective location on the PC board.

of the circuit board using your end-cutters.

Now take a pair of end-cutters and trim the excess

This project contains thirteen silicon diodes and a

resistor leads. Cut the leads flush to the edge of the Zener diode at D4. These diodes also have polarity

circuit board. Now, locate and install the remaining

which must be observed if the circuit is going to work resistors in their correct positions on the PC board. Then correctly. You will notice that each diode will have a use your end-cutters and remove the extra lead lengths.

black or white colored band at one edge of the diode’s Note that capacitors generally come from two major

body. The colored band represents the diode’s cathode groups or types. Non-polar types, such as the ones in lead. Check your schematic and parts layout diagrams

this project, which have no polarity, can be placed in when installing these diodes on the circuit board. Place either direction on the circuit board. The other type of all the diodes on the circuit board and solder them in capacitors are called polarized types, these capacitors place on the PC board. Then cut the excess component

have polarity and have to be inserted on the board with leads with your end-cutters.

respect to their polarity marking in order for the circuit The telephone Frustrator circuit utilizes three NPN

to operate correctly. On these types of capacitors, you transistors at Q1, Q2, and Q3. Transistors generally have will observe that the components actually have a plus or three leads, a Base lead, a Collector lead and an Emitter minus marking or a black or white band with a plus or lead. Refer to the schematic and you will notice that there minus marking on the body of the capacitors.

will be two diagonal leads pointing to a vertical line. The Next refer to Table 11-2, this chart helps to

vertical line is the transistor’s base lead and the two determine value of small capacitors. Many capacitors

diagonal lines represent the collector and the emitter. The are quite small in physical size. Therefore

diagonal lead with the arrow on it is the emitter lead, and manufacturers have devised a three-digit code which

this should help you install the transistor onto the circuit can be placed on the capacitor instead of the actual

board correctly. Transistor Q1 must be a high-voltage value. The code occupies a much smaller space on the

transistor, rated at 300 V, to withstand the high-voltage capacitor and can usually fit nicely on the capacitor ringing signal on the telephone line. Go ahead and install body, but without the chart the builder would have a

the transistors on the PC board and solder them in place, difficult time determining the capacitor’s value.

then follow-up by cutting the excess components leads with your end-cutter.

Now locate the capacitors from the component pile

and try and locate capacitor C1, which should be

The Frustrator circuit utilizes five ICs. ICs must

marked with a (104), this capacitor has a .1 μF value.

be handled carefully and installed properly in order for Let’s go ahead and install C1 on the circuit board and the circuit to work perfectly. Use anti-static techniques then solder it in place on the circuit board. Now take when handling the ICs to avoid damage from static

your end-cutters and cut the excess capacitor leads flush electricity when moving them about and installing

to the edge of the circuit board. Once you have installed them. It is wise to install integrated circuit sockets as a C1, you can move on to installing the remaining low

cheap form of insurance against a possible circuit

profile components. Now locate and install the larger failure at some later point in time. Install the IC sockets electrolytic capacitors. Use good quality electrolytic or on the PC board and solder them in place. Integrated

tantalum capacitors for the timing circuits (C3 and C6) circuits have to be installed correctly for the circuit to to assure accurate timing. Capacitor C10 should have

work, so you must pay strict attention to inserting

low leakage since it is placed in a high impedance

them correctly into their sockets. Each integrated

circuit. Remember the larger electrolytic capacitors have circuit has a locator either in the form of a small

polarity which must be observed if the circuit is to work indented circle or a notch, or cutout at the top end

properly. Failure to install the electrolytic capacitors of the IC package. Pin 1 of the IC will be just to the correctly can damage the component or other

left of the locator.

components when power is first applied to the circuit The Frustrator circuit employs a single LED, and

Chapter Eleven: The Frustrator upon power-up. Install the capacitors in their correct it must be oriented correctly if the circuit is to

72

Chapter Eleven: The Frustrator

function properly. An LED has two leads, a cathode and switch if used along with the speaker can be mounted

an anode lead. The anode lead will usually be the longer on the front panel of the chassis box.

of the two leads and the cathode lead will usually be the The Frustrator unit does not have to be installed near shorter lead, just under the flat side edge of the LED; the telephone; it can be placed anywhere convenient to this should help orient the LED on the PC board. Solder an AC power receptacle and the telephone line. For a

the LEDs to the PC board and then trim the excess leads.

professional installation job you should terminate the Now is a good time to take a short break. After the

pair of telephone line wires in a modular plug, and

break we will inspect the circuit board for any possible install the unit as you would any telephone accessory.

“cold” solder joints or “short” circuits. Take a careful Since the Frustrator has a bridge rectifier circuit at the look at each of the PC solder joints; they should all look telephone line input terminals, the polarity of the

clean and shiny. If any of the solder joints look dull, connection to the telephone line is not significant, just dark, or blobby, then you unsolder the joint, remove the be sure you connect to the red and green wires of the solder and then resolder the joint all over again. Next, existing telephone line.

examine the PC board for any short circuits. Short

circuits can be caused from two circuit traces touching Troubleshooting

each other due to a stray component lead that stuck to the PC board from solder residue or from solder blobs If your Frustrator circuit does not appear to function bridging the solder traces.

correctly once powered up, you will need to disconnect Table 15-3 is a chart which illustrates the wiring for the circuit from the phone line and carefully inspect the the jumper in accordance with your selection. For

circuit board. It is likely that you made a soldering or example, if you want the Frustrator to answer the

parts placement mistake during construction. Pick up

telephone after the fourth ring, you would connect the the circuit board with the foil side facing upwards

jumper between pin 10 of U3 and pins 1 and 2 of U2.

toward you. Carefully inspect the circuit board against Be sure to use only one jumper.

the parts placement diagram and the schematic to make The finished circuit board can be placed in a small

sure that the proper component was inserted in the

metal chassis box along with a loudspeaker. The circuit correct PC hole. You may have placed the wrong

board can be centered in the bottom of the chassis box, resistor at a particular location. You may have inserted a and mounted atop four 1⁄

diode backwards.

4′′ standoffs. A power switch

can be installed ahead of the fuse at F1. The fuse

Examine the circuit board closely for “cold” solder

holder and line cord can exit the rear of the chassis.

joints. Solder joints should appear clean, bright and A two-circuit terminal strip can be mounted on the rear smooth. If you see any solder joints that look dark,

panel to permit hookup to the phone line. The on-off

rough, or blobby, then use a solder sucker or wick to remove the solder. Now go ahead and resolder the joint.

Table 11-3

Finally, examine the PC board once again for possible Ring jumper list

short circuits. Short circuits are often caused by stray or remainder component leads which may have stuck to

# Rings

Integrated Circuit

Pin Number

the PC board, often from excess solder flux which is

very sticky. Look for stray leads which may bridge

1

U3

Pin #2

components traces on the PC board. Once your

2

U3

Pin #4

examination is complete you can move on.

3

U3

Pin #7

4

U3

Pin #10

Check out

5

U3

Pin #1

6

U3

Pin #5

Before you attempt to place the unit in operation it must 7

U3

Pin #6

be checked out to ascertain that it is working properly.

8

U3

Pin #9

This can be done very easily using an ordinary DC

9

U3

Pin #11

voltmeter or oscilloscope.

73

It is recommended that you check out the power

timing of U1 is too short or too long, change the value supply before you place any of the ICs in their sockets.

of R3 to bring the timing to within the 2–4-s timing

With no ICs installed, plug the line cord into a 115-V

range. Smaller values of R3 will reduce timing;

AC receptacle. Be careful to stay away from the wires larger values will increase it. When you are satisfied feeding the transformer primary! Measure the voltage

that the timing of U1 is correct, disconnect the power across C11. It should be about 7.8 V DC. If you do

cord and allow C11 to discharge. Then place the

not read the correct voltage (within 10%) you will have remaining ICs in their sockets, observing orientation.

to troubleshoot the problem before you can proceed to Insert the remaining integrated circuits in their

the next part of the check-out procedure. If the voltage respective sockets. If you have any difficulty in

is correct, leave the negative side of the voltmeter

installing the transistors or ICs, you could ask a

connected to the negative side of C11, and measure the knowledgeable electronics enthusiast to help you.

B+ voltage at pin 8 of U1 and U4, pin 14 of U2,

The Frustrator may be placed in operation by

and pin 16 of U3. Each of these terminals must read

connecting the line input wires to the telephone line and B+ voltage, about 7.8 V. When you are satisfied that

plugging in the AC power cord. If the LED does not

all voltages are correct, disconnect the unit from the light when power is first applied, U4 has been triggered power line and allow C11 to discharge.

by the sudden application of power and is in its timing One final check must be made before you place the

cycle. Allow about 30 s for the LED to come on.

Frustrator into operation; the timing of U1. To do this, Reset the circuit to standby mode by picking up the

place only U1 in its socket, observing proper

telephone receiver for about 5 s and then replacing it.

orientation. Connect a DC voltmeter or scope between

You can check the operation of the circuit by dialing pin 3 of U1 and circuit common. Now, with power

your number from another line (not an extension phone applied to the circuit take a short piece of wire and on the same line), and observing how many rings it

momentarily short pin 2 of U1 to circuit common being takes for the Frustrator to answer your phone. You

very careful not to touch any other part of the circuit.

might have a friend dial your number and then signal

This will cause U1 to “one-shot,” and can be observed you with a Touch Tone rendition of Jingle Bells: 999

by the voltmeter of scope indicating B+ voltage for

999 9#789. Once you have established that the

about three seconds. You may trigger U1 several times Frustrator is working properly, you are ready to thwart with the jumper wire, each time noting the number of

all those would-be telephone pitchmen. Be sure to tell seconds that the voltage remains high. This period must your friends and relatives about your secret, or they be more than two seconds and less than four. If the

will be frustrated too.

Chapter Eleven: The Frustrator

74

Chapter 12

Hold Circuits and Projects

R2

330 ohm, 1⁄ W,

2

Parts list

5% resistor

C1

47 μF, 50 V

Telephone Hold and

electrolytic capacitor

Line¯in¯Use Indicator

C2

10 μF, 50 V

R1

180 K ohm, 1⁄ W,

4

electrolytic capacitor

5% resistor

T1

600 to 600 audio

R2

10 K ohm, 1⁄ W,

4

matching transformer

5% resistor

S1

SPST toggle switch

R3

100 K ohm, 1⁄ W,

4

J1

mini 1⁄” earphone jack

5% resistor

8

Misc

PC board, wire,

R4, R5

1 K ohm, 1⁄ W,

4

enclosure, hardware,

5% resistor

etc.

R6

47 ohm, 1⁄ W,

4

Universal Hold Circuit

5% resistor

R1, R4

56 K, 1⁄ W,

R7

2.2 K ohm, 1⁄ W,

8

4

5% resistor

5% resistor

R2, R5

10 K, 1⁄ W,

R8

470 ohm, 1⁄ W,

8

4

5% resistor

5% resistor (optional)

R3

0.056 K, 1⁄ W,

8

Q1, Q2

MPSA42 NPN

5% resistor

transistor

R6, R7

1 MEG, 1⁄ W,

8

SCR1

2N5064 –.8 amp

5% resistor

200¯PIV SCR

C1, C3

.1 MFD 50 V

LED1, LED

LEDs

metalized film

S1

momentary

capacitor

pushbutton N/O

C2

1,000 MFD 16 V

PL1

modular 4¯circuit

electrolytic capacitor

telephone jack

C4

.1 MFD 250 V

Misc

PC board, wire,

polyester capacitor

enclosure, hardware,

C5

1 MFD 50 V

etc.

electrolytic capacitor

Basic Music¯on¯Hold

C6, C8

.01 MFD 50 V

R1

100 ohm, 1⁄ W,

metalized film

4

5% resistor

capacitor

75

Copyright © 2009 by The McGraw-Hill Companies, Inc. Click here for terms of use.

C7

4.7 MFD 35 V

Automatic Music¯on¯hold

electrolytic

R1, R2, R5, R6

capacitor

100 K ohm, 1⁄ W,

4

D1

light emitting diode

5% resistor

D2

1N4744 15 V

R3, R4, R8, R14

1 watt Zener diode

10 K ohm, 1⁄ W,

4

5% resistor

D3, D4, D5

1N914

silicon diode

R7

300 K ohm, 1⁄ W,

4

5% resistor

D6

1N4739 9.1 V

1 watt Zener diode

R9

39 K ohm, 1⁄ W,

4

5% resistor

BR1

DF04 1 AMP

400 V DIP bridge

R10

2 K ohm, 1⁄ W,

4

rectifier

5% resistor

IC1

H11C1 SCR

R11

1.2 K ohm, 1⁄ W,

4

optoisolator

5% resistor

IC2

4N28 transistor

R12

2.7 K ohm, 1⁄ W,

4

optoisolator

5% resistor

IC3

555 timer

R13

6.6 K ohm, 1⁄ W,

4

DC Electronics

5% resistor

IC4

CD22204 DTMF

R15

18 K ohm, 1⁄ W,

4

decoder DC Electronics

5% resistor

or Circuit Specialists

R16

10 ohm, 1⁄ W,

4

5% resistor

IC5

78L05 voltage

regulator

R17

680 ohm, 1⁄ W,

4

5% resistor

XTAL

3.579545 MHz

crystal

VR1

10 K PC trimmer

potentiometer

T1

600 to 600 ohm

transformer

C1, C2, C30

.02 μF,

250 V, ceramic

T2

12 V DC 100 MA

capacitor

wall transformer

C3, C4, C33, C34, C37

Misc

PC board, IC

.1 μF, 50 V ceramic

sockets, wire

capacitor

RJ¯11phone plug,

chassis, etc.

C5, C6, C12, C13, C29

10 μF, 35 V

Kit available:

electrolytic capacitor

Glolab Corp.

C7

47 μF, 35 V

307 Pine Ridge Drive

electrolytic capacitor

Wappingers Falls,

C9, C14, C35

100 μF,

NY 12590

35 V electrolytic

Fax (845) 297

capacitor

¯9772

www.glolab.com/order/

C10

100 nF, 35 V,

Chapter Twelve: Hold Circuits and Projects

parts.html

capacitor

76

Chapter Twelve: Hold Circuits and Projects

C11

47 nF, 35 V

D8

Red LED

capacitor

D10

BB909 - VHF

C15

680 pF, 35 V

varactor diode

ceramic capacitor

D11

3 V Zener diode

C16

10 nF, 35 V

L1

78 nH metal can coil

polystyrene capacitor

L2

70 nH metal can coil

C17

3.9 nF, 35 V

XTL

3.58 MHz color

capacitor

burst crystal

C18

3.3 nF, 35 V

S1, S2

normally open

capacitor

pushbutton switches

C19

220 pF, 35 V

RY1, RY2

12 V DPDT

capacitor

mini relays

C20

68 pF, 35 V

capacitor

T1

600 to 600 mini

isolation transformer

C21

82 pF, 35 V

capacitor

Misc

PC board,

IC sockets, wire,

C22

470 pF, 35 V

enclosure, etc.

capacitor

Automatic Music

C23, C24, C28

100 nF,

¯on¯hold

Power Supply

35 V capacitor

BR1

silicon diode

C25

22 nF, 35 V

bridge −100 V, −1¯amp

capacitor

R18, R19

470 ohm,

C26

180 pF, 35 V

1

⁄ w, 5%

capacitor

4

C31

450 μF, 50 V

C27

330 pF, 35 V

electrolytic capacitor

capacitor

C33, C37

.1 μF, 50 V

U1

Teltone 8870¯01

ceramic capacitor

(C.P. Claire)

C35

100 μF, 35 V

U2

MC14082 – dual

electrolytic capacitor

4¯input AND gate

C32, C36

10 μF, 50 V

U3

LM324N – Op¯Amp

electrolytic capacitor

(National)

U6

LM78L09 +9 V

U4

TDA7088T – FM

regulator

receiver chip

(Phillips

U7

LM7805 +5 V

¯NXP)

regulator

U5

LM366 audio

amplifier IC

U8

LM7812 +12 V

regulator

Q1

MPSA13 dual

transistor

F1

1 Amp fuse fast blow

D1, D2, D3, D4

1N4003

T2

110 V AC to 18 V AC

silicon diode

transformer .500 mA.

D5, D6, D9, D12

1N4003

Misc

PC board, wire,

silicon diode

standoffs, etc.

77

Most new phones and modems work even if the

Project 1: Telephone hold

polarity is reversed. For this circuit to work properly polarity must be observed.

and Line-in-Use

In this project, two simple circuits combine in order to Line-in-Use circuit

take the hassle out of sharing phone lines! Now it is convenient to inform others when we want to use the

The Line-in-Use section of the circuit consists of Q1 and phone or to see when it is in use. The simple circuit Q2, LED1 and R1 through R4. When the phone is

revolves around a pair of MPSA42 transistors, a silicon on-hook, R1 and R2, which form a simple voltage

controlled rectifier and a pair of light emitting diodes.

divider, supply 600 mV to the Base of Q1. That causes The schematic for the Telephone Hold and Line-in-Use

Q1 to turn on, pulling its collector to near ground

monitor is shown in Figure 12-1.

potential. The low voltage at the collector of Q1 is

applied to the Base of Q2, keeping Q2 in the cut-off

The Line-in-Use section of the circuit revolves

state, Since no current flows through Q2, LED1 does

around the Q1 and Q2, which were chosen for their

not light. But when the phone is taken off-the-hook the collector to emitter breakdown voltage of 300 V,

normal telephone line voltage drops, thereby reducing while the telephone hold section is built around the

the bias voltage applied to Q1. The reduction in bias 2N5064 SCR, which has a blocking voltage of

current causes Q1 to turn off. With Q1 turned off, its 200 V. Each section draws about 5 mA when active.

collector voltage rises to a level sufficient to bias The phone line has three states; on-hook,

transistor Q2 into conduction. With Q2 now conducting, off-hook, and on-hook ringing. When on-hook, the

current flows through Q2 and LED1, causing the LED

line voltage is typically 40 to 60 V; when off-hook

to light, indicating that the line is in use.

the line voltage ranges from 5 to 6 V, and when

ringing 70 to 140 V. The reasons for the great

variation are the length of lines from the phone

Line hold circuit

central office, and the resistance of the long lines or wires. Typically the positive (+) wire is known as

The line hold portion of the project consists of S1, R5

RING and is red, while the (−) minus wire or

through R7, LED2, and the SCR. Two of the resistors,

common is called TIP.

R5 and R6, form a voltage divider that is connected in series with switch S1.

When S1 is pressed and held with the phone

Modular

off-hook, current flows through the voltage divider to phone jack

the gate of SCR1. That provides sufficient current to cause SCR1 to fire, but not enough current through it to cause it to latch. When the phone is placed back

S1

on-hook, the line voltage increases, causing a current of R2

R4

R1

R3

sufficient magnitude to flow through R7to latch SCR1

LED2

and light LED1. Even after releasing S1, the LED

LED1

remains on, signaling that the line is on hold. When any SCR1

R5

phone on the line is picked up, the line voltage drops Q1

Q2

again to around 5 V, so that the SCR is starved for

current and turns off, releasing the hold on the line.

R7

R6

Resistor R8 is optional; that resistor is included in the circuit only if a flashing unit is used for LED2 in the line hold portion of the circuit to attract more attention.

Figure 12-1

Telephone hold and Line-in-Use monitor.

If you do use a flashing LED in the line hold circuit, Chapter Twelve: Hold Circuits and Projects Courtesy of Poptronix change the value of R7 to 1,000 ohms and add

78

Chapter Twelve: Hold Circuits and Projects

R8 across the LED, as indicated. Resistor R8 helps to Now locate your schematic diagram and parts

keep the latching current flowing through the SCR

layout diagram along with all of the components

during the blinking LED’s off cycle, so as not to disrupt needed to build the project. Once all the components

the operation of the line hold portion of the circuit. It is are in front of you, you can check them off against the ill advised to use a blinking LED for LED1, as it can project parts list to make sure you are ready to start generate annoying clicking sounds.

building the project.

Refer now to the resistor color code chart shown in

Circuit assembly

Table 12-1, which will help you identify the resistors for the project.

Before we begin building the Telephone Hold and

Note that each resistor will have either three or four Line-in-Use Monitor, you will first need to find a clean, color bands, which begin at one end of the resistor’s well-lit worktable or workbench. Next we will gather a body. The first colored band represents the resistor’s small 25–30-W pencil tipped soldering iron, a length

first digit, while the second color represents the second of 60/40 tin–lead solder, and a small canister of

digit of the resistor’s value. The third colored band Tip Tinner, available at your local RadioShack

represents the resistor’s multiplier value, and the fourth store. Tip Tinner is used to condition the soldering tip color band represents the resistor’s tolerance value.

between solder joints. You drive the soldering tip into If there is no fourth colored band then the resistor

the compound and it cleans and prepares the soldering has a 20% tolerance value. If the resistor’s fourth band tip. Next grab a few small hand tools, try and locate is silver then the resistor has a 10% tolerance value and small flat blade and Phillips screwdrivers. A pair of if the fourth band is gold then the resistor’s tolerance needle-nose pliers, a pair of tweezers along with a

value will be 5%.

magnifying glass, and a pair of end-cutters and we

Finally, we are ready to begin assembling the project.

will begin constructing the project.

So let’s get started. The prototype project was

The author’s prototype of the project was assembled

constructed on a single-sided printed circuit board or on a small printed circuit board, measuring 2 × 2 1⁄2′′.

PCB. With your PC board in front of you, we can now

If you have created your own PC board, now you can

begin populating the circuit board. We are going to

begin populating the circuit board with components.

place and solder the lowest height components first,

Table 12-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

No color

20%

79

the resistors and diodes. First, locate our first resistor R1.

The LEDs for this project can be either the same or

Resistor R1 has a value of 180k ohms and is a 5%

different colors, as desired. The Line-Hold LED could tolerance type. Now take a look for a resistor whose

be a red blinking LED, while the in-Use LED could be

first color band is red, red, brown, and gold. From the a green one.

chart you will notice that brown is represented by the As mentioned, the Hold and Line-in-Use indicator

digit (1), and the second band is gray, which is

circuit could be mounted inside your existing telephone represented by (8). Notice that the third or multiplier base if this is large enough, or it could be mounted in a band is yellow or (10,000), so (1) (8) × 10,000 =

small plastic enclosure. You could elect to mount the 180,000 ohms. Go ahead and place R1 on the PC board

project in a small plastic box with a telephone jack at in its respective location and solder it in place on the both ends, so that you could plug your telephone into board. Take a pair of end-cutters and trim the excess the project, or you could simply connect a 4-wire cord resistor leads, cutting the leads flush to the edge of the with a 4-conductor modular plug and plug it into a

circuit board. Now install the remaining resistors and telephone wall jack or extension jack if desired. You solder them in place on the circuit board. Remember to could build a Hold and Line-in-Use indicator circuit

trim the excess component leads with your end-cutters.

and place one at each phone for convenience.

It is advisable to install the lowest profile components first, so let’s go ahead and install the remaining resistors Installation and use

onto the circuit board. Go ahead and solder the resistors in their respective locations on the PC board, then

As mentioned earlier, the polarity of your telephone

trim the excess component leads using a small pair of lines may be not be properly indicated by the coloring end-cutters. Cut the excess leads flush to the edge of the of the wiring. Measure the actual polarity of the

circuit board. This project has no capacitors, so we will telephone line with a multi-meter, so that you will be not have to worry about identifying them.

sure you are connecting the positive (+) circuit-board The Telephone Hold and Line-in-Use circuit contains two trace to the RING input or PL1 and the negative trace to NPN silicon transistors Q1 and Q2. Transistors generally the TIP terminal. The board can be installed inside your have three leads, a Base lead, a Collector lead, and an telephone housing or mounted inside a small plastic

Emitter lead. Refer to the schematic and you will notice box. Using the Line-in-Use circuit requires no

that there will be two diagonal leads pointing to a vertical instruction and using the Hold circuit is simple; with the line. The vertical line is the transistor’s base lead and the phone off-hook, press and hold S1, and then place the two diagonal lines represent the collector and the emitter.

phone on-hook and release S1. The LED will stay lit

The diagonal lead with the arrow on it is the emitter lead, until any phone is taken off the hook again.

and this should help you install the transistor on to the circuit board correctly. Once the two identical transistors have been identified you can go ahead and install them on the PC board. Remember to trim the excess component

Project 2: Basic

leads flush to the edge of the circuit board.

Music-on-Hold

The Hold and Line-in-Use circuit also utilizes a

sensitive gate SCR shown at SCR1. SCR devices

What is more annoying than calling someone and

also have three leads, but unlike a transistor, which has getting placed on-hold? Being placed on-hold is a bit a base, collector, and emitter, an SCR has an anode,

more tolerable when you can listen to some music

cathode, and a gate lead. The SCR for this project looks while you are waiting. The Basic Music-on-Hold circuit much like a transistor, but make sure you can properly requires no external power source and uses the voltage identify it before installing it on the PC board. The across the phone line to power the circuit. You do not symbol for an SCR is a diode with an angled lead

have to spend a lot of money to construct your own

connected to the cathode end. Once you have

Music-on-Hold project. Now you can build a simple,

identified and determined the leads, you can go

low cost manual on-hold circuit in just a few minutes Chapter Twelve: Hold Circuits and Projects ahead and install the SCR.

by constructing the Music-on-Hold circuit depicted

80

Chapter Twelve: Hold Circuits and Projects

Normal

Green

S1

+C1

T1

+C2

+

J1

Hold

Telephone

R1

Radio audio

R2

line

D1

−

Red

Figure 12-2

Basic manual Music-on-Hold circuit

in Figure 12-2. With a small handful of components and 25–30-W pencil tipped soldering iron, a length of

about a half hour of your time you can build this simple 60/40 tin–lead solder, and a small canister of Tip Tinner, Music-on-Hold circuit.

available at your local RadioShack store, Tip Tinner is The Music-on-Hold circuit consists of two resistors, a used to condition the soldering tip between solder

capacitor, an LED, a matching transformer and an SPST

joints. You drive the soldering tip into the compound toggle switch. You simply connect the Music-on-Hold

and it cleans and prepares the soldering tip. Next grab a circuit to the phone line and connect the output of the few small hand tools; try and locate small flat blade and matching transformer to a radio earphone jack on an

Phillips screwdrivers. A pair of needle-nose pliers, a FM radio and you are ready to go!

pair of tweezers along with a magnifying glass, and a pair of end-cutters and we will begin constructing the project. Now locate your schematic diagram along with Circuit description

all of the components needed to build the project. Once all the components are in front of you, you can check The input to the Basic Music-on-Hold circuit is fed to them off against the project parts list to make sure you the telephone line via the red and green telephone wires.

are ready to start building the project. Now, locate

The red telephone line is connected directly to SPST

Tables 12-1 and 12-2, and place them in front of

switch S1. You can connect the circuit directly to a

you. Table 12-1, illustrates the resistor code chart and telephone jack via RJ11 plug, or wire it directly into a how to read resistors, while Table 12-2 illustrates the telephone wall jack. The opposite side of S1 is coupled capacitor code chart which will aide you in constructing to 100 ohm resistor in series with a red LED connected the project.

across the telephone line. This forms the on-hold

Refer now to the resistor color code chart in

indicator, while resistor R1 forms the actual “hold”

Table 12-1, which will help you identify the resistors circuit. Capacitor C1 is used to couple the audio from for this project. Note that each resistor will have either the phone line to the matching transformer at T1. The three or four color bands, which begin at one end of the 600 to 600 ohm Transformer T1 is used to isolate the

resistor’s body. The first colored band represents the phone line from your radio sound source. The

resistor’s first digit, while the second color represents secondary output from the audio matching transformer

the second digit of the resistor’s value. The third colored is fed to capacitor C2. The opposite end of C2 is then band represents the resistor’s multiplier value, and the fed directly to a mini 1⁄8′′ audio chassis jack. The Basic fourth color band represents the resistor’s tolerance Music on-hold circuit is simple but quite efficient and value. If there is no fourth colored band then the resistor will perform flawlessly.

has a 20% tolerance value. If the resistor’s fourth band is silver then the resistor has a 10% tolerance value and Circuit assembly

if the fourth band is gold then the resistor’s tolerance value will be 5%.

Before we get started building the Basic Music-on-Hold Finally, we are ready to begin assembling the project.

circuit, you will need to locate a clean, well-lit

Let’s finally get started. The Basic Music-on-Hold

worktable or workbench. Next we will gather a small

project was constructed on a single-sided printed circuit 81

Table 12-2

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

1.0

1R0

3,900

3.9

.0039

392

1.2

1R2

4,700

4.7

.0047

472

1.5

1R5

5,600

5.6

.0056

562

1.8

1R8

6,800

6.8

.0068

682

2.2

2R2

8,200

8.2

.0082

822

2.7

2R7

10,000

10

.01

103

3.3

3R3

12,000

12

.012

123

3.9

3R9

15,000

15

.015

153

4.7

4R7

18,000

18

.018

183

5.6

5R6

22,000

22

.022

223

6.8

6R8

27,000

27

.027

273

8.2

8R2

33,000

33

.033

333

10

100

39,000

39

.039

393

12

120

47,000

47

.047

473

15

150

56,000

56

.056

563

18

180

68,000

68

.068

683

22

220

82,000

82

.082

823

27

270

100,000

100

.1

104

33

330

120,000

120

.12

124

39

390

150,000

150

.15

154

47

470

180,000

180

.18

184

56

560

220,000

220

.22

224

68

680

270,000

270

.27

274

82

820

330,000

330

.33

334

100

.0001

101

390,000

390

.39

394

120

.00012

121

470,000

470

.47

474

150

.00015

151

560,000

560

.56

564

180

.00018

181

680,000

680

.68

684

220

.00022

221

820,000

820

.82

824

270

.00027

271

1,000

1

105

330

.00033

331

1,500

1.5

155

390

.00039

391

2,200

2.2

225

470

.00047

471

2,700

2.7

275

560

.00056

561

3,300

3.3

335

680

.00068

681

4,700

4.7

475

820

.00082

821

6.8

685

1,000

1.0

.001

102

10

106

1,200

1.2

.0012

122

22

226

1,500

1.5

.0015

152

33

336

1,800

1.8

.0018

182

47

476

Chapter Twelve: Hold Circuits and Projects

82

Chapter Twelve: Hold Circuits and Projects

Table 12-2—cont’d

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

2,200

2.2

.0022

222

68

686

2,700

2.7

.0027

272

100

107

3,300

3.3

.0033

332

157

157

Code = 2 significant digits of the capacitor value + number of zeros to follow 10 pF = 100

For values below 10 pF, use “R” in place of decimal e.g. 8.2 pF = 8R2

100 pF = 101

1,000 pF = 102

22,000 pF = 223

330,000 pF = 334

1 μF = 105

board, but you could elect to build the circuit on a

Next, refer to Table 12-2. This chart helps to

perf-board. With your PC board in front of you, you can determine the value of small capacitors. Many

now begin populating the circuit board. We are going

capacitors are quite small in physical size, therefore to place and solder the lowest height components first, manufacturers have devised a three-digit code which

the resistors and diodes. First locate our first resistor can be placed on the capacitor instead of the actual

R1. Resistor R1 has a value of 330 ohms and is a

value. The code occupies a much smaller space on the

5% tolerance type. Now take a look for a resistor whose capacitor and can usually fit nicely on the capacitor first color band is orange, orange, brown, and gold.

body, but without the chart the builder would have a

From the chart you will notice that red is represented by difficult time determining the capacitor’s value.

the digit (3), and again the second band is red, which is Now locate the capacitors from the component pile

represented by (3). Notice that the third color is brown and try and locate capacitor C1, which should be

and the multiplier is (10), so (3) (3) × 10 = 330 ohms.

marked 47 μF. Note that both C1 and C2 are electrolytic Go ahead and install R1 on the PC board and solder it capacitors, so they will have polarity which must be

in place. Now, take a pair of end-cutters and trim the observed when mounting these components on the PC

excess resistor leads flush to the edge of the PC board.

board. Go ahead and place C1 and C2 on the circuit

Now install the remaining resistors and solder them in board and solder them in place. Now take your

their respective locations. Remember to trim the excess end-cutters and cut the excess component leads flush

component leads.

to the edge of the circuit board. Once you have

Note that capacitors generally come from two major

installed the resistors and capacitors, you can move

groups or types. Non-polar types, such as the ones in on to installing the remaining components.

this project, which have no polarity, can be placed in either direction on the circuit board. The other type of Now install the LED, observing that the cathode is

capacitors are called polarized types, these capacitors connected to the bottom end of resistor R2. You may

have polarity and have to be inserted on the board

want to leave at least a half inch of lead length on the with respect to their polarity marking in order for the LED, so that it can be placed flush to the enclosure and circuit to operate correctly. On these types of

the LED can shine outside the mounting enclosure. You capacitors, you will observe that the components

could also elect to mount the LED directly on the

actually have a plus or minus marking or a black or

chassis or enclosure.

white band with a plus or minus marking on the

Now locate transformer T1. Since the transformer is

body of the capacitors.

a 600 to 600 ohm transformer both the primary and

83

secondary are the same, so you can designate either side as primary or secondary. Most small matching

Project 3: Universal Hold

transformers have two small mounting tabs. Drill two

small holes for the mounting tabs, then place the

Circuit

transformer on the PC board, and bend the tabs under

the board to secure the transformer to the PC board. You If you have a touch tone telephone service, you can now can solder the tabs to the ground plane of the PC board, put a call on hold from any phone in the house, even

if there is a common ground plane.

from cordless phones and phones without a hold button, by plugging this device into any telephone jack,

The on-off switch at S1 can be either a PC mount

anywhere in the house. Just one of these Universal Hold switch which can be mounted directly on the PC board, or Circuits adds the call hold feature to every phone that you could elect to mount the switch off the circuit board has a keypad with a # (pound) key. To put a call on

directly on the enclosure. The 1⁄8 inch mini audio jack can hold, you press the # key and hang the phone up. The

be mounted directly on the chassis box if desired.

# key function remains activated for five seconds after Once the circuit board is finished, you will need to

the key is pressed and released so you can hang up

decide how you will connect the circuit to the phone

phones that have a keypad in the handset.

line. You could elect to attach a 1–2′ length of

2-conductor phone wire from the Music-on-Hold circuit The Universal Hold Circuit detects the dual tone,

to the telephone line, or you could place a 2-conductor multi frequency (DTMF) tone that is generated when

jack on the Music-on-Hold chassis and then wire a plug the # key is pressed, and then activates a circuit that to a phone jack at the wall.

partially loads the telephone line so that the central office thinks a phone is still off-hook even after it is Next, you will have to construct or buy a 1⁄8′′ plug to hung up. When any phone is again picked up, the hold

1⁄8′′ plug audio coax cable. You can build you own cable function is canceled. The Universal Hold project is

if desired by purchasing two 1⁄8′′ mini plugs and a

shown in Figure 12-3.

1–3′ length of mini audio coax cable. One end of the

cable will plug into the jack on the Music-on-Hold

The Universal Hold schematic diagram is illustrated

circuit enclosure and the other end of the cable will in Figure12-4. The telephone line is connected to

plug into the earphone jack of an FM radio tuned to

the hold components through bridge rectifier BR1 so

your favorite station.

the input is not polarity sensitive and the input lines may be connected either way. BR1 always connects

the positive side of the line to Zener diode D2 and

Circuit operation

the negative side of the line to U2. If L1 is positive, current flows into the circuit through bridge diode section In order to utilize the Basic Music-on-Hold circuit, you A and back out through diode section D into L2. If L2 is will have to connect the circuit to the phone line as shown and to the earphone jack of an FM radio tuned to your favorite station. Then you simply have to establish your telephone call, and when you place the phone call

“on-hold” you simply have to switch the toggle switch from the “NORMAL” position to the “HOLD” position.

When you return to the phone call you will need to switch S1 back to the normal position. If the phone is not

switched back to the normal position, you will not be able to hang-up the phone line or receive new phone calls.

Your Basic Music-on-Hold project is now ready to

serve you; it will perform flawlessly for many years to come and you will pleased with your new low-cost

Chapter Twelve: Hold Circuits and Projects Music-on-Hold feature with a minimum cash outlay.

Figure 12-3

Universal Hold Circuit. Courtesy of GloLab

84

Chapter Twelve: Hold Circuits and Projects

+5 V

1

3

U5

R4

C2

2

5

1

R5

U1

D1

R2

+

C3

6

R3

D5

C1

R1

4

2

D2

XTL

R6

D4

Phone

1

5

4 3

1

13

12

11

10

9

8

6

A

1

U3

14

U2

U4

B

C5

Line

C

3

2

6

4

5 6

7 8

4

1

2

3

4

5

6

7

D

+

BR1

R7

C6

D3

+

C4

C7

C8

D6

T1

T2

+12 V

Wall

120 V AC

“wart”

−

12 V

Power supply

Figure 12-4

Universal Hold Circuit (Courtesy GloLab Corp)

positive, current flows in through diode section C and out LED (we’ll tell you more about this later). When the

through diode section B into L1. The telephone line also SCR conducts, current flows through BR1, D2, D1, U1,

connects to tone decoder U4 through C4 and T1. Opto-

U2 and back through BR1, placing a load on the line

isolator IC1 contains a silicon controlled rectifier (SCR) that keeps the central office circuits active. A 15-V

having a characteristic that makes it continue to conduct drop across D2, a 2-V drop across D1, a 1.5-V drop

current, or latch on, once turned on by current flowing across the LED in U2, and about a 1.5-V drop across

through an optically coupled LED within the IC.

the diodes in BR results in the normal 48-V

The SCR conduction continues even after the LED

open circuit line voltage across L1; L2 is clamped to current is removed, providing that enough anode current is about 20 V, which allows line current to flow but is a available to sustain it. When the SCR anode voltage is higher voltage than when a telephone loads the line.

removed and conduction stops, it will not resume when Now when a phone is picked up and the line voltage

voltage is re-applied until again triggered by LED current.

drops to about 8 volts or less, there is no longer enough This characteristic makes the SCR opto-isolator ideal voltage to produce conduction through D2, D1, U1, U2, for a line hold application. When all phones are hung up and BR1 and the hold function is canceled. LED D1 is

(on-hook) the voltage across the telephone line is about provided to indicate that a call is on hold.

48 V. When a phone is picked up (off-hook) it places

The telephone line also connects through C4 and

a load on the line and a current of about 20 mA flows transformer T1 to capacitor C8 which couples the

through the phone which causes the line voltage

DTMF signal to the input of U4, a Harris CD22204

to drop to about 3 to 8 V, depending on the telephone unit.

dual tone, multi-frequency tone decoder integrated

Current also flows through circuits in the central office, circuit used to detect the # key tone (see block diagram indicating that the phone has been picked up.

shown in Figure 12-5).

A call is put on hold when all phones are hung up

The 3.57 MHz crystal XTAL generates a clock

and the SCR in U1 is triggered on by circuits driving its required by the decoder. Zener diode D6 clamps its

85

Band pass

filters

Pre-processor

Band

697

Zero

Amplitude

Analog

split

crossing

770

detectors

in

filters

60 HZ

detect

Pre

7

BS1

reject

emp

852

941

Timing

BS2

1209

circuits

1336

ATB 11

1477

12 DV

XEN 6

1633

Strobe

10

÷ 8

Clock

Clocks

Xin

2 D1

Im

XTL

1 D2

Output

Output

decode

register

Voltage

14 D4

9

Regulator

ref

Xout

13 D8

Data clear

3 EN

4

8

VPD

VSS

Figure 12-5

CD22204 touch-tone decoder. Courtesy of Intersil Corp input to prevent damage from transients. The decoder

has four outputs that produce a hexadecimal code

Table 12-3

corresponding to the tones it receives when a key is

DTMF decoder output codes

pressed as shown in Table 12-3.

DIGIT

D4

D3

D2

D1

When these outputs are further decoded, the “1” or “0”

status of all four outputs usually must be considered to 1

0

0

0

1

get a unique hexadecimal number for each DTMF tone.

2

0

0

1

0

Notice, however, that a “1” occurs simultaneously in

3

0

0

1

1

both the pins 13 and 14 outputs only when the # key is 4

0

1

0

0

pressed. This makes using the outputs easier, since only 5

0

1

0

1

two hexadecimal bits must be considered to decode the 6

0

1

1

0

# key. The binary decoding is done by a logical AND

7

0

1

1

1

circuit consisting of two diodes, D4 and D5, whose

8

1

0

0

0

cathode terminals must both be at an up level or logical 9

1

0

0

1

“1” for their anodes, which are connected together, to 0

1

0

1

1

be pulled up by R5. This up level discharges C1 through

#

1

1

0

0

R4 into the positive supply.

A

1

1

0

1

When the # key is released the DTMF signal stops,

B

1

1

1

0

pins 13 and 14 go down again and a down level pulse is C

1

1

1

1

produced by time constant C1, R4 at the pin 2 trigger Chapter Twelve: Hold Circuits and Projects

D

0

0

0

0

input of timer U3. Since the IC3 trigger input must

86

Chapter Twelve: Hold Circuits and Projects

receive a negative transition to start a timing cycle, the Once all the components are in front of you, you can

cycle does not start until the # key is released. When the check them off against the project parts list to make sure timing cycle starts, U3 output pin 3 goes up for 5 s and you are ready to start building the project. Now, locate drives current through R3 into the LED within U1

Tables 12-1 and 12-2, and place them in front of you.

which places its SCR in a potentially conducting state Table 12-1 illustrates the resistor code chart and how where it needs only to have sufficient voltage applied to to read resistors, while Table 12-2 illustrates the capacitor its anode terminal to make it heavily conduct and latch code chart, which will aid you in constructing the project.

on, a condition that occurs when the phone is hung up.

The 5 s output from U3 keeps U1 LED current flowing

Finally, we are ready to begin assembling the project.

long enough to hang up the phone and have the required So let’s get started. The prototype was constructed on a anode voltage applied to maintain conduction. The time single-sided printed circuit board or PCB. With your

duration is controlled by R7 and C7 and may be altered PC board in front of you, we can now begin populating by changing the value of R7. U2 is an opto-isolator with the circuit board. Now refer to the resistor color code a transistor output. After the # key is pressed and the chart shown in Table 12-1. You will note that each

phone is hung up, telephone line current flowing

resistor will have either three or four color bands, which through the LED in U2 turns its transistor on, which

begin at one end of the resistor’s body. The first colored resets timer IC3 and terminates its timing cycle. This band represents the resistor’s first digit, while the reset function removes current from the LED in IC1 and second color represents the second digit of the resistor’s allows a hold to be canceled immediately after initiating it value. The third colored band represents the resistor’s without having to wait for the 5-s cycle to complete. The multiplier value, and the fourth color band represents transistor within U2 also performs a power-on reset by the resistor’s tolerance value. If there is no fourth having its base coupled through C5 to the positive supply.

colored band then the resistor has a 20% tolerance

When power is turned off, C5 discharges through D3.

value. If the resistor’s fourth band is silver then the resistor has a 10% tolerance value and if the fourth band Power is supplied by a 12-V DC wall transformer and

is gold then the resistor’s tolerance value will be 5%.

by U5, a 78L05 5-V regulator, and is filtered by C2 and C3. The power supply, DTMF decoder, and timing

We are going to place and solder the lowest height

circuits are isolated from the telephone line by the

components first, the resistors and diodes. First locate opto-isolators and transformer T1.

our first resistor R1. Resistor R1 has a value of 10k ohms and is a 5% tolerance type. Now take a look for a resistor whose first color band is brown, black, orange, Circuit assembly

and gold. From the chart you will notice that brown is represented by the digit (1), the second color band is Before we begin constructing the Universal Hold

black, which is represented by (0). Notice that the third Circuit, you will need to locate a clean, well-lit

color is orange and the multiplier is (1,000), so

worktable or workbench. Next, we will gather a small

(1) (0) × 1,000 = 10,000 or 10 K ohms.

25–30-W pencil tipped soldering iron, a length of 60/40

Go ahead and locate where resistor R1 goes on the

tin–lead solder, and a small canister of Tip Tinner,

PC and install it, next solder it in place on the PC board, available at your local RadioShack store; Tip Tinner is and then with a pair of end-cutters trim the excess

used to condition the soldering tip between solder

component leads flush to the edge of the circuit board.

joints. You drive the soldering tip into the compound Next locate the remaining resistors and install them in and it cleans and prepares the soldering tip. Next grab a their respective locations on the main controller

few small hand tools, and try and locate small flat blade PC board. Solder the resistors to the board, and

and Phillips screwdrivers. A pair of needle-nose pliers, a remember to cut the extra lead with your end-cutters.

pair of tweezers along with a magnifying glass, and a pair of end-cutters and we will begin constructing the Next refer to Table 12-2; this chart helps to determine project. Now locate your schematic diagram and parts

the value of small capacitors. Many capacitors are quite layout diagram along with all of the components needed small in physical size. Therefore manufacturers have

to build the project.

devised a three-digit code which can be placed on the 87

capacitor instead of the actual value. The code occupies these diodes on the circuit board. Place all the diodes on a much smaller space on the capacitor and can usually the circuit board in their respective locations and solder fit nicely on the capacitor body, but without the chart them in place on the PC board. The diode bridge on the the builder would have a difficult time determining the right side of the schematic can be installed now. After capacitor’s value.

soldering the diodes and the diode bridge in place in Note that capacitors generally come from two major

their respective locations, remember to cut the excess groups or types. Non-polar types, such as the ones in component leads with your end-cutters flush to the

this project, have no polarity and can be placed in either edge of the circuit board.

direction on the circuit board. The other type of

The Universal Hold Circuit contains five integrated

capacitors are called polarized types, these capacitors circuits (ICs). The two main integrated circuits are the have polarity and have to be inserted on the board with 14 pin Touch-Tone decoder at U4 and the 555 Timer

respect to their polarity marking in order for the circuit chip at U3. The Universal Hold Circuit also utilizes two to operate correctly. On these types of capacitors, you opto-isolator packages for interfacing. You will notice will observe that the components actually have a plus or that both opto-isolators are different; the 4N28 uses minus marking or a black or white band with a plus or a transistor, while the H11C1 uses an SCR. Both

minus marking on the body of the capacitors.

packages will be smaller 6-pin DIP sized packages

Capacitors must be installed properly with respect to and they should be handled like integrated circuits.

polarity in order for the circuit to work properly. Failure The LM78L05 IC is a 5-V regulator at U5.

to install electrolytic capacitors correctly could cause ICs are often static sensitive, so they must be handled damage to the capacitor as well as to other components with care. Use a grounded anti-static wriststrap and stay in the circuit when power is first applied.

seated in one location when handling the ICs. Take out Now look for the lowest profile capacitors from the

a cheap insurance policy by installing IC sockets for component stack and locate capacitor C1, which is

each of the ICs. In the event of a possible circuit failure, labeled (100) or 100 pF. Note that there are a number it is much easier to simply unplug a defective IC, than of small capacitors in the circuit that may not be labeled trying to unsolder 14 or more pins from a PC board

with their actual value, so you will have to check

without damaging the board. Integrated circuits have to Table 12-2 to learn how to use the three-digit capacitor be installed correctly if the circuit is going to work code. Go ahead and place C1 on the circuit board and

properly. IC packages will have some sort of markings solder it in place. Now take your end-cutters and cut the which will help you orient them on the PC board. An IC

excess component leads flush to the edge of the circuit will have either a small indented circle, a cutout, or board. Next, locate the remaining low profile capacitors notch at the top end of the IC package. Pin 1 of the IC

and install them on the printed circuit board, then solder will be just to the left of the notch, or cutout. Refer to the them in place. Remember to trim the extra component

manufacturer’s pin-out diagram, as well as the schematic leads. There are a number of electrolytic capacitors in when installing these parts. Accidental reversal of

the circuit and placing them with respect to their proper pin insertion can cause the integrated circuit to fail. If you polarity is essential for proper operation of the circuit.

doubt your ability to correctly orient the ICs, seek the Once you have located the larger electrolytic capacitors help of a knowledgeable electronics enthusiast.

install them in their respective locations and solder them Next, identify the quartz crystal, which connects

in place. Finally, trim the excess component leads.

between pins 9 and 10 of U4. Place the 3.579545 MHz

The Universal Hold Circuit contains a number of

crystal (XTAL) in its proper location and solder it

silicon diodes and a Zener diode. Diodes, as you will into place.

remember, always have some type of polarity markings, Next, locate transformer T1 and place it on the circuit which must be observed if the circuit is going to work board. Check the manufacturer’s specification sheet for correctly. You will notice that each diode will have a the actual wiring of your particular transformer. Many black or white colored band at one edge of its body. The 600 to 600 ohm transformers will have three windings

colored band represents the diode’s cathode lead. Check for both the primary winding and the secondary

Chapter Twelve: Hold Circuits and Projects your schematic and parts layout diagrams when installing winding. You will want to make sure that you use the

88

Chapter Twelve: Hold Circuits and Projects

correct wires for both the primary and secondary

battery holder and mount it to the bottom of the

connections. Install the transformer then solder the leads plastic box and solder the battery clip wire to the

to the PC board, remembering to trim the excess leads.

circuit board.

Once the main Universal Hold Circuit board has been

completed, take a short break and then we will inspect Testing

the PC board for possible “cold” solder joints and

“short” circuits. Pick up the PC board with the foil side Connect the hold circuit to the telephone line and plug facing upwards facing you. Carefully inspect the solder the wall transformer into an AC outlet. Pick a phone up, joints, which should look smooth, clean, and bright.

press the # key and hang it up within 5 s. D1 should

If any of the solder joints look dull, dark, or blobby, then light. Pick a phone up and D1 should go out. Press

you should remove the solder with a solder sucker or a the # key, wait about 8 s and hang the phone up.

solder wick and then resolder the joint all over again.

D1 should not light.

Now we will inspect the PC board for possible short

circuits. Short circuits can be caused from small solder blobs bridging the circuit traces or from cut component Operation

leads which can often stick to the circuit board once they have been cut. A sticky residue from solder will often The 5 s timing cycle that starts after the # key is released trap component leads across the circuit traces. Look

gives ample time to hang up a phone with a keypad on

carefully for any bridging wires across circuit traces.

the handset. If the keypad is on the telephone base the #

Once this take is complete, we can move on to

key can be pressed while the phone is being hung up. If installing the circuit board into a plastic box, as shown the # key is pressed for reasons other than to place a in Figure 12-6.

call on hold, such as to signal the end of a number entry Locate a suitable enclosure within which to house

after using a fax back service, the timing cycle will end the circuit board. Arrange the circuit board and the

after 5 s and will probably not be active when the phone transformer on the bottom of the chassis box. Now,

is hung up; to be sure that the line is not on hold after locate four 1⁄

using the # key just pick the phone up and hang up

4′′ standoffs, and mount the PC board

between the standoffs and the bottom of the chassis box.

again. Have fun and enjoy your new Universal Hold

If you selected a convention relay you will have to

Circuit project.

mount it on the chassis and wire it to the PC board. If you selected a non-PC board transformer then you will have to mount the transformer to the base of the chassis box and wire it to the circuit board. Locate a 9-V

Project 4: Automatic

Music-on-Hold

Impress your callers by adding an FM Music-on-Hold

feature to your telephone. If you thought a Music-on-Hold feature for your telephone was only for high-budget

professions, think again. You will learn how you can

add FM Music-on-Hold to any analog telephone line

with a Touch Tone telephone. It is ideal for homes,

offices, or small businesses. Some of the features of this design include: LED status indication audio

volume control, built-in antenna, only one operating

adjustment, and a mute function to eliminate “hiss”

in between stations. You can build this Music-on-Hold Figure 12-6

Universal Hold Circuit with case.

project in three or so hours and for less than

Courtesy of GloLab

about $70.

89

Music-on-Hold circuit is powered by a separate

multi-voltage output power supply, which is plugged

into a standard 120-V AC outlet.

When a key on any Touch Tone telephone is

depressed, the signal is passed through U3-d, an

LM324N balanced amplifier The purpose of this

amplifier is two fold; it acts as a balance to unbalanced matching network, and its gain is set to 0.1 to act as a line-voltage attenuator. Capacitors C1 and C2 block the phone line’s 48 V DC from entering the amplifier.

The ringing voltage is limited by R1 and R2. The ratio of R3 to R1 sets the gain of U3:d to 0.l. Resistor R4

Figure 12-7

Music on hold circuit. Courtesy of Poptronix

biases U3:d between supply voltage and ground. This

allows the circuit to operate from the single +6.0 V

Construction, test, and alignment are made easy due

DC power supply line. The output of the balance

to the use of specialized ICs, namely a single FM

amplifier passes through coupling capacitor C3 and

receiver chip, U4, and a DTMF decoder U1. There are

is then decoded by U1, a Teltone 8870-01 dual

no special coils to wind, and no tricky circuit

multi-frequency (DTMF) decoder IC.

adjustments are required. All you need is a DMM to test The output of U1 is a 4-bit word whose codes are

and align the circuit; see Figure 12-7.

listed in Table 12-3.

It is connected to U2:b, a 4,082 dual quad-input

On-hold circuit

AND gate, so that the output of that IC (pin 13) is

normally low and goes high only when the “∗” key is

Let’s take a look at how the Music-on-Hold unit works.

pressed. Therefore, when the “∗” key is decoded by U1, A block diagram of the unit is shown in Figure 12-8,

pins 1, 2, and 13 are high while pin 14 is low. To switch and the schematic in Figure 12-9.

the output of U2-b high, four logic-high inputs present.

The FM on-hold device connects to an analog

The high inputs are provided by U1 pins 1, 2, and l3

telephone line via an RJ11 modular jack. The automatic and U2:a pin 1.

On-hold logic

Balance

amplifier

U2-b

RY1

U1

Telephone

U3-d

DTMF

line

Input

decoder

“*” key

U2-a

Antenna

decode

Seizure

RY2

network

Audio

amplifier

FM receiver

T1

U4

U3-c

tuner

Chapter Twelve: Hold Circuits and Projects Figure 12-8 Music-on-Hold block diagram. Courtesy of Poptronix 90

+5 V

C4

+6 V

R3

R7

+12 V

18

10

+12

R6

17 16

3

14

Q1

C1

14

10

B

D1

Phone

4

R9

−

12

12

13

R1

2

U2:b

line

8870-01

11

11

+

D2

R5

C3

+

12

7

C6

9

U3:d

13

XTL

U1

8

15

4

1

5

1

U2:a

4

3

5

6

9

+6

D3

D5

2

7

C30

C2

R2

R4

R8

+

D4

D6

6 V

D9

C5

RY1

R10

S1:a

R13

D11

S2

C16

C15

C14

C24

C25

C26

C27

C28

R12

L1

D7

C23

+9 V

1

8

7

10

13

4

R17

+

16

C17

RY2

C7

R11

+6 V

9

U4

D10

C22

8

S1

15

6

C29

LED1

J1

C18

S1:b

C10

D8

1

8

11

2

5

6

C9

+

C21

C8

L2

U5

1

3

12

2

C13

−

4

C11

14

7

C20

R14

C12

T1

C19

R16

R15

VR1

91

Figure 12-9

Automatic Music-on-Hold project. Courtesy of Poptronix In order for U2:a’s output to go high, it must also

Kick-back capacitor C5 ensures the loop current is

have four logic inputs. Two of those are provided by

reduced below the drop-out current for RY2. That

R7, D10, and C27. Those components ensure that the

reduction in current turns off LED1, disconnects the

internal power supply is operating. That will prevent music, and reconnects the caller.

the unit from seizing the phone line if power is lost or If the telephone is not hung up within the 4 s time-out removed while it is connected to the phone line. The

period, RY1 will deactivate and the project will be taken remaining two inputs are provided by a logic high from out of the “STANDBY” mode and placed in the

U1 pin l2, which is the data valid output pin, assuring

“NORMAL” mode. LED1 will not be lit, and the caller

proper operation of U1 by providing internal checks.

will be disconnected if the telephone is hung up.

When those checks are valid, DV will output a logic

high. That prevents false triggering due to voice or

Latching push-button switch S1 is used to tune in the other tones that occur during normal telephone usage.

desired station. When it is in the IN position, the seizure When the “∗” key is depressed, U2:b goes high, which

network is placed across the telephone line and the

in turn charges C4 and turns on switching transistor Q1.

output of the tuner is also connected (regardless of the That activates relay RYl. Diode D1 prevents DC voltage status of J1). That allows you to hear the output of the from bleeding back into U2:b pin l3. The time-base

FM tuner and adjust the station tuning and volume.

oscillator for U1 is formed from a 3.58-MHz

(A feature of the receiver is the elimination of

crystal XTL and R5.

inter-station “hiss,” therefore no audio will be present until a station is tuned in.

The normally open contacts of RY1 close, and D7,

R9, RY2, R10, C5. LED1, transformer (T1) and the four diodes from the polarity bridge (D3-D6) are connected FM receiver circuit

across the telephone line and effectively “seize” it. That combination of components is referred to as the seizure At the heart of the FM receiver circuit is U4,

network. The unit is now in a STANDBY mode. If

a TDA7088T FM receiver chip. This IC has a

jumper J1 is in the IN position and a station is tuned in frequency-locked loop system with intermediate

to the FM tuner, that station will be heard on the

frequency (IF) 70 KHz. The IF can be chosen by active telephone line. If it is in the OUT position, the station RC filters. The receiver is tuned via pushbutton switches, will not be heard until the phone is hung up.

which select the desired radio stations. A block diagram of the FM receiver chip is shown in Figure 12-10.

Relay RY1 will stay activated for approximately four

seconds. That delay is determined by the RC network of The FM receiver contains a mixer section, where the

R6/C4. Diode D2 prevents relay-coil induction-induced antenna enters the circuit and the input filters reside. The

“spikes” from appearing on the +12-V DC power

VCO is fed directly to the mixer section as shown.

supply line. If the telephone is hung up within the four The tuning section of the circuit is centered around pins 1, second time-out period, additional loop current will

15, and 16. The IF limiter is coupled to the all-pass filter flow through the seizure network and activate RY2.

and demodulator circuit, which feeds the loop filter. The That causes the normally open contacts of RY2 to close.

loop filter is then coupled into the search tuning circuit.

The project is now in the “on-hold” mode, LED1 will

The receiver chip pin-outs are illustrated in Table 12-4.

be brightly lit, and the selected radio station will be The antenna “piggy-backs” or utilizes one telephone

heard in the telephone line regardless of the position of line and the RJ11 cable. The RF signal travels through jumper J1. After the four second time-out period, RYl that path and is coupled via DC blocking capacitor C30

will deactivate. The loop current flowing through RY2

to RF input bandpass filter. This broadband low-Q filter keeps the seizure network across the telephone line and consists of C20, C21, and L2. Its primary purpose is to the unit remains on-hold.

pass RF energy in the 8.0- to 108.0-MHz range while

To return to the call, the telephone can be picked up.

attenuating RF energy from above and below that

The loop current flowing through the seizure network is frequency range. The bandpass filter serves to suppress reduced because of the double termination. RY2

potential interfering energy from outside the

Chapter Twelve: Hold Circuits and Projects deactivates, and the seizure network is disconnected.

commercial FM broadcast band.

92

Run

180 pf

3.3 nf

3.9 nf

.1

470 pf

μF

Antenna

330 pf

22 nf

6

7

8

9

10

13

15

3

If

11

6 K

5.4 K

2.2 K

2.2 K

limiter

+

82

1

pf

All pass

V1

5 K

filter

70

Mixer

68

nW

10 K

Vp

pf

12

Demodulator

5

6 K

−

BB910

L

61

Loop filter

T

VCO

78

V2

nH

4

AF

−1

+

V2

10 nf

14

V2

3 V

5.6 K

X

8

+

+

AF

16

Search

V3

.1 μF

tuning

R

Mute

S

Reset

1

.1 μF

2

VoAF

1.8 nf

22 K

93

Figure 12-10

TDA-7088T FM receiver block diagram

Table 12-4

The audio signal from the receiver chip passes through TDA7088T FM receiver chip pin-outs

C13 and VR1 to the inverting input of audio amplifier U5.

Feedback resistor C29 controls the gain of the amplifier Symbol

Pin

Description

from 0 to 20. Transformer T1 matches the amplifier’s

MUTE

1

mute output

output impedance to the telephone line impedance.

VoAF

2

audio frequency output signal

The multi-output power supply for the automatic

LOOP

3

AF loop filter

Music-on-Hold circuit is shown in Figure 12-11.

Vp

4

+3 V supply voltage

The power supply consists of a transformer which

OSC

5

oscillator resonant circuit

steps down the 110 V AC to 18 V AC; the output from

IFFB

6

IF feedback

the transformer is sent to a rectifier and filter capacitors CLP1

7

low pass capacitor of 1-dB amplifier

at C31 and C32. The output from the filter is next sent V

to diode D12 and then on to U8, a 12-V regulator. The oIF

8

IF output to external coupling

capacitor (high-pass)

12 volts from this first regulator are then used to feed the remaining two regulators which provide 9 V, through Vilf

9

IF input to limiter amplifier

U6 and 5 volts through U7. A 6-V output is provided

CLP2

10

low-pass capacitor of IF limiter

from a voltage divider off the 12-V regulator.

ViRF

11

radio frequency input

ViRF

12

radio frequency input

CLIM

13

limiter offset voltage capacitor

Construction

GND

14

ground (0 V)

The entire FM hold circuit is mounted on one

CAP

15

all-pass filter capacitor/input

double-sided PC board. The use of a single-sided

for search tuning

board will work as long as the jumper wires are added TUNE

16

electrical tuning/AFC output

to the top where necessary. We recommend that a

PC board be used because of the VHF range involved

in this project. The importance of proper soldering

The FM receiver is tuned using S1, the manual tune

cannot be emphasized enough for VHF circuits. It is

search pushbutton switch, and the reset pushbutton

recommended that the flux residue be removed from

switch at S2. The AFC or automatic frequency control

the completed PC board using a mild on-CFC cleaner

of the local oscillator is accomplished using the Varicap that is not harmful to plastics. Always read the

diode at D10.

manufacturer’s label.

LM7809

In

Out

U6

+9 V

+

+

C36

C37

LM7805

110 V AC

Out

In

LM7812

U7

+5 V

D12

F1

BRI

C34

1

0

G

U8

+12 V

+2

+

+

R19

G

C33

+6 V

+

C31

C32

R18

C35

Chapter Twelve: Hold Circuits and Projects Figure 12-11 Automatic Music-on-Hold power supply 94

Chapter Twelve: Hold Circuits and Projects

value. If the resistor’s fourth band is silver then the Static sensitive devices

resistor has a 10% tolerance value and if the fourth band is gold then the resistor’s tolerance value will be 5%.

Observe electrostatic discharge precautions when

We are going to place and solder the lowest height

handling individual semiconductors as well as the

components first, the resistors and diodes. First locate completed circuit board. Component leads should be

our first resistor R1. Resistor R1 has a value of

pre-formed before inserting them in the board. Before 10 K ohms and is a 5% tolerance type. Now take a look you begin construction, there are few things to keep

for a resistor whose first color band is brown, black, in mind.

orange, and gold. From the chart you will notice that Before we begin constructing the Music-on-Hold

brown is represented by the digit (1), and the second circuit, you will need to locate a clean, well-lit

color band is black, which is represented by (0).

worktable or workbench. Next, we will gather a small

Notice that the third color is orange and the multiplier 25–30-W pencil tipped soldering iron, a length of 60/40

is (1,000), so (1) (0) × 1,000 = 10,000 or 10 K ohms.

tin–lead solder, and a small canister of Tip Tinner,

Go ahead and locate where resistor R1 goes on the

available at your local RadioShack store; Tip Tinner is PC and install it; next solder it in place on the PC

used to condition the soldering tip between solder

board, and then with a pair of end-cutters trim the

joints. You drive the soldering tip into the compound excess component leads flush to the edge of the circuit and it cleans and prepares the soldering tip. Next grab board. Next, locate the remaining resistors and install a few small hand tools, try and locate small flat blade them in their respective locations on the main controller and Phillips screwdrivers. A pair of needle-nose pliers, PC board. Solder the resistors to the board, and

a pair of tweezers along with a magnifying glass, and a remember to cut the extra lead with your end-cutters.

pair of end-cutters and we will begin constructing the Next refer to Table 12-2. This chart helps to

project. Now locate your schematic diagram and parts

determine the value of small capacitors. Many

layout diagram along with all of the components needed capacitors are quite small in physical size, so

to build the project.

manufacturers have devised a three-digit code which

Once all the components are in front of you, you can

can be placed on the capacitor instead of the actual

check them off against the project parts list to make value. The code occupies a much smaller space on the

sure you are ready to start building the project. Now, capacitor and can usually fit nicely on the capacitor locate Tables 12-1 and 12-2, and place them in front of body, but without the chart the builder would have a

you. Table 12-1, illustrates the resistor code chart and difficult time determining the capacitor’s value.

how to read resistors, while Table 12-2 illustrates the Note that capacitors generally come from two major

capacitor code chart which will aide you in constructing groups or types. Non-polar types, such as the ones in the project.

this project, have no polarity and can be placed in

Finally, we are ready to begin assembling the project, either direction on the circuit board. The other type of so let’s get started. The prototype was constructed on a capacitors are called polarized types, these capacitors single-sided printed circuit board or PCB. With your PC

have polarity and have to be inserted on the board with board in front of you, we can now begin populating the respect to their polarity marking, in order for the

circuit board. Now refer to the resistor color code chart circuit to operate correctly. On these types of capacitors, shown in Table 12-1. You will note that each resistor you will observe that the components actually have a

will have either three or four color bands, which begin plus or minus marking or a black or white band with

at one end of the resistor’s body. The first colored band a plus or minus marking on the body of the capacitors.

represents the resistor’s first digit, while the second Capacitors must be installed properly with respect to color represents the second digit of the resistor’s value.

polarity in order for the circuit to work properly.

The third colored band represents the resistor’s

Failure to install electrolytic capacitors correctly

multiplier value, and the fourth color band represents could cause damage to the capacitor as well as

the resistor’s tolerance value. If there is no fourth to other components in the circuit when power is

colored band then the resistor has a 20% tolerance

first applied.

95

Now look for the lowest profile capacitors from the

You should use IC sockets for all ICs. Integrated

component stack and locate capacitor C1, it is labeled circuit sockets are a low cost form of insurance against (100) or 100 pF. Note that there are a number of small circuit failure at possible later date. Integrated circuits capacitors in the circuit that may not be labeled with their usually have some form of “key” at the top edge of the actual value, so you will have to check Table 12-2 to IC package. This key will either be a small indented

learn how to use the three-digit capacitor code. Go ahead circle at the top left of the IC package or a cut-out at and place C1 on the circuit board and solder it in place.

the top edge of the package. Usually pin 1of the IC is Now take your end-cutters and cut the excess component just to the left of the cut-out or indented circle. Insert leads flush to the edge of the circuit board. Next, locate the ICs carefully into the IC sockets using a grounded the remaining low profile capacitors and install them on anti-static wristband. When installing the transformer the printed circuit board, then solder them in place.

T1, bend the tabs flush against the PC board. The

Remember to trim the extra component leads. There are a audio matching transformer has a “P” indicating the

number of electrolytic capacitors in the circuit and

primary side. The primary mounts towards the outside

placing them in the circuit with respect to their proper of the board. C6 should be mounted vertically with the polarity is essential for proper operation of the circuit.

body in the hold closest to D4. The shields of coils L1

Once you have located the larger electrolytic capacitors and L2 should be soldered to the ground on the circuit install them in their respective locations and solder them board. The FM radio chip should be soldered directly

in place. Finally, trim the excess component leads.

to the PC board. This is a surface mounted component

When installing polarized capacitors be sure to orient so take care in handling this small component. Be sure them so their values can be easily read. This will help to use a small pencil tip soldering and be sure to

if troubleshooting is needed later on.

quickly solder the connections to the PC board. The

LED should be mounted about a 1⁄2′′ away from the PC

The Music-on-Hold circuit uses a number of diodes,

board. Mount D10 flush against the PC board to avoid

including a Zener diode and a Varicap diode. Diodes

stray capacitance. The crystal has no polarity so it can are generally two lead devices which have polarity.

be mounted in either direction. The relays are both the Usually you will find a white or black band at one side same type and are interchangeable.

of the diode package. The colored band denotes the

diode’s cathode lead. When installing the diodes make The following pre-test steps should be done after all sure to observe the correct polarity; failure to do so components have been installed. Check that all

will result in the circuit not working correctly. Note components are mounted in their proper location. Verify that diodes D1 through D9 are convention silicon

polarized components are properly oriented and that all diodes, while D10 is a Varicap diode and D11 is a

pads and connections have been properly soldered and

Zener diode. Locate and install LED1, which is D8

de-fluxed. Once those steps have been completed, you

and located at one end of the transformer and the

can begin bench testing.

junction of R11 and C7. Solder the diodes in their

respective locations and then remember to trim the

Testing and alignment

excess lead with your end-cutters.

The circuit uses a single dual transistor at Q1.

The only instrument needed to test the unit is a DMM.

Transistors are three lead devices, which have a

Connect the power pack or a +15- to +28-V DC power

Collector, a Base and Emitter lead. The base lead is

source to the input. Connect AC power to the power pack.

generally in the input lead which is drawn perpendicular Do not connect the unit to the phone line at this time.

to a vertical line in its symbol. The emitter lead will Once the phone line is connected, dial your own

always have an arrow shown on it. In this project the number to eliminate the signal tone and off-hook

base lead is connected to R9, while the emitter lead is warning tone. Turn the receiver on by depressing

connected and ground and finally the collector lead is pushbutton switch S1. Set the tuning potentiometer to connected to the anode of diode D2. Go ahead and

the extreme counter-clockwise position (low end of the install transistor Q1 and solder it in place, then trim the band). Note that due to the mute function, there is

Chapter Twelve: Hold Circuits and Projects excess leads.

silence until a station is received.

96

Chapter Twelve: Hold Circuits and Projects

Turn the volume control potentiometer (VR1) 1⁄2 to 3⁄4

OUT position (circuit open), music will not be heard

clock-wise. Adjust the slug in L2 until the station

in the handset when the “∗” key is depressed. It will, operating at the lowest dial setting in your area is

however be heard by the caller when the phone is hung received with the loudest audio output. Use care when up. With J1 in the IN position (circuit closed), music adjusting the slug as it is quite delicate and easily will be heard every time the “∗” key is depressed.

broken. Next, set the tuning potentiometer to the

If you would like to connect an external antenna or

extreme clockwise position (top end of the band).

RF source, such as cable, to the tuner, you connect it to Tune back down towards the bottom end of the band

the junction of C20 and C30. It may be advantageous to (counter-clockwise) until the station operating at the disconnect the phone-line antenna by breaking the

highest frequency is received.

connection at C30.

Tune through the entire range to verify all stations

It is easy to use the FM on-hold unit. To place a

available to your area are being received. The receiver caller on hold, press the star “∗” key on any Touch Tone section was designed with a mute function built-in to telephone. That places the unit in a standby mode and allow only the strongest stations to be received. That the LED lights dimly. The telephone must be hung up

makes tuning easier and suppresses images or “ghost”

within four seconds for the caller to be placed on hold.

stations that appear in the wrong part of the tuning dial.

When that is done, the LED lights brightly. If it is not Release the pushbutton and hang up the phone. You can hung up within four seconds, the unit resets itself and check for proper operation by having a friend call and the LED goes out. The caller will be disconnected if the be placed on hold by depressing the star “∗” key.

phone is hung up.

After a caller has been placed on hold, all you have to Installation and use

do is pick up the telephone to return to the conversation (any telephone connected to the line, Touch Tone, or

A special feature of this project allows you to select rotary). When the handset is picked up, the brightly lit when the music is present in the handset. Some

LED will extinguish, the music will go off, and you will telephone services (call waiting, call forwarding, voice be connected to the caller.

mail) require the use of the “∗” key. With J1 in the

97

Chapter 13

Telephone Ringer Projects

C1

470 nF, 250 volt

Parts list

mylar capacitor

C2

10 μF, 15 V

Silent Cell Phone Ringer

electrolytic capacitor

R1

100 K ohm, 1⁄ W,

4

D1, D2

20 V Zener

5% resistor

diodes

R2

3.9 K ohm, 1⁄ W,

4

D3, D4

1N4007 silicon

5% resistor

diodes

R3

1 megohm, 1⁄ W,

4

D5, D6

1N4007 silicon

5% resistor

diodes

C1, C2

100 nF, 63 V

D7

super bright red LED

polyester capacitor

D8

12 V Zener diode

C3

220 μF, 25 V

electrolytic capacitor

BZ

12 V electronic

buzzer

D1

ultra¯bright LED

J1

RJ

D2

BAT42 schottky

¯11 PC board type

¯

telephone socket

barrier diode or

1N5819 diode

Misc

PC board, wire,

IC socket, hardware,

Q1

BC547 NPN transistor

connectors, enclosure,

U1

TS555CN or 7555 CMOS

etc

timer IC

Kit is available from

L1

sensor coil –

Velleman, Inc

130–150T of .2 mm

Kit - K8087

enameled wire

(see text)

Telephone Ring Detector

B1

1.5 volt AAA battery

R1

1 megohm, 1⁄ W,

2

5% resistor

Misc

PC board, wire,

IC socket, enclosure,

R2

2.2 K ohm, 1⁄ W,

4

battery holder/

5% resistor

clip, etc.

R3

15 K ohm, 1⁄ W,

4

Remote Telephone Ringer

5% resistor

R1

1 megohm, 1⁄ W,

R4

100 K ohm, 1⁄ W,

2

4

5% resistor

5% resistor

R2

2.2 K ohm, 1⁄ W,

R5

1 K ohm, 1⁄ W,

4

4

5% resistor

5% resistor

98

Copyright © 2009 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Chapter Thirteen: Telephone Ringer Projects

C1

470 nF, 250 volt

R7

10 K ohms, 1⁄ W,

4

mylar capacitor

5% resistor

C2

100 μF, 25 V

R8

4.7 K ohms, 1⁄ W,

4

electrolytic capacitor

5% resistor

C3

47 μF, 25 V

R9

100 K ohms, 1⁄ W,

4

electrolytic capacitor

5% resistor

D1, D2

20 volt Zener

R10, R11

4.7 K ohms,

diodes

1 W, 5% resistor

D3, D4

1N4007 silicon

R12

5-10 K ohms, 1 W,

diodes

5% resistor (see text)

D5, D6, D8

1N4007

R13

1 megohm, 1⁄ W,

4

silicon diodes

5% resistor

D7

super bright red LED

C1

6,800 pF, 35 V

D9

1N4148 silicon diode

ceramic or mylar

capacitor

Q1

BC557 PNP transistor

C2, C10, C12

.1 μF,

U1

4N27 opto¯coupler IC

35v ceramic capacitor

J1

RJ¯11 PC board type

telephone socket

C3, C11

.001 μF, 35 V

ceramic capacitor

J2

coaxial switched

power jack

C4

22 pF, 35 V NPO

ceramic capacitor

RY1

VR15M121C – SPDT -

12 V DC - 360 ohm -

C5

47 pF, 35 V NPO

PC board type relay

ceramic capacitor

Misc

PC board, wire,

C6

2.2 μF, 250 V mylar

IC socket, hardware,

capacitor

enclosure, etc

C7

33 μF, 35 V

Ext

12 V - 100 mA—

electrolytic capacitor

“wall¯wart” power

C8

.47 μF, 35 V

supply

ceramic capacitor

Kit is available from

C9

10 pF, 35 V NPO

Velleman, Inc

ceramic capacitor

Kit - K8086

D1, D2

1N4148 silicon

Wireless Telephone

diode

Ringer

Q1

2N2646 uni¯junction

R1

68 K ohms, 1⁄ W,

transistor

4

5% resistor

Q2, Q3

2N5179 NPN RF

R2

150 ohms, 1⁄ W,

silicon transistor

4

5% resistor

Q4

2N6659 N¯Channel

R3, R5

47 K ohms, 1⁄ W,

Field

4

¯Effect

5% resistor

transistor

R4, R6

1 K ohms, 1⁄ W,

Q5

2N2907 PNP silicon

4

5% resistor

transistor

99

U1

HCPL¯3700

D1, D2, D3, D4

1N4004

Opto¯Coupler IC

silicon diode

B1

9¯V transistor radio

Q1

2N3053 transistor

battery

NPN

L1

inductor hand¯wound

Q2

TIP47 or NTE287

(see text)

transistor NPN

S1

SPST switch

Q3, Q6, Q7, Q8

NTE287

Misc

PC board, whip

transistor NPN

antenna, enclosure,

Q4, Q5

NTE288

battery clip,

transistor PNP

hardware, etc.

U1

74HC14 IC

Telephone Ring Generator

L1

10 mH coil

R1

150 K ohm 1⁄ W,

4

S1

momentary pushbutton

5% resistor

switch

R2

100 ohm 1⁄ W,

4

Misc

PC board, wire,

5% resistor

connectors, chassis

R3, R13, R14

470 ohm

box, etc.

1

⁄ W, 5% resistor

2

R4

75 ohm 1⁄ W,

4

5% resistor

Project 1: Silent Cellular

R5, R7, R8

10 K ohm

1

⁄ W, 5% resistor

Phone Ringer

4

R6

300 K ohm 1⁄ W,

4

The Silent Cellular Phone Ringer is a novel yet simple 5% resistor

circuit designed to work with your personal cell phone.

R9

50 K ohm trim

Suppose you are in an important meeting, at the doctor’s potentiometer

office, and it is not permitted to have your cell ring in R10

22 K ohm 1⁄ W,

public. This circuit will allow you to monitor a cell 4

5% resistor

phone quietly or remotely when silence is needed.

R11, R12, R15, R16

The heart of the Silent Cell Phone Ringer circuit is the 1 K ohm 1⁄ W,

integrated circuit (IC) at U1, which is shown in Figure 13-1.

2

5% resistor

The circuit is designed to detect when an incoming

C1

.01 μF, 35 V

cellular phone is arriving but will alert you silently via ceramic disk capacitor

an LED. This circuit must be placed within 6′′ or so

from your cell phone, so its sensor coil at L1 can detect C2, C3

1,000 μF,

the field emitted by the cell phone receiver during an 35 V electrolytic

incoming call.

capacitor

The signal detected by the sensor coil is amplified by C4

22 μF, 35 V

transistor Q1 and drives the mono-stable input if U1.

electrolytic capacitor

The integrated circuit’s output voltage is doubled by C2

C5

4 μF, 35 V

and D2 in order to drive the high efficiency ultra-bright electrolytic capacitor

LED at a suitable peak-voltage. The Silent Cell Phone C6

1 μF, 35 V

Ringer circuit is powered by a single 1.5-V battery. The Chapter Thirteen: Telephone Ringer Projects

electrolytic capacitor

circuit draws less than 200 μA, so no power on-off

100

Chapter Thirteen: Telephone Ringer Projects

D1

Circuit assembly

R2

R3

Before we begin building the Silent Cellular Phone

R1

8

4

C3

2

+

Ringer, you will need to locate a clean, well-lit

+

U1

3

B1

worktable or workbench. Next we will gather a small

C1

7

6

1

25–30-W pencil tipped soldering iron, a length of 60/40

tin–lead solder, and a small canister of Tip Tinner

Q1

L1

C2

D2

available at your local RadioShack store; Tip Tinner is used to condition the soldering tip between solder

joints. You drive the soldering tip into the compound and it cleans and prepares the soldering tip. Next grab a few small hand tools; try and locate small flat blade Figure 13-1

Silent Cellular Phone Ringer (Courtesy

and Phillips screwdrivers. A pair of needle-nose pliers, Redcircuits.com)

a pair of tweezers along with a magnifying glass, and a pair of end-cutters and we will begin constructing the switch was used. Sensitivity of the circuit depends on project. Now locate your schematic diagram and parts

the sensor coil. The sensor Coil L1 consists of 130 to layout diagram along with all of the components needed 150 turns of .2 mm enameled wire on a 5 cm diameter

to build the project. Once all the components are in

form. The coil is an air core type, so you will have to front of you, you can check them off against the project remove the form once the coil is constructed. Once the parts list to make sure you are ready to start building the form is removed, wrap the coil in some electrical tape.

project. Now, locate Tables 13-1 and 13-2, and place

You could also elect to use a standard commercial

them in front of you.

10 mH miniature inductor but sensitivity will be

Table 13-1 illustrates the resistor code chart and how to lower. The integrated circuit at U1 must be a CMOS IC

read resistors, while Table 13-2 illustrates the capacitor timer such as a TS555CN or a 7555 which operates

code chart which will aide you in constructing the project.

1.5 V. A BAT46 Schottky-barrier diode should be

used for diode D2, although you could substitute

Refer now to the resistor color code chart shown in

a 1N5819 diode.

Table 13-1, which will assist you in identifying the

Table 13-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

No color

20%

101

Table 13-2

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

1.0

1R0

3,900

3.9

.0039

392

1.2

1R2

4,700

4.7

.0047

472

1.5

1R5

5,600

5.6

.0056

562

1.8

1R8

6,800

6.8

.0068

682

2.2

2R2

8,200

8.2

.0082

822

2.7

2R7

10,000

10

.01

103

3.3

3R3

12,000

12

.012

123

3.9

3R9

15,000

15

.015

153

4.7

4R7

18,000

18

.018

183

5.6

5R6

22,000

22

.022

223

6.8

6R8

27,000

27

.027

273

8.2

8R2

33,000

33

.033

333

10

100

39,000

39

.039

393

12

120

47,000

47

.047

473

15

150

56,000

56

.056

563

18

180

68,000

68

.068

683

22

220

82,000

82

.082

823

27

270

100,000

100

.1

104

33

330

120,000

120

.12

124

39

390

150,000

150

.15

154

47

470

180,000

180

.18

184

56

560

220,000

220

.22

224

68

680

270,000

270

.27

274

82

820

330,000

330

.33

334

100

.0001

101

390,000

390

.39

394

120

.00012

121

470,000

470

.47

474

150

.00015

151

560,000

560

.56

564

180

.00018

181

680,000

680

.68

684

220

.00022

221

820,000

820

.82

824

270

.00027

271

1,000

1

105

330

.00033

331

1,500

1.5

155

390

.00039

391

2,200

2.2

225

470

.00047

471

2,700

2.7

275

560

.00056

561

3,300

3.3

335

680

.00068

681

4,700

4.7

475

820

.00082

821

6.8

685

1,000

1.0

.001

102

10

106

1,200

1.2

.0012

122

22

226

1,500

1.5

.0015

152

33

336

1,800

1.8

.0018

182

47

476

Chapter Thirteen: Telephone Ringer Projects

102

Chapter Thirteen: Telephone Ringer Projects

Table 13-2—cont’d

Three-digit capacitor codes

pF

nF

m F

CODE

pF

nF

m F

CODE

2,200

2.2

.0022

222

68

686

2,700

2.7

.0027

272

100

107

3,300

3.3

.0033

332

157

157

Code = 2 significant digits of the capacitor value + number of zeros to follow 10 pF = 100

For values below 10 pF, use “R” in place of decimal e.g. 8.2 pF = 8R2

100 pF = 101

1,000 pF = 102

22,000 pF = 223

330,000 pF = 334

1 μF = 105

resistor values. Note that each resistor will have either board and remember to trim the excess leads from

three or four color bands, which begin at one end of the the board.

resistor’s body. The first colored band represents the Note that capacitors generally come from two major

resistor’s first digit, while the second color represents groups or types. Non-polar types, such as the ones in the second digit of the resistor’s value. The third colored this project, have no polarity and can be placed in either band represents the resistor’s multiplier value, and the direction on the circuit board. The other type of

fourth color band represents the resistor’s tolerance capacitors are called polarized types, these capacitors value. If there is no fourth colored band then the resistor have polarity and have to be inserted on the board with has a 20% tolerance value. If the resistor’s fourth band respect to their polarity marking in order for the circuit is silver then the resistor has a 10% tolerance value and to operate correctly. On these types of capacitors, you if the fourth band is gold then the resistor’s tolerance will observe that the components actually have a plus or value will be 5%.

minus marking or a black or white band with a plus or So finally we are ready to begin assembling the

minus marking on the body of the capacitors.

project, so let’s get started. The prototype project was constructed on a single-sided printed circuit board or Next, refer to Table 13-2; this chart helps to

PCB; with your PC board in front of you, we can now

determine the value of small capacitors. Many

begin populating the circuit board. We are going to

capacitors are quite small in physical size, so

place and solder the lowest height components first, the manufacturers have devised a three-digit code which

resistors and diodes. First locate our first resistor R1.

can be placed on the capacitor instead of the actual

Resistor R1 has a value of 100 K ohms and is a 5%

value. The code occupies a much smaller space on the

tolerance type. Now take a look for a resistor whose

capacitor and can usually fit nicely on the capacitor first color band is brown, black, yellow, and gold. From body, but without the chart the builder would have a

the chart you will notice that brown is represented by difficult time determining the capacitor’s value.

the digit (1), and the second band is black, which is Now locate the capacitors from the component pile

represented by (0). Notice that the third color is brown and try and locate capacitor C1, which should be

and the multiplier is (10,000), so (1) (0) × 10,000 =

marked with a (104), this capacitor has a 100 nF value.

100,000 ohms.

Now that you can read the resistor and capacitor charts, Go ahead and place R1 on the circuit board and

let’s go ahead and place R1 and C1 on the circuit board solder it in place. Next take your end-cutters and trim and solder them in place. Now take your end-cutters and the excess component leads from the resistor. Locate the cut the excess component leads flush to the edge of the remaining resistors and solder them in place on the

circuit board. Once you have installed the first two

103

components, you can move on to installing the

your enclosure, you may want to leave 1⁄2′′ of lead length remaining resistors and capacitors.

on the diodes.

This project contains Schottky-barrier silicon diode at Finally, it is time to install the coil, L1. Remember D2. These diodes also have polarity, which must be

coil L1 is composed of 130–150 turns of enameled

observed if the circuit is going to work correctly. You wire. The enameled wire has a coating on its entire

will notice that each diode will have a black or white length, so you will have to scrape about a 1⁄8′′ of coating colored band at one edge of the diode’s body. The

off each end of the wire, so you can solder the wire to colored band represents the diode’s cathode lead.

the circuit board. It is usually recommended to mount Check your schematic and parts layout diagrams when

the coil at one end of the circuit board, so it can face installing the diode on the circuit board, then solder it in outwards. Now locate your 1.5-V AAA single cell

place, remembering to cut the excess component leads.

battery holder and mount it in your chosen enclosure

The Silent Cell Phone Ringer circuit also utilizes one and wire the holder to the circuit board.

transistor at Q1, a PNP transistor. These generally have Now that the circuit board has been completed, you

three leads, a Base lead, a Collector lead and an Emitter can take a short well deserved break and when we

lead. Refer to the schematic and you will notice that return we will inspect the circuit board for any “cold”

there will be two diagonal leads pointing to a vertical solder joints or “short” circuits.

line. The vertical line is the transistor’s base lead and Pick up the circuit board with the foil side facing

the two diagonal lines represent the collector and the upwards toward you. First we will attempt to locate any emitter. The diagonal lead with the arrow on it is the cold solder joints on the circuit board. Take a look at all emitter lead, and this should help you install the

the solder joints. The solder joints should all look clean, transistor onto the circuit board correctly. Go ahead bright, and shiny. If any of the solder joints look dark, and install the transistor on the PC board and solder dull, or blobby then you will have to remove the solder it in place, then follow-up by cutting off the excess from the joint with a solder sucker or wick, and

component leads.

re-solder the joint all over again.

The Silent Cellular Phone Ringer circuit contains

Next we will examine the PC board for any possible

a single IC at U1. Note that the IC is a 555 timer,

short circuits. Short circuits can be caused by a solder but it is a low power version of the 555. The IC timer blob bridging across the circuit traces or it could be is a CMOS version of the timer; use a TS555CN or

caused by stray component leads. Often solder can leave 7555 which runs on a single 1.5-V AAA cell. ICs

a sticky residue, and cut component leads can attach

have to be installed in a particular way in order to

themselves to this residue and cause a short between

function properly. You will note that at the top end

circuit traces. Look carefully for any solder blobs or of the package, you will see a small cutout of notch.

stray leads bridging the circuit traces. When everything Pin 1 will be just to the left of this notch. When

looks good, you can move on to mounting the circuit

installing the IC pay close attention to orienting the into your favorite enclosure.

chip correctly and refer to the schematic and parts

layout diagrams. It would be very prudent to install

an IC socket for the timer IC, in the unlikely event

Operation

of a circuit failure. It is much easier to simply unplug an IC rather than trying to unsolder a number of

Once the circuit has been inspected, you can mount it in pins from the circuit board in the event of a

a plastic enclosure, and you must use a plastic enclosure circuit failure.

since metal would block the radio waves between the

When installing the indicator LED, D1, be sure to

phone and your ringer circuit. Once the circuit is

pay particular attention to the orientation. The symbol mounted, insert an AAA battery into the battery holder for an LED is a diode, it therefore has an anode and

to apply power to the circuit. Place the Silent Cellular cathode. Usually the anode lead is longer and this will Phone Ringer close to your cell phone and have

help orient the LED when mounting it on the PC board.

someone call your cell phone. Once the cell phone rings Chapter Thirteen: Telephone Ringer Projects Depending upon how you mount the circuit board in the LED on your Silent Cellular Phone Ringer should

104

Chapter Thirteen: Telephone Ringer Projects

begin blinking. By letting the phone ring for a

while you can experiment with the distances between

the cell phone and your Silent Cellular Phone

Ringer circuit.

In the event that your circuit does not function, you will have to remove power and once again inspect the

circuit board for any errors. The most common errors

for circuit failure include improper orientation of

electrolytic capacitors, diodes, and semiconductors such as transistors.

Another cause for failure is the incorrect orientation on any integrated circuits. Once you have carefully

re-inspected the circuit board, you can apply power

and re-test the circuit all over again.

Have fun using your new Silent Cellular Phone

Ringer circuit. The Silent Cell Phone Ringer is ideal for those important business meetings or for when the baby is sleeping.

Figure 13-2

Remote telephone ring indicator.

Project 2: Remote

Courtesy of Velleman Kits

telephone ringer –

w/buzzer and LED

to a 1 megohm resistor in parallel with a 470 nF

capacitor. The ring signal is then passed on through two 20-V Zener diodes; back-to-back in series with a

The Remote Telephone Ringer project is illustrated in 2.2 K ohm resistor. Resistor R2 is next coupled to a

Figure 13-2. This handy circuit can be placed in a

diode bridge consisting of diodes D3 through D6. The

remote location such as a garage or patio to alert

diode bridge converts the AC ringing signal to a DC

you of an incoming telephone call. It could also be

output to drive the LED on and off with the ringing

used to alert you of an incoming call with the buzzer pulses. The output of the LED is then passed on to a

off when someone is sleeping. The remote ringer

12-V Zener diode which limits the voltage to

project is great for noisy environments, for the hearing the buzzer at BZ. A filter capacitor is placed across the impaired, as additional ringer, or to replace an existing buzzer leads to help smooth the voltage signal to the ringer. The Remote Telephone Ringer is simply

DC powered buzzer. The plus lead of the buzzer is

connected in parallel with the phone line and requires connected to the plus side of the filter capacitor, while no external power supply, and consumes a modest

the minus lead of the buzzer goes to ground.

10 mA from the phone line. The circuit simply

plugs into a standard RJ-11 telephone jack at any

location.

Circuit assembly

The clever ringer/flasher circuit shown in Figure 13-3

Before we begin building the Remote Telephone Ringer, plugs into any RJ-11 phone jack and will alert you

let’s first find a clean, well-lit worktable or workbench.

when the phone is ringing with a bright LED and

Next we will gather a small 25–30-W pencil tipped

electronic buzzer.

soldering iron, a length of 60/40 tin–lead solder, and a The circuit begins at the RJ-11 phone jack at the left small canister of Tip Tinner, available at your local of the diagram. Pin 4 of the phone jack is first coupled RadioShack store; Tip Tinner is used to condition the 105

R1

J1

RJ11

D1

D2

4

R2

D3

3

D4

2

1

C1

BZ

+

Phone

jack

D7

+

−

D6

D5

D8

C2

Figure 13-3

Remote telephone ringer with LED and buzzer. Courtesy of Velleman Kits soldering tip between solder joints. You drive the

constructed on a single-sided printed circuit board or soldering tip into the compound and it cleans and

PCB. With your PC board in front of you, we can now

prepares the soldering tip. Next grab a few small hand begin populating the circuit board. We are going to

tools, try to locate small flat blade and Phillips

place and solder the lowest height components first, the screwdrivers. A pair of needle-nose pliers, a pair of resistors and diodes. First locate our first resistor R1.

tweezers along with a magnifying glass, and a pair of Resistor R1 has a value of 1 megohm and is a 5%

end-cutters and we will begin constructing the project.

tolerance 1⁄2-W type. Now take a look for a resistor

Now locate your schematic diagram and parts layout

whose first color band is brown, black, green, and gold.

diagram along with all of the components needed to

From the chart you will notice that brown is represented build the project. Once all the components are in front by the digit (1), the second band is black, which is

of you, you can check them off against the project parts represented by (0). Notice that the third color is green list to make sure you are ready to start building the and the multiplier is (100,000), so (1) (0) × 100,000 =

project. Now, locate Tables 13-1 and 13-2, and place

1,000,00 or 1 megohm.

them in front of you.

Go ahead and install R1 on the circuit board and

Table 13-1 illustrates the resistor code chart and

solder it in place in its respective position. Locate your how to read resistors, while Table 13-2 illustrates the end-cutters and trim the excess component leads. Cut

capacitor code chart which will aid you in constructing the excess leads flush to the edge of the circuit board.

the project.

Now locate the remaining resistors and place them on

the circuit board and solder them in place, remembering Refer now to the resistor color code chart shown in

to trim the excess component leads with your

Table 13-1, which will help you to identify the resistor end-cutters.

values for the project. Note that each resistor will have either three or four color bands, which begin at one end Note that capacitors generally come from two major

of the resistor’s body. The first colored band represents groups or types. Non-polar types, such as the ones in the resistor’s first digit, while the second color

this project, have no polarity and can be placed in either represents the second digit of the resistor’s value. The direction on the circuit board. The other type of

third colored band represents the resistor’s multiplier capacitors are called polarized types; these capacitors value, and the fourth color band represents the resistor’s have polarity and have to be inserted on the board with tolerance value. If there is no fourth colored band then respect to their polarity marking in order for the circuit the resistor has a 20% tolerance value. If the resistor’s to operate correctly. On these types of capacitors, you fourth band is silver then the resistor has a 10%

will observe that the components actually have a plus or tolerance value and if the fourth band is gold then the minus marking or a black or white band with a plus or resistor’s tolerance value will be 5%.

minus marking on the body of the capacitors.

Finally, we are ready to begin assembling the project, Next refer to Table 13-2; this chart helps to determine Chapter Thirteen: Telephone Ringer Projects so now let’s get started. The prototype project was the value of small capacitors. Many capacitors are quite 106

Chapter Thirteen: Telephone Ringer Projects

small in physical size, so manufacturers have devised a Since the circuit is telephone line powered, you will not three-digit code which can be placed on the capacitor have to worry about powering the circuit.

instead of the actual value. The code occupies a much Once all the components have been mounted and

smaller space on the capacitor and can usually fit

soldered on to the circuit board, you can take a short nicely on the capacitor body, but without the chart the break and when we return, we will inspect the circuit builder would have a difficult time determining the

board for any possible “cold” solder joints and “short”

capacitor’s value.

circuits. Pick up the circuit board with the foil side Now locate the capacitors from the component pile

facing upwards toward you. Take a close look at the

and try and locate capacitor C1, which should be

solder joints. They should all look clean, bright, and marked with a three-digit code marked (474) or 470 nF.

shiny. If any of the solder joints look dull, dark, or Capacitor C1 will be rated at 250 V, and may be

blobby then you should remove the solder from the joint somewhat large. Next locate C2, a 10 μF electrolytic

with a solder sucker or wick and resolder the joint all capacitor. Now, let’s go ahead and place C1 and C2

over again.

on the circuit board and solder them in place. Now

Now, let’s move to inspect the circuit board for any

take your end-cutters and cut the excess component

possible short circuits. Short circuits can be caused from leads flush to the edge of the circuit board. Once you solder blobs bridging across the circuit traces or from have installed the first two components, you can move stray component leads bridging across the circuit traces.

on to installing the remaining components. Remember

Solder residue often traps cut component leads to the to trim the excess component leads after the solder

foil side of the PC board; unchecked, this could cause joints are completed.

damage to the circuit if not removed before power is

applied to the circuit for the first time. Now we are The Remote Telephone Ringer project utilizes two

ready to install the circuit board into the enclosure of 20-V and one 12-V Zener diode. The project also

your choice. Mount the circuit board at the bottom of contains four silicon diodes at D3 through D6. Diodes your chassis box, on 1⁄4′′ standoffs. Mount the circuit have polarity which must be observed if the circuit is board at one edge of the enclosure, so that the telephone going to work correctly. You will notice that each diode jack can protrude from the case. If you chose to use a will have a black or white colored band at one edge of non-PC board type buzzer, then you will have to mount the diode’s body. The colored band represents the

the buzzer on the front panel of the enclosure. Mount diode’s cathode lead. Check your schematic and parts

the super bright LED, on the front panel of the case, so layout diagrams when installing these diodes on the

that it can protrude from the case

circuit board. Place all the diodes on the circuit board and solder them in place on the PC board. Then cut the excess component leads with your end-cutters flush to Operation

the edge of the PC board.

Once your circuit is mounted in your favorite enclosure The Remote Telephone Ringer circuit employs a

and the circuit attached to the phone line, you are ready single super bright LED at D7. Note that the symbol for to test the circuit. Remember, the phone line has a

an LED is similar to a diode which has two leads, a

polarity and it will affect how the circuit operates.

cathode lead and an anode lead. The cathode lead will Connect the Remote Phone Ringer to the phone line in

be the shorter of the two leads and schematically is the your chosen area and then have someone call your

flat line in the symbol.

telephone number and listen for the Remote Ringer

Finally, you can go ahead and mount the PC type

circuit to come alive. In the event that the circuit does Piezo buzzer on the circuit board. Pay close attention to not work immediately, you will have to first check the the pinouts on the Piezo buzzer, one lead will be the polarity of the phone line connection or possibly

plus or red lead, while the other lead is the ground or recheck the circuit for any errors. The most common

minus lead. In order for the circuit to work properly, the reason for circuit failure is improper orientation of the plus buzzer lead must be connected to the cathodes

electrolytic capacitors, diodes, and semiconductors

of D7 and D8 and to the plus side of capacitor C2.

such as transistors and of course ICs. Recheck your

107

circuit carefully and once inspected and errors fixed, capacitor. The ring signal is then passed on through

you install the circuit into its enclosure and retest 22-V Zener diodes; back-to-back in series with a

the circuit. Now you can go ahead and install the

2.2 K ohm resistor. Resistor R2 is next coupled to a

Remote Telephone Ringer in your shop, barn or

diode bridge consisting of diodes D3 through D6. The

basement.

diode bridge converts the AC ringing signal to a DC

output to drive the LED on and off with the ringing

pulses. The output of the bright LED is then passed

on to an LED driver in an opto-coupler IC. The LED

Project 3: Telephone ring

inside the opto-coupler activates the NPN transistor

detector – w/LED and

when the phone signal is present. The more powerful the transistor inside the opto-coupler drive, the more powerful relay output

the switching transistor at Q1, which in turn operates the relay at RLY1. Power for Q1 and the relay are provided The Telephone Ring Detector project is illustrated in by a 12-V DC, 100 mA “wall-wart” power supply cube.

Figure 13-4; this handy circuit can be placed anywhere If jumper J1 is installed the relay will be operated on a to alert you of an incoming telephone call with both

continuous basis, if the jumper is left open the relay LED and relay control which can be used to drive a

closes when the phone line rings. The relay used has both siren, load noise maker, or strobe light.

normally open and normally closed contacts which can be The Telephone Ring Detector project is great for

wired in series with an external power supply used to noisy environments, for the hearing impaired, as an

drive a siren, bell, or strobe lamp if desired.

additional ringer, or to replace an existing ringer.

The Telephone Ring detector is connected in parallel

Circuit assembly

with the phone line at any location that uses a standard RJ-11 telephone jack. Power to the ring detector circuit Before we begin building the Telephone Ring Detector

is provided by a 12-V external power supply.

circuit, let us first find a clean, well-lit worktable or The clever Ring Detector circuit shown in Figure 13-5

workbench. Next we will gather a small 25–30-W

plugs into any RJ-11 phone jack and will alert you when pencil tipped soldering iron, a length of 60/40 tin–lead the phone is ringing with a bright LED and relay control solder, and a small canister of Tip Tinner, available at which can be used to control a siren, strobe lamp,

your local RadioShack store; Tip Tinner is used to

or loud bell.

condition the soldering tip between solder joints. You The circuit begins at the RJ-11 phone jack at the left drive the soldering tip into the compound and it cleans of the diagram. Pin 3 of the phone jack is first coupled and prepares the soldering tip. Next grab a few small to a 1 megohm resistor in parallel with a 470 nF

hand tools; try and locate small flat blade and Phillips screwdrivers. A pair of needle-nose pliers, a pair of tweezers along with a magnifying glass, and a pair of end-cutters and we will begin constructing the project.

Now locate your schematic diagram and parts layout

diagram along with all of the components needed to

build the project. Once all the components are in front of you, you can check them off against the project parts list to make sure you are ready to start building the project. Now, locate Tables 13-1 and 13-2, and place

them in front of you.

Table 13-1 illustrates the resistor code chart and

how to read resistors, while Table 13-2 illustrates the Figure 13-4

Remote telephone ring relay controller.

capacitor code chart which will aid you in constructing Chapter Thirteen: Telephone Ringer Projects Courtesy of Velleman Kits the project.

108

Chapter Thirteen: Telephone Ringer Projects

J2

D8

+

+ C2

R4

R1

DC Input

RJ-II

D1

D2

R3

Q1

R2

D3

4

D4

3

2

1

C1

RLY1

J1

R5

J1

Phone

D7

Output

1

6

5

Jack

N/O

D6

D5

C3

+

2

4

D9

N/C

UI

C3

Figure 13-5

Telephone ring detector with LED and relay control. Courtesy of Velleman Kits Refer now to the resistor color code chart shown in

end-cutters and trim the excess component leads. Cut the Table 13-1, which will help you to identify the resistor excess leads flush to the edge of the circuit board. Now values for the project. Note that each resistor will have locate the remaining resistors and place them on the

either three or four color bands, which begin at one end circuit board and solder them in place, remembering to of the resistor’s body. The first colored band represents trim the excess component leads with your end-cutters.

the resistor’s first digit, while the second color

Note that capacitors generally come from two major

represents the second digit of the resistor’s value. The groups or types. Non-polar types, such as the ones in third colored band represents the resistor’s multiplier this project, have no polarity and can be placed in either value, and the fourth color band represents the resistor’s direction on the circuit board. The other type of

tolerance value. If there is no fourth colored band then capacitors are called polarized types, these capacitors the resistor has a 20% tolerance value. If the resistor’s have polarity and have to be inserted on the board with fourth band is silver then the resistor has a 10%

respect to their polarity marking in order for the circuit tolerance value and if the fourth band is gold then the to operate correctly. On these types of capacitors, you resistor’s tolerance value will be 5%.

will observe that the components actually have a plus or Finally, we are ready to begin assembling the project, minus marking or a black or white band with a plus or so now let’s get started. The prototype project was

minus marking on the body of the capacitors.

constructed on a single-sided printed circuit board or PCB. With your PC board in front of you, we can now

Next refer to Table 13-2; this chart helps to determine begin populating the circuit board. We are going to

the value of small capacitors. Many capacitors are quite place and solder the lowest height components first, the small in physical size, so manufacturers have devised a resistors and diodes. First locate our first resistor R1.

three-digit code which can be placed on the capacitor Resistor R1 has a value of 1 megohm and is a 5%

instead of the actual value. The code occupies a much tolerance 1⁄

smaller space on the capacitor and can usually fit

2-W type. Now take a look for a resistor

whose first color band is brown, black, green, and gold.

nicely on the capacitor body, but without the chart the From the chart you will notice that brown is represented builder would have a difficult time determining the

by the digit (1), the second band is black, which is

capacitor’s value.

represented by (0). Notice that the third color is green Now locate the capacitors from the component pile

and the multiplier is (100,000), so (1) (0) × 100,000 =

and try and locate capacitor C1, which should be

1,000,00 or 1 megohm.

marked with a three-digit code marked (474) or 470 nF.

Go ahead and install R1 on the circuit board and

Capacitor C1 will be rated at 250 V, and may be

solder it in place in its respective position. Locate your somewhat large. Next locate C2 and C3. Now, let us go 109

ahead and place C1, C2, and C3 on the circuit board

PC board without damaging the board. ICs have

and solder them in place. Now take your end-cutters and to be installed correctly if the circuit is going to work cut the excess component leads flush to the edge of the properly. IC packages will have some sort of markings circuit board. Once you have installed the first two

which will help you orient them on the PC board. An IC

components, you can move on to installing the

will have either a small indented circle, a cut-out or notch remaining components. Remember to trim the excess

at the top end of the IC package. Pin 1 of the IC will be component leads after the solder joints are completed.

just to the left of the notch, or cutout. Refer to the manufacturer’s pin-out diagram, as well as the schematic The Telephone Ring Detector project utilizes two

when installing these parts. If you doubt your ability 20-V and one 12-V Zener diode. The project also

to correctly orient the ICs, then seek the help of a

contains six silicon diodes at D3 through D6, as well as knowledgeable electronics enthusiast to help you.

D8 and D9. Diodes have polarity, which must be

observed if the circuit is going to work correctly. You The Telephone Ring Detector circuit employs a single

will notice that each diode will have a black or white super bright LED at D7. Note that the symbol for an

colored band at one edge of the diode’s body. The

LED is similar to a diode which has two leads, a

colored band represents the diode’s cathode lead. Check cathode lead and an anode lead. The cathode lead will your schematic and parts layout diagrams when

be the shorter of the two leads and schematically is the installing these diodes on the circuit board. Place all the flat line in the symbol.

diodes on the circuit board and solder them in place on Finally, you can go ahead and mount the PC type

the PC board. Then cut the excess component leads with relay on the circuit board. Pay close attention to the your end-cutters flush to the edge of the PC board.

pinouts when installing the relay, do not mix-up the coil The Telephone Ring Detector utilizes single

and the contact pins.

conventional transistor. Transistors are generally three Once all the components have been mounted and

lead devices, which must be installed correctly if the soldered on to the circuit board, you can take a short circuit is to work properly. Careful handling and proper break and when we return, we will inspect the circuit orientation in the circuit is critical. A transistor will board for any possible “cold” solder joints and “short”

usually have a Base lead, a Collector lead, and an

circuits. Pick up the circuit board with the foil side Emitter lead. The base lead is generally a vertical line facing upwards toward you. Take a close look at the

inside a transistor circle symbol. The collector lead is solder joints. They should all look clean, bright, and usually a slanted line facing towards the base lead and shiny. If any of the solder joints look dull, dark, or the emitter lead is also a slanted line facing the base blobby then you should remove the solder from the joint lead but it will have an arrow pointing towards or away with a solder sucker or wick and resolder the joint all from the base lead. Now, identify the two transistors, over again.

refer to the manufacturer’s specification sheets as well Now, let’s move to inspect the circuit board for any

as the schematic and parts layout diagrams when

possible short circuits. Short circuits can be caused from installing the two transistors. If you have trouble

solder blobs bridging across the circuit traces or from installing the transistors, get the help of an electronics stray component leads bridging across the circuit traces.

enthusiast with some experience. Install the transistors Solder residue often traps cut component leads to the in their respective locations and then solder.

foil side of the PC board; unchecked, this could cause The ring detector circuit contains an ICs opto-damage to the circuit if not removed before power is

coupler, at U1. Integrated circuits are often static

applied to the circuit for the first time. Now we are sensitive, so they must be handled with care. Use a

ready to install the circuit board into the enclosure of grounded anti-static wriststrap and stay seated in one your choice. Mount the circuit board in the bottom of location when handling the ICs. Take out a cheap

the chassis box using 1⁄4′′ plastic standoffs. Mount the insurance policy by installing IC sockets for each of circuit board so the RJ-11 phone jack is closest to one the ICs. In the event of a possible circuit failure, it is end of the box, so that you can cut a hole for the jack to much easier to simply unplug a defective IC, that

protrude. Next install the coaxial power jack; if you Chapter Thirteen: Telephone Ringer Projects trying to unsolder 14 or 16 or more pins from a chose to use a chassis mounted jack, then you will have 110

Chapter Thirteen: Telephone Ringer Projects

to line up the jack with the hole drilled on the side or rear of the chassis box. You can install an RCA jack or screw terminals for the relay output pins on the rear of the chassis box. You can install the LED on the front panel of the chassis box if desired.

Operation

Once your circuit is mounted in your favorite enclosure and attached to the phone line, you are ready to test the circuit. Remember, the phone line has a polarity and

this will affect how the circuit operates. Connect the Telephone Ring Detector to the phone line in the area of your choice and apply power to the ring detector circuit.

Next, have someone call your telephone number, then

listen and watch for the telephone ring circuit to come alive. In the event that the circuit does not work

Figure 13-6

Wireless telephone ringer. Courtesy of

immediately, you will have to first check the polarity of CQ Communication

the phone line connection or possibly recheck the

circuit for any errors. The most common reason for

circuit failure is improper orientation of the electrolytic Only one radio is needed in any given installation, but capacitors, diodes, and semiconductors such as

because this is an RF transmitter project, any number of transistors and of course integrated circuits. Recheck you radios can be used if more than one person wants to

circuit carefully and once inspected and errors fixed, you listen for an incoming call signal from different remote can install the circuit into its enclosure and retest the locations. Transmitter power from the Ringer is low

circuit. Now you can go ahead and install the Telephone enough so that the project will not interfere with your Ring Detector in your shop, barn or basement, or

neighbors’ FM reception.

anywhere you like, for long reliable operation.

Totally automatic in operation, this project does not even require a power switch, though you can include

one to permit you to turn it off when it will not be used Project 4: Wireless

for weeks or months at a time.

telephone ringer

Circuit description

This poor man’s cordless telephone works with an

FM radio to remotely signal when your wired telephone The Wireless Telephone Ringer schematic is shown

rings. A cordless telephone is a useful consumer

in Figure 13-7. The cordless telephone transmitter

electronic device. Though it lets you originate calls, its consists of a telephone ring signal detector U2,

major benefit is in alerting you to incoming calls when which is followed by a two stage transmitter

you are not near enough to a wired tone to hear it ring.

consisting of Q2 and Q3 that operates on the 88 to

If the alert feature is all you really need, the Wireless l08 MHz FM broadcast band. The transmitter’s

Telephone Ringer presented will do the job

carrier frequency is modulated by uni-junction

inexpensively, though you will have to get to a wired transistor oscillator Q1, whose operating frequency

phone to answer the call (see Figure 13-6).

is set at about 2 KHz.

This Wireless Ringer is easy to build because the

Power for the transmitter and audio oscillator

“receiver” section already exists. It is an ordinary

is provided by 9-V battery B1. This battery is

portable FM radio that can be picked up for $10 or less.

automatically switched through to the project’s circuits 111

9 V

B1

Telephone

+

line

Antenna

S2

Q5

S1

e

c

C10

PWR

R9

C6

L1

b

R5

R6

C11

C12

R1

R3

R11

R10

R7

R8

c

b

R12

8

Q1

e

D1

1

Q2

Q4

C9

B2

c

Q3

D2

b

6

UI

4

G

B1

e

C4

C2

2 3

5

R13

C7

C8

C1

R4

R2

C3

C5

Figure 13-7

Wireless telephone ringer. Courtesy of CQ Communications to deliver current only in the presence of the ring signal Uni-junction transistor Q1 is connected into the

that announces an incoming call. Current demand from

circuit to forma free running relaxation oscillator. When the battery is very modest. Because of the automatic

9-V DC power is applied to the circuit, CI charges up at power-up feature, useful battery life should therefore be a rate determined by the RC time constant of R1

extremely long.

and C1. When the potential across C1 reaches about

50% of the supply voltage, Q1 suddenly conducts and

Transistor Q2 and its associated components make

dumps most of the charge on C1 into R2.

up a traditional grounded base Colpitts oscillator

whose frequency of oscillation is determined by the

Now partially discharged, C1once again begins to

values of L1, C4, and C5. To meet the criteria to

charge, as it did initially, until Q1 breaks into

sustain oscillation, it is necessary that the base and conduction and dumps the charge into R2. This

collector of the transistor be connected to opposite

charge/discharge action repeats at the rate of about

ends of an LC tank circuit, with the transistor’s emitter 2,000 times per second for as long as power is applied connected somewhere between these two points. In the

to the circuit.

circuit, this is accomplished by placing the base of

When Q1 conducts, a voltage spike appears across

Q2 at RF ground potential by means of C3 and the

R2 as a result of the discharge action of C1. This

emitter about one-third the way up from ground,

voltage is capacitively coupled, via C2, to the base of which is accomplished through the voltage divider

Q2 and causes a very slight variation in this transistor’s action of C4 and C5.

operating current at the 2 KHz audio-frequency rate at A traditional Colpitts oscillator has two capacitors

which Q1 is operating. As a result, the frequency of

connected in series with each other to form the voltage operation of Q2 is modulated so that its output signal, divider needed in an oscillator circuit of this type.

amplified by Q3 and radiated by the antenna, can be

Contrast this to the Hartley oscillator, which is similar detected by the discriminator circuit in any FM radio or in design to the Colpitts oscillator, except that a tapped receiver that is within range and is tuned to the project’s inductor is used to provide voltage division. Transistor carrier frequency. When this signal is detected, the

Q2 is forward biased by R3 to sustain oscillation when FM radio will produce a pulsed 2 KHz tone to inform

Chapter Thirteen: Telephone Ringer Projects power is applied to the circuit.

you that your telephone is ringing.

112

Chapter Thirteen: Telephone Ringer Projects

IC U1 is a special opto-coupler device, which is

in the transmitter. When closed, this switch applies

utilized as a telephone ring signal detector to respond to forward-bias to Q4 without the need for the ring signal the pulses on the telephone line to which it is connected.

to be present. Pressing S1 verifies the operating

Contained inside this chip are a bridge rectifier, 5-V

condition of the transmitter by allowing you to listen regulator, and transient suppression circuits that prevent for the 2-KHz tone (this time continuous as long as

damage to the IC and false operation in the event of a S1 is closed) in the FM radio being used as the

random voltage spike on the telephone line.

system’s receiver.

During standby, U1 presents a high impedance to the

telephone line and does not affect either outgoing or incoming calls. When the 90-V, 20-Hz ring signal

Construction

appears across the line to announce an incoming call, the energy of the incoming signal triggers the opto-Since this project operates in the VHF radio range, it is coupler and +5 V DC appears at the output of U1 at

important that you adhere to RF construction techniques pin 6. This regulated voltage is then fed to the gate of to obtain proper operation. Printed circuit board wiring, enhancement mode N-channel field effect transistor Q4.

therefore, is mandatory. The PC board must be copper

clad on both sides. One side has no copper removed

Transistors Q4 and Q5 and their associated circuitry

from it during the etching process (except for small

make up an automatic electronic switch that permits

areas, which will be discussed presently), while the

current from B1 to flow to the rest of the project’s

other is etched to remove all copper from it except as circuitry only in the presence of the telephone ring

needed for interconnecting conductors. The solid copper signal. At all other times, the switch “opens” and

side of the board serves as both an RF ground plane and disconnects the battery from the circuit.

circuit, common to which all grounded component leads Battery voltage is fed to the emitter of Q5, which

are to be soldered. You can fabricate your own printed cannot conduct current until its base is forward-biased.

circuit board.

During standby, Q4’s gate-to-source voltage is zero

If you fabricate your own board, be sure to first coat because U1 is idle and thus is delivering no voltage to one entire side with etch resist or mask it with tape to the circuit. The drain-to-source resistance of Q4 is

prevent the etchant from eating away any copper. After essentially infinite under this condition, so no base or etching the board to bring out the required copper trace collector current flows through Q5. An output or load pattern, remove the etch resist (or tape) from both sides resistor was placed between the output pin 6 and pin 8.

of it. Then drill all component lead holes, as indicated This resistor should have a value between 5 K and

by the solder pad centers. Though you do not etch the 10 K ohms for best results.

top (ground plane) side of the board, you must still

When Q4 is switched on by the voltage that appears

clear copper from around all holes through which

at its gate in response to the ring signal, this transistor’s component leads must pass and are not to connect drain-to-source resistance becomes almost zero,

to the ground plane.

allowing base current to flow out of Q5 and causing this Use about a 1⁄16′′ drill bit to remove about a

transistor to saturate. This places almost the full battery 1⁄8′′ diameter circle of copper around each indicated voltage in the collector of Q5 and allows the transmitter hole. After placing the bit in the hole, gently rotate to operate.

it by hand to clear way the copper. Do not use a power Since the time constant of C8 and R11 is relatively

or pin drill for this operation; the danger of accidentally short, Q4 operates only during each two second burst of drilling clear through and ruining the board is too great.

ring-signal energy produced by telephone company

Instead, use a very sharp, preferably new, bit. The

equipment. This produces a sound in the portable FM

sharper the bit, the faster and easier will be the manual radio that is similar in cadence to the normal telephone drilling task.

ring signal.

Bear in mind that the holes into which component

To verify that the circuit is operating normally,

leads that are to be grounded must not be cleared of

open TEST pushbutton switch S1 has been included

copper. Otherwise, it will be difficult, if not impossible, 113

to solder these leads to the copper on the top of the has a 20% tolerance value. If the resistor’s fourth band board. When the board is ready to be populated, start by is silver then the resistor has a 10% tolerance value and plugging the leads of the resistors into the indicated if the fourth band is gold then the resistor’s tolerance holes and soldering them into place. (Note: All

value will be 5%.

components mount on the ground plane side of the

So finally we are ready to begin assembling the

board.) Next, install and solder into place the capacitors project; let’s get started. The prototype project was and diodes, taking care to properly orient the latter.

constructed on a single-sided printed circuit board or Then go ahead and install the transistors in their

PCB. With your PC board in front of you, we can now

respective locations. Remember that just one

begin populating the circuit board. We are going to

orientation-sensitive component incorrectly installed on place and solder the lowest height components first, the the board will render the circuit inoperative and may resistors and diodes. First locate our first resistor R1.

even result in damage to itself and/or nearby

Resistor R1 has a value of 100 K ohms and is a 5%

components.

tolerance type. Now take a look for a resistor whose

Before we begin building the Wireless Telephone

first color band is brown, black, yellow, and gold. From Ringer, you will need to locate a clean, well-lit

the chart you will notice that brown is represented by worktable or workbench. Next we will gather a small

the digit (1), and the second band is black, which is 25–30-W pencil tipped soldering iron, a length of 60/40

represented by (0). Notice that the third color is brown tin–lead solder, and a small canister of Tip Tinner,

and the multiplier is (10,000), so (1) (0) × 10,000 =

available at your local RadioShack store; Tip Tinner is 100,000 ohms.

used to condition the soldering tip between solder

Go ahead and place R1 on the circuit board and solder joints. You drive the soldering tip into the compound it in place. Next take your end-cutters and trim the excess and it cleans and prepares the soldering tip. Next grab a component leads from the resistor. Locate the remaining few small hand tools, try to locate small flat blade and resistors and solder them in place on the board and

Phillips screwdrivers. A pair of needle-nose pliers, a remember to trim the excess leads from the board.

pair of tweezers along with a magnifying glass, and a pair of end-cutters and we will begin constructing the Note that capacitors generally come from two major

project. Now locate your schematic diagram and parts

groups or types. Non-polar types, such as the ones in layout diagram along with all of the components needed this project, have no polarity and can be placed in either to build the project. Once all the components are in

direction on the circuit board. The other type of

front of you, you can check them off against the project capacitors are called polarized types; these capacitors parts list to make sure you are ready to start building the have polarity and have to be inserted on the board with project. Now, locate Tables 13-1 and 13-2, and place

respect to their polarity marking in order for the circuit them in front of you.

to operate correctly. On these types of capacitors, you will observe that the components actually have a plus or Table 13-1 illustrates the resistor code chart and

minus marking or a black or white band with a plus or how to read resistors, while Table 13-2 illustrates the minus marking on the body of the capacitors.

capacitor code chart which will aid you in constructing the project.

Next refer to Table 13-2, this chart helps to determine value of small capacitors. Many capacitors are quite small Refer now to the resistor color code chart shown in

in physical size, so manufacturers have devised a three-Table 13-1, which will assist you in identifying the

digit code which can be placed on the capacitor instead of resistor values. Note that each resistor will have either the actual value. The code occupies a much smaller space three or four color bands, which begin at one end of the on the capacitor and can usually fit nicely on the capacitor resistor’s body. The first colored band represents the body, but without the chart the builder would have a

resistor’s first digit, while the second color represents difficult time determining the capacitor’s value.

the second digit of the resistor’s value. The third colored band represents the resistor’s multiplier value, and the Now locate the capacitors from the component pile

fourth color band represents the resistor’s tolerance and try and locate capacitor C1, which should be

Chapter Thirteen: Telephone Ringer Projects value. If there is no fourth colored band then the resistor marked with a (104); this capacitor has a 100 nF value.

114

Chapter Thirteen: Telephone Ringer Projects

Now that you can read the resistor and capacitor charts, sure that no turns short to each other, the ground plane go ahead and place R1 and C1 on the circuit board and on the board, or any nearby components.

solder them in place. Now take your end-cutters and cut When you have completed wiring the board, examine

the excess component leads flush to the edge of the

the assembly; try carefully for inadvertent “short”

circuit board. Once you have installed the first two

circuits between closely spaced pads inductors. Pay

components, you can move on to installing the

particular attention to the top of the board to verify all remaining resistors and capacitors.

grounded leads are properly soldered to the ground

It is important that you use the specified components plane and that all leads that are not supposed to be

for C4, C5, C6, Q2, and Q3. The transistors are rated grounded are fully insulated from the ground plane.

for high-frequency amplifier applications, as in this If in doubt about the latter, use an ohmmeter set to its project, and the capacitors are temperature-stable to lowest range or an audible continuity tester to verify maintain stable operating frequency.

that you have the required insulation between

component lead and ground plane in each case.

Note that Q2 and Q3 have four leads: one each

Check all joints for good soldering. If any

for emitter, base, collector and case. The case lead

connection appears to be suspicious, re-flow the

must be soldered to the ground plane on the board to

solder on it. If you locate a solder bridge, re-flow

provide an RF shield for the transistor in both cases.

the solder and use solder wick or a solder sucker to

All transistor grounded leads and grounded pads

remove it. Most problems in projects like this can

of the other components are soldered to a common

be attributed to poor soldering.

ground.

Plug the IC into the socket, making sure you properly Use a socket for IC U1. It will not be necessary to

orient it. Also, make certain that no pins overhang the solder grounded pins 3 and 7 to the top of the board

socket or fold under between the socket and IC as you ground plane. These two pins will automatically be

push it home. For optimum circuit stability, it is best to grounded through the copper paths on the bottom of

house the circuit assembly inside an all-metal enclosure the board after soldering the socket into place. Be

that has a movable top to permit internal access for

sure, however, that all holes for the socket,

fine tuning the tank circuit. Use an enclosure that is at except those for pins 3 and 7, are cleared of copper on least 2′′ high so that you can mount the circuit board the top surface. Though you must hand-wind inductor

assembly horizontally and spaced about 1⁄4 or 1⁄2′′

L1, the procedure for doing so is very simple. Start with above the bottom panel. Use metal spacers to mount

a length of solid bare hookup wire or enameled magnet the assembly so that the copper border around the

wire. If the latter, use fairly heavy wire so that it readily solder side is electrically connected to the metal of holds its shape without having to use a coil form, and the enclosure, to ensure that the metal box is also at scrape away the enamel coating a distance of 1⁄4′′

RF ground potential.

at both ends of the wire. This wire must be exactly

A telescoping-type transistor radio replacement

41⁄2′′ long to ensure that the circuit will tune to

antenna that extends to l2 to 18′′ is suitable for use the center of the FM broadcast band. Wrap the wire

with this project. Bear in mind, however, that you

around an ordinary lead pencil so that you end up with should use as short an antenna as needed for consistent 31⁄2′′ closely spaced turns with two tails that are parallel operation at the desired range over which the project is to each other and of equal length on opposite sides of to be used.

the pencil. Slide the coil off the pencil and gently

Use plastic hardware to mount the antenna to

spread the turns evenly so that the inductor’s two leads the enclosure so that it does not short to any part

drop into the L1 holes in the board.

of the metal box. Also, locate the antenna close

Adjust the height of the coil above the ground plane

to the connecting pad on the printed circuit board

surface of the board so that 1⁄16′′ of lead length protrudes where the connection between the two is as short

from the center of each pad on the bottom of the

as possible. Capacitor C11 will be used to make

board. Solder both leads into place. If you use hookup the actual connection between antenna and the

wire to wind the coil, inspect the installation to make collector of Q3.

115

Power switch S2 should be included if you anticipate

Also, U1 need not be installed in its socket at this time.

long periods of time (weeks or more) during which the During testing, the circuit board assembly and antenna project will not be used. This switch and TEST

should be mounted in and on the project’s enclosure to pushbutton switch S1 should be located on the top or

avoid any shift in frequency after circuit tuning. With a side of the enclosure where it will not physically or 9-V battery plugged into the snap connector, operate the electrically interfere with the circuit board assembly, transmitter either by having an assistant hold down the and as far as possible from the antenna so that when

TEST button continuously or by temporarily connecting operating either there will be minimum hand

a wire jumper across the terminals of S1.

capacitance effect coupled to the antenna circuit.

Place the FM radio 10 or 20′ away from the

Use a snap-type battery connector to make connection

transmitter to obviate overloading the radio with

to the 9-V battery used for B1. Be sure to wire this

excessive signal strength. Now very slowly tune across connector so that the battery’s negative terminal

the FM band until you hear the transmitted 2-KHz

(connector’s black insulated lead) connects to the

audio tone. If you are unable to detect any signal from ground plane on the circuit board. Then plug the red

the transmitter, its carrier may be tuned outside the insulated connector wire into the hole at B1, and solder FM radio’s band. In this event, change the transmitter’s into place. Secure the battery inside the enclosure

operating frequency by spreading or compressing the

with either a standard 9-V battery clip or a length of turns of L1 to raise or lower, respectively, the frequency double-sided foam tape.

until you are able to find the tone within the FM band.

Connection to the telephone line must be made via a

Be careful to avoid shorting the turns to each other or telephone cord that has a modular connector at the end the circuit board’s ground plane! When you do hear the that attaches to the telephone line. Such cords are

2-KHz tone, tune the FM radio to a dead spot on the

readily available from any outlet that stocks telephone dial and place it about 20′ away from the transmitter.

accessories. Use of a modular connector is an FCC

Now use a plastic tuning tool to adjust the spread of requirement, aside from the fact that it makes it easy to the turns of L1 until you once again hear the 2-KHz

plug in and remove the project from any phone

tone. Work very carefully because only a very slight

connector block.

adjustment of the coil’s turns should yield the proper If the only cord you can obtain has connectors at both results. Remember, to raise the frequency, spread

ends, cut off one connector. Then remove about 1′′ of the turns; and to lower it, compress them. Check that outer plastic jacket and strip an inch of insulation from the signal is still present in the radio when you place the the ends of the exposed red and green insulated

cover on the project’s enclosure. If necessary, tweak conductors. (If there are other conductors besides the the coil slightly to keep reception of the tone signal red and green lines, clip them off flush with the plastic at the dead spot on the FM dial. If you are unable to jacket.) This project’s circuit is AC coupled to the

hear the 2-KHz audio tone in the FM radio at any setting telephone line. Therefore, it is necessary to observe any of the dial and with any spreading or compression of the particular polarity when wiring the telephone cord into coil’s turns, you will have to troubleshoot the circuit.

the circuit via the indicated holes in the circuit board.

Start by checking the electronic switch, using a DC

Route the cord into the enclosure through a rubber

voltmeter to check the reading at the collector of Q5

grommet-lined hole and tie a knot in it about 3′′ from to verify that the Q4/Q5 switching circuit is operating.

the prepared end inside the box, to serve as a strain Use a multi-meter with at least a 20,000-ohms input

relief, before lugging the wires into the board’s holes sensitivity for this test. You should obtain a reading and soldering them into place.

between 5 and 9 V when the TEST button is closed,

assuming the battery is reasonably fresh.

Operation

Carefully check the circuit board assembly to make

sure you installed all components in their respective Use an ordinary FM broadcast-band radio (portable or

locations, that the components are of the correct value otherwise) to check out circuit operation. For initial or number in each case, and that the diodes and

Chapter Thirteen: Telephone Ringer Projects tests, do not connect the project to the telephone line.

transistors are properly oriented. Also make sure that 116

Chapter Thirteen: Telephone Ringer Projects

none of the turns of L1 are touching each other. Review radio’s tuning. To use the project, connect it to the the winding instructions for the coil to ascertain that telephone line and place your FM radio some distance

you have wound it correctly.

away from it. To verify that the system is working, press the TEST button. That is all there is to it. You can now Use the DC voltmeter to measure the voltage across

carry the radio with you and have confidence that you R4, which should yield a reading of 4 V when Q2 is

will not miss a call as long as you are within range of drawing current. To check the Q1 circuit, you need an the project’s transmitter.

oscilloscope. Use the scope to observe the sawtooth

waveform across C1; presence of this waveform

indicates that the 2-KHz oscillator is operating as it Project 5: Telephone ring

should. Once you are satisfied that the circuit is

performing properly with the TEST pushbutton switch

generator

closed, unsnap the connector from the battery and

install U1 in its socket. Observe correct orientation.

A Telephone Ring Generator is extremely useful for

This done, snap the connector back onto the battery and testing telephones and telephone circuits, as well as for plug the project’s phone cord into any convenient

creating your own telephone intercom systems. You can telephone line outlet. Now have a friend call your

easily create your own very useful ring generator by

number. When your phone rings, you will hear the

building this transistorized project.

project’s 2-KHz ring signal in your FM radio, verifying The Telephone Ring Generator is highlighted in the

that the project is operating properly. Once you have schematic diagram in Figure 13-8.

tuned the project to dead spot on the FM dial, it is best to change the length of the antenna. If you do change its The ringing generator circuit generates the necessary length, a very slight change in operating frequency may high voltage from a simple switching mode power

result, which will require slight adjustment of the

supply which employs a CMOS Schmitt Trigger square

+9 V

R2

C2

+

S1

L1

R1

R4

D4

D1

R3

10

C4

UI:e

UI:d

11

R10

Q2

Ring output

+

C5

C1

+ 120 V

D3

R5

Q1

D2

R6

R7

Q4

Q5

UI:f

C3

+

R13

R8

R9

Q3

Q8

Q6

R12

R14

UI:a

UI:b

C6

R11

Q7

R16

+

R15

UI:c

UI

Figure 13-8

Telephone ring generator. Courtesy of Bill Bowden 117

wave oscillator, 10 mH inductor, high voltage switching small canister of Tip Tinner, available at your local transistor (TIP47 or other high voltage, 1 amp transistor, RadioShack store; Tip Tinner is used to condition the and a driver transistor (2N3053). The inductor should soldering tip between solder joints. You drive the

have a low DC resistance of 1.5 ohms or less. The

soldering tip into the compound and it cleans and prepares switching supply must have a load connected to prevent the soldering tip. Next grab a few small hand tools, try to the voltage from rising too high, so a 22 K resistor is locate small flat blade and Phillips screwdrivers. A pair used across the output which limits the voltage output to of needle-nose pliers, a pair of tweezers along with a about 120 V DC with the phone ringer disconnected and magnifying glass, and a pair of end-cutters and we will about 90 V DC connected.

begin constructing the project. Now locate your schematic diagram and parts layout diagram along with all of the The output voltage can be adjusted by changing the

components needed to build the project. Once all the

value of the 150 K resistor between pins 10 and 11

components are in front of you, you can check them off which will alter the oscillator frequency (frequency is against the project parts list to make sure you are ready to around 800 Hz as shown). The supply is gated on and off start building the project. Now, locate Tables 13-1 and by a second Schmitt Trigger oscillator (pins 12 and 13) 13-2, and place them in front of you.

so that the phone rings for about 2 s and then

the circuit idles for about 1 min between rings. These Table 13-1 illustrates the resistor code chart and

times can be adjusted with the 10 K and 300 K resistors how to read resistors, while Table13-2, illustrates the connected to pin 12. The push button shown is used to capacitor code chart, which will aid you in constructing manually ring the phone.

the project.

The 25 Hz ringing frequency is generated by another

Refer now to the resistor color code chart shown in

Schmitt Trigger oscillator (pins 1and 2) which controls Table 13-1, which will help you to identify the resistor the H bridge transistor output circuit. The six transistors values for the project. Note that each resistor will have in the output stage, i.e., the four NPN and the two PNP

either three or four color bands, which begin at one end types, should be high voltage types rated at 200 V

of the resistor’s body. The first colored band represents collector to emitter or more. The ringer will only draw the resistor’s first digit, while the second color

around 10 mA, so the output transistors can have a low represents the second digit of the resistor’s value. The current rating but must have a high voltage rating. I used third colored band represents the resistor’s multiplier TIP47s and small signal PNPs of unknown numbers that

value, and the fourth color band represents the resistor’s I had on hand, but other types such as NTE287 (NPN)

tolerance value. If there is no fourth colored band then and NTE288 (PNP) should work. Both have a 300 V

the resistor has a 20% tolerance value. If the resistor’s C-E rating and cost less than a dollar.

fourth band is silver then the resistor has a 10%

tolerance value and if the fourth band is gold then the The two 470 ohm resistors connected to the output

resistor’s tolerance value will be 5%.

serve to limit the current in case the output is shorted.

They should limit the surge to around 120 mA, which

So let’s get started; we are ready to begin assembling should be low enough to prevent damage. The circuit

the project. The prototype project was constructed on a draws around 250 mA when the ring signal is present so single-sided printed circuit board or PCB. With your

if you want to operate it from batteries, six ‘D’ type PC board in front of you we can now begin populating

alkaline cells are recommended. It probably will not

the circuit board. We are going to place and solder the work with a small 9-V battery.

lowest height components first, the resistors and diodes.

First locate our first resistor R1. Resistor R1 has a value of 150 K ohms and is a 5% tolerance type. Now take a

Circuit assembly

look for a resistor whose first color band is brown,

green, yellow, and gold. From the chart you will notice Before we begin building the Telephone Ring Generator, that brown is represented by the digit (1), the second let’s first locate a clean, well-lit worktable or workbench.

band is green, which is represented by (5). Notice that Next we will gather a small 25–30-W pencil tipped

the third color is yellow and the multiplier is (10,000), Chapter Thirteen: Telephone Ringer Projects soldering iron, a length of 60/40 tin–lead solder, and a so (1) (5) × 10,000 = 150,000 ohms.

118

Chapter Thirteen: Telephone Ringer Projects

Go ahead and place R1 on the circuit board and then

your schematic and parts layout diagrams when

solder it in its respective location on the circuit board.

installing these diodes on the circuit board. Note that all Now locate your end-cutters and trim the excess resistor the diodes are 1N4004 silicon diodes. Place all the

leads. Cut the excess leads flush to the edge of the

diodes on the circuit board and solder them in place on circuit board. Now install the remaining resistors and the PC board. Then remember to cut the excess

solder them in place, remembering to trim the excess

component leads with your end-cutters.

component leads.

The Telephone Ring Generator circuit also utilizes

Note that capacitors generally come from two major

eight transistors. Transistors generally have three leads, groups or types. Non-polar types, such as the ones in a Base lead, a Collector lead and an Emitter lead.

this project, have no polarity and can be placed in either Refer to the schematic and you will notice that there direction on the circuit board. The other type of

will be two diagonal leads pointing to a vertical line.

capacitors are called polarized types, these capacitors The vertical line is the transistor’s base lead and the have polarity and have to be inserted on the board with two diagonal lines represent the collector and the

respect to their polarity marking in order for the circuit emitter. The diagonal lead with the arrow on it is the to operate correctly. On these types of capacitors, you emitter lead, and this should help you install the

will observe that the components actually have a plus or transistor onto the circuit board correctly. Go ahead minus marking or a black or white band with a plus or and install the transistors on the PC board and solder minus marking on the body of the capacitors.

them in place, then follow-up by cutting the excess

Next refer to Table 13-2; this chart helps to determine component leads, flush to the edge of the circuit board.

the value of small capacitors. Many capacitors are quite The Telephone Ring Generator circuit also employs a

small in physical size, so manufacturers have devised a single inductor at L1, it is a common 10 mH

three-digit code which can be placed on the capacitor commercial inductor readily available from Mouser or

instead of the actual value. The code occupies a much Digi-Key Electronics.

smaller space on the capacitor and can usually fit nicely on The Telephone Ring Generator utilizes a single IC at

the capacitor body, but without the chart the builder would U1. The IC is a 74HC14, which contains six inverter

have a difficult time determining the capacitor’s value.

circuits. It is recommended that you use an IC socket Now locate the capacitors from the component pile

for the IC, as a cheap insurance policy against possible and try and locate capacitor C1, which should be

later circuit failure. When installing the integrated marked with a (103), this capacitor has a .01 μF value.

circuit, you will have to pay close attention to the

Now that you can read the resistor and capacitor charts, mounting of the device to ensure proper operation of

let go ahead and place R1 and C1 on the circuit board the circuit. ICs will always have either a small

and solder them in place. Now take your end-cutters and indented circle, or a small cutout at the top end of

cut the excess component leads flush to the edge of the the IC package. Pin 1 will always be just to the left circuit board. Once you have installed the first two

of the cutout or circle. Refer to the schematic and

components, you can move on to installing the

parts layout diagrams when installing the IC to

remaining resistors and capacitors. There are a number ensure proper orientation.

of electrolytic type capacitors in this circuit, so pay Once the circuit board has been completed, you can

particular attention to the polarity when installing them take a short well deserved break and when we return we on the circuit board. Remember to trim the excess

will inspect the circuit board for any possible “cold”

component leads using your end-cutters, cutting the

solder joints or “short” circuits. Pick up the circuit leads flush to the edge of the circuit board.

board with the foil side facing upwards toward you.

This project contains four silicon diodes at D1

Examine the board carefully. Look at all the solder

through D4. These diodes also have polarity which must joints. The solder joints should all look clean, shiny, and be observed if the circuit is going to work correctly. You bright, if any solder joints look dull, dark, or blobby will notice that each diode will have a black or white then you should use a solder sucker or wick to remove colored band at one edge of the diode’s body. The

the solder and then re-solder the joint all over again.

colored band represents the diode’s cathode lead. Check Once you have inspected the circuit for cold solder

119

joints, we can move onto inspecting the board for

be mounted at the front or rear of the chassis box for possible short circuits. Short circuits can be caused easy access.

from solder blobs bridging across the circuit traces or Now connect up your power supply or batteries and

from cut components bridging across circuit traces.

power up the ringer circuit. Connect the output of the Often solder residue can trap or cut component leads

Telephone Ringer circuit to a telephone bell or AC

which can bridge across circuit traces causing a short voltmeter for test and once power is applied you can

circuit. You want to try to avoid short circuits before press switch S1 to read 120 V AC on your AC meter or

power is applied for the first time in order not to

if a telephone bell is attached to the output of the ringer damage the circuit.

circuit, you should hear the bell ring.

In the event of a circuit failure and no voltage is

Operation

present at the output of the ringer circuit, you will have to remove power from the circuit and inspect

Once the circuit has been built and inspected,

it for any errors. The most common cause for circuit

you can mount it in a suitable metal chassis box. You errors is incorrect placement of critical components

will want to mount the circuit on standoffs above the such as electrolytic capacitors, diodes and

metal bottom of the chassis box to avoid shorting to

transistors. Generally the builder has made a mistake ground or metal of the box. You will likely want to

in installing these components through making a

install a power switch in series with the power supply polarity error. Also check the orientation of the

to the power input of the circuit through L1. You could integrated circuit in its socket. This is another

elect to power the circuit with a suitable power supply common cause for error.

or from “D” or “C” cell batteries if desired. The

Once the circuit has been finally inspected, you can

momentary switch at S1 can be mounted at the side or

reconnect the power supply or batteries and retest the top of the chassis box.

Telephone Ringer Generator for proper operation.

You will need to mount a 2-position terminal block

Hopefully this time around the circuit will perform

for the ringer’s output wires. The terminal block could flawlessly. Good luck!

Chapter Thirteen: Telephone Ringer Projects

120

Chapter 14

Phone Line Status Circuits

and Projects

Q3

IRF510 Power

Parts list

MOSFET

D1

1N914 Diode

Phone In¯Use Indicator

RLY1

SPDT 6¯V relay

R1

3.3 K ohm, 1⁄ W,

2

5% resistor

Load

Buzzer or bell

R2

33 K ohms, 1⁄ W,

Misc

PC board, wire,

2

5% resistor

phone connectors,

hardware, enclosure,

R3

56 K ohms, 1⁄ W,

2

etc.

5% resistor

9¯V Power Supply

R4

22 K ohms, 1⁄ W,

2

5% resistor

R1

240 ohm 1⁄ W,

2

5% resistor

R5

4.7 K ohms, 1⁄ W,

2

5% resistor

R2

5 K ohm potentiometer

(PC¯trim)

D1, D2, D3, D4

1N4001

silicon diodes

R3

1 K ohm 1⁄ W,

4

5% resistor

D5

red LED – LED¯1

C1

1,000 μF, 35 V

D6

green LED – LED¯2

electrolytic

Q1, Q2 2N 3392 transistor

capacitor

Misc PC board,

C2

10 μF, 35 V

enclosure, wire,

electrolytic capacitor

hardware, sockets,

C3

.01 μF, 35 V disc

etc.

capacitor

Cut Phone Line Detector

D1, D2

1N4001 silicon

R1, R2, R3

20 megohm

diode

1

⁄ W, 5% resistor

2

D3

Red LED

R4

2.2 megohm 1⁄ W,

2

U1

LM317 adjustable

5% resistor

regulator

C1

0.47 μF 250 V mylar

T1

110 to 25 V center

capacitor

tapped transformer

Q1

2N3904 transistor

(.500 mA)

Q2

2N3906 transistor

S1

SPST toggle switch

121

Copyright © 2009 by The McGraw-Hill Companies, Inc. Click here for terms of use.

P1

110-V power plug

F1

2-amp 3AG Fuse

Misc

PC board, wire,

Misc

PC board, wire,

enclosure, etc.

hardware, power plug,

etc.

Phone Line¯in¯Use Relay

Controller

Single Phone Line Status

Light

R1, R2, R3

3.3 megohm,

1

⁄ W, 5% resistor

R1, R2, R4

4.7 megohm,

2

1

⁄ W, 5% resistor

R4

10 K ohm, 1⁄ W,

2

4

5% resistor

R3

15 K ohms, 1⁄ W,

4

5% resistor

D1

1N4004 silicon diode

R5

1 K ohms, 1⁄ W,

Q1

IFR510/511 – MOSFET

4

5% resistor

(Radio shack)

C1

10 μF, 25-V

RLY1

12-V DC relay –

electrolytic capacitor

120 ohm coil

C2

.15 μF, 25-V

Misc

PC board, wire,

polyester capacitor

hardware, enclosure,

load, etc.

D1, D2, D3, D4

1N4004

silicon diodes

12-V DC Power Supply

D6, D7

1N4148 silicon

R1

10 K ohms, 1⁄ W,

4

diodes

5% resistor

R2

2.2 ohm, 1 W,

D5

15-V Zener diode

5% resistor

D8

Red LED

C1

2,200 μF, 35-V

U1

74HC14 Hex inverting

Electrolytic

Schmitt Trigger IC

capacitor

B1

two “C” or “D”

C2

10 μF, 35-V

cells

electrolytic

Misc

PC board, wire,

capacitor

IC socket, battery

C3

.01 μF, 35-V

holders, etc.

disc capacitor

Two¯Line Phone Status

D1, D2

1N4001 silicon

Indicator

diode

R1, R6, R15

4.7 megohm,

D3

1N4742A Zener diode

1

⁄ W, 5% resistor

2

Q1

TIP31 – NPN

R2, R3, R13, R14

transistor

10 megohm, 1⁄ W,

2

Q2

2N3904 NPN

5% resistor

transistor

R4, R9, R12

100 K ohms,

1

T1

25.2-V center

⁄ W, 5% resistor

4

tapped transformer –

R5, R11

470 K ohms,

1.5

1

¯ampere

⁄ W, 5% resistor

4

S1

SPST toggle – on¯off

R7, R10

270 ohms, 1⁄ W,

4

Chapter Fourteen: Phone Line Status Circuits

switch

5% resistor

122

Chapter Fourteen: Phone Line Status Circuits

R8

22 megohm, 1⁄ W,

4

C3

1,000 μF, 35-V

5% resistor

electrolytic capacitor

C1

10 μF, 25-V

D1, D2

1N4007 silicon

electrolytic capacitor

diode

C2

.047 μF, 25-V

Q1

SL100 transistor

mylar capacitor

U1, U2

MCT2E

D1, D2, D3, D4

1N4004

opto¯coupler

silicon diodes

U3

74LS123 Dual

D5, D6, D7, D8

1N4004

retriggerable

silicon diodes

monostable

D9, D14

1N4744 –

multivibrator

15-V Zener diodes

LDR

light dependent

D11, D12, D13

1N4148

resistor

silicon diodes

RLY1

5¯V relay

U1

74HC132 – Quad

L1

lamp

2¯input NAND Schmitt

Misc

PC board, wire,

Trigger

IC sockets, hardware,

OPT1, OPT2

opto¯coupler

enclosure, etc.

OPI¯123 OPTEK

5¯V Smart Phone Light

B1

2¯”C” or “D” cells

Power Supply

Misc

PC board,

R1

1 K ohm, 1⁄-W,

IC socket, wire,

2

5% resistor

hardware, enclosure,

etc.

C1

1,000 μF, 35-V

electrolytic capacitor

Smart Phone Light

C2

10 μF, 35-V

R1, R2

20 K ohm, 1⁄ W,

4

electrolytic capacitor

5% resistor

C3

.01 μF, 35-V

R3

100 K ohm, 1⁄ W,

4

disk capacitor

5% resistor

D1, D2

1N4001 silicon

R4, R5

47 K ohms, 1⁄ W,

4

diode

5% resistor

D3

Red LED

R6

10 K ohms, 1⁄ W,

4

5% resistor

U1

LM7805 – 5¯V

regulator IC

R7

1 K ohms, 1⁄ W,

4

5% resistor

T1

110 to 25-V

center tapped

R8

22 K ohms, 1⁄ W,

4

transformer – 1 amp

5% resistor

S1

SPST toggle switch –

C1

1 μF, 250-V paper

on

capacitor

¯off

F1

Fuse – 1 amp

C2

47 μF, 35-V

electrolytic

Misc

PC board,

capacitor

hardware, wire, etc.

123

Phone Line Vigilant

LED2

Red LED

R1

56 K ohms, 1⁄ W,

Q1, Q2, Q3, Q4

BC547

4

5% resistor

transistor

R2, R3, R8

100 K ohms,

Q5, Q6, Q8, Q9, Q19

1

⁄ W, 5% resistor

BC547 transistor

4

R4, R9

1 K ohms, 1⁄ W,

Q7

SL100 transistor

4

5% resistor

S1

On¯Off toggle switch

R5, R10

5.6 K ohms,

Buzz

Piezo buzzer

1

⁄ W, 5% resistor

4

Batt

4¯ 1.5-V “AA”

R6

470 ohms, 1⁄ W,

4

cells

5% resistor

T1

110 volt primary,

R7, R17

10 K ohms, 1⁄ W,

4

9-V secondary

5% resistor

@ 500 mA

R11

4.7 K ohms, 1⁄ W,

4

Misc

PC board, wire,

5% resistor

hardware, modular

R12

220 ohms, 1⁄ W,

jack, etc.

4

5% resistor

R13, R16

1.2 K ohms,

1

⁄ W, 5% resistor

Project 1: Phone In-Use

4

R14, R15

22 K ohms,

indicator

1

⁄ W, 5% resistor

4

VR1, VR2

1 megohm

Tired of having your phone calls interrupted by family potentiometer

members, roommates, or co-workers picking up the

VR3

1 K ohm

phone handset, while you are in a conversation? This

potentiometer

Phone Line In-use Indicator circuit will show others

when the phone is in use, so they will be alerted not to C1

10 μF, 35-V

pickup a phone extension.

electrolytic capacitor

C2

22 μF, 35-V

electrolytic capacitor

Circuit description

C3

470 μF, 35-V

electrolytic capacitor

The Phone In-Use Indicator circuit is illustrated in

Figure 14-1. When all the phones are on-hook,

C4

1,000 μF, 35-V

transistor Q2’s base is turned on by a voltage divider electrolytic capacitor

switch circuit, which consists of R3 and R5. Note that D1, D2, D3, D4

1N4007

the value for R5 causes the device to switch over at

silicon diodes

about 9 V. This can be changed to facilitate other

D5, D6, D7, D8

1N4007

voltage levels if desired. Transistor Q2 allows current silicon diodes

to flow through R2 and LED2 or D6, indicating that

the phone line is not in use. It also effectively grounds D9

3.3-volt Zener diode

the base of Q1 and forces LED1 or D5 to remain

D10

9.1-volt Zener

off. When the voltage drops because a telephone goes

diode

off-hook, Q2 stops conducting, allowing a small

LED1

Green LED

Chapter Fourteen: Phone Line Status Circuits

flow of current from R2, D6, and R4 to Q1’s base.

124

Chapter Fourteen: Phone Line Status Circuits

60/40 tin–lead solder, and a small canister of Tip Tinner, R1

R2

R3

available at your local RadioShack store; Tip Tinner is used to condition the soldering tip between solder

Tip

D6

joints. You drive the soldering tip into the compound D5

D2

and it cleans and prepares the soldering tip. Next grab a D1

−

+

To

few small hand tools, try to locate small flat blade and telephone

line

D3

Q1

Phillips screwdrivers. A pair of needle-nose pliers, a D4

R4

pair of tweezers along with a magnifying glass, and a Q2

Ring

pair of end-cutters and we will begin constructing the R5

project. Now locate your schematic diagram and parts

layout diagram along with all of the components needed to build the project. Once all the components are in

Figure 14-1

Phone In-Use indicator circuit. Courtesy

front of you, you can check them off against the project of Poptronix

parts list to make sure you are ready to start building the project. Now, locate Tables 14-1 and 14-2, and place

When that occurs, Q1 conducts, energizing D5, and D6 is them in front of you.

deprived of sufficient current to light up. The bridge Table 14-1 illustrates the resistor code chart and

rectifier compensates for a possible reversal between the how to read resistors, while Table 14-2 illustrates

tip and ring phone wires, and rectifies the ring signal to the capacitor code chart which will aid you in

power the circuit.

constructing the project.

Refer now to the resistor color chart shown in

Circuit assembly

Table 14-1, which will help you to identify the resistors for the project. Note that each resistor will have either Before we begin constructing the Phone In-Use

three or four color bands, which begin at one end of the Indicator, you will need to locate a clean, well-lit

resistor’s body. The first colored band represents the worktable or workbench. Next we will gather a small

resistor’s first digit, while the second color represents 25–30-W pencil tipped soldering iron, a length of

the second digit of the resistor’s value. The third colored Table 14-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

No color

20%

125

Table 14-2

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

1.0

1R0

3,900

3.9

.0039

392

1.2

1R2

4,700

4.7

.0047

472

1.5

1R5

5,600

5.6

.0056

562

1.8

1R8

6,800

6.8

.0068

682

2.2

2R2

8,200

8.2

.0082

822

2.7

2R7

10,000

10

.01

103

3.3

3R3

12,000

12

.012

123

3.9

3R9

15,000

15

.015

153

4.7

4R7

18,000

18

.018

183

5.6

5R6

22,000

22

.022

223

6.8

6R8

27,000

27

.027

273

8.2

8R2

33,000

33

.033

333

10

100

39,000

39

.039

393

12

120

47,000

47

.047

473

15

150

56,000

56

.056

563

18

180

68,000

68

.068

683

22

220

82,000

82

.082

823

27

270

100,000

100

.1

104

33

330

120,000

120

.12

124

39

390

150,000

150

.15

154

47

470

180,000

180

.18

184

56

560

220,000

220

.22

224

68

680

270,000

270

.27

274

82

820

330,000

330

.33

334

100

.0001

101

390,000

390

.39

394

120

.00012

121

470,000

470

.47

474

150

.00015

151

560,000

560

.56

564

180

.00018

181

680,000

680

.68

684

220

.00022

221

820,000

820

.82

824

270

.00027

271

1,000

1

105

330

.00033

331

1,500

1.5

155

390

.00039

391

2,200

2.2

225

470

.00047

471

2,700

2.7

275

560

.00056

561

3,300

3.3

335

680

.00068

681

4,700

4.7

475

820

.00082

821

6.8

685

1,000

1.0

.001

102

10

106

1,200

1.2

.0012

122

22

226

1,500

1.5

.0015

152

33

336

1,800

1.8

.0018

182

47

476

Chapter Fourteen: Phone Line Status Circuits

126

Chapter Fourteen: Phone Line Status Circuits

Table 14-2—cont’d

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

2,200

2.2

.0022

222

68

686

2,700

2.7

.0027

272

100

107

3,300

3.3

.0033

332

157

157

Code = 2 significant digits of the capacitor value + number of zeros to follow 10 pF = 100

For values below 10 pF, use “R” in place of decimal e.g. 8.2 pF = 8R2

100 pF = 101

1,000 pF = 102

22,000 pF = 223

330,000 pF = 334

1 μF = 105

band represents the resistor’s multiplier value, and the Note that capacitors generally come from two major

fourth color band represents the resistor’s tolerance groups or types. Non-polar types, such as the ones in value. If there is no fourth colored band then the resistor this project, have no polarity and can be placed in either has a 20% tolerance value. If the resistor’s fourth band direction on the circuit board. The other type of

is silver then the resistor has a 10% tolerance value and capacitors are called polarized types; these capacitors if the fourth band is gold then the resistor’s tolerance have polarity and have to be inserted on the board with value will be 5%.

respect to their polarity marking in order for the circuit to operate correctly. On these types of capacitors, you Finally, we are ready to begin assembling the project, will observe that the components actually have a plus or so let’s get started. The prototype project was

minus marking or a black or white band with a plus or constructed on a single-sided printed circuit board or minus marking on the body of the capacitors

PCB. With your PC board in front of you, we can now

begin populating the circuit board. We are going to

This project contains four silicon diodes. Diodes will place and solder the lowest height components first, the always have some type of polarity markings, which

resistors and diodes. First locate our first resistor R1.

must be observed if the circuit is going to work

Resistor R1 has a value of 3.3 K ohms and is a

correctly. You will notice that each diode will have a 5% tolerance type. Now take a look for a resistor

black or white colored band at one edge of the diode’s whose first color band is orange, orange, red, and gold.

body. The colored band represents the diode’s cathode From the chart you will notice that orange is

lead. Check your schematic and parts layout diagrams

represented by the digit (3), the second color band is when installing these diodes on the circuit board.

orange, which is represented by (3). Notice that the

Note that diodes D1 through D4 are all 1N4004 silicon third color is red and the multiplier is (100), so

diodes. Place all the diodes on the circuit board and (3) (3) × 100 = 3,300 ohms. Go ahead and place R1

solder them in place on the PC board. Then cut the

on the circuit board and solder it in place. Now take excess component leads with your end-cutters flush to your end-cutters and cut the excess component leads

the edge of the circuit board.

flush to the edge of the circuit board. Once you have The Phone In-Use Indicator utilizes two conventional

installed the first resistor, you can move on to

transistors. Transistors are generally three lead devices, installing the remaining resistors and then the

which must be installed correctly if the circuit is to remaining low profile components. Solder these

work properly. Careful handling and proper orientation components in place in their respective locations

in the circuit is critical. A transistor will usually have on the circuit board.

a Base lead, a Collector lead, and an Emitter lead.

127

The base lead is generally a vertical line inside a

them to mount the circuit board inside of the case. Next, transistor circle symbol. The collector lead is usually a you will have to connect the circuit to the phone line.

slanted line facing towards the base lead and the emitter This can be done using a length of 4-conductor phone

lead is also a slanted line facing the base lead, but it will wire with a modular plug attached at one end of the

have an arrow pointing towards or away from the base

cable. The modular plug end can then simply plug into lead. Before installing the two transistors refer to the a telephone jack, and the wire ends of the cable can

parts specification sheets as well as the parts layout connect to the circuit itself. You could also elect to hard-diagram and the schematic. Be sure to orient the

wire the circuit directly to the phone line without the transistors prior to inserting them into the circuit board.

modular plugs if desired.

If you are in doubt as to how to mount the transistors, have a knowledgeable electronics enthusiast help you.

Now, insert the transistors onto the circuit board and Operation

solder them in place, remembering to cut the excess

component leads with your end-cutters flush to the edge Once your circuit has been mounted in an enclosure and of the circuit board.

wired to the phone line, you are now ready to test the circuit. When all phones are on-hook the green LED is The Phone In-Use Indicator circuit uses two LEDs,

lit up, indicating that the telephone is not now in use.

which also must be oriented correctly if the circuit is to When someone does pick up a phone in the house the

function properly. An LED has two leads, a cathode and red LED will light up indicating that someone has now an anode lead. The anode lead will usually be the longer picked up a phone or it is now in use. Your Phone

of the two leads and the cathode lead will usually be the In-use Indicator is now ready to serve you for many

shorter lead, just under the flat side edge of the LED; years to come. Now you will know if someone has

this should help orient the LED on the PC board.

picked up a telephone extension before you try to use Solder the LEDs to the PC board and then trim the

the telephone.

excess leads.

Once the circuit board has been completed, take a

short break and then we will inspect the PC board for possible “cold” solder joints and “short” circuits. Pick Project 2: Cut phone line

up the PC board with the foil side facing upwards

toward you. Carefully inspect the solder joints; these detector

should look smooth, clean, and bright. If any of the

solder joints look dull, dark, or blobby, then you should The Cut Phone Line Detector is a novel circuit to detect remove the solder with a solder sucker or a solder wick when the phone line has been cut or broken somewhere

and then resolder the joint all over again.

along the line entering your home. If you have a home alarm system which dials the police or a neighbor then Now we will inspect the PC board for possible short

it is imperative that your phone line loop is always

circuits. Short circuits can be caused from small solder present. When the circuit detects that a phone line has blobs bridging the circuit traces or from cut component been cut, it activates a MOSFET which can be used to

leads, which can often stick to the circuit board.

drive a relay, motor, or local siren to alert your or your A sticky residue from solder will often trap component neighbors.

leads across the circuit traces. Look carefully for any bridging wires across circuit traces. Once this inspection is complete, we can move on to installing the circuit Circuit description

board into some sort of plastic enclosure.

The circuit is line powered so you will need no

The phone line is connected to the circuit as shown in external power supply or batteries. Next, you will need the schematic Figure 14-2. The green phone wire is

to mount the circuit board inside of a plastic enclosure.

normally the minus lead and the red wire is generally Lay the circuit board inside of a suitable plastic case to the plus lead. The green lead is connected to resistor Chapter Fourteen: Phone Line Status Circuits check the fit. Locate some mounting standoffs and use R1, followed by resistor R2. The red telephone wire is 128

Chapter Fourteen: Phone Line Status Circuits

+ 9 V DC

R4

N/o

N/C

RLY1

Q3

D

G

R1

−

Q2

S

Green

R2

Q1

R3

Buzzer

Telephone

or

Buzz

line

Bell

C1

D1

+

Red

Figure 14-2

Cut-phone detector

connected to the ground to the circuit ground at the

adjusted by trimming potentiometer R2, a 5 K pot. The junction of C1, D1 the emitter of Q1, the collector

output of the regulator is then fed to two capacitors, a of Q2 and the source of the power MOSFET at Q3.

10 μF electrolytic and a .01 μF bypass capacitor. The The 48-V nominal voltage on the phone line is fed to

regulator should be adjusted to 9 V DC before

the first transistor at Q1 which is used to drive the connecting it to the Cut Line Detector circuit.

second transistor at Q2, which in turn activates the

MOSFET and pulls-in the relay at RLY1. When the

Circuit assembly

phone handset is picked up, the voltage across the

phone line drops to about 6 V, which is still enough

Before we begin constructing the Cut Phone Line

to hold the relay from dropping out. But if the phone Detector, you will need to locate a clean, well-lit

line is cut or broken, then all voltage disappears from worktable or workbench. Next we will gather a small

the input of the circuit, the relay drops, and the contacts 25–30-W pencil tipped soldering iron, a length of

at the relay are used to activate an alarm buzzer or

60/40 tin–lead solder, and a small canister of Tip Tinner, bell to alert you. The Cut Phone Line Detector is

available at your local RadioShack store; Tip Tinner is powered from a 9-V DC power supply, which is

used to condition the soldering tip between solder

shown in Figure 14-3.

joints. You drive the soldering tip into the compound The 9-V power supply utilizes a center tapped

and it cleans and prepares the soldering tip. Next grab 25-V transformer at T1. The two-diode rectifier is

a few small hand tools; try to locate small flat blade coupled to a voltage regulator chip at U1, which is an and Phillips screwdrivers. A pair of needle-nose pliers, adjustable voltage regulator. The voltage output is

a pair of tweezers along with a magnifying glass,

LM317

S1

D1

1

3

U1

+ 9 V

2

T1

R1

R3

Primary

Secondary

+

+

C1

C2

C3

R2

P1

D3

D2

Figure 14-3

9-V power supply circuit

129

and a pair of end-cutters and we will begin constructing leads with your end-cutters flush to the edge of the

the project. Now locate your schematic diagram and

circuit board.

parts layout diagram along with all of the components Note that capacitors generally come from two major

needed to build the project. Once all the components are groups or types. Non-polar types, such as the ones in in front of you, you can check them off against the

this project, have no polarity and can be placed in either project parts list to make sure you are ready to start direction on the circuit board. The other type of

building the project. Now, locate Tables 14-1 and 14-2, capacitors are called polarized types; these capacitors and place them in front of you.

have polarity and have to be inserted on the board with Table 14-1 illustrates the resistor code chart and

respect to their polarity marking in order for the circuit how to read resistors, while Table 14-2 illustrates the to operate correctly. On these types of capacitors, you capacitor code chart which will aid you in constructing will observe that the components actually have a plus or the project.

minus marking or a black or white band with a plus or Refer now to the resistor color code chart shown in

minus marking on the body of the capacitors.

Table 14-1, which will help you to determine the proper Next refer to Table 14-2; this chart helps to determine resistors for the project. Note that each resistor will the value of small capacitors. Many capacitors are quite have either three or four color bands, which begin at small in physical size, so manufacturers have devised a one end of the resistor’s body. The first colored band three-digit code which can be placed on the capacitor represents the resistor’s first digit, while the second instead of the actual value. The code occupies a much color represents the second digit of the resistor’s value.

smaller space on the capacitor and can usually fit

The third colored band represents the resistor’s

nicely on the capacitor body, but without the chart the multiplier value, and the fourth color band represents builder would have a difficult time determining the

the resistor’s tolerance value. If there is no fourth capacitor’s value.

colored band then the resistor has a 20% tolerance

Now locate the capacitor from the component pile

value. If the resistor’s fourth band is silver then the and try and locate capacitor C1, which may be labeled resistor has a 10% tolerance value and if the fourth band

.47 μF or (474); remember this is the three-digit code is gold then the resistor’s tolerance value will be 5%.

representing the actual value. Go ahead and place

Finally, we are ready to begin assembling the project, C1 on the circuit board and solder it in place.

so let’s get started. The prototype project was

Now take your end-cutters and cut the excess

constructed on a single-sided printed circuit board or component leads flush to the edge of the circuit board.

PCB. With your PC board in front of you, we can now

Once you have installed the capacitor, you can move

begin populating the circuit board. We are going to place on to installing the remaining low profile

and solder the lowest height components, first the resistors components.

and diodes.. First locate our first resistor R1. Resistor R1

This project contains a number of silicon diodes.

has a value of 20 megohms and is a 5% tolerance type.

Diodes will always have some type of polarity

Now take a look for a resistor whose first color band is markings, which must be observed if the circuit is going red, black, blue, and gold. From the chart you will notice to work correctly. You will notice that each diode will that red is represented by the digit (2), the second color have a black or white colored band at one edge of the band is black, which is represented by (0). Notice that the diode’s body. The colored band represents the diode’s third color is blue and the multiplier is (1,000,000), so cathode lead. Check your schematic and parts layout

(2) (0) × 1,000,000 = 20,000,000 ohms. Once you have

diagrams when installing these diodes on the circuit

identified resistor R1, go ahead and install it on the board. Note, this circuit only has a single diode at D1.

PC board, then solder it in place. Next trim the excess Place the diodes on the circuit board and solder them in component lead lengths with your end-cutter. Now go

place on the PC board. Then cut the excess component

ahead and locate the remaining resistors and insert them leads with your end-cutters.

in to the circuit board at their respective locations, then solder them in place. Now solder the resistors at The Cut Phone Line Detector utilizes two conventional Chapter Fourteen: Phone Line Status Circuits their locations, and remember to trim the excess transistors. Transistors are generally three lead devices, 130

Chapter Fourteen: Phone Line Status Circuits

which must be installed correctly if the circuit is to work A sticky residue from solder will often trap component properly. Careful handling and proper orientation in the leads across the circuit traces. Look carefully for any circuit is critical. A transistor will usually have a Base bridging wires across circuit traces. Once this inspection lead, a Collector lead, and an Emitter lead. The base is complete, we can move on to installing the circuit lead is generally a vertical line inside a transistor circle board into some sort of plastic enclosure.

symbol. The collector lead is usually a slanted line

You will also need to connect the circuit to the phone facing towards the base lead and the emitter lead is also a line. This can be done using a length of 4-conductor

slanted line facing the base lead, but it will have an arrow phone wire with a modular plug attached at one end of pointing towards or away from the base lead. Pay careful the cable. The modular plug ends can then simply plug attention to the pinouts of the transistors and refer to the into a telephone jack. You could elect to hard-wire the schematic, parts layout, and component specification

circuit directly to the phone line without the modular sheets when installing the transistors onto the circuit plugs if desired. The circuit is powered from a 9-V

board. If you are uncertain of your abilities, have a power supply. You could elect to either build or buy your knowledgeable electronics enthusiast help you. Once you 9-V power supply. A simple solution is to utilize a

have identified the transistor and MOSFET leads and can 110-V to 9-V DC cube or “wall wart” power available

confirm the correct orientation you can install these from your local Radio Shack or electronic outlet.

components on the circuit board. Solder the transistors to their respective locations, then remember to cut the excess lead lengths with your wire cutters.

Operation

Now you can install the relay on to the circuit board.

At some point, uou will have to decide what type of alarm Check over your circuit one more time to make sure all device you wish to connect to the relay. The relay has both the components are mounted at their correct locations.

normally open and normally closed contacts. Note that Once you circuit has been mounted in an enclosure and when the circuit is powered, the relay remains in its rest wired to the phone line, you will be ready to test the position as shown, but as soon as the circuit is connected circuit. Connect up the load or buzzer to the normally to the phone line the relay will pull-in and be activated.

closed relay contacts. Now connect the telephone line to The load will have to be connected to the normally closed the circuit and finally apply power to the circuit. If all is contacts, as shown in the schematic. Depending upon what well the buzzer will be quiet. Now disconnect the phone type of relay you chose for this project, you can go ahead line from the circuit; the buzzer should sound indicating and mount it. If you chose a small PC board type relay you the phone line is broken or cut. If nothing happens, you can mount this on the printed circuit board. If you chose a will have to make sure that your power supply is

larger style, then you will have to mount the relay off the working and that it is connected properly to the circuit, PC board either in a relay socket or with some sort of i.e. observe the polarity connections. If the circuit still mounting strap to the bottom of the chassis box.

does not work, remove the power and check to make

sure all the components are installed in their proper Once the circuit board has been completed, take a

locations and that the diodes and transistors have been short break and then we will inspect the PC board for installed correctly. Your Cut Phone Line Detector should possible “cold” solder joints and “short” circuits. Pick give you many years of reliable service.

up the PC board with the foil side facing upwards

toward you. Carefully inspect the solder joints, these should look smooth, clean, and bright. If any of the

Project 3: Phone line-

solder joints look dull, dark, or blobby, then you should remove the solder with a solder sucker or a solder wick in-use relay controller

and then resolder the joint all over again.

Now we will inspect the PC board for possible short

The Phone Line-in-Use Relay Controller can alert you

circuits. Short circuits can be caused from small solder to someone using or picking up a phone extension, or it blobs bridging the circuit traces from cut component

will permit you to control a load of your choice, such as leads, which can often stick to the circuit board.

a bell, buzzer, alarm siren, or talking voice reminder!

131

The Phone Line In-use Controller circuit is shown in

60/40 tin–lead solder, and a small canister of Tip Tinner, Figure 14-4. The circuit is designed to close a relay available at your local RadioShack store; Tip Tinner is when any extension goes off-hook either by accident

used to condition the soldering tip between solder

or intention. The circuit is pretty straightforward; the joints. You drive the soldering tip into the compound phone line is connected to points marked A and B in

and it cleans and prepares the soldering tip. Next grab a the diagram. The plus (+) phone lead is connected to

few small hand tools; try to locate small flat blade and point A, while the minus (−) phone line lead is

Phillips screwdrivers a pair of needle-nose pliers, a pair connected to point B. A capacitor is placed across the of tweezers along with a magnifying glass, and a pair of line at C1. Note that the voltage at the gate of the

end-cutters and we will begin constructing the project.

MOSFET should be negative at about 1–3 V with

Now locate your schematic diagram and parts layout

respect to the source when the phones are on-hook. The diagram along with all of the components needed to

voltage at the gate should be positive 8–10 V with

build the project. Once all the components are in front respect to the source (ground) when any phone

of you, you can check them off against the project parts extension is off-hook. A high impedance meter is

list to make sure you are ready to start building the needed to measure the on-hook voltages accurately.

project. Now, locate Tables 14-1 and 14-2, and place

The Phone Line In-use Controller circuit should draw

them in front of you.

less than 5 μA from the phone line. The relay (RLY1)

Table 14-1 illustrates the resistor code chart and

used for controlling the external load is a 12-V DC

how to read resistors, while Table 14-2 illustrates the 120 ohm coil, but almost any small 12-V DC relay

capacitor code chart which will aid you in constructing should work. Power supply regulation should be

the project.

+/− 2 V. The circuit provides both normally closed

Refer now to the resistor color code chart shown in

and normally open circuit contacts for external

Table 14-1, which will help you identify the resistors control of the alarm load device. The circuit is

used in the project. Note that each resistor will have powered from a 12-V DC power supply illustrated

either three or four color bands, which begin at one

in Figure 14-5.

end of the resistor’s body. The first colored band

represents the resistor’s first digit, while the second Circuit assembly

color represents the second digit of the resistor’s

value. The third colored band represents the resistor’s Before we begin constructing the Phone Line-in-Use

multiplier value, and the fourth color band represents Controller, you will need to find a clean, well-lit

the resistor’s tolerance value. If there is no fourth worktable or workbench. Next we will gather a small

colored band then the resistor has a 20% tolerance

25–30-W pencil tipped soldering iron, a length of

value. If the resistor’s fourth band is silver then

the resistor has a 10% tolerance value and if the

fourth band is gold then the resistor’s tolerance

+ 12 V DC

value will be 5%.

A

R1

Finally, we are ready to begin assembling the project, (+)

RLY1

so let’s get started. The prototype project was

N/C

constructed on a single-sided printed circuit board or To

D1

PCB. With your PC board in front of you, we can now

telephone

C1

R3

N/O

line

begin populating the circuit board. We are going to

D

Q1

place and solder the lowest height components first, the B

resistors and diodes. First locate our first resistor R1.

(−)

R2

R4

G

S

Resistor R1 has a value of 3.3 megohm and is a 5%

tolerance type. Now take a look for a resistor whose

first color band is orange, orange, green, and gold. From Figure 14-4

Phone line in-use relay controller.

the chart you will notice that orange is represented by Chapter Fourteen: Phone Line Status Circuits Courtesy of Bill Bowden the digit (3); the second color band is orange, which is 132

Chapter Fourteen: Phone Line Status Circuits

S1

F1

D1

Q1

R2

T1

+ 12 V DC

110 V AC

Q2

D2

R1

+

+

C1

D3

C2

C3

GND

Figure 14-5

12-V DC power supply

represented by (3). Notice that the third color is green circuit board. Once you have installed these first three and the multiplier is (100,000), so (3) (3) × 100,000 =

components, you can move on to installing the

3.3 megohms.

remaining low profile components.

Locate resistors R2 and R3 and place them in their

This project contains a single silicon diode. Diodes

respective locations on the PC board. Now you can

will always have some type of polarity markings, which solder them in place and then trim the excess

must be observed if the circuit is going to work

component leads flush to the edge of the circuit board correctly. You will notice that each diode will have a using your end-cutters.

black or white colored band at one edge of the diode’s Note that capacitors generally come from two major

body. The colored band represents the diode’s cathode groups or types. Non-polar types, such as the ones in lead. Check your schematic and parts layout diagrams

this project, have no polarity and can be placed in either when installing the diode on the circuit board. Note the direction on the circuit board. The other type of

diode is a 1N4004 diode. Place the diode on the circuit capacitors are called polarized types; these capacitors board and solder it in place on the PC board. Then cut have polarity and have to be inserted on the board with the excess component leads with your end-cutters.

respect to their polarity marking in order for the circuit The Phone Line-in-Use Relay Controller utilizes a

to operate correctly. On these types of capacitors, you single MOSFET transistor. Transistors are generally

will observe that the components actually have a plus or three lead devices, which must be installed correctly minus marking or a black or white band with a plus or if the circuit is to work properly. Careful handling and minus marking on the body of the capacitors.

proper orientation in the circuit is critical. This type Next refer to Table 14-2. This chart helps to

of MOSFET transistor has three leads, a Gate lead, a

determine the value of small capacitors. Many

Drain lead and a Source lead. The gate lead is

capacitors are quite small in physical size, so

connected to resistor R4, while the drain lead is

manufacturers have devised a three-digit code which

connected to the relay, and the source lead is connected can be placed on the capacitor instead of the actual

to ground. Be extremely careful when installing the

value. The code occupies a much smaller space on the

MOSFET since it is static sensitive and can be easily capacitor and can usually fit nicely on the capacitor damaged by static. If you have an anti-static band,

body, but without the chart the builder would have a

wear it while installing the MOSFET. If not, do not

difficult time determining the capacitor’s value.

move around or stand on a carpet when installing

Now locate the capacitor C1 from the component

the MOSFET. Be sure to refer to the component

stack, this capacitor will be labeled 0.1 μF, and will be specification sheet, and the schematic and parts layout a small size capacitor marked with (104); remember this diagrams when installing the MOSFET. Once you are

is the three-digit code representing the actual value. Go sure of its pin-out and orientation, you can go ahead ahead and place capacitor C1 on the circuit board and and install it on the circuit board. Solder it in place solder it in place. Now take your end-cutters and cut very carefully and then remove the excess component

the excess component leads flush to the edge of the

leads with your end-cutters.

133

Now you can go ahead and mount the relay. If you

phone line, and this can be done using a length of

chose a small PC board type relay, you can mount the

4-conductor phone wire with a modular plug attached

relay on the printed circuit board. If you chose a larger at one end of the cable, then you can connect the

conventional type relay, they you will have to use a

red and green wires to the phone line inputs. The

relay socket or small strap to mount the relay to the modular plug ends can then simply plug into a

chassis box.

telephone jack. You could also elect to hard-wire the Once the circuit board has been completed, take a

circuit directly to the phone line without the modular short break and then we will inspect the PC board for plugs if desired.

possible “cold” solder joints and “short” circuits. Pick up the PC board with the foil side facing upwards

Operation

toward you. Carefully inspect the solder joints; these should look smooth, clean, and bright. If any of the

Once your circuit has been mounted in an enclosure

solder joints look dull, dark, or blobby, then you should and wired to the phone lines, you will be ready to test remove the solder with a solder sucker or a solder wick the circuit. With power applied to the circuit and the and then resolder the joint all over again.

phone attached, you are ready to test the circuit. Have Now we will inspect the PC board for possible short

someone pickup a phone extension and the relay

circuits. Short circuits can be caused from small solder should then pull-in. In the event the circuit does not blobs bridging the circuit traces from cut component

work properly, you will need to remove the power and

leads, which can often stick to the circuit board.

disconnect the phone line and carefully examine the

A sticky residue from solder will often trap component circuit board for any errors. Check both circuit boards leads across the circuit traces. Look carefully for any very carefully. Common construction errors include

bridging wires across circuit traces.

placing components in the wrong location, reading

You will need to locate or build a 12-V DC power

the resistor color codes incorrectly, and installing

supply for this project. You could elect to simply

electrolytic capacitors backwards. Common

purchase a small 12-V “cube” or “wall wart” power

mistakes also include incorrect installation of

supply at a local electronics shop, such as a 12-V DC

diodes and transistors and ICs. Make sure the

550 mA power supply, or you could build the power

diodes, capacitors, transistors, and ICs have been

supply shown in Figure 14-5. The 12-V power supply is oriented correctly in the circuit. Once you have

built around a 25.2 V transformer, which takes 110 V AC

found and corrected your mistake, you can re-connect

and converts it to 25 V. The center tap connects to

the power supply and phone line and then re-test the

ground, while the two secondary leads are sent to two circuit. Also note that if the circuit does not operate diodes which rectify the AC to DC. The DC is first

once at this point, you may have to swap the telephone filtered by capacitor C1. A pass transistor at

line lead around. The Phone Line-in-Use Relay Controller Q1 is current limited by the Zener diode at D3. The 12-V

should serve you for many years to come.

DC output is filtered once again by capacitors C2 and C3, which provide a clean well filtered 12 V DC supply.

Once the power supply and the main Phone Line-in-Use

Project 4: Single phone

Controller circuit have been completed, you will want to wrap some sort of case or enclosure around the circuit line status light

and power supply. Locate a suitable enclosure for the project. Center the circuit boards inside the case and use It is always handy to know quickly at a glance if a

standoffs to mount the circuit board inside the case.

telephone is in use or if it is ringing. This circuit will Once the circuit boards are mounted securely, you

allow you to shut-off your ringer while others are

will have to mount the fuse holder on the rear of the sleeping and watch for the light to indicate someone is chassis as well as the power switch. You will need to calling late at night. This single line telephone status run the power line cord out the rear of the chassis.

light is easy to build and is powered from 3-V batteries Chapter Fourteen: Phone Line Status Circuits Finally, you will also need to connect the circuit to the for six months or longer. See Figure 14-6.

134

Chapter Fourteen: Phone Line Status Circuits

+ 3 V

+

B1

C1

U1:d

R5

R3

D7

9

14

8

R1

U1:f

5

6

13

12

D8

U1:c

D6

R4

R2

U1:e

11

10

D5

D4

D3

U1:b

3

4

1

2

D1

7

D2

U1:a

+

C2

Phone

A

line

B

Figure 14-6

Single line phone status light. Courtesy of Dave Johnson & Associates Circuit description

Circuit assembly

The sensing part of the circuit begins at the telephone Before we begin constructing the Single Line Phone

line input terminals (A) and (B). The telephone line

Status Indicator, you will need to locate a clean, well-lit connects directly to a diode bridge circuit consisting worktable or workbench. Next we will gather a small

of diodes D1 through D4. The diode bridge converts

25–30 W pencil tipped soldering iron, a length of

the incoming AC ringing voltage to DC and provides

60/40 tin–lead solder, and a small canister of Tip Tinner, clean DC voltage to the Zener diode at D5. The voltage available at your local RadioShack store; Tip Tinner is from the Zener is next passed on to a Hex Schmitt

used to condition the soldering tip between solder

triggered inverter at U1:c. The Hex inverter cleans up joints. You drive the soldering tip into the compound the signal slightly, and the output of the inverter is then and it cleans and prepares the soldering tip. Next grab a fed to a silicon diode at D6. The telephone status signal few small hand tools; try to locate small flat blade and is then coupled to resistor R4, which is in parallel with Phillips screwdrivers. A pair of needle-nose pliers, a inverter section U1:a. Diode D7 and series resistor R3

pair of tweezers along with a magnifying glass, and a are used to prevent current “back-flow.” The resulting pair of end-cutters and we will begin constructing the status signal is then inverted once again and at the

project. Now locate your schematic diagram and parts

“bank” of inverters placed in parallel. The output of the layout diagram along with all of the components needed inverter bank is then coupled to the indicator LED at to build the project. Once all the components are in

D8. The average current when the LED is flashing is

front of you, you can check them off against the project about 120 μA and the forward peak LED current is

parts list to make sure you are ready to start building the 15 mA, so the circuit does not draw very much

project. Now, locate Tables 14-1 and 14-2, and place

current from the battery and therefore no power

them in front of you.

switch is utilized and the 3-V battery supply should

last six months or more. The Single Line Telephone

Table 14-1 illustrates the resistor code chart and

Status Light is not polarity sensitive and can be

how to read resistors, while Table 14-2 illustrates the connected to the phone line without fear of damaging

capacitor code chart which will aid you in constructing the circuit.

the project.

135

Refer now to the resistor color code chart shown in

Next refer to Table 14-2. This chart helps to

Table 14-1, which will help you identify the resistors determine the value of small capacitors. Many

for the project. Note that each resistor will have either capacitors are quite small in physical size, so

three or four color bands, which begin at one end of the manufacturers have devised a three-digit code which

resistor’s body. The first colored band represents the can be placed on the capacitor instead of the actual

resistor’s first digit, while the second color represents value. The code occupies a much smaller space on the

the second digit of the resistor’s value. The third colored capacitor and can usually fit nicely on the capacitor band represents the resistor’s multiplier value, and the body, but without the chart the builder would have a

fourth color band represents the resistor’s tolerance difficult time determining the capacitor’s value.

value. If there is no fourth colored band then the resistor Now locate the capacitors from the component pile

has a 20% tolerance value. If the resistor’s fourth band and try and locate capacitor C1, which is an electrolytic is silver then the resistor has a 10% tolerance value and capacitor and will be labeled 10 μF; it should have a if the fourth band is gold then the resistor’s tolerance small black or white band with a plus or minus marking value will be 5%.

on or near the band. Be sure to observe this polarity Finally, we are ready to begin assembling the

marking when installing this capacitor on the circuit project, so let’s get started. The prototype project was board. Next locate capacitor C2, a .15 μF capacitor,

constructed on a single-sided printed circuit board or which will be a small size capacitor marked with (154).

PCB. With your PC board in front of you, we can now

Remember, this is the three-digit code representing the begin populating the circuit board. We are going to

actual value (refer to Table 14-2). Go ahead and place place and solder the lowest height components first, the R1, C1, and C2 on the circuit board and solder them in resistors and diodes. First locate our first resistor R1.

place. Now take your end-cutters and cut the excess

Resistor R1 has a value of 4.7 megohms and is a

component leads flush to the edge of the circuit board.

5% tolerance type. Now take a look for a resistor

Once you have installed these first three components, you whose first color band is yellow, violet, green, and

can move on to installing the remaining low profile

gold. From the chart you will notice that yellow is

components.

represented by the digit (4), the second color band is This project contains a number of silicon diodes as

violet, which is represented by (7). Notice that the

well a Zener diode. Diodes will always have some type third color is green and the multiplier is (100,000), of polarity markings, which must be observed if the

so (4) (7) × 100,000 = 4,700,000 ohms. Go ahead and

circuit is going to work correctly. You will notice that place R1 on the PC board and solder it in its respective each diode will have a black or white colored band at location. Next, use your end-cutter to trim the excess one edge of the diode’s body. The colored band

component leads flush to the edge of the PC board.

represents the diode’s cathode lead. Check your

Now locate the remaining resistors and place them

schematic and parts layout diagrams when installing

on the PC board at their proper location. Next, solder these diodes on the circuit board. Note that D5 is a

them in place, and remember to trim the excess

Zener diode. Diodes D1 through D4 are all 1N4004

lead lengths.

diodes which are the phone line input diodes. They

all have a larger voltage/current rating since they are Note that capacitors generally come from two major

placed on the telephone line. The remaining diodes,

groups or types. Non-polar types, such as the ones in D6 and D7, are small signal silicon diodes. Place all this project, have no polarity and can be placed in either the diodes on the circuit board and solder them in

direction on the circuit board. The other type of

place on the PC board. Then cut the excess component

capacitors are called polarized types; these capacitors leads with your end-cutters flush to the edge of the

have polarity and have to be inserted on the board with circuit board.

respect to their polarity marking in order for the circuit to operate correctly. On these types of capacitors, you This Single Line Status Light circuit also contains

will observe that the components actually have a plus or one IC at U1. ICs will also have some sort of marking minus marking or a black or white band with a plus or to help you orient them on the PC board. Often there

Chapter Fourteen: Phone Line Status Circuits minus marking on the body of the capacitors.

will be a small indented circle, a small notch, or cutout 136

Chapter Fourteen: Phone Line Status Circuits

at the top end of the IC package. Pin of the device will of 4-conductor phone wire with a modular plug attached be just to the left of the notch, or cutout. It is highly at one end of each of the cables. Since the circuit is not recommended that the circuit builder use IC sockets

sensitive to incorrect polarity, you can connect the red for the ICs. IC sockets are low cost insurance

and green wires from each cable to each of the phone

against a possible circuit failure at some later date.

line inputs. The modular plug ends can then simply plug It is much easier to simply unplug an IC rather than

into a telephone jack. You could elect to hard-wire the trying to unsolder many IC pins from a PC board

circuit directly to the phone line without the modular without causing damage to the PC board. Go

plugs if desired.

ahead and install the IC on the PC board and solder

it in place.

Operation

The Single Line Phone Status Light circuit uses

a single indicator LED at D8, which also must be

Once you circuit has been mounted in an enclosure and oriented correctly if the circuit is to function properly.

wired to the phone line, you are now ready to test the An LED has two leads, a cathode and an anode lead.

circuit. Have someone call phone line and look for the The anode lead will usually be the longer of the two

LED to flash at D8. You can also test the in-use function leads and the cathode lead will usually be the shorter by simply picking up the phone receiver and looking at lead, just under the flat side edge of the LED; this

the LED. Your Single Line Phone Status Light is now

should help orient the LED on the PC board. Solder

ready to serve you for many years to come.

the LEDs to the PC board and then trim the

Now you will know if your phone line is ringing and

excess leads.

if someone has picked up an extension while you are on Once the circuit board has been completed, take a

the phone. Two “C” or “D” cell batteries should last for short break and then we will inspect the PC board for at least 6 months.

possible “cold” solder joints and “short” circuits. Pick up the PC board with the foil side facing upwards

toward you. Carefully inspect the solder joints; these should look smooth, clean, and bright. If any of the

Project 5: Two-Line Phone

solder joints look dull, dark, or blobby, then you should status indicator

remove the solder with a solder sucker or a solder wick and then resolder the joint all over again.

Many home businesses use multiple phone lines. This

Now we will inspect the PC board for possible short

circuit gives you a visual indication when a line is in circuits. Short circuits can be caused from small solder operation. The two AA battery cells should provide

blobs bridging the circuit traces from cut component

enough power for about one year of operation. The

leads, which can often stick to the circuit board.

circuit is line polarity insensitive.

A sticky residue from solder will often trap component leads across the circuit traces. Look carefully for any The Two-Line Phone Status Indicator circuit will

bridging wires across circuit traces. Once this inspection allow you to monitor the status of two telephone lines is complete, we can move on to installing the circuit using a single circuit. The 2-line phone monitor is

board into some sort of plastic enclosure.

depicted in Figure 14-7. The phone line enters the

circuit at two different points (A) and (B) for phone line Locate a suitable enclosure to house the circuit and

number one and at terminals (C) and (D) for phone

the 2-cell battery holder. Choose a two “C” or “D” cell number two.

battery holder for the circuit, arrange the battery holder and circuit board within the enclosure, and mount the The first diodes bridge, on phone line #1, consists of circuit board on standoffs within the enclosure. The

diodes D1 through D4. The resulting line status signal is battery can be hardwired directly to the circuit and the passed to resistor R2 and then through D9 which drives batteries should last at least 6 to 12 months with normal transistor Q1. Transistor Q1 is then used to drive the operation. You will also need to connect the circuit to photo transistor Q2, which applies current to LED D10.

the two phone lines. This can be done using two lengths LED D10 forms the “sending” unit in an opto-coupler

137

S1

+ 3 V

+

+

B1

C1

D1

+

R1

3 V

+

Q2

A

+ 3 V

+ 3 V

D2

Q1

Phone

Q3

R2

line

D3

D9

D10

14

D13

#1

R3

1

R7

Opt-1

U1:a

3

2

B

R4

+ 3 V

D4

R5

D11

13

4

6

U1:d

Sms

U1:b

11

12

flash

5

D13

R9

R6

D12

R8

C2

D5

R15

+ 3 V

+

Q5

+ 3 V

C

D6

Q6

Phone

Q4

R14

D14

line

D7

D16

D15

R13

9

#2

8

U1:c

Opt-2

10

R10

7

R12

D

R11

D8

Figure 14-7

Two-Line Phone status indicator. Courtesy of Dave Johnson & Associates which activates the “receive” unit in the opto-coupler.

drives the photo transistor at Q5. The isolated line

Q3 receives the isolated light signal which is passed on

#2 status signal once at photo transistor Q4 is next

to D11 and U1:a. This divided signal now goes in two

passed on to U1:c, which drives D14 when phone line

directions. The signal is sent to the input of a 74HC132,

#2 is activated. The line status signal is also split at the a Quad 2-input NAND Schmitt trigger IC, at U1:a.

junction of R11 and U1:c. The signal is sent via

This NAND Schmitt Trigger is used to drive the LED at D12 to one input of U1:b. The output of U1:b is fed

D13. LED D13 will indicate when phone line #1 is in

directly via pin 6 on to pin12 of U1:d which provides use. Remembering the divided signal we talked about

a “flash” signal when the phone line #2 rings. This

earlier, let’s now go back to the junction or R5 and D11.

flash signal is coupled back to pin9 of U1:c in order to Diode D11 directs the output from the opto-coupled

flash the LED at D14 when a ring signal is present on ring signal from telephone line #1 and feeds it to U1:b, phone line #2.

which is sent to U1:d. The output from U1:d is a “flash”

signal which is sent back to U1:a on pin 1. This circuit Circuit assembly

allows the ring signal to flash the LED at D13 on

telephone line #1.

Before we begin constructing the Two-Line Phone

Phone line #2 accepts the telephone line at terminals Status Indicator, you will need to find a clean, well-lit (C) and (D) and directs the line status signal through the worktable or workbench. Next we will gather a small

diode bridge at D5 through D8. The diode bridge passes 25–30-W pencil tipped soldering iron, a length of

Chapter Fourteen: Phone Line Status Circuits the line input signal on to transistor Q6 which in turn 60/40 tin–lead solder, and a small canister of Tip Tinner, 138

Chapter Fourteen: Phone Line Status Circuits

available at your local RadioShack store; Tip Tinner is Go ahead and place resistor R1 on the PC board and

used to condition the soldering tip between solder

solder it in place in its respective location. Next take your joints. You drive the soldering tip into the compound end-cutters and trim the excess component leads flush to and it cleans and prepares the soldering tip. Next grab a the edge of the circuit board. Next locate the remaining few small hand tools; try to locate small flat blade and resistors and place them in their correct locations and Phillips screwdrivers. A pair of needle-nose pliers,

solder them in place, remembering to trim the excess

a pair of tweezers along with a magnifying glass, and a leads with your end-cutters.

pair of end-cutters and we will begin constructing the Next refer to Table 14-2; this chart helps to determine project. Now locate your schematic diagram and parts

the value of small capacitors. Many capacitors are quite layout diagram along with all of the components needed small in physical size, so manufacturers have devised a to build the project. Once all the components are in

three-digit code which can be placed on the capacitor front of you, you can check them off against the project instead of the actual value. The code occupies a much parts list to make sure you are ready to start building the smaller space on the capacitor and can usually fit

project. Now, locate Tables 14-1 and 14-2, and place

nicely on the capacitor body, but without the chart the them in front of you.

builder would have a difficult time determining the

Table 14-1 illustrates the resistor code chart and

capacitor’s value.

how to read resistors, while Table 14-2 illustrates the Note that capacitors generally come from two major

capacitor code chart which will aid you in constructing groups or types. Non-polar types, such as the ones in the project.

this project, have no polarity and can be placed in either Refer now to the resistor color code chart shown in

direction on the circuit board. The other type of

Table 14-1, which will assist you in identifying the

capacitors are called polarized types; these capacitors resistors used in this project. Note that each resistor will have polarity and have to be inserted on the board with have either three or four color bands, which begin at respect to their polarity marking in order for the circuit one end of the resistor’s body. The first colored band to operate correctly. On these types of capacitors, you represents the resistor’s first digit, while the second will observe that the components actually have a plus or color represents the second digit of the resistor’s value.

minus marking or a black or white band with a plus or The third colored band represents the resistor’s

minus marking on the body of the capacitors.

multiplier value, and the fourth color band represents Now locate the capacitors from the component pile

the resistor’s tolerance value. If there is no fourth and try and locate capacitor C1, which is an electrolytic colored band then the resistor has a 20% tolerance

capacitor will be labeled 10 μF, and should have a small value. If the resistor’s fourth band is silver then the black or white band with a plus or minus marking on or resistor has a 10% tolerance value and if the fourth band near the band. Be sure to observe this polarity marking is gold then the resistor’s tolerance value will be 5%.

when installing this capacitor on the circuit board. Next Finally we are ready to begin assembling the project, locate capacitor C2, which will be a small size capacitor so let’s get started. The prototype project was

marked with (473); remember this is the three-digit

constructed on a single-sided printed circuit board or code representing the actual value (refer to Table 14-2).

PCB. With your PC board in front of you, we can now

Go ahead and place C1 and C2 on the circuit board and begin populating the circuit board. We are going to

solder them in place. Now take your end-cutters and cut place and solder the lowest height components first, the the excess component leads flush to the edge of the

resistors and diodes. First, locate our first resistor R1.

circuit board. Once you have installed these first three Resistor R1 has a value of 220 ohms and is a 5%

components, you can move on to installing the

tolerance type. Now take a look for a resistor whose first remaining low profile components.

color band is yellow, violet, green, and gold. From the chart This project contains a number of silicon and Zener

you will notice that yellow is represented by the digit (4), diodes. Diodes will always have some type of polarity the second color band is violet, which is represented by markings, which must be observed if the circuit is going (7). Notice that the third color is green and the multiplier to work correctly. You will notice that each diode will is (100,000), so (4) (7) × 100,000 = 4,700,000 ohms.

have a black or white colored band at one edge of the 139

diode’s body. The colored band represents the diode’s opto-coupler and the integrated circuit on the PC board cathode lead. Check your schematic and parts layout

and solder them in place.

diagrams when installing these diodes on the circuit

The Two-Line Phone Status Indicator circuit uses two

board. Note that D9 and D16 are both Zener diodes.

LED, which also must be oriented correctly if the

Diodes D1 through D8 are all 1N4004 diodes, which

circuit is to function properly. An LED has two leads, a are the phone line input diodes. They all have a larger cathode and an anode lead. The anode lead will usually voltage/current rating since they are placed on the

be the longer of the two leads and the cathode lead will telephone line. The remaining diodes are all small

usually be the shorter lead, just under the flat side edge signal silicon diodes. Place all the diodes on the

of the LED, this should help orient the LED on the

circuit board and solder them in place on the PC board.

PC board. Solder the LEDs to the PC board and then

Then cut the excess components lead with your

trim the excess leads.

end-cutters.

Once the circuit board has been completed, take a

The Two-Line Phone Status Indicator utilizes four

short break and then we will inspect the PC board for conventional transistors and two photo opto-coupler

possible “cold” solder joints and “short” circuits. Pick transistors. Transistors are generally three lead

up the PC board with the foil side facing upwards

devices, which must be installed correctly if the

toward you. Carefully inspect the solder joints; these circuit is to work properly. Careful handling and

should look smooth, clean, and bright. If any of the

proper orientation in the circuit is critical. A transistor solder joints look dull, dark, or blobby, then you should will usually have a Base lead, a Collector lead, and an remove the solder with a solder sucker or a solder wick Emitter lead. The base lead is generally a vertical line and then resolder the joint all over again.

inside a transistor circle symbol. The collector lead is Now we will inspect the PC board for possible short

usually a slanted line facing towards the base lead and circuits. Short circuits can be caused from small solder the emitter lead is also a slanted line facing the base blobs bridging the circuit traces from cut component

lead but it will have an arrow pointing towards or

leads, which can often stick to the circuit board.

away from the base lead.

A sticky residue from solder will often trap component The photo opto-coupler transistor consists of an

leads across the circuit traces. Look carefully for any LED and photo transistor in a small DIP package

bridging wires across circuit traces. Once this inspection which looks like a small IC. These will often

is complete, we can move on to installing the circuit have a small notch, or cutout at the top end of the

board into some sort of plastic enclosure.

plastic package. Generally pin 1 of the device is

Locate a suitable enclosure to house the circuit and

just to the left of this notch, or cutout. Pay careful the 2-cell battery holder. Choose a two “C” or “D” cell attention to the pinouts of these devices and use

battery holder for the circuit and arrange the battery the schematic and parts layout and component

holder and circuit board within the enclosure and

specification sheets to install these opto-couplers

mount the circuit board on standoffs within the

onto the circuit board.

enclosure. The battery can be hardwired directly to

This circuit also contains an IC at U1. ICs will also the circuit and the batteries should last at least

have some sort of marking to help you orient them

6 to 12 months with normal operation. You will also

on the PC board. Often there will be a small indented need to connect the circuit to the two phone lines. This circle, a small notch, or cutout at the top end of the can be done using two lengths of 4-conductor phone

IC package. Pin of the device will be just to the left wire with a modular plug attached at one end of each

of the notch, or cutout. It is highly recommended

of the cables. Since the circuit is not sensitive to

that the circuit builder use IC sockets for the ICs.

incorrect polarity, you can connect the red and green IC sockets are low cost insurance against a possible

wires from each cable to each of the phone line inputs.

circuit failure at some later date. It is much easier to The modular plug ends can then simply plug into a

simply unplug an IC rather than trying to unsolder

telephone jack. You could elect to hardwire the circuit many IC pins from a PC board with out causing

directly to the phone line without the modular plugs

Chapter Fourteen: Phone Line Status Circuits damage to the PC board. Go ahead and install the if desired.

140

Chapter Fourteen: Phone Line Status Circuits

automatically turn on a “night-light” for a period of Operation

time, so you can see where the telephone is and perhaps take notes or write down a important message. The

Once your circuit has been mounted in an enclosure and Smart Phone Light will assist you getting your slippers wired to the phone lines, you are now ready to test it.

on or finding a pad and paper at your night-stand. This Have someone call phone line #1 first and look for the is a very handy circuit; you may want to build a few of LED to flash at D13. Then have someone call phone

them and place them in different bedrooms, or give one line #2 and you should see LED D14 start to flash with to an older person.

the ringing. You can also test the in-use function by simply picking up each phone receiver on each line and looking at the LEDs. Your Two-Line Phone Status

Circuit description

Indicator is now ready to serve you for many years to come. Now you will know if a phone line is ringing or The Smart Phone Light circuit shown in Figure 14-8 is if someone has picked up an extension.

used to switch on a lamp when the telephone rings.

The circuit uses only two ICs, and it can be built quite easily. A light dependent resistance (LDR), with about Project 6: Smart phone

5 kilo-ohms resistance in the ambient light and greater than 100 kilo-ohms in darkness, is at the heart of the light

circuit. The circuit is fully isolated from the phone lines and it draws current only when the phone rings.

The Smart Phone Light is designed to switch on a lamp The circuit provides automatic switching on of a

when the telephone rings. If the ambient room lighting lamp during darkness when the phone is kept in a

is insufficient when the phone rings, the circuit will place such as the bedroom. The lamp can be battery

+ 5 V

LDR

16

RLY1

R3

CEXT

CEXT

14

6

D2

C2

C3

1

5

+

U3:A

+

R4

R5

U3:B

R2

15

7

U1

R7

A

A

5

Q1

1

13

9

Q

B

Q

2

4

L1

2

10

B

R6

3

Ring

11

12

8

4

CLR

CLR

R8

Q

Q

C1

R1

U2

1

5

N/C

S1

110 V AC

D1

2

4

Tip

Figure 14-8

Smart phone light project

141

powered to provide light during power failure or

sensitivity of LDR can be changed by changing

load shedding. This avoids delay in attending

resistance R2 connected at collector of the transistor in to a call. The light switches off automatically after light monitor circuit. Similarly, switch-on period of the a programmable time period and it needs no attention

lamp can be controlled by changing capacitor C3’s

at all. If required, the lamp lighting period

value in the second 74123(B) monostable circuit. The

can be extended by simply pressing a pushbutton

diagram shown in Figure 14-9 illustrates the timing

switch (S1). The first part of the circuit functions as waveforms during different circuit modes of operation.

a ring detector.

When telephone is on-hook, around 48 V DC is

Circuit assembly

present across the TIP and RING terminals. The diode

in the opto-coupler is “off” during this condition and it Before we begin constructing the Smart Phone Light

draws practically no current from he telephone lines.

circuit, you will need to find a clean, well-lit worktable The opto-coupler also isolates the circuit from the

or workbench. Next we will gather a small 25–30-W

telephone lines. Transistor in the opto-coupler is

pencil tipped soldering iron, a length of 60/40 tin–lead normally “off” and a voltage of +5 V is present at the solder, and a small canister of Tip Tinner, available at ring indicator line. When telephone rings, an AC voltage your local RadioShack store; Tip Tinner is used to

of around 70–80 V AC, which is present across the

condition the soldering tip between solder joints. You telephone lines, is used to turn on the diode inside the drive the soldering tip into the compound and it cleans opto-coupler (IC2), which in turn switches on a

and prepares the soldering tip. Next grab a few small transistor inside the opto-coupler. The voltage at its collector passes through 0-V level during ringing to

trigger IC3 74LS123(A) monostable flip-flop. The other A Day/night indicator

opto-coupler (IC1) is used to detect the ambient light 5 V

condition. When there is sufficient light, LDR has a low resistance of about 5 kilo-ohms and the transistor inside the opto-coupler is in “on” state. When there is

0 V

insufficient light available, the resistance of LDR

Ambient

Dark

light on

increases to a few megohms and the transistor switches to “off” state. Thus the DC voltage present at the

collector of transistor inside the opto-coupler is

B Ring indicator

normally 0 V and it jumps to 5 V when there is no light 5 V

or insufficient light. The 74LS123 retriggerable

monostable multivibrator is used to generate a

programmable pulse-width. The first monostable

0 V

No

Ring detect

74LS123(A) generates a pulse from the trigger input

ring

available during ringing, provided its pin 2 input

(marked B) is logic high (i.e. during darkness).

It remains high for the programmed duration and

C Monostable

5 V

switches back to 0 V at the end of the pulse period. This high-to-low transition (trailing edge) is used to trigger the second monostable flip-flop 74LS123(B) in the

same package. Output of the second monostable is used D Monostable

to control a relay. The lamp being controlled via the N/O contacts of the relay gets switched “on.” The “on”

Program

period can be extended by simply pressing pushbutton

delay

switch S1. If nobody attends the phone, the light turns Lamp switched on

Light off

off automatically after the specific time period equal to Chapter Fourteen: Phone Line Status Circuits the pulse-width of the second flip-flop. The light Figure 14-9

Smart phone light waveforms

142

Chapter Fourteen: Phone Line Status Circuits

hand tools, and try to locate small flat blade and

excess leads flush to the edge of the circuit board. Next Phillips screwdrivers. A pair of needle-nose pliers,

locate the remaining resistors, place them in their proper a pair of tweezers along with a magnifying glass, and a locations, then solder them in place. Remember to cut pair of end-cutters and we will begin constructing the the excess lead lengths with your end-cutters.

project. Now locate your schematic diagram and parts

Note that capacitors generally come from two major

layout diagram along with all of the components needed groups or types. Non-polar types, such as the ones in to build the project. Once all the components are in

this project, have no polarity and can be placed in either front of you, you can check them off against the project direction on the circuit board. The other type of

parts list to make sure you are ready to start building the capacitors are called polarized types, these capacitors project. Now, locate Tables 14-1 and 14-2, and place

have polarity and have to be inserted on the board with them in front of you.

respect to their polarity marking in order for the circuit Table 14-1 illustrates the resistor code chart and

to operate correctly. On these types of capacitors, you how to read resistors, while Table 14-2 illustrates the will observe that the components actually have a plus or capacitor code chart which will aid you in constructing minus marking or a black or white band with a plus or the project.

minus marking on the body of the capacitors.

Refer now to the resistor color chart in Table 14-1,

Next refer to Table 14-2; this chart helps to determine which will help you to identify the resistor values for the value of small capacitors. Many capacitors are quite this project. Note that each resistor will have either small in physical size, so manufacturers have devised a three or four color bands, which begin at one end of the three-digit code which can be placed on the capacitor resistor’s body. The first colored band represents the instead of the actual value. The code occupies a much resistor’s first digit, while the second color represents smaller space on the capacitor and can usually fit

the second digit of the resistor’s value. The third colored nicely on the capacitor body, but without the chart the band represents the resistor’s multiplier value, and the builder would have a difficult time determining the

fourth color band represents the resistor’s tolerance capacitor’s value.

value. If there is no fourth colored band then the resistor Now locate the capacitors from the component pile

has a 20% tolerance value. If the resistor’s fourth band and try and locate capacitor C1, which is an electrolytic is silver then the resistor has a 10% tolerance value and capacitor will be labeled 1 μF, and it should be a large if the fourth band is gold then the resistor’s tolerance 250 volt paper non-electrolytic capacitor with no

value will be 5%.

polarity markings. Next locate capacitor C2, which will Finally we are ready to begin assembling the project, be 47 μF electrolytic capacitor, while C3 is a 1,000 μF

so let’s get started. The prototype project was

electrolytic capacitor. Go ahead and place R1, C1, C2, constructed on a single-sided printed circuit board or and C3 on the circuit board and solder them in place on PCB; with your PC board in front of you, we can now

the circuit board. Now take your end-cutters and cut the begin populating the circuit board. We are going to

excess component leads flush to the edge of the circuit place and solder the lowest height components first, the board. Once you have installed these first three

resistors and diodes. First, locate our first resistor R1.

components, you can move on to installing the

Resistor R1 has a value of 20 K ohms and is a 5%

remaining low profile components.

tolerance type. Now take a look for a resistor whose

This project contains a two of silicon diodes. Diodes first color band is red, black, orange, and gold. From the will always have some type of polarity markings, which chart you will notice that red is represented by the

must be observed if the circuit is going to work

digit (2), the second color band is black, which is

correctly. You will notice that each diode will have a represented by (0). Notice that the third color is orange black or white colored band at one edge of the diode’s and the multiplier is (1,000), so (2) (0) × 1,000 = 20,000

body. The colored band represents the diode’s cathode or 20 K ohms.

lead. Check your schematic and parts layout diagrams

Go ahead and place resistor R1 in its respective

when installing these diodes on the circuit board. Note, location on the PC board. Solder it in place and then diodes D1 and D2 are both 1N4007 silicon diodes.

trim the excess leads using your end-cutters. Cut the Place the two diodes on the circuit board and solder

143

them in place on the PC board. Then cut the excess

As mentioned, the heart of the Smart Phone Light

components leads flush to the edge of the PC board

circuit uses two LEDs, which also must be oriented

with your end-cutters.

correctly if the circuit is to function properly. The LDR

does not have polarity, so it can be installed in either The Smart Phone Light utilizes one conventional

direction.

transistor and two opto-couplers. Transistors are

generally three lead devices, which must be installed If you elected to use a PC board type relay at RLY1,

correctly if the circuit is to work properly. Careful you can go ahead and mount it on the PC board and

handling and proper orientation in the circuit is critical.

wire it up. If you elected to use a non PC board style A transistor will usually have a Base lead, a Collector relay then you will have to wire it up to the circuit with lead, and an Emitter lead. The base lead is generally a separate wiring, and then mount the relay using a strap vertical line inside a transistor circle symbol. The

mounted to the bottom of the chassis box.

collector lead is usually a slanted line facing towards Once the circuit board has been completed, take a

the base lead and the emitter lead is also a slanted line short break and then we will inspect the PC board for facing the base lead but it will have an arrow pointing possible “cold” solder joints and “short” circuits. Pick towards or away from the base lead.

up the PC board with the foil side facing upwards

The photo opto-couplers consist of an LED and

toward you. Carefully inspect the solder joints; these photo transistor in a small DIP package which will

should look smooth, clean, and bright. If any of the

look like a small IC. The opto-couplers will often have solder joints look dull, dark, or blobby, then you should a small notch, or cutout at the top end of the plastic remove the solder with a solder sucker or a solder wick package. Generally pin 1 of the device is just to the and then resolder the joint all over again.

left of this notch, or cutout. Pay careful attention to Now we will inspect the PC board for possible short

the pinouts of these devices and use the schematic

circuits. Short circuits can be caused from small solder and parts layout and component specification

blobs bridging the circuit traces from cut component

sheets to install the opto-couplers onto the circuit

leads, which can often stick to the circuit board.

board. Go ahead and install the transistor at Q1

A sticky residue from solder will often trap component and the opto-couplers at U1 and U2. Solder them

leads across the circuit traces. Look carefully for any in place and remember to trim the excess

bridging wires across circuit traces. Once this inspection component leads.

is complete, we can move on to installing the circuit This circuit also contains an IC at U3. ICs will also board into some sort of plastic enclosure.

have some sort of marking to help you orient them on

If you elected to build a 5-V power supply you can

the PC board. Often there will be a small indented

refer to the schematic shown in Figure 14-10.

circle, a small notch, or cutout at the top end of the IC package. Pin of the device will be just to the left The power supply can be constructed on a PC board,

of the notch, or cutout. It is highly recommended

with the transformer mounted directly on the chassis.

that the circuit builder use IC sockets for the ICs.

Power is applied to the transformer primary. The

IC sockets are low cost insurance against a possible

secondary winding of the 25 V center tapped

circuit failure at some later date. It is much easier transformer is sent to two diodes, and then fed to the to simply unplug an IC rather than trying to unsolder 1,000 μF capacitor at C1. The 5-V regulator is

many IC pins from a PC board with out causing

mounted on a small heat sink and isolated from the

damage to the PC board. After installing the

PC board. The output of the regulator is coupled to

integrated circuit socket, you can insert the IC

capacitor C2 followed by C3. Resistor R1 and the

into its socket. The transistor, opto-couplers,

LED are wired in series across the 5-V power

and the IC must be installed properly, so as

supply output.

not to damage the components or other components

Arrange the circuit board and power supply, if you

in the circuit. If you doubt your abilities, have a

elected to build one, within the enclosure and mount the knowledgeable electronics enthusiast help you install circuit board on standoffs within the case. The power Chapter Fourteen: Phone Line Status Circuits these components.

supply can be hardwired directly to the Smart Phone

144

Chapter Fourteen: Phone Line Status Circuits

LM7805

S1

F1

D1

U1

+ 5 V DC

T1

R1

+

+

+

C1

C2

C3

D3

110 V AC

GND

D2

Figure 14-10

Smart phone light 5-V power supply

Light circuit. You will also need to connect the circuit to the phone line. This can be done using two lengths of Project 7: Telephone line

4-conductor phone wire with a modular plug attached at one end of each of the cables. The modular plug ends

vigilant

can then simply plug into a telephone jack. You could elect to hard-wire the circuit directly to the phone line The Telephone Line Vigilant circuit will guard against without the modular plugs if desired. The load or lamp misuse of your telephone lines. It monitors telephone at L1 can be a small 110-V lamp if desired which is

lines round the clock and provides visual as well as

connected to the relay. A 110-V AC power source is

audio warning when someone is using your telephone

wired in series with the lamp to the relay, and you are lines. The Vigilant can alert you anywhere in the house.

almost ready to try out the circuit for the first time.

Another advantage of using this circuit is that one

comes to know of the misuse and/or snapping of the

lines instantaneously on its occurrence. This enables the Operation

telephone subscriber to take necessary measures

immediately.

Once your circuit has been mounted in an enclosure and Even when you, the subscriber, are using this

wired to the phone lines, you will be ready to test the telephone while the vigilant circuit is on, the buzzer circuit. Connect up a 5-V power supply to the circuit.

beeps once every 5 s, since the vigilant circuit cannot Next, connect the circuit to the phone line. Now you

distinguish between self-use of the subscriber lines or can press switch S1 and the lamp at L1 should light-up.

that of any unauthorized person. Thus to avoid

If that works you can move on to testing the circuit.

unnecessary disturbance, it is advisable to install the Turn off the lights in the room and then have someone vigilant unit away from the phone. However, if one

call your phone number. As the phone rings you should wishes to place the unit near the telephone then switch see the lamp L1 light-up for the duration of the timing S1 may be flipped to “off” position to switch off the circuit controlled by C2/R4 and R5/C3. If nothing

buzzer. But remember to flip the switch to “on” position happens when the phone rings, you may have made a

while replacing the handset on cradle.

mistake in building the circuit. Disconnect the power supply and the phone line from the circuit. Carefully examine the circuit board to make sure that all the

Circuit description

components are in their respective locations and

oriented correctly. Have an electronics enthusiast

The Telephone Line Phone Vigilant circuit is illustrated recheck your wiring to make sure that you did not make in Figure 14-11. The circuit may be divided into two

any mistakes. Once your problem has been corrected

parts. The first part comprises Zener D9, transistors you can reconnect the power supply and the phone line T1 to T4 and diode D5. It is used to verify whether

and your Smart Phone Light is ready to serve you.

the telephone line loop is intact or discontinuous.

145

R1

VR1

D9

R4

R6

R7

D1

D2

Telephone

R2

Q1

line

LED1

Q4

D3

D4

Q2

R3

Q3

+

C1

R5

VR2

D5

D10

Q7

Q10

R9

R11

R12

R13

R14

R15

R16

VR3

Q5

+

D6

Q6

+

C2

C3

−

S1

LED2

Off-on

R8

R10

Q9

Q8

Buzz

+9 V

T1

D7

D8

+

+

110 V

C4

B1

Figure 14-11

Telephone line vigilant

The second part comprising Zener D10 and transistors

capacitor C1 is used to check telephone line conditions T5 to T10 is used to check whether the telephone line is as per Table 14-3. This circuit draws negligible current in use (or misuse) or not. The Zener diode D9 (3.3 V) from the telephone line; thus when it is connected

conducts when phone line loop is intact and not broken.

to the telephone line, the normal telephone operation Zener D9 sets control voltage for transistors T1, T2, and is not affected.

T3 to conduct and for T4 to cut off. As a result, green When phone line loop is discontinuous, no voltage is

LED lights but no sound is heard from the buzzer. The available across capacitor C1. Thus Zener D9 and

Phone Vigilant circuit is insensitive to telephone line transistors T1, T2, and T3 do not conduct while

polarity at the input to the circuit; proper DC polarity is T4 conducts. Now green LED extinguishes and a

maintained across C1 due to bridge rectifier comprising continuous sound is heard from the buzzer. When

diodes D1 to D4. The DC voltage developed across

telephone line is all right but is not in use, Zener D10

Table 14-3

Phone line vigilant status condition chart

Number

Line Condition

Green LED

Red LED

Line Voltage

Audio Indication

1

disconnected

not lit

lit up

0 V

continuous sound

2

line inuse

lit up

lit up

9 V DC

beep-every 5 sec

Chapter Fourteen: Phone Line Status Circuits 3

line not in use

lit up

not lit

48 V DC

no sound

146

Chapter Fourteen: Phone Line Status Circuits

conducts as voltage across capacitor C1 is quite high.

correct resistor values for the project. Note that each This results in conduction of transistors T5 and T6 and resistor will have either three or four color bands, which cutting off of transistor T7 (as collector of transistor T6

begin at one end of the resistor’s body. The first colored is near ground potential). Thus positive 9 V rail is not band represents the resistor’s first digit, while the extended to the following multi-vibrator circuit built second color represens the second digit of the resistor’s around transistors T8 and T9. Consequently, the red

value. The third colored band represents the resistor’s LED is not lit and buzzer does not sound. When phone

multiplier value, and the fourth color band represents line is in use, Zener D10 does not conduct. As a result, the resistor’s tolerance value. If there is no fourth transistors T5 and T6 also do not conduct, while

colored band then the resistor has a 20% tolerance

transistor T7 conducts. Now +9 V is extended to multi-value. If the resistor’s fourth band is silver then the vibrator circuit. This multi-vibrator is designed such resistor has a 10% tolerance value and if the fourth band that collector of transistor T9 goes high once every 5 s is gold then the resistor’s tolerance value will be 5%.

to forward bias transistor T10 and it conducts. Thus at Finally we are ready to begin assembling the project, every 5 s interval a beep sound is heard from buzzer.

so let’s get started. The prototype project was

The beep sound interval can be increased or decreased constructed on a single-sided printed circuit board or by changing the value of capacitor C3, while the

PCB. With your PC board in front of you, we can now

volume can be adjusted with the help of preset VR3.

begin populating the circuit board. We are going to

place and solder the lowest height components first, the resistors and diodes. First locate our first resistor R1.

Circuit assembly

Resistor R1 has a value of 56 K ohms and is a 5%

tolerance type. Now take a look for a resistor whose

Before we begin constructing the Telephone Line

first color band is green, blue, orange, and gold. From Vigilant, you will need to find a clean, well-lit

the chart you will notice that green is represented by the worktable or workbench. Next we will gather a small

digit (5), the second color band is blue, which is

25–30-W pencil tipped soldering iron, a length of

represented by (6). Notice that the third color is orange 60/40 tin–lead solder, and a small canister of Tip Tinner, and the multiplier is (1,000), so (5) (6) × 1,000 = 56,000

available at your local RadioShack store; Tip Tinner is or 56 K ohms. Once you have placed resistor R1 on the used to condition the soldering tip between solder

circuit board, you can go ahead and install it on the joints. You drive the soldering tip into the compound board and solder it place. Trim the excess lead length and it cleans and prepares the soldering tip. Next grab a with a pair of end-cutters flush to the edge of the circuit few small hand tools; try to locate small flat blade and board. Next, identify the remaining resistors and place Phillips screwdrivers. A pair of needle-nose pliers, a them on the PC board and solder them in place.

pair of tweezers along with a magnifying glass, and a Remember to cut the excess lead lengths with your

pair of end-cutters and we will begin constructing the end-cutters.

project. Now locate your schematic diagram and parts

layout diagram along with all of the components needed Note that capacitors generally come from two major

to build the project. Once all the components are in

groups or types. Non-polar types, such as the ones in front of you, you can check them off against the project this project, have no polarity and can be placed in either parts list to make sure you are ready to start building the direction on the circuit board. The other type of

project. Now, locate Tables 14-1 and 14-2, and place

capacitors are called polarized types, these capacitors them in front of you.

have polarity and have to be inserted on the board with respect to their polarity marking in order for the circuit Table 14-1 illustrates the resistor code chart and

to operate correctly. On these types of capacitors, you how to read resistors, while Table 14-2 illustrates the will observe that the components actually have a plus or capacitor code chart which will aid you in constructing minus marking or a black or white band with a plus or the project.

minus marking on the body of the capacitors.

Refer now to the resistor color code chart shown in

Electrolytic capacitors must be installed correctly in Table 14-1, which will assist you in identifying the

order for the circuit to work properly.

147

Next refer to Table 14-2, this chart helps to determine circuit is to function properly. An LED has two leads a the value of small capacitors. Many capacitors are quite cathode and an anode lead. The anode lead will usually small in physical size, so manufacturers have devised a be the longer of the two leads and the cathode lead will three-digit code which can be placed on the capacitor usually be the shorter lead, just under the flat side edge instead of the actual value. The code occupies a much of the LED. This should help orient the LED on the

smaller space on the capacitor and can usually fit

PC board. Solder the LEDs to the PC board and then

nicely on the capacitor body, but without the chart the trim the excess leads.

builder would have a difficult time determining the

Now locate the three capacitors from the component

capacitor’s value.

pile and try and locate capacitor C1, which is an

This project contains a number of silicon and Zener

electrolytic capacitor and will be labeled 10 μF; it

diodes. Diodes will always have some type of polarity should have a small black or white band with a plus or markings, which must be observed if the circuit is going minus marking on or near the band. Be sure to observe to work correctly. You will notice that each diode will this polarity marking when installing this capacitor on the have a black or white colored band at one edge of the circuit board. Next locate capacitor C2, which is a 22 μF

diode’s body. The colored band represents the diode’s capacitor, and next locate C3, which is a 470 μF. When cathode lead. Check your schematic and parts layout

installing the capacitors be sure to refer to the schematic diagrams when installing these diodes on the circuit

and parts layout diagrams to ensure that you install the board. Note that D9 and D10 are both Zener diodes.

capacitors correctly. Installing the capacitors backwards Diodes D1 through D4 and diodes D5 through D8 are

can damage them as well as other components when

all 1N4007 silicon diodes. Place all the diodes on the power is first applied to the circuit. Install the capacitors circuit board and solder them in place. Then cut the

onto the circuit board and then solder them in place.

excess component leads with your end-cutters.

Remember to trim the excess leads.

The Telephone Line Phone Vigilant circuit utilizes

Once the circuit board has been completed, take a

10 conventional transistors. Transistors are generally short break and then we will inspect the PC board for three lead devices, which must be installed correctly possible “cold” solder joints and “short” circuits. Pick if the circuit is to work properly. Careful handling

up the PC board with the foil side facing upwards

and proper orientation in the circuit is critical.

toward you. Carefully inspect the solder joints; these A transistor will usually have a Base lead, a Collector should look smooth, clean, and bright. If any of the

lead, and an Emitter lead. The base lead is generally a solder joints look dull, dark, or blobby, then you should vertical line inside a transistor circle symbol. The

remove the solder with a solder sucker or a solder wick collector lead is usually a slanted line facing towards and then resolder the joint all over again.

the base lead and the emitter lead is also a slanted

Now we will inspect the PC board for possible short

line facing the base lead but it will have an arrow

circuits. Short circuits can be caused from small solder pointing towards or away from the base lead.

blobs bridging the circuit traces from cut component

Transistors must be installed correctly in order for

leads, which can often stick to the circuit board.

the circuit to function properly. Failure to install

A sticky residue from solder will often trap component them correctly could possible damage the transistors

leads across the circuit traces. Look carefully for any as well as other components.

bridging wires across circuit traces. Once this inspection Refer to the schematic and the parts layout diagrams

is complete, we can move on to installing the circuit as well as the transistor specification sheets before board into some sort of plastic enclosure.

installing the transistors onto the circuit board. Once Locate a suitable enclosure to house the circuit and the you are certain you can identify the proper orientation 4-cell “AA” battery holder. Locate a four cell battery of the transistors, go ahead and place them on the

holder for the circuit and arrange the battery holder and circuit board. Next you can solder the transistors in their circuit board within the enclosure and mount the circuit respective locations and then trim the excess leads.

board on standoffs within the enclosure. The battery can The Telephone Line Vigilant circuit employs two

be hardwired directly to the circuit and the batteries Chapter Fourteen: Phone Line Status Circuits LEDs, which also must be oriented correctly if the should last at least 6 to 12 months with normal operation.

148

Chapter Fourteen: Phone Line Status Circuits

You will also need to connect the circuit to the two phone the circuit. With power applied to the circuit and the lines. This can be done using two lengths of 4-conductor phone connected, observe the status LEDs when the

phone wire with a modular plug attached at one end of phone is on-hook. Now pick up the phone handset

each of the cables. Since the circuit is not sensitive to and observe the LEDs and you should begin to hear

incorrect polarity, you can connect the red and green wires the buzzer. Thus, to avoid unnecessary disturbance,

from each cable to each of the phone line inputs. The it is advisable to install the vigilant unit away from modular plug ends can then simply plug into a telephone the phone. However, if one wishes to place the unit

jack. You could elect to hard-wire the circuit directly to near the telephone then switch S1 may be flipped to

the phone line without the modular plugs if desired.

the “off” position to switch off the buzzer. But

remember to flip the switch to the “on” position

while replacing the handset on cradle. Various

Operation

telephone line conditions and audio-visual indications available are summarized in Table 14-3. The

Once your circuit has been mounted in an enclosure

Telephone Line Vigilant will serve you in many ways

and wired to the phone line, you will be ready to test for years to come.

149

Chapter 15

Telephone and Phone

Line Testers

S1

SPST Power switch

Parts list

S2

Rotary switch –

3¯position – single

Simple Telephone Line

pole

Tester

S3

pushbutton switch—

R1, R2

680 ohms, 1⁄ W,

2

normally open type

5% resistor

J1

1

⁄′′ stereo headphone

D1

Green LED

8

jack

D2

Red LED

Misc

PC board, IC

Misc

PC board,

socket, wire, terminal

4¯conductor wire,

block, enclosure, etc.

hardware, modular

telephone plug, etc.

Telephone Line Tester

Off¯Line Telephone Tester

R1

4.7 K ohms, 1⁄ W,

4

5% resistor

R1

270 ohms, 1⁄ W,

4

5% resistor

R2

10 ohm potentiometer

R2, R3

1.2 K ohms, 1⁄ W,

R3

50 K ohm

4

5% resistor

potentiometer

R4

150 ohm, 1⁄ W,

R4

100 K ohm, 1⁄ W,

4

4

5% resistor

5% resistor

C1, C2

1,000 μF, 63-V

R5, R6

470 ohm, 1⁄ W,

2

electrolytic capacitor

5% resistor

D1, D2, D3, D4

1N4007

R7

10 K ohm, 1⁄ W,

4

silicon diodes

5% resistor

D5

1N5408 silicon diode

D1, D2, D3, D4, D5

D6

Red LED

1N4003 silicon

diodes

Q1

BC148 NPN transistor

D6

Red LED

Q2

BC368 NPN transistor

U1

UM66 Music chip IC

U1

UM66 Integrated

circuit

S1

DPDT toggle or slide

switch

T1, T2

110-V AC –

24-V AC transformer @

M1

0-1 mA current panel

500 mA

meter

150

Copyright © 2009 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Chapter Fifteen: Telephone and

P1

modular phone plug

S1, S2

SPDT toggle

switch

Misc

PC board, wire,

hardware, chassis box,

F1

5 amp fast blow

standoffs, etc.

fuse

Telephone Line Simulator

P1

110-V AC – grounded

plug

R1, R2

560 ohms, 1⁄ W,

2

Misc

PC board, wire,

5% resistor

terminal strips,

R3

2.2 K ohms, 1⁄ W,

4

enclosure, etc.

5% resistor

R4, R7

27 K ohms, 1⁄ W,

4

5% resistor

Project 1: Simple

R5

270 K ohms, 1⁄ W,

4

5% resistor

Telephone Line Tester

R6

330 ohms, 1⁄ W,

4

If you are a contractor, home builder, building new

5% resistor

homes, or a home remodeler or even a home owner

R8

1.8 K ohms, 1⁄ W,

4

rewiring your own home or office, then you will

5% resistor

appreciate this simple Phone Line Tester Project. The R9

220 ohms, 1⁄ W,

Simple Telephone Line Tester will assist you in figuring 4

5% resistor

out the mysteries of telephone line wiring.

R10

3.9 K ohms, 1⁄ W,

The Telephone Line Tester shown in Figure 15-1

4

5% resistor

illustrates a simple 2-LED line tester. The LEDs

indicate whether a line of telephone jack is

C1

10 μF, 50-V

electrolytic capacitor

C2

22 μF, 50-V

Modular

electrolytic capacitor

phone

plug

C3

470 μF, 50-V

Phone Line

electrolytic capacitor

D1

1N4001 silicon diode

D2

SCR – Silicon

controlled rectifier

D3

Red LED

D1

Q1, Q2

2N3904 NPN

transistor

Green LED

R1

U1

LM317T adjustable

680 Ω

regulator IC

Testers

T1

Transformer 110-V AC

Red LED

D2

primary – 40-V AC

secondary

R2

RY1

DPDT – 24-V DC relay

680 Ω

RY2

SPDT – 24-V DC

relay

Figure 15-1

Phone line tester

151

wired correctly, has reversed polarity, or is

glass, and a pair of end-cutters and we will begin

disconnected from the telephone system.

constructing the project. Now locate your schematic

The Simple Telephone Line Tester circuit plugs into a diagram and parts layout diagram along with all of the modular telephone jack and was designed to give a

components needed to build the project. Once all the

quick status check of a telephone line and jack wiring.

components are in front of you, you can check them off If the green LED lights up, the jack is wired properly, against the project parts list to make sure you are ready Testers and the outlet is operational. If the red LED lights up, to start building the project. Now, locate Table 15-1, and the wiring to the jack is reversed. If neither LED lights place it in front of you. Table 15-1 illustrates the resistor up, then the telephone jack is not wired to the telephone code chart and how to read resistors.

system. This is a handy tester to take around the home Each resistor will have either three or four color

or building site for a quick and easy test of the

bands, which begin at one end of the resistor’s body.

telephone wiring. The circuit is simple to construct

The first colored band represents the resistor’s first and easy to use.

digit, while the second color represents the second digit of the resistor’s value. The third colored band represents Circuit assembly

the resistor’s multiplier value, and the fourth color band represents the resistor’s tolerance value. If there is no fourth colored band then the resistor has a 20%

Phone Line Before we begin constructing the Simple Phone Line Tester, you will need to locate a clean, well-lit

tolerance value. If the resistor’s fourth band is silver, worktable or workbench. Next we will gather a small

then the resistor has a 10% tolerance value and if the 25–30-W pencil tipped soldering iron, a length of

fourth band is gold then the resistor’s tolerance value 60/40 tin–lead solder, and a small canister of Tip Tinner, will be 5%.

available at your local RadioShack store; Tip Tinner is Finally we are ready to begin assembling the project, used to condition the soldering tip between solder

so let’s get started. The prototype project was

joints. You drive the soldering tip into the compound constructed on a single-sided printed circuit board or and it cleans and prepares the soldering tip. Next

PCB. With your PC board in front of you, we can now

grab a few small hand tools, try to locate small flat begin populating the circuit board. We are going to

blade and Phillips screwdrivers. A pair of needle-nose place and solder the lowest height components first, the pliers, a pair of tweezers along with a magnifying

resistors and the diodes. First, locate our first resistor R1.

Table 15-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

Chapter Fifteen: Telephone and

No color

20%

152

Chapter Fifteen: Telephone and

Resistor R1 has a value of 680 ohms and is a

5% tolerance type. Now take a look for a resistor whose Operation

first color band is blue, gray, brown, and gold. From the chart you will notice that blue is represented by Once your circuit has been mounted in an enclosure,

the digit (6), the second color band is gray, which is you will be ready to test the circuit. Simply plug the represented by (8). Notice that the third color is brown modular jack into a telephone jack and one of the LEDs and the multiplier is (10), so (6) (8) × 10 = 680 ohms.

should light up immediately. If the green LED lights up then the circuit is wired correctly, but if the red LED

Go ahead and place R1 and R2 on the circuit board

lights up then the telephone jack is wired backwards.

and solder them in place. Now take your end-cutters and If neither LED lights up, then the circuit is dead and cut the excess component leads flush to the edge of the there is no voltage on the line or your jack is not wired circuit board. Once you have installed these

to the active telephone line. Your Simple Telephone

components, you can move on to installing the

Line Tester is now ready to serve you for many years to remaining components.

come, and you will be glad you built this handy tester!

The Simple Telephone Line Tester circuit utilizes two LEDs, which also must be oriented correctly if the

circuit is to function properly. An LED has two leads a cathode and an anode lead. The anode lead will usually Project 2: Off-Line

be the longer of the two leads and the cathode lead will Telephone tester

usually be the shorter lead, just under the flat side edge of the LE; this should help orient the LED on the PC

The Off-Line Telephone Tester is a combination phone

board. Solder the LEDs to the PC board and then trim

tester that will allow you test a telephone in a number of the excess leads.

different ways. The Off-line tester can ring your test Once the circuit board has been completed, take a

phone, it can test the side-tone audio within the phone, short break and then we will inspect the PC board for it can test audio from the phone to a pair of headphones.

possible “cold” solder joints and “short” circuits. Pick The Off-line Phone Tester can also test phone dialing by up the PC board with the foil side facing upwards

listening to the attached headphones. It also contains a toward you. Carefully inspect the solder joints, these music generator, which supplies music to the phone

should look smooth, clean, and bright. If any of the

handset to test the earphone in the phone.

solder joints look dull, dark, or blobby, then you should Phone Line

The multi-purpose Off-Line Telephone Tester is

remove the solder with a solder sucker or a solder wick illustrated in the schematic at Figure 15-2. The Off-Line and then resolder the joint all over again.

Telephone Tester circuit does not require any telephone Now we will inspect the PC board for possible short

line for testing a telephone instrument, so you do not circuits. Short circuits can be caused from small solder have to jeopardize you phone line by testing a faulty blobs bridging the circuit traces or from cut component phone set. The circuit is so simple that it can be easily leads which can often stick to the circuit board once assembled, even by a novice having very little

they have been cut. A sticky residue from solder will knowledge of electronics.

often trap component leads across the circuit traces.

A telephone line can be considered as a source of

Look carefully for any bridging wires across circuit

about 50 V DC with a source impedance of about

traces. Once this inspection is complete, we can move 1 kilo-ohm. During ringing, in place of DC, an

Testers

on to installing the circuit board into some sort of

AC voltage of 70 to 80 V (at 17 to 25 Hz) is present

plastic enclosure.

across the telephone line. When the subscriber lifts the Finally, you will also need to connect the circuit to the handset, the same is sensed by the telephone exchange phone line. This can be done using a 6′′ length of

and the ringing AC voltage is disconnected and DC is

4-conductor phone wire with a modular plug attached at reconnected to the line. Lifting of the handset from the one end of the cable. The modular plug can then simply telephone cradle results in shunting of the line’s two plug into a telephone jack, which you will want to test.

wires by low impedance of the telephone instrument.

153

DS

R3

S1

R1

D1

D3

R2

S3

T1

Testers

2

1 R4

110 V AC

U1

+

C2

Q1

D2

D4

3

J1

B

Q2

C

Stereo

D6

A

headphone

jack

S2

N/C

−

S

T2

To telephone

C1

under test

P

+

Phone Line

+

Figure 15-2

Off-Line Telephone tester

As a result, 50 V DC level drops to about 12 V

high voltage across primary of transformer T2. The

across the telephone instrument. During conversation, circuit also incorporates a music IC at U1, whose output the audio gets superimposed on this DC voltage. Since is connected to secondary of transformer T2 via switch any DC supply can be used for testing a telephone

S2 after suitably boosting its output with the help of instrument, the same is derived here from AC mains

Darlington transistor pair Q1 and Q2. This output can using step-down transformer T1.

be used to test the audio section of any telephone

The center-tap of the transformer’s secondary has

instrument. After having assembled the circuit

been used as common for the two full-wave rectifiers—

satisfactorily, the following procedure may be followed one comprising diodes D1 and D2 together with

for testing a telephone instrument:

smoothing capacitor C1 and the other formed by diodes D3 and D4 along with filter capacitor C2. The former

Circuit assembly

supplies about 12 V for the telephone instrument

through primary of transformer T2 which thus simulates Before we begin constructing the Off-Line Telephone

a source of impedance, and a choke which blocks

Tester, you will need to find a clean, well-lit worktable or AC audio signals present in the secondary of

workbench. Next we will gather a small 25–30-W pencil transformer T2. The audio or AF signal available in

tipped soldering iron, a length of 60/40 tin–lead solder, secondary of T2 is sufficiently strong to directly drive a and a small canister of Tip Tinner, available at your local 32-ohm headset which is connected to the circuit

RadioShack store; Tip Tinner is used to condition the through headphone jack J1 via rotary switch S2.

soldering tip between solder joints. You drive the

During ringing, a pulsating DC voltage from

soldering tip into the compound and it cleans and prepares transformer T1 via rectifier diode D5, push-to-on switch the soldering tip. Next grab a few small hand tools;

S3, and contact “B” of rotary switch S2 is applied

try and locate small flat blade and Phillips screwdrivers.

across secondary of transformer X2. The boosted

A pair of needle-nose pliers, a pair of tweezers along with voltage available across primary of transformer T2 is a magnifying glass, and a pair of end-cutters and we will sufficient to drive the ringer in the telephone instrument.

begin constructing the project. Now locate your schematic Please avoid pressing of switch S3 for more than a few diagram and parts layout diagram along with all of the Chapter Fifteen: Telephone and seconds at a time to prevent damage to the circuit due to components needed to build the project.

154

Chapter Fifteen: Telephone and

Once all the components are in front of you, you can

to operate correctly. On these types of capacitors, you check them off against the project parts list to make will observe that the components actually have a plus or sure you are ready to start building the project.

minus marking or a black or white band with a plus or Now, locate Table 15-1 and place it in front of you.

minus marking on the body of the capacitors.

Table 15-1 illustrates the resistor code chart and

Capacitors must be installed properly with respect to how to read resistors.

polarity in order for the circuit to work properly. Failure Each resistor will have either three or four color

to install electrolytic capacitors correctly could cause bands, which begin at one end of the resistor’s body.

damage to the capacitors as well as to other components The first colored band represents the resistor’s first in the circuit when power is first applied.

digit, while the second color represents the second digit Now locate the capacitors from the component stack

of the resistor’s value. The third colored band represents and locate capacitor C1, which is an electrolytic

the resistor’s multiplier value, and the fourth color band capacitor and will be labeled 1,000 μF; it should have a represents the resistor’s tolerance value. If there is no small black or white band with a plus or minus marking fourth colored band then the resistor has a 20%

on or near the band. Be sure to observe this polarity tolerance value. If the resistor’s fourth band is silver marking when installing this capacitor on the circuit then the resistor has a 10% tolerance value and if the board. Next locate capacitor C2, also a 1,000 μF

fourth band is gold then the resistor’s tolerance value capacitor. Go ahead and place C1 and C2 on the

will be 5%.

circuit board and solder them in place. Now take your Finally we are ready to begin assembling the project, end-cutters and cut the excess component leads flush to so let’s get started. The prototype project was

the edge of the circuit board. Once you have installed constructed on a single-sided printed circuit board or these components, you can move on to installing the

PCB; with your PC board in front of you, we can now

remaining low profile components.

begin populating the circuit board. We are going to

The Off-Line Telephone Tester project contains five

place and solder the lowest height components first, the silicon diodes. Diodes, as you will remember, will

resistors and diodes. First, locate our first resistor R1.

always have some type of polarity markings, which

Resistor R1 has a value of 270 ohms and is a 5%

must be observed if the circuit is going to work

tolerance type. Now take a look for a resistor whose

correctly. You will notice that each diode will have a first color band is red, violet, brown, and gold. From the black or white colored band at one edge of its body.

chart you will notice that red is represented by the

The colored band represents the diode’s cathode lead.

digit (2), the second color band is violet, which is

Check your schematic and parts layout diagrams when

Phone Line

represented by (7). Notice that the third color is brown installing these diodes on the circuit board. Note that and the multiplier is (10), so (2) (7) × 10 = 270 ohms.

Diodes D1 through D4 are all 1N4007 diodes, which

Go ahead and locate where resistor R1 goes on the

form the diode bridge, which is connected to the

PC and install it, next solder it in place on the PC board, transformer at T1. Diode D5 above R1 is a 1N5408

and then with a pair of end-cutters trim the excess

silicon diode. Place all the diodes on the circuit board component leads flush to the edge of the circuit board.

in their respective locations and solder them in place.

Next locate the remaining resistors and install them in After soldering in the diodes, cut the excess component their respective locations on the PC board. Solder the leads with your end-cutters flush to the edge of the

resistors to the board, and remember to cut the extra circuit board.

leads with your end-cutters.

The Off-Line Telephone Tester utilizes two

Testers

Note that capacitors generally come from two major

conventional transistors. Transistors are generally three groups or types. Non-polar types, such as the ones in lead devices, which must be installed correctly if the this project, have no polarity and can be placed in either circuit is to work properly. Careful handling and proper direction on the circuit board. The other type of

orientation in the circuit is critical. A transistor will capacitors are called polarized types, these capacitors usually have a Base lead, a Collector lead, and an

have polarity and have to be inserted on the board with Emitter lead. The base lead is generally a vertical line respect to their polarity marking in order for the circuit inside a transistor circle symbol. The collector lead is 155

usually a slanted line facing towards the base lead and Once this task is complete, we can move on to

the emitter lead is also a slanted line facing the base installing the circuit board into an aluminum enclosure.

lead but it will have an arrow pointing towards or away Locate a suitable enclosure to house the circuit board.

from the base lead. Now, identify the two transistors, Arrange the circuit board and the two transformers on and refer to the manufacturer’s specification sheets as the bottom of the chassis box. Now, locate four 1⁄4′′

well as the schematic and parts layout diagrams when

standoffs, and mount the PC board between the

Testers installing the two transistors. If you have trouble standoffs and the bottom of the chassis box. Leave room installing the transistors, get the help of an electronics for the two transformers, and try to mount them on

enthusiast with some experience. Install the transistors opposite sides of the board, displaced by 90 degrees.

in their respective locations and then solder them in Mount the transformers to the base of the chassis box place. Remember to trim the excess component leads

and wire them to the circuit board.

with your end-cutters.

Next, mount the rotary switch, the On—Off switch,

The Off-line Phone Tester circuit also contains a

and pushbutton switch to the front panel of the chassis single integrated circuit at U1. Integrated circuits will box and wire them to the circuit board. The LED can be also have some sort of marking to help you orient

mounted on the circuit board with extra long leads so it them on the PC board. The music generator has a

could show through the front panel, or it could be

non-conventional pin-out, since it only contains three mounted on the front directly. Connect the LED to the Phone Line pins. Refer to the manufacturer’s pin-out diagram, as circuit board if not already done.

well as the schematic when installing this part.

Finally, you will need to connect the Off-line Tester The Off-line Phone Tester circuit utilizes a single

to the phone under test. You could elect to install a LED at D6, which also must be oriented correctly if the modular phone jack on the chassis box and then simply circuit is to function properly. An LED has two leads, a use a modular to modular phone cable to connect the

cathode and an anode lead. The anode lead will usually circuit to the phone you wish to test. You could also be the longer of the two leads and the cathode lead will elect to hard-wire a cable to the circuit and use a

usually be the shorter lead, just under the flat side edge grommet to bring the 4-wire cable out of the chassis

of the LED; this should help orient the LED on the PC

box. The opposite end of your cable could have a

board. You may want to leave about a 1⁄2 lead length on modular plug which can be quickly connected to the

the LED, in order to have the LED protrude through the phone you wish to test. Once the circuit has been

enclosure box. Solder the LEDs to the PC board and

completed and the circuit wired, you will be ready to then trim the excess leads.

test the circuit and a telephone.

Once the circuit board has been completed, take a

short break and then we will inspect the PC board for possible “cold” solder joints and “short” circuits. Pick Circuit operation

up the PC board with the foil side facing upwards

toward you. Carefully inspect the solder joints, these First, connect the telephone to the terminals marked

should look smooth, clean, and bright. If any of the

“To Telephone Under Test” and switch on power to the

solder joints look dull, dark, or blobby, then you should circuit (switch S1). Next, in order to test the ringer remove the solder with a solder sucker or a solder wick portion, flip switch S2 to position “B” and press S3 for and then resolder the joint all over again.

a moment. You should hear the ring in the event that the Now we will inspect the PC board for possible

ringer circuit of the telephone under test is working.

short circuits. Short circuits can be caused from small Please ensure that handset is on cradle during this test.

solder blobs bridging the circuit traces from cut

Finally, for testing the audio section, flip switch S1 to component leads which can often stick to the circuit

position “C” and connect a headphone to jack J1. Pick board once they have been cut. A sticky residue from

up the telephone handset and speak into its microphone.

solder will often trap component leads across the

If audio section is working satisfactorily, you should be circuit traces. Look carefully for any bridging wires able to hear your speech via the headphone. If you dial Chapter Fifteen: Telephone and across circuit traces.

a number, you should be able to hear the pulse clicks or 156

Chapter Fifteen: Telephone and

pulse tone in the headphone, depending on whether the The Telephone Line Tester can be built into a small

telephone under test is functioning in pulse or tone

chassis box with the LED indicator and meter on the

mode. If the telephone under test has a built-in musical front panel to instantly show you the line status. The hold facility, on pressing the “hold” button you should LED at D6 is connected in series with resistor D5 and be able to hear the music. Now flip switch S2 to

R7 and will instantly inform you of the telephone line position “A.” You should be able to hear music

polarity.

generated by U1 through the earpiece of the handset of If the green wire is the positive phone lead and the

the telephone under test, indicating proper functioning red wire the negative phone wire, the circuit is correctly of the AF amplifier section. Your Off-Line Telephone

wired and the LED will remain off. If the wiring is

Tester is ready to help you and/or your family and

reversed, then the red indicator LED will light up.

friends to test your new found phones.

With switch S1 set for LINE/RING, both S1(a) and

S1(b) are open and the meter indicates the condition of the line voltage. Any line-voltage reading in the LINE

Project 3: Telephone line

OK range indicates a line voltage that is higher than 40 V DC. If the telephone is caused to ring, either by tester

using a ring-back number or by dialing from another

phone, the meter will indicate RING OK, and LED

If you build houses or remodel houses or are just

will pulse—indicating AC, if the ringing voltage/current re-wiring your own or trouble shooting a telephone

is correct. The actual position of the meter’s pointer problem for your self or friend, then you will find this depends on how many ringers are connected across the

Telephone Line Tester extremely helpful and a real

telephone line.

time saver.

When S1 is closed, the voltage range of the meter is

The Telephone Line Tester project, shown in

changed and a nominal load resistance of 230 ohms

Figure 15-3, is connected to a conventional telephone (R5 and R6) is connected across the line to emulate the line through modular connector P1, at the right of the off-hook load of the telephone. If the meter indicates circuit.

LOOP OK, you can be certain that you have sufficient

The Telephone Line Tester is powered from the

loop voltage for satisfactory telephone operation. If you telephone line, so there is no external power needed

place another load on the line, perhaps by taking an

for the circuit.

extension telephone off-hook, the meter reading will

Phone Line

+

−

D6

D1

D3

R5

R6

Telephone

M1

D5

plug

P1

Loop

S1:b

R7

D2

D4

line/ring

Testers

R1

R3

R4

Line/ring

Loop

R2

S1:a

Figure 15-3

Telephone line tester. Courtesy of Poptronix

157

almost invariably drop below the LOOP OK range.

begin populating the circuit board. We are going to

If lifting the handset causes the meter reading to drop, place and solder the lowest height components first, the you can at least be certain that the telephone’s hook resistors and diodes. First, locate our first resistor R1.

switch is working and that the repeat coil is connected Resistor R1 has a value of 4,700 ohms and is a 5%

to the telephone line.

tolerance type. Now take a look for a resistor whose

first color band is yellow, violet, red, and gold.

Testers

From the chart you will notice that yellow is

Circuit assembly

represented by the digit (4), the second color band

is violet, which is represented by (7). Notice that

Before we begin constructing the Phone Line Tester,

the third color is red and the multiplier is (100), so you will need to find a clean, well-lit worktable or

(4) (7) × 100 = 4,700 or 4.7 K ohms.

workbench. Next we will gather a small 25–30-W

Go ahead and place R1 on the circuit board in its

pencil tipped soldering iron, a length of 60/40 tin–lead respective location and solder it in place. Now take

solder, and a small canister of Tip Tinner, available at your end-cutters and cut the excess component leads

your local RadioShack store; Tip Tinner is used to

flush to the edge of the circuit board. Once you have condition the soldering tip between solder joints. You installed these first three components, you can move

drive the soldering tip into the compound and it cleans on to installing the remaining resistors and the other Phone Line and prepares the soldering tip. Next grab a few small low profile components. Locate the remaining resistors hand tools, try to locate small flat blade and Phillips from the parts pile and install them in their proper

screwdrivers. A pair of needle-nose pliers, a pair of location on the circuit board. Next solder them in

tweezers along with a magnifying glass, and a pair of place and remember to trim the excess lead lengths

end-cutters and we will begin constructing the project.

when you are finished. Finally locate and install the Now locate your schematic diagram and parts layout

50 K ohm potentiometer at R3 and the 10 K ohm

diagram along with all of the components needed to

potentiometer at R2. Now, solder them to the

build the project. Once all the components are in front circuit board.

of you, you can check them off against the project

This project contains five silicon diodes. Diodes, you parts list to make sure you are ready to start building will remember, will always have some type of polarity the project. Now, locate Table 15-1 and place it in front markings, which must be observed if the circuit is going of you.

to work correctly. You will notice that each diode will Table 15-1 illustrates the resistor code chart and how have a black or white colored band at one edge of the to read resistors.

diode’s body. The colored band represents the diode’s Each resistor will have either three or four color

cathode lead. Check your schematic and parts layout

bands, which begin at one end of the resistor’s body.

diagrams when installing these diodes on the circuit

The first colored band represents the resistor’s first board. Note that all five diodes are 1N4003 silicon

digit, while the second color represents the second digit diodes. Place all the diodes on the circuit board and of the resistor’s value. The third colored band represents solder them in place. Then trim the excess component

the resistor’s multiplier value, and the fourth color band leads with your end-cutters, cutting the leads flush to represents the resistor’s tolerance value. If there is no the edge of the circuit board.

fourth colored band then the resistor has a 20%

The Telephone Line Tester circuit uses two LEDs,

tolerance value. If the resistor’s fourth band is silver which also must be oriented correctly if the circuit is to then the resistor has a 10% tolerance value and if the function properly. Remember that LEDs have two leads, fourth band is gold then the resistor’s tolerance value a cathode and an anode lead. The anode lead will

will be 5%.

usually be the longer of the two leads and the cathode Finally, we are ready to begin assembling the project, lead will usually be the shorter lead, just under the flat so let’s get started. The prototype project was

side edge of the LED; this should help orient the LED

constructed on a single-sided printed circuit board or on the PC board. Solder the LEDs to the PC board and

Chapter Fifteen: Telephone and PCB. With your PC board in front of you, we can now then trim the excess leads.

158

Chapter Fifteen: Telephone and

Finally, you will need to install the LINE/RING—

polarity, since the tester’s LED polarity indicator is LOOP switch, at S1. The DPDT toggle switch consists

always connected when the tester is plugged in. If the of two switch sections S1(a) and S1(b), which are wired green wire is the positive phone lead and the red wire to the two different portions of the circuit.

the negative phone wire, the circuit is correctly wired Once the circuit board has been completed, take a

and the LED will remain off. If the wiring is reversed, short break and then we will inspect the PC board for then the red indicator LED will light up.

possible “cold” solder joints and “short” circuits. Pick With both S1(a) and S1(b) in the open position,

up the PC board with the foil side facing upwards

the meter indicates the condition of the line voltage.

toward you. Carefully inspect each solder joint. The

Any line-voltage reading in the LINE OK range

solder joints should look smooth, clean, and bright. If indicates a line voltage that is higher than 40 V DC.

any of the solder joints look dull, dark, or blobby, then If the telephone line rings, either by using a ring-back you should remove the solder with a solder sucker or a number or by dialing from another phone, the meter will solder wick and then resolder the joint all over again.

indicate RING OK, and LED will pulse—indicating AC,

Now we will inspect the PC board for possible

if the ringing voltage/current is correct. Note that the short circuits. Short circuits can be caused from small position of the meter’s pointer depends on how many

solder blobs bridging the circuit traces from cut

ringers are connected across the telephone line.

component lead, which can often stick to the circuit

When switch S1 is closed, the voltage range of the

board once they have been cut. A sticky residue from

meter is changed and a nominal load resistance across solder will often trap component leads across the circuit the line becomes 230 ohms. The two parallel resistors traces. Look carefully for any bridging wires across

R5 and R6 are thus connected across the line to emulate circuit traces. Once this inspection is complete, we can the off-hook load of the telephone. If the meter

move on to installing the circuit board into some sort of indicates LOOP OK, you can be certain that you have

plastic enclosure.

sufficient loop voltage for satisfactory telephone

Locate a suitable plastic case for the project and place operation.

the circuit board in the middle of the enclosure. Use If you place another load on the line, perhaps by

four 1⁄2′′ standoffs to mount the circuit board to the taking an extension telephone off-hook, the meter

base of the enclosure.

reading will almost invariably drop below the LOOP

You will want to mount the meter, the two

OK range. If lifting the handset causes the meter

potentiometers and the LINE/RING—LOOP switch and

reading to drop, you can at least be certain that the Phone Line

the LED on the front panel of the enclosure.

telephone’s hook switch is working and that the repeat Finally, you will need to connect the tester circuit to coil is connected to the telephone line.

the phone line, this can be done using an 10′′ length of The handy Telephone Line Tester will rapidly inform

4-conductor phone wire with a modular plug attached at you of the telephone line conditions quite quickly

one end of the cable. Now you can take the four colored without any guess work.

cable wires and connect the red and green wires to the circuit board. The modular plug can then simply plug

into a telephone jack that you want to test.

Project 4: Telephone line

simulator

Operation

Testers

The Telephone Line Simulator can save you time and

Once your circuit has been mounted in an enclosure and money when trying to determine if a telephone is

the modular plug attached to the circuit, you will be working correctly or not. Perhaps you wish to wire all ready to test the circuit. Your Telephone Line Tester is the rooms in your home with telephones or you want to now ready to serve you!

add a number of phones in different rooms, such as

The instant that the tester is connected to the

your office, shop, or barn and you acquired a number of telephone line, you will have an indication of the

used telephones. In this situation you will want to make 159

sure all of the phones work before you go to the trouble close, thus energizing RY2. When RY2 is energized,

of installing them in the house. The Telephone Line

RY1 is removed from the circuit and a 60 Hz, 37-V

Simulator will fit that bill nicely, since it will test a p-p sine wave is placed on the telephone lines, causing single phone or two telephones at once. It will simulate the telephone to ring. Because RY1 is removed from the telephone on-hook as well as off-hook conditions. It

circuit, capacitor C2 starts discharging through R7. It will provide power to two phones at once so you can

takes about one second for the capacitor to discharge to Testers pick up both phones and listen for the side-tone while about 2.4 V DC. That lower voltage level causes the

talking between phones, as well as testing the quality of voltage controlled switch to disable RY2, removing the each of the phones. The Telephone Line Simulator can

ring voltage from the telephone lines and putting RY1

also ring each of the telephones to test their ringers as back in the circuit. If one telephone is still off-hook and well as answering machines (see Figure 15-4).

one is on-hook, the cycle is repeated.

Circuit description

Circuit assembly

The helpful and handy Telephone Line Simulator

Before we begin constructing the Telephone Line

project is depicted in Figure 15-5.

Simulator, you will need to find a clean, well-lit

Phone Line

In operation, when both handsets are on-hook, resistors worktable or workbench. Next we will gather a small

R1 and R2 supply power to them. When both handsets

25–30-W pencil tipped soldering iron, a length of

are off-hook, they transmit and receive their own audio.

60/40 tin–lead solder, and a small canister of Tip Tinner, There are two terminal blacks which supply power to up available at your local RadioShack store; Tip Tinner is to two different phones, through resistors R1 and R2.

used to condition the soldering tip between solder

If switch S1 is closed, resistor R6 simulates a telephone joints. You drive the soldering tip into the compound line being plugged into J2, permitting the testing of and it cleans and prepares the soldering tip. Next grab a only one phone. Now consider the situation where one

few small hand tools; try to locate small flat blade

handset is on-hook and one is off-hook. That causes the and Phillips screwdrivers. A pair of needle-nose pliers, on-hook line to go to 24 V DC and the off-hook line to a pair of tweezers along with a magnifying glass, and a go to 7 V DC. The coil of the relay RY1 is connected

pair of end-cutters and we will begin constructing the across the two telephone lines, and the voltage

project. Now locate your schematic diagram and parts

difference between the two lines energizes it.

layout diagram along with all of the components needed When the contacts or RY1 are closed, C2 charges

to build the project. Once all the components are in

through R4; it takes about one second for C2 to

front of you, you can check them off against the project charge to 12 V DC.

parts list to make sure you are ready to start building the The 12 V DC across C2 causes a voltage controlled

project. Now, locate Table 15-1, and place it in front of switch consisting of R5, R8, Q1, Q2, and SCR1 to

you. Table 15-1 illustrates the resistor code chart and how to read resistors.

Each resistor will have either three or four color

bands, which begin at one end of the resistor’s body.

The first colored band represents the resistor’s first digit, while the second color represents the second digit of the resistor’s value. The third colored band represents the resistor’s multiplier value, and the fourth color band represents the resistor’s tolerance value. If there is no fourth colored band then the resistor has a 20%

tolerance value. If the resistor’s fourth band is silver then the resistor has a 10% tolerance value and if the fourth band is gold then the resistor’s tolerance value Chapter Fifteen: Telephone and Figure 15-4 Telephone line simulator will be 5%.

160

Chapter Fifteen: Telephone and

+V

R1

VAC

+V

J1

R2

D3

RY2-b

RJ-11

R3

Black

Red

Green

RY2-a

Yellow

R5

Q1

J2

RJ-11

Q2

RY2

Black

Red

R7

Green

D2

R4

Yellow

+

R6

C2

Dual phones

RY1

+

C1

S1

R8

Single

VAC

phone

D1

3

2

V1

V0

+V

F1

S2

U1

P1

Adj

+

C3

R9

1

R10

Phone Line

Figure 15-5

Telephone-line simulator. Courtesy of Poptronix

Finally, we are ready to begin assembling the project, Once you have identified resistor R1, go ahead and

so let’s get started. The prototype project was install it in its respective location on the circuit board.

constructed on a single-sided printed circuit board or Next, you can solder it in place and then trim the excess PCB. With your PC board in front of you, we can now

component lead with a pair of end-cutters. Trim the

begin populating the circuit board. We are going to

excess leads flush to the edge of the circuit board. Now, place and solder the lowest height components first, the locate the remaining resistors and place them in their resistors and diodes. First, locate our first resistor R1.

correct locations and then solder them in place.

Testers

Resistor R1 has a value of 560 ohms and is a 5%

Remember to trim the excess component leads when

tolerance type. Now take a look for a resistor whose

finished.

first color band is green, blue, brown, and gold. From Next refer to Table 15-2, this chart helps to determine the chart you will notice that green is represented by the value of small capacitors.

digit (5), the second color band is blue, which is

represented by (6). Notice that the third color is brown Many capacitors are quite small in physical size, so

and the multiplier is (10), so (5) (6) × 10 = 560 ohms.

manufacturers have devised a three-digit code which

161

Table 15-2

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

1.0

1R0

3,900

3.9

.0039

392

1.2

1R2

4,700

4.7

.0047

472

Testers 1.5

1R5

5,600

5.6

.0056

562

1.8

1R8

6,800

6.8

.0068

682

2.2

2R2

8,200

8.2

.0082

822

2.7

2R7

10,000

10

.01

103

3.3

3R3

12,000

12

.012

123

3.9

3R9

15,000

15

.015

153

4.7

4R7

18,000

18

.018

183

5.6

5R6

22,000

22

.022

223

6.8

6R8

27,000

27

.027

273

8.2

8R2

33,000

33

.033

333

Phone Line 10

100

39,000

39

.039

393

12

120

47,000

47

.047

473

15

150

56,000

56

.056

563

18

180

68,000

68

.068

683

22

220

82,000

82

.082

823

27

270

100,000

100

.1

104

33

330

120,000

120

.12

124

39

390

150,000

150

.15

154

47

470

180,000

180

.18

184

56

560

220,000

220

.22

224

68

680

270,000

270

.27

274

82

820

330,000

330

.33

334

100

.0001

101

390,000

390

.39

394

120

.00012

121

470,000

470

.47

474

150

.00015

151

560,000

560

.56

564

180

.00018

181

680,000

680

.68

684

220

.00022

221

820,000

820

.82

824

270

.00027

271

1,000

1

105

330

.00033

331

1,500

1.5

155

390

.00039

391

2,200

2.2

225

470

.00047

471

2,700

2.7

275

560

.00056

561

3,300

3.3

335

680

.00068

681

4,700

4.7

475

820

.00082

821

6.8

685

1,000

1.0

.001

102

10

106

1,200

1.2

.0012

122

22

226

1,500

1.5

.0015

152

33

336

1,800

1.8

.0018

182

47

476

Chapter Fifteen: Telephone and

162

Chapter Fifteen: Telephone and

Table 15-2—cont’d

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

2,200

2.2

.0022

222

68

686

2,700

2.7

.0027

272

100

107

3,300

3.3

.0033

332

157

157

Code = 2 significant digits of the capacitor value + number of zeros to follow 10 pF = 100

For values below 10 pF, use “R” in place of decimal e.g. 8.2 pF = 8R2

100 pF = 101

1,000 pF = 102

22,000 pF = 223

330,000 pF = 334

1 μF = 105

can be placed on the capacitor instead of the actual

you can move on to installing the remaining low profile value. The code occupies a much smaller space on the

components.

capacitor and can usually fit nicely on the capacitor This project contains a number of single silicon

body, but without the chart the builder would have a

diodes and an SCR or Silicon Controlled Rectifier.

difficult time determining the capacitor’s value.

Diodes will always have some type of polarity markings, Note that capacitors generally come from two major

which must be observed if the circuit is going to work groups or types. Non-polar types, such as the ones in correctly. You will notice that each diode will have a this project, have no polarity and can be placed in either black or white colored band at one edge of its body.

direction on the circuit board. The other type of

The colored band represents the diode’s cathode lead.

capacitors are called polarized types; these capacitors Check your schematic and parts layout diagrams when

have polarity and have to be inserted on the board with installing the diodes on the circuit board. Note that Phone Line

respect to their polarity marking in order for the circuit diode D1 is a 1N4001 diode. Place the diodes on the

to operate correctly. On these types of capacitors, you circuit board and solder them in place on the PC board.

will observe that the components actually have a plus or Then cut the excess component leads with your

minus marking or a black or white band with a plus or end-cutters. The circuit also utilizes a single SCR at D2.

minus marking on the body of the capacitors.

An SCR device is a semiconductor device with three

leads, a cathode, an anode and a gate lead. The SCR has Now try and locate the three electrolytic capacitors

an anode and cathode much the same as a diode, so the from the component pile. Capacitor C1, which is an

symbol for the device also has a straight horizontal line, electrolytic capacitor, will be labeled 10 μF, and it which is the cathode, while the anode is the arrow that should have a small black or white band with a plus or points to the cathode. Use the manufacturer’s data sheet minus marking on or near the band. Be sure to observe as well as the schematic and parts layout sheets when this polarity marking when installing the capacitors on Testers

installing the SCR. If you are not confident that

the circuit board. Next locate capacitor C2, which will you can install the SCR without assistance, then

be labeled 22 μF, and locate, identify, and install

ask a knowledgeable friend or electronics enthusiast

capacitor C3, which will be marked 470 μF. Go ahead

for some help.

and solder the capacitors in place on the circuit board.

Now take your end-cutters and cut the excess

The Phone Line Simulator utilizes two conventional

component leads flush to the edge of the circuit board.

transistors at Q1 and Q2, both are 2N3904 NPN types.

Once you have installed the resistors and capacitors, A transistor will usually have a Base lead, a Collector 163

lead, and an Emitter lead. The base lead is generally should look smooth, clean, and bright. If any of the

a vertical line inside a transistor circle symbol. The solder joints look dull, dark, or blobby, then you should collector lead is usually a slanted line facing towards remove the solder with a solder sucker or a solder wick the base lead and the emitter lead is also a slanted line and then resolder the joint all over again.

facing the base lead but it will have an arrow pointing Now we will inspect the PC board for possible short

towards or away from the base lead. Identify the

circuits. Short circuits can be caused from small solder Testers transistor leads and their respective location and then blobs bridging the circuit traces from cut component

install the transistors on the PC board. Once this is leads, which can often stick to the circuit board once accomplished, you can solder the transistors in place they have been cut. A sticky residue from solder will and then cut the excess component leads flush to the

often trap component leads across the circuit traces.

edge of the circuit board.

Look carefully for any bridging wires across circuit

This circuit also contains a single IC regulator IC at traces. Once this inspection is complete, we can move U1. ICs will also have some sort of marking to help you on to installing the circuit board into some sort of

orient them on the PC board. Often there will be a small plastic enclosure.

indented circle, a small notch or cutout at the top end of Locate a suitable enclosure to house the circuit board.

the IC package. Pin of the device will be just to the left Place the circuit board and the transformer on the

of the notch or cutout. It is highly recommended that Phone Line

bottom of the chassis box or enclosure and center them the circuit builder use IC sockets for the ICs. IC sockets for the best fit inside the case. If you chose non-PC

are low cost insurance against a possible circuit failure board relays, you will have to secure them to the bottom at some later date. It is much easier to simply unplug an of the enclosure. Install four 1⁄4′′ standoffs between the IC rather than trying to unsolder many IC pins from a circuit board and the bottom of the chassis box, in order PC board without causing damage to the PC board.

to secure the circuit board. Mount the transformer to the Solder the IC socket to the PC board and then insert the base of the chassis box. Mount two 4-position terminal IC into the socket.

blocks on the front of the chassis box along with

The Phone Line Simulator circuit utilizes a single

switches S1 and S2, and connect them to the circuit

LED at D3, which also must be oriented correctly if the board. Mount the chassis mounted fuse holder

circuit is to function properly. An LED has two leads, a on the rear of the enclosure and drill a hole to pass the cathode and an anode lead. The anode lead will usually power cord through the rear panel.

be the longer of the two leads and the cathode lead will Finally, you will need to make up two phone test

usually be the shorter, just under the flat side edge of cables which go between the terminal blocks and the

the LED; this should help orient the LED on the PC

phones under test. Make up two 2′ lengths of

board. You may want to leave about a 1⁄2 inch of lead 4-conductor phone wire with a modular plug attached at length in order for the LED to extend from the PC

one end of each of the two cables. The free wire ends of board through to the outside of the enclosure. Solder the the cables are wired directly to the terminal blocks, one LED to the PC board and then trim the excess leads.

for each phone. When you are ready to test a phone,

If you purchased PC board type relays, you can

simply plug one of the modular plugs into the phone

install them on the PC board now. Take your time to

under test.

identify the correct wiring before installation. If you elected to purchase non-PC board style relays, you will have to secure them to the bottom of the chassis box

Operation

and wire them to the circuit board directly using #22

gauge insulated hookup wire.

Once your circuit has been mounted in an enclosure,

Once the circuit board has been completed, take a

you will be ready to test the circuit. Connect one of the short break and then we will inspect the PC board for modular phone plugs to a telephone that you wish to

possible “cold” solder joints and “short” circuits. Pick test at J1. Then connect up a second phone to the

up the PC board with the foil side facing upwards

terminals at J2. Plug the circuit into a wall socket to Chapter Fifteen: Telephone and toward you. Carefully inspect the solder joints, these connect it to a 110-V power source. Make sure you

164

Chapter Fifteen: Telephone and

have a 1⁄2 amp fuse in the fuse holder and then

ringer circuit. You can repeat the sequence by placing toggle switch S1 to DUAL PHONE position and switch

both phones on-hook and picking up the opposite

S2 to the “on” position. The LED at D3 should light up phone and listening to side-tone when you talk. After once power is applied to the circuit. With both phones 30 s you should hear the other phone ringing. This

on-hook, you should be able to measure 24 V across

handy Telephone Line Simulator will save you both

J1 and J2. Next pick up the one of the phones; you

time and money when trying to determine if used

should read 24 V across the on-hook phone and 7 V

phones are suitable for installation in a home, office, across the off-hook phone line. Talk into the

shop, or barn. The Phone Line Simulator will serve

microphone of the off-hook phone and you should

you for many years and you may have your friends

hear yourself through the side-tone. After about 30 s or and or relatives wanting to borrow it from time

so the on-hook phone should start to ring, testing the to time.

Phone Line

Testers

165

Chapter 16

FM Telephone Transmitter

L2

8 turn enameled

Parts list

copper wire, wound on

1

⁄” form - (see text)

8

Phone FM Transmitter

L3

6 turn tinned

R1

100 ohms, 1⁄ W,

4

copper wire

5% resistor

Misc

PC board, wire,

R2

33 K ohms, 1⁄ W,

4

hardware, wire,

5% resistor

enclosure, etc.

R3

10 K ohms, 1⁄ W,

4

CK202 – Phone

5% resistor

Transmitter

R4

47 K ohms, 1⁄ W,

4

Kit available from:

5% resistor

Carls’s Electronics

R5

390 ohms, 1⁄ W,

4

www.electronickits.com

5% resistor

Would you like to be able to amplify a phone call so

C1

27 pF or 22 pF,

everybody can hear it? Or perhaps you would like a way 35 V ceramic capacitor

to record phone calls for record-keeping purposes?

C2

100 nF, 35 V ceramic

If either idea sounds good to you, then you might want capacitor (104)

to build the FM Telephone Transmitter described in this C3

22 nF, 35 V ceramic

article (see Figure 16-1).

capacitor (223)

It is a simple yet ingenious device that connects in

C4

1 nF, 35 V ceramic

series with a phone line, and derives its power from the capacitor (102)

phone itself. The FM Telephone Transmitter circuit will C5

5.6 pF, 35 V

transmit both sides of a conversation to an FM radio

ceramic capacitor

tuned to between 90 and 95 MHz.

C6, C7

47 pF, 35 V

The FM Telephone Transmitter circuit is built on a

ceramic capacitor

PC board that is so small it can easily be fitted inside the housing of a telephone base, thus making it an

Q1

BC547,BC548, 2N2222,

or NTE123A transistor

Q2

ZTX320, 2N3563 or

NTE 108 transistor

D1, D2, D3, D4

1N4148

silicon diodes

L1

6 turn enameled

copper wire, wound on

Figure 16-1

TeleXmit wireless phone bug. Courtesy of

1

⁄” form - (see text)

Electronickits.com

8

166

Copyright © 2009 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Chapter Sixteen: FM Telephone Transmitter

instant pseudo-speak earphone. Keep in mind, though,

capacitance of the transistor. The junction capacitance is that it is illegal to listen to or record a telephone a function of the potential difference applied to the base conversation without informing all involved parties.

of the transistor. Components R1 and C4 act as a low

There are many legitimate reasons for wanting to

pass filter. Capacitor C3 forms a high frequency shunt.

broadcast a telephone call to an FM receiver. For

Coil L2 is called an RFC (radio frequency shunt.) It

example, when someone calls long distance, he or she

decouples the power and audio from the transmitter

does not have the time or cannot afford to stay on long, amplifier circuit itself. The coils L1 through L3 are all but everybody at home still wants to hear his or her

air-core coils, which are hand wound by the builder.

voice. Or perhaps you want to record a phone call so

Coil L1 is formed with #22 ga enameled magnet wire

that you have a record of some electronic banking you loosely wound on a 1⁄8′′ drill bit, while L2 is formed did or deal you made. Many other applications can be

with eight turns loosely wound over a 1⁄8′′ drill bit using found for this interesting project.

#22 ga enameled magnet wire. Remember to scrape

off a 1⁄8′′ of insulation in order to solder the coils to the Besides being small in size, the Telephone

circuit. Coil L3 is formed by wrapping six turns of

Transmitter is also “small” in price. Only a handful of tinned copper wire. The winding will need to be spaced low cost parts are needed to build the project.

1 mm apart. Coil L3 is tapped between the top of the

first turn of L3 and the circuit board.

Circuit description

Circuit assembly

The FM Telephone Transmitter is shown in the

schematic at Figure 16-2.

Before we begin building the Telephone Transmitter

The circuit is basically a radio frequency (RF)

project, let us first find a clean, well-lit worktable or oscillator that operates around 93 MHz. Power for the workbench. Next we will gather a small 20–30-W

circuit is derived from the full wave diode bridge, formed pencil tipped soldering iron, a length of 60/40 tin–lead by diodes D1 through D4. Components C1, C8, L3, and

solder, and a small canister of Tip Tinner, available at Q1 form the main FM oscillator. In this FM transmitter your local RadioShack store, along with a few small

circuit L1, C6, and Q2 form the power amplifier section hand tools. Try to locate small flat blade and Phillips of the unit. Audio from the telephone lines is coupled screwdrivers. A pair of needle-nose pliers, a pair of through R3 and C2 into the base of Q1 to modulate the tweezers along with a magnifying glass, and a pair of oscillator. This is done by varying the junction

end-cutters and we will begin constructing the project.

R1

R3

L2

R4

D1

D2

C1

C8

C3

L3

R2

C6

L1

A

C2

c

b

To phone

Q1

C5

line

B

E

C7

c

b

Q2

C4

E

D3

D4

R5

86 to 95 MHZ

Figure 16-2

FM telephone transmitter. Courtesy of DIY Electronics 167

Locate your schematic diagram along with all of the

first color band is brown, black, brown, and gold.

components to build the project. Once all the

From the chart you will notice that brown is represented components are in front of you, you can check them off by the digit (1), and black is represented by (0). Notice against the project parts list to make sure you are ready that the third color is brown and the multiplier is (10), to start building the project. Now locate Tables 16-1

so 10 × 10 = 100 ohms. Now place resistor R1 into its and 16-2, and place them in front of you.

proper location and solder it in place. Next, use a pair Table 16-1 illustrates the resistor code chart and how of end-cutters to trim the excess resistor leads. Cut the to read resistors, while Table 16-2 illustrates the capacitor excess component leads flush to the edge of the circuit code chart that will aid you in constructing the project.

board. Now locate the remaining resistors and place

them in their respective locations on the PC board.

Refer now to the resistor color code chart shown in

Solder the resistors in place and remember to trim the Table 16-1, which will help you identify the resistors in excess component lead with your end-cutters.

this project. Note that each resistor will have either three or four color bands, which begin at one end of the Note that capacitors generally come from two major

resistor’s body. The first colored band represents the groups or types. Non-polar types, such as the ones in resistor’s first digit, while the second color represents this project, have no polarity and can be placed in either the second digit of the resistor’s value. The third colored direction on the circuit board. The other type of

band represents the resistor’s multiplier value, and the capacitors are called polarized types, these capacitors fourth color band represents the resistor’s tolerance have polarity and have to be inserted on the board with value. If there is no fourth colored band then the resistor respect to their polarity marking in order for the circuit has a 20% tolerance value. If the resistor’s fourth band to operate correctly. On these types of capacitors, you is silver then the resistor has a 10% tolerance value and will observe that the components actually have a plus or if the fourth band is gold then the resistor’s tolerance minus marking or a black or white band with a plus or value will be 5%.

minus marking on the body of the capacitors.

Finally, we are ready to begin assembling the project, Next, refer to Table 16-2; this chart helps to

so let’s get started. First, locate our first resistor R1.

determine the value of small capacitors. Many

Resistor R1 has a value of 100 ohms and is a

capacitors are quite small in physical size, so

5% tolerance type. Now take a look for a resistor whose manufacturers have devised a three-digit code which

Table 16-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

Chapter Sixteen: FM Telephone Transmitter

No color

20%

168

Chapter Sixteen: FM Telephone Transmitter

Table 16-2

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

1.0

1R0

3,900

3.9

.0039

392

1.2

1R2

4,700

4.7

.0047

472

1.5

1R5

5,600

5.6

.0056

562

1.8

1R8

6,800

6.8

.0068

682

2.2

2R2

8,200

8.2

.0082

822

2.7

2R7

10,000

10

.01

103

3.3

3R3

12,000

12

.012

123

3.9

3R9

15,000

15

.015

153

4.7

4R7

18,000

18

.018

183

5.6

5R6

22,000

22

.022

223

6.8

6R8

27,000

27

.027

273

8.2

8R2

33,000

33

.033

333

10

100

39,000

39

.039

393

12

120

47,000

47

.047

473

15

150

56,000

56

.056

563

18

180

68,000

68

.068

683

22

220

82,000

82

.082

823

27

270

100,000

100

.1

104

33

330

120,000

120

.12

124

39

390

150,000

150

.15

154

47

470

180,000

180

.18

184

56

560

220,000

220

.22

224

68

680

270,000

270

.27

274

82

820

330,000

330

.33

334

100

.0001

101

390,000

390

.39

394

120

.00012

121

470,000

470

.47

474

150

.00015

151

560,000

560

.56

564

180

.00018

181

680,000

680

.68

684

220

.00022

221

820,000

820

.82

824

270

.00027

271

1,000

1

105

330

.00033

331

1,500

1.5

155

390

.00039

391

2,200

2.2

225

470

.00047

471

2,700

2.7

275

560

.00056

561

3,300

3.3

335

680

.00068

681

4,700

4.7

475

820

.00082

821

6.8

685

1,000

1.0

.001

102

10

106

1,200

1.2

.0012

122

22

226

1,500

1.5

.0015

152

33

336

1,800

1.8

.0018

182

47

476

(Continued)

169

Table 16-2—cont’d

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

2,200

2.2

.0022

222

68

686

2,700

2.7

.0027

272

100

107

3,300

3.3

.0033

332

157

157

Code = 2 significant digits of the capacitor value + number of zeros to follow 10 pF = 100

For values below 10 pF, use “R” in place of decimal e.g. 8.2 pF = 8R2

100 pF = 101

1,000 pF = 102

22,000 pF = 223

330,000 pF = 334

1 μF = 105

can be placed on the capacitor instead of the

Refer to the schematic and you will notice that there actual value. The code occupies a much smaller

will be two diagonal leads pointing to a vertical line.

space on the capacitor and can usually fit nicely on

The vertical line is the transistor’s base lead and the the capacitor body, but without the chart the builder two diagonal lines represent the collector and the

would have a difficult time determining the

emitter. The diagonal lead with the arrow on it is the capacitor’s value.

emitter lead, and this should help you install the

Now locate the capacitors from the component

transistors onto the circuit board correctly. Go ahead pile and try and locate capacitor C1, which should

and install the two transistors on the PC board and

be marked with either a 22 pF (223) or a 27 pF (227)

solder them in place, then follow-up by cutting the

value. Let’s go ahead and place C1 on the circuit

excess component leads.

board and then solder it in place. Now take your

When constructing the coils, note that L1 and L2

end-cutters and cut the excess capacitor leads flush

have enamel insulation lacquer on them. This must be

to the edge of the circuit board. Once you have

physically removed from both ends of the coil before it installed C1, you can move on to installing the

can be soldered. You must use a knife to scrape off the remaining capacitors.

insulation so you solder both ends of each coil to the The FM Phone Transmitter project contains silicon

circuit board. After constructing L3, you will need to diodes at D1 through D4. These diodes also have

spread out the turns of the coil about 1 mm apart. The polarity which must be observed if the circuit is going coil turns should not touch each other or the bottom of to work correctly. You will notice that each diode will the circuit board. You must now solder a connection or have a black or white colored band at one edge of the tap on the top of the first turn in the L3 coil to the pad diode’s body. The colored band represents the diode’s next to the coil, closest to the junction of C1, C8,

cathode lead. Check your schematic and parts layout

and R1. Solder a piece of wire to the top of the first turn diagrams when installing these diodes on the circuit

as shown on the parts layout diagram. Then solder the board. Place the four diodes on the circuit board and other end to the pad immediately next to the L3 coil.

solder them in place. Then cut the excess component

Next, attach a 3′′ length of wire with an alligator

leads with your end-cutters.

clip on the end to the pads between the diodes

The Telephone Transmitter circuit also utilizes two

marked—TO LINE. No antenna is needed. The phone

transistors. You can substitute a number of different line itself acts as a sufficient aerial. The telephone types (see parts list). Transistors generally have three transmitter attaches in series with ONE of the phone

Chapter Sixteen: FM Telephone Transmitter leads, a Base lead, a Collector lead, and an Emitter lead.

wires. Note that there are two wires going to your phone, 170

Chapter Sixteen: FM Telephone Transmitter

Telephone

transmitter

Operation

Red

A

B

Phone wires

When there is a signal on the phone line (that is, when to wall jack

you pick up the handset) the circuit will transmit the Green

conversation over a distance of about 100′. In particular Telephone

it will radiate from the phone line itself. It is a passive Figure 16-3

Phone-transmitter connection

device; there is no battery. It uses the signal on the phone line for power. No aerial is needed,it feeds back the RF signal into the phone line, which radiates it in usually a red wire and a green wire. Cut one of these the FM band.

wires and connect the phone transmitter in series with the phone line wire that you cut as shown in Figure 16-3.

Note that some countries may ban any electronic

Attach one alligator clip to one cut end and the other device which attaches to the telephone. It is the

alligator clip to the other cut end. Take your phone off responsibility of the purchaser to check the legal

the hook and turn on an FM radio at about 93 MHz.

requirements for the operation of this project and to It should be very easy to tune into the transmission.

obey them.

Take a portable FM receiver outside and follow the

If you simply wish to monitor a single phone, then

phone line; you should easily be able to hear the room you could just mount the Telephone Transmitter inside noise where the transmitter is located.

that particular phone case. However, if you wish to

listen to all the phone calls of all the phones in the house then you will have to place the Telephone

Calibration

Transmitter in series with the first incoming telephone line when it arrives in your basement area. You can

The telephone transmitter may need to be calibrated or encase the transmitter in a small metal box, with

adjusted for proper operation on the frequency of your provision for a small antenna to protrude from the case choice. The resonant frequency of the L1-C6 amplifier in order to radiate a signal into the air.

circuit should be adjusted to match the resonant

oscillator frequency of C1, C9-L3. If you want to try calibration you will need a frequency meter, a CRO, or Troubleshooting

just trial and error. Calibrate by moving the coils of L1

further apart. With C1 at 27 pF you will find that the If your telephone transmitter does not appear to

transmitter tunes into the FM band in the 86–95 MHz

function correctly, you will need to disconnect the

area. With C1 at 22 pF the band is raised to about

circuit from the phone line and carefully inspect the 90–95 MHz (depending on the coil spacing). If you want circuit board. It is likely that you made a soldering to move this tunable area still higher to over 100 MHz or parts placement mistake during construction.

range then replace C1 by a 15 pF or 10 pF capacitor.

Pick up the circuit board with the foil side of the

This assumes that the on-hook voltage is about the

circuit board facing upwards toward you. Carefully

standard 48 V. If the on-hook voltage of an extension inspect the circuit board against the parts placement phone network is lower, say about 39 V, C1 will have to diagram and the schematic to make sure that the

be lower in the 15 pF to 10 pF range to be in the

proper component was inserted in the correct

commercial FM band in this case. Note that you should PC holes. You may have placed the wrong resistor

not hold the transmitter physically in your hands if you at a particular location. You may have inserted a

try to do a calibration. Your own body capacitance when capacitor or diode backwards and this could prevent

you touch it is more than enough to change the

the circuit from working properly.

oscillation frequency of the whole unit. You can

Once this preliminary inspection is over, you can

experiment to get greater transmission range away from inspect the circuit board for any possible “cold” solder the phone line by adding an aerial (about 150 cm of

joints or “short” circuits. Take a careful look at each of 26 gauge wire) to the collector of Q2.

the PC solder joints; they should all look clean and shiny.

171

If any of the solder joints look dull, dark, or blobby, to a stray component lead that stuck to the PC board

then you unsolder the joint, remove the solder and then from solder residue, or from solder blobs bridging the resolder the joint all over again. Next, examine the

solder traces. Once you have fully examined the circuit PC board for any short circuits. Short circuits can be board, you can reconnect the circuit board back to the caused from two circuit traces touching each other due phone line and try out the phone transmitter once again.

Chapter Sixteen: FM Telephone Transmitter

172

Chapter 17

Telephone Project

C7

.04 μF, 50 V Discap

Parts list

capacitor (.04 or 403)

C8

.02 μF, 50 V Discap

Telephone Project

capacitor (.02 or 203)

R1, R2, R3, R4

47 K,

1

C10, C11

30 pF, 50 V

⁄ W, 5% resistor

4

Discap capacitor (30)

R5, R23

10 K, 1⁄ W,

4

D1, D2, D3, D4

1N4004

5% resistor

or 1N4007 Silicon

R6, R9, R11, R21

100 K,

diodes

1

⁄ W, 5% resistor

4

D8

55C2V7/1N5223 2.7 V

R7

2.2 K, 1⁄ W,

4

Zener Diode

5% resistor

D7

55C4V7/1N5230 4.7 V

R8

1 Megohm 1⁄ W,

4

Zener Diode

5% resistor

Q1, Q5

9014 C

R10, R14

150 K, 1⁄ W,

4

Transistor NPN

5% resistor

Q2

2N5401 Transistor

R12, R13, R15, R20

PNP 325401

3.3 K, 1⁄ W,

4

5% resistor

Q3

2N5551 Transistor

NPN

R16, R17, R22

15 K,

1

⁄ W, 5% resistor

Q4

9013H Transistor NPN

4

R18

10 ohm, 1⁄ W,

U1

HM9102 Integrated

4

5% resistor

Circuit (IC)

R19

120 ohms, 1⁄ W,

X1

Resonator 3.58 MHz

4

5% resistor

LP1, LP2, LP3, LP4

C1

47 μF, 50 V Mylar

Neon Bulb

(474/470)

S1, S3

SPST Switch

C2

.01 μF, 50 viscap

S2

SPDT Hook Switch

(.01 or 103)

S4

pushbutton

C3, C4, C9

47 μF 35 V

Electrolytic capacitor

KB

Number keypad −

3 × 4 keypad switch

C5

300 pF, 50 V

matrix

Discap (300)

MIC

Microphone

C6

1 μF, 50 V

Electrolytic capacitor

SPK

Speaker

173

Copyright © 2009 by The McGraw-Hill Companies, Inc. Click here for terms of use.

BZ

Piezo buzzer disc

Table 17-1

Telephone glossary

J1

Modular Telephone

Jack

DTMF

Dual tone multifrequency

Misc

PC board,

Electret

A microphone made up of a capacitor

IC sockets, case,

Microphone

with a dielectric that holds a permanent

telephone cord, wire,

electric charge

battery clip

FET

Field effect transistor

Model AK-700 / PT-323 K

Hook-Switch

A switch inside the phone which closes

Telephone Kit

when the receiver is lifted

Kit available from:

IC

Integrated circuit

Elenco Electronics

FCC

Federal Communication Commission

The Telephone Project features a modern phone handset Local Loop

The pair of wires between a telephone set

with both pulse and tone dialing, automatic redial,

and the telephone company Central Office

ringer switch, visual ring indication, and dialer. This Mark Interval

The portion of a dial pulse during which

project is also a great learning tool for electronics loop current is flowing

enthusiasts as it describes and details each telephone Pulse Dialing

A dialing system in which the number of

component and explains how they work together to

pulses on the local loop represents the

form a complete useable telephone. The telephone

number dialed

project shown in Figure 17-1 consists of five major

Ring Wire

The red (negative) wire of the local

components: The handset, consisting of the transmitter telephone loop

and receiver handset section, the dialer section, the Sidetone

The sound heard from the telephone

network section, and the ringer section.

receiver due to the speaker’s own voice

Before we get started talking about the telephone

Space Interval

The portion of the dial pulse during which

project, refer to Table 17-1, which lists a phone term current is not flowing

glossary.

Tip Wire

The green (positive) wire of the local

Everyone knows that the telephone is used to transmit telephone loop

and receive voice signals, allowing two people with

Tone Dialing

A dialing system in which a combination

telephones to communicate with each other, but to be of of two frequencies on the local loop

practical value, the telephone must be connected to a represent the number dialed

USOC

Universal Service Order Code

Zener Diode

A diode that has nearly constant voltage

drop over a wide range of reverse current

switching network capable of connecting each telephone to many other telephones. To accomplish this switching, each subscriber telephone is connected to the telephone company’s Central Office by two wires referred to as

the Local Loop. A simplified diagram of this connection is shown in Figure 17-2.

The Tip and Ring designation of the + and − leads

comes from the days of the manual switchboard. The tip of the plug the operator used to connect telephones

carried the (+) lead and the ring immediately behind the Chapter Seventeen: Telephone Project Figure 17-1 Telephone project. Courtesy of Elenco tip carried the (−) lead. Now when a subscriber wishes 174

Chapter Seventeen: Telephone Project

Central office

Local loop

Subscriber

telephone

Switch

network

Ring (−)

Ringing

signal

generator

48 V DC

Current

relay

Control

signal

Tip (+)

generators

Figure 17-2

Local telephone loop circuit

to place a call, he or she merely picks up the telephone picks up the telephone, voice communication is

and a small current flows in the local loop. This

established.

current picks a relay in the Central Office (CO)

A simplified diagram of a traditional rotary dial

indicating that service is being requested. When the

telephone phone is illustrated in Figure 17-3, and the CO is ready to accept the number being called, a dial major components of the telephone are described below.

tone is sent to the calling telephone. The dial pulses, or tones, then signals to the CO the number of the

telephone being called. A path is then established to Audio section: The handset

that telephone. This path may be a simple wire

connection to a telephone connected to the same CO

First we are going to discuss the main phone

or it may go via wire, microwave link, or satellite to components or subsections. The first major components a telephone connected to a distant CO. To signal

of a telephone are the transmitter or microphone and

the incoming call, a ringing signal is placed on the

receiver or earphone.

local loop of the called telephone. The ringing signal In the older standard rotary dial phones, the

is a 90 V AC 20 Hz signal superimposed on the

transmitter or microphone consists of a metal

48 V DC present on the local loop. A ringing tone is

diaphragm and a metal case, which are insulated from

also sent to the calling telephone. When the called party each other. The case is filled with carbon granules.

Dial

Balance

network

L3

C2

L1

L2

S1

S2

R3

C3

R1

R2

C1

Phone line

V2

Transmitter

Receiver

Ringer

V1

microphone

earphone

Figure 17-3

Rotary dial telephone set

175

Insulator

Coil

Diaphragm

Case

Diaphragm

Carbon

granules

AC

input

Permanent

magnet

Current

Speaker

frame

Figure 17-5

Headphone/speaker

Figure 17-4

Transmitter or microphone

Ring telephone line input connections are fed to a

When you speak into the transmitter, the sound waves

diode bridge made up of diodes D1 through D4.

of your voice strike the diaphragm and cause it to

The bridge ensures that a positive voltage is fed to

vibrate. This causes the carbon granules to compress

the telephone circuit regardless of the polarity of the and expand. When compressed, the resistance of the

input. This is done to protect the integrated circuit and carbon granules is less than when expanded. The change other components that may be damaged by a reversal

of resistance causes a corresponding change in the

of polarity. When the hook switch is not depressed,

current. The current thus varies in step with the sound the telephone is ready to transmit and receive.

waves of your voice, using a standard carbon

The incoming signal from the CO is sent via

microphone (see Figure 17-4).

R20 and C6 to the speaker amplifier made up of

In our modern electronic telephone project the

transistor Q5. This amplifier drives the speaker.

transmitter or microphone consists of an electret type Transmission begins when you speak into the

microphone.

microphone. The microphone used is an electret type.

This type of microphone is made up of a capacitor

There are several different types of receivers or

with a dielectric material which holds a permanent

earphone types. In principle, they work the same as the electric charge. Sound waves striking a plate of this speakers in your radio and TV. The speaker consists of a capacitor cause the plate to vibrate and thus generate small coil attached to a diaphragm. The coil is mounted a small voltage across the capacitor. This voltage is over a permanent magnet. Coil current in one direction amplified by a Field Effect Transistor (FET) mounted

causes the coil and diaphragm to be repelled from the inside the microphone. The signal from the microphone permanent magnet. Coil current in the other direction is then amplified and sent to the Central Office via the causes the coil and diaphragm to be attracted to the

local loop. A portion of the signal is also sent to the permanent. If a current of audio frequency is sent

speaker amplifier to provide the desired side-tone.

through the coil, the diaphragm vibrates and generates sound waves in step with the current. Thus, if the

current from the transmitter is sent through the

The induction coil/balance

coil, the sound produced in the speaker or earphone

network

will duplicate the sound striking the microphone

(see Figure 17-5).

When transmitting and receiving is done over the same The Electronic Telephone Set schematic diagram is

two wires, the problem arises that current from the

Chapter Seventeen: Telephone Project shown in Figure 17-6. In operation, the main Tip and transmitter flows through the receiver. The speaker then 176

P2

P1

Q2

Tip

D1

S2

R15

C5

R20

Q4

D3

R16

R1

Phone

Hook

R13

R14

line

switch

D4

+

P3

C4

R17

R19

Ring

D2

R8

R10

C7

R12 D5

D6

SP+

+

+

C8

D7

R18

C6

C3

Speaker

Q3

L1

R1

R22

Pulse-tone

R21

L2

R2

C2

R9

S3

+

SP−

Q5

R23

D8

L3

R3

C9

L4

R4

5

14

7

10

12

Mic

Mic

1

13

R1

S1

2

9

R2

Ring

U1

XTL

switch

3

8

R3

6 ND

B3

4

11

R4

R5

C1

C2

C3

C4

B

C10

C11

15

16

17

18

6

C1

BZ

1

2

3

B1

B2

4

5

6

R6

R7

7

8

9

0

#

177

Q1

Figure 17-6

Electronic telephone circuit. Courtesy of Elenco Electronics hears his or her own voice from the receiver. This is When the switch (S3) is in the Tone position—potential called side-tone. Too much side-tone may be

pin mode—GND and Dial will be for tone signals.

objectionable to the speaker and cause them to speak

When the switch (S3) is in the Pulse position—potential too softly. A small amount of side-tone is desirable to pin mode—VDD (4.7 V) and Dial will be used for pulse

keep the telephone from sounding dead. The induction

signals.

coil and balance network limit the side-tone. The

The HM9102 integrated circuit (IC) has a built-in

impedance of the balance network approximately

oscillator (clock) which is used for tone generation and matches the impedance of the local telephone line loop.

other timing functions. Because the frequency of dialing Thus, about half of the current from the transmitter

tones must be precise for the telephone CO to

flows through L1 and the local loop and the other half recognize them, a ceramic resonator (X) is used to

flows through L2 and the balance network. The currents accurately control the frequency of the IC’s oscillator.

in L1 and L2 induce voltages in L3 of opposite polarity, This oscillator’s frequency is 3.58 MHz, and it is

which limits the voltage across the receiver to an

divided down to lower frequencies inside the IC.

acceptable level. When receiving a signal from the local loop, the currents in L1 and L2 induce voltages in

The DC voltage at the Tip and Ring inputs is fed to

L3 of the same polarity. These voltages combine to

the dialer IC via the diode bridge, the hook switch,

drive the receiver.

resistor R14, and diode D5. Since excessive voltage may damage the IC, Zener diode D7 limits the voltage to less than 4.7 V. When the phone goes on-hook, the charge on Keypad: Dialer section

capacitor C3 provides the small current needed for the IC memory circuits to retain the last number dialed.

In older phones, the pulse dialing is accomplished by Tone dialing is accomplished with a keyboard of

the familiar rotary dial. The dial is rotated to the stop 12 keys arranged in four rows and three columns. Low

and then released. A spring in the dialer returns the dial frequencies of 697, 770, 852, and 941 are associated

to its null position. As the dial returns, the dial switch with rows R1 through R4 and high frequencies of 1,209, (S2) opens and closes at a fixed rate. This switch is in 1,336, and 1,477 Hz are associated with columns C1

series with the hook switch. Opening the switch

through C3. To send each digit, two frequencies are sent interrupts the current in the local loop. A series of to the CO simultaneously. For this reason, this method current pulses is thus sent out on the local telephone of dialing is referred to as dual tone multifrequency line loop. The number of pulses sent corresponds to the (DTMF). The different frequencies are generated by

digit dialed. Dialing “0” sends ten pulses. The dial

connecting a capacitor to different taps of a transformer pulses are sent at a rate of 10 pulses per second (100 ms to establish a resonant circuit of the correct frequency.

between pulses). Each pulse consists of a mark interval Each of the 3 keys of row 1 is mechanically connected (loop current) and a space interval (no loop current).

to switch SR1. Similarly, each of the other rows and

In America, the mark interval is 40 ms and the space

columns are connected to their corresponding switches.

interval is 60 ms giving a mark/space ratio of 40/60.

Thus, pressing any key closes two switches and

In Europe, the mark space ratio is usually 33/67.

generates two frequencies. Pressing a 6, for example, Fortunately, the telephone CO responds to two types

closes switches SR2 and SC3 and generates 770

of dialing signals, both pulse and tone signals. Our

and 1,477 Hz.

modern electronic Telephone Project provides both

Keyboard inputs C1 through C3 and R1 through R4

pulse and tone dialing functions. The main elements

accept the column and row inputs from the keyboard;

of the dialer section in the Telephone Project are the see Figure 17-7.

keyboard and the dialer IC HM9102. These two

components perform all of the functions of the rotary dial When a row and a column line are connected, the

found in older telephones. The HM9102 is the tone/pulse digit corresponding to that row and column is stored in switchable dialer with last number redial which is

the IC memory. The dial pulses start when the first

fabricated with CMOS technology. The HM9102

button is pushed. In a conventional rotary dial, the

Chapter Seventeen: Telephone Project turns transistor Q3 on or off to generate dial pulses.

pulses are sent as the rotor returns to its null position.

178

Chapter Seventeen: Telephone Project

C1

C2

C3

capacitor, C1, to block the 48 V DC when the phone is 1209 Hz 1336 Hz 1477 Hz

on-hook. The diagram in Figure 17-9 illustrates the bell SR1

found in older telephone sets.

1

2

3

R1 697 Hz

Notice that the ringer consists of a permanent magnet SR2

4

5

6

attached to an armature. Our modern Telephone Project R2 770 Hz

SR3

circuit uses a small buzzer to simulate the bell or ringer 7

8

9

R3 852 Hz

of an old phone.

SR4

0

#

R4 941 Hz

To signal an incoming call, the CO places a

90 V AC 20 Hz signal on top of the 48 V DC. If the

ringer switch (S1) is closed, transistor Q1 conducts

SC3

during the 1⁄2 cycle that the ring terminal is positive.

SC2

The collector to emitter voltage is applied to the buzzer, causing it to change dimensions. The feedback lead is SC1

connected to the base of transistor Q1 through resistor R7, causing the circuit to oscillate at about 3 KHz.

Figure 17-7

There is no oscillation during the negative portion of Touch-tone dial

the 20 Hz signal. The buzzing sound is thus produced

by the buzzer changing dimensions, during the positive This may take about one second if a zero is dialed. The portion of the 20 Hz ringing signal. The four neon bulbs next digit is entered only when the preceding digit is LP1 through LP4 and resistors R1, R2, R3, and R4 are

transmitted. With the HM9102 dialer IC, scanning of

also connected across the tip and ring inputs. When

the keyboard continues while the dial pulses are being the ringing signal causes the voltage across the bulbs transmitted, as shown in Figure 17-8.

to exceed about 100 V, the bulbs conduct, giving

When the number is dialed, a memory section in the

a visual indication of the incoming call. Install the IC is loaded with each digit as it is dialed. Later, if the following parts. The hammer attached to the armature

redial button (#) is pressed, the IC automatically

thus strikes one bell and then the other to produce the dials the digits you previously entered (for Pulse Mode).

ringing sound.

For Tone Mode, button (#) – execute “#”. The button

“*” for Pulse Mode – execute pause (pause time 3.6 s), Hook switch

for Tone Mode – execute “*”.

When the hook switch is open (on-hook) no current

The ringer section

flows in the local loop, the hook-switch or HKS input of the IC is grounded through resistor R9. This enables The telephone ringer in the Telephone Project is

the keyboard inputs; when the phone is on the hook,

connected across the tip and ring inputs in series with a a small current flows through resistors R8 and R9;

2

3

Loop

current

0

Space 60 ms

Pulse period

100 ms

Mark 40 ms

Figure 17-8

Pulse-dialer spacing

179

Hammer

calling telephone. The dial tone stops when the first digit is dialed.

Bell

Phone Circuit: General assembly

Permanent

Armature

magnet

Before we begin constructing the Telephone project,

you will need to find a clean, well-lit worktable or

workbench. Next, we will gather a small 25–30 W

pencil tipped soldering iron, a length of 60/40 tin–lead solder, and a small canister of Tip Tinner, available at your local RadioShack store; Tip Tinner is used to

condition the soldering tip between solder joints. You drive the soldering tip into the compound and it cleans Coils

and prepares the soldering tip. Next grab a few small Figure 17-9

Ringer or bell

hand tools; try to locate small flat blade and Phillips screwdrivers. A pair of needle-nose pliers, a pair of this biases the HKS input to about 2 V which disables tweezers along with a magnifying glass, and a pair of the keyboard inputs. The 48 V DC from the battery

end-cutters and we will begin constructing the project.

in the CO appears on the tip and ring input to the

Now locate your schematic diagram and parts layout

telephone set. When the receiver is lifted, the hook

diagram along with all of the components needed to

switch closes and a current of about 20 to 120 mA

build the project. The Telephone project was

flows in the local loop. The resistance of the local

constructed on a rectangular printed circuit board

loop drops the voltage at the telephone to about 6 V.

Once all the components are in front of you, you can

The current picks a relay in the CO which tells

check them off against the project parts list to make other equipment there that service is being

sure you are ready to start building the project. Now, requested. When the CO is ready to accept the

locate Tables 17-2 and 17-3, and place them in

number being called, a dial tone is sent to the

front of you.

Table 17-2

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

Chapter Seventeen: Telephone Project

No color

20%

180

Chapter Seventeen: Telephone Project

Table 17-3

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

1.0

1R0

3,900

3.9

.0039

392

1.2

1R2

4,700

4.7

.0047

472

1.5

1R5

5,600

5.6

.0056

562

1.8

1R8

6,800

6.8

.0068

682

2.2

2R2

8,200

8.2

.0082

822

2.7

2R7

10,000

10

.01

103

3.3

3R3

12,000

12

.012

123

3.9

3R9

15,000

15

.015

153

4.7

4R7

18,000

18

.018

183

5.6

5R6

22,000

22

.022

223

6.8

6R8

27,000

27

.027

273

8.2

8R2

33,000

33

.033

333

10

100

39,000

39

.039

393

12

120

47,000

47

.047

473

15

150

56,000

56

.056

563

18

180

68,000

68

.068

683

22

220

82,000

82

.082

823

27

270

100,000

100

.1

104

33

330

120,000

120

.12

124

39

390

150,000

150

.15

154

47

470

180,000

180

.18

184

56

560

220,000

220

.22

224

68

680

270,000

270

.27

274

82

820

330,000

330

.33

334

100

.0001

101

390,000

390

.39

394

120

.00012

121

470,000

470

.47

474

150

.00015

151

560,000

560

.56

564

180

.00018

181

680,000

680

.68

684

220

.00022

221

820,000

820

.82

824

270

.00027

271

1,000

1

105

330

.00033

331

1,500

1.5

155

390

.00039

391

2,200

2.2

225

470

.00047

471

2,700

2.7

275

560

.00056

561

3,300

3.3

335

680

.00068

681

4,700

4.7

475

820

.00082

821

6.8

685

1,000

1.0

.001

102

10

106

1,200

1.2

.0012

122

22

226

1,500

1.5

.0015

152

33

336

1,800

1.8

.0018

182

47

476

(Continued)

181

Table 17-3—cont’d

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

2,200

2.2

.0022

222

68

686

2,700

2.7

.0027

272

100

107

3,300

3.3

.0033

332

157

157

Code = 2 significant digits of the capacitor value + number of zeros to follow 10 pF = 100

For values below 10 pF, use “R” in place of decimal e.g. 8.2 pF = 8R2

100 pF = 101

1,000 pF = 102

22,000 pF = 223

330,000 pF = 334

1 μF = 105

Table 17-2 illustrates the resistor code chart and

the digit (4), the second color band is violet, which is how to read resistors, while Table 17-3 illustrates the represented by (7). Notice that the third color is orange capacitor code chart which will aid you in constructing and the multiplier is (1,000), so (4) (7) × 1,000 = 47,000

the project.

or 47 K ohms. Go ahead and place resistor R1 in its

Refer now to the resistor color code chart shown in

proper location on the circuit board and solder it in Table 17-2, which will help you identify the resistors in place. Use a pair of end-cutters to trim the excess

this project. Note that each resistor will have either resistor leads. Cut the excess leads flush to the edge of three or four color bands, which begin at one end of the the PC board. Now locate and install the remaining

resistor’s body. The first colored band represents the resistors in their proper locations; solder them in place resistor’s first digit, while the second color represents and remember to cut the excess component leads with

the second digit of the resistor’s value. The third colored your end-cutters.

band represents the resistor’s multiplier value, and the Note that capacitors generally come from two major

fourth color band represents the resistor’s tolerance groups or types. Non-polar types, such as the ones in value. If there is no fourth colored band then the resistor this project, have no polarity and can be placed in either has a 20% tolerance value. If the resistor’s fourth band direction on the circuit board. The other type of

is silver then the resistor has a 10% tolerance value and capacitors are called polarized types; these capacitors if the fourth band is gold then the resistor’s tolerance have polarity and have to be inserted on the board with value will be 5%.

respect to their polarity marking in order for the circuit Finally, we are ready to begin assembling the

to operate correctly. On these types of capacitors, you Telephone project, so let’s get started. The prototype of will observe that the components actually have a plus or the Telephone project was constructed on a single-sided minus marking or a black or white band with a plus or printed circuit board or PCB. With the PC board in front minus marking on the body of the capacitors.

of you, we can now begin populating the circuit board.

Capacitors must be installed properly with respect to We are going to place and solder the lowest height

polarity in order for the circuit to work properly. Failure components first, the resistors and the diodes. First, to install electrolytic capacitors correctly could cause locate the first four resistors, R1 through R4. These damage to the capacitors as well as to other components resistors have a value of 47 K ohms and are a

in the circuit when power is first applied.

5% tolerance type. Now take a look for a resistor whose Next refer to Table 17-3. This chart helps to determine first color band is yellow, violet, orange, and gold. From the value of small capacitors. Many capacitors are quite Chapter Seventeen: Telephone Project the chart you will notice that yellow is represented by small in physical size, so manufacturers have devised a 182

Chapter Seventeen: Telephone Project

three-digit code which can be placed on the capacitor refer to the manufacturer’s specification sheets as well instead of the actual value. The code occupies a much as the schematic and parts layout diagrams when

smaller space on the capacitor and can usually fit nicely installing the two transistors. If you have trouble

on the capacitor body, but without the chart the builder installing the transistors, get the help of an electronics would have a difficult time determining the capacitor’s enthusiast with some experience. Install the transistors value.

in their respective locations and then solder them in Now look for the capacitors from the stack of

place. Remember to trim the excess components leads

components and locate capacitor C1, which is a small

with your end-cutter.

capacitor labeled (561) or .47 μF. Refer to Table 17-3

The Electronic Telephone Project circuit contains a

to find code (561) and you will see that it represents a single integrated circuit (IC). ICs are often static

capacitor value of .47 μF. Go ahead and place C1 on the sensitive, so they must be handled with care. Use a

circuit board and solder it in place. Now take your

grounded anti-static wrist strap and stay seated in one end-cutters and cut the excess component leads flush to location when handling the integrated circuits. Take out the edge of the circuit board. Now you can move on to a cheap insurance policy by installing IC sockets for installing the remaining capacitors. Locate and install each of the ICs. In the event of a possible circuit failure, the smallest physical sized capacitors first then move it is much easier to simply unplug a defective IC, than on to installing the larger electrolytic types. Place the trying to unsolder 14 or 16 pins from a PC board

capacitors in their respective locations and solder them without damaging the board. ICs have to be installed

in place on the PC board.

correctly if the circuit is going to work properly. IC

packages will have some sort of markings which will

The Telephone Project contains six of silicon diodes

help you orient them on the PC board. An IC will

and two Zener diodes. Diodes, as you will remember, will have either a small indented circle, a cut-out or notch always have some type of polarity markings, which must at the top end of the IC package. Pin 1 of the IC will be observed if the circuit is going to work correctly. You be just to the left of the notch or cut-out. Refer to will notice that each diode will have a black or white the manufacturer’s pin-out diagram, as well as the

colored band at one edge of the diode’s body. The colored schematic, when installing these parts. If you doubt you band represents the diode’s cathode lead. Check your

ability to correctly orient the ICs, then seek the help of schematic and parts layout diagrams when installing these a knowledgeable electronics enthusiast to help you.

diodes on the circuit board. Place all the silicon diodes on the circuit board in their respective locations and solder The Electronic Telephone Project circuit employs four them in place on the PC board. The Zener diodes are

neon indicators which are installed in parallel through located at D7 and D8; you can find their locations, place series resistors. The neon lamps have no polarity, so they them on the PC board, and solder them in place on the can be installed in either direction safely. Solder the board. After soldering in the diodes and the diode bridge, neon lamps to the PC board and then trim the excess

remember to cut the excess component leads with your

leads. Next, locate the crystal at XTL and install it in its end-cutters flush to the edge of the circuit board.

proper location between pins 8 and 9 of U1.

The Electronic Telephone Project utilizes five

Finally, you can install the SPDT TONE-PULSE slide

conventional transistors. Transistors are generally three switch at S3, the HOOKSWITCH at S2, and the RINGER

lead devices, which must be installed correctly if the switch at S1. The HOOKSWITCH is a leaf spring type

circuit is to work properly. Careful handling and proper SPDT switch and the RINGER switch S1 is an SPDT

orientation in the circuit is critical. A transistor will slide switch. Solder the switches in to their respective usually have a Base lead, a Collector lead, and an

locations and trim the excess leads as necessary.

Emitter lead. The base lead is generally a vertical line inside a transistor circle symbol. The collector lead is usually a slanted line facing towards the base lead and Audio circuit assembly

the emitter lead is also a slanted line facing the base lead but it will have an arrow pointing towards or away Next, we will install the electret microphone between from the base lead. Now, identify the two transistors, ground and pin 13 of U1. The microphone’s (+)

183

marking should face pin 13 and the ground or case body with your soldering iron. If not already in place, snap connection goes to ground. Identify two wires (4′′ red the dial buttons onto the contact pad. Peel the backing and 3′′ gray), microphone, and microphone pad. Cut the off of the dial label and place it on the top case (make 4′′ red wire down to 2′′ and the 3′′ gray wire to 2′′. Use sure that the holes line up). Insert the buttons through the 2′′ red and 2′′ gray stranded wires and strip 1⁄8′′ of the holes in the front plate. Be sure that the # “2” button insulation off of each end. Identify the microphone.

is in the hold marked “ABC”, if you are building the kit Bend the wires and very carefully solder the wires to version of the project. With the contact pad lying flat on the microphone. Peel the backing off one side of the

the front side, insert the keyboard’s PC board under the microphone pads and place them onto the microphone.

two upper retaining tabs. Push the lower restraining

Peel the second backing off of the microphone pads and tab back and snap the PC board in place. Fasten the

thread the wires through the hole in the PC board from PC board in place with the two 1⁄4′′ screws. Reconnect the solder side. Solder the red wire to the hole marked the speaker wires. If your kit contains extra wires,

MIC on the PC board and the gray wire to the hole

please disregard them. Insert the hook button into the marked GND on the PC board. Place the microphone on

top of the case. Check that there are no burrs on the the PC board on the solder side.

sides of the button. It must move freely once installed.

Locate and install the earphone/speaker between the

Cut any excess plastic off of the case. Make sure that cathode of Zener diode D8 and the collector of Q5.

the top of the middle post is level with or below the Identify the speaker with pad, 3′′ gray wire, and the two outside posts.

second half of the 4′′ red wire (the first half was used for the microphone). Cut a 2′′ piece from the 3′′ gray Ringer assembly

wire and strip 1⁄8′′ of insulation off both ends. Solder the red wire to the speaker + and the gray wire to the

Identify the ringer switch. The ringer switch is mounted speaker −. Solder the red wire to SP+ on the PC board on the copper side of the PC board. Insert the switch and the gray wire to SP−.

tabs into the holes provided and solder the three

Now locate and install the piezo buzzer element. The

terminals. Be sure that the switch is perpendicular to the piezo buzzer element has three leads, the outermost

PC board. To anchor the switch in place, grasp the

ring-lead connects to B3, the middle circle ring-lead switch tabs with your pliers and give a 1⁄8 turn. Identify connects to B1, and the inner or center lead connects to the telephone cord. Solder the red wire to the ring

B2, as shown on the schematic diagram.

jumper and the green wire to the tip jumper. Identify the Now identify the hook-switch. The hook-switch

buzzer and buzzer pad. Use three 2′′ wires of different mounts to the copper side of the PC board. Insert the color (red, orange, and gray) to connect the buzzer to switch tabs into the mounting holes and twist the tabs 1⁄

the PC board. Identify the red and orange wire and cut 8

of a turn as was done with the ringer switch. Solder the a 2′′ piece of wire off the 3′′ gray wire. If needed, strip 1

switch’s contacts to the PC board using two pieces of

⁄8′′ of insulation off of each end. Tin the buzzer with discarded resistor leads and a 3′′ gray stranded wire.

solder in the locations. Tin both ends of the three 2′′

wires. Carefully solder the three 2′′ wires onto the

buzzer. Thread the three wires through the buzzer pad and then through the hole from the solder side of the Keypad-dialer assembly

PC board. Solder the three wires to the PC board. The gray wire goes to B1, the orange wire goes to B2, and The keypad switch assembly is a standard Grayhill or

the red wire goes to B3.

equivalent 3 × 4 normally open push button key switch matrix. Insert the ribbon cable through the holes in the main PC board and solder. Insert the ribbon cable

Final assembly

through the holes in the keyboard PC board. Solder the ribbon cable to the keyboard’s PC board. Carefully

Place the PC board on the top case so that the ringer inspect the ribbon cable solder joints. If there are many switch is in the ringer switch hole, the TONE-PULSE

Chapter Seventeen: Telephone Project solder bridges between adjacent pads, remove them switch is in the tone/pulse hole, and the two mounting 184

Chapter Seventeen: Telephone Project

holes on the PC board line up with the mounting posts drywall, you should use drywall screws. Drywall screws on the top case. If the PC board does not stay lined up are available at most hardware stores.

with the two mounting posts, insert one or both of the The procedure for connecting the telephone to the

5⁄8′′ screws to keep it in place. Check the following: telephone service line depends on the present

(1) Be sure that the speaker wires do not lie between the termination of your line. If your line terminates in a speaker and the telephone top case. (2) Be sure that

modular jack, you need only to plug in the telephone

the keyboard ribbon cable is in the notch in the side cord and the installation is complete. Modular jacks

of the PC board and does not extend out over the

may be recognized by the distinctive shape of the outlet.

edge of the top case. (3) Make sure that no leads from If your telephone service wiring terminates in an old the PC board touch the 1⁄4′′ screws mounting the keypad.

type hard wired jack, you may either (1) replace it with (4) Be sure that the keyboard PC board does not hit the a modular jack if your telephone is to be installed in the buzzer. Loop the telephone cord through the strain relief same place, or (2) install a modular jack in a new

tabs on the bottom case. Place the bottom case over the location and connect it to the hard wired jack with a top case. Be sure that the telephone cord is in the notch length of 4-conductor telephone wire. Modular jacks are at the base of the bottom case. Snap the bottom case in available in most stores where telephones are sold. To place and secure it with two 5⁄8′′ screws. The telephone replace the old type jack: Loosen the screw from the

number label with its cover mounts over the two

green wire and remove the wire. Loosen each of the

5⁄8′′ screws. Insert the tabs at each end of the label into remaining screws and remove the wires. Unscrew the

the slots along side the screws.

mounting screws and remove the base of the old jack.

Once the Telephone Project circuit board has

Your jack may look somewhat different, but it should

been completed, take a short break and when we

have the red, green, yellow, and black wires and the

return we will inspect the PC board for possible “cold”

four marked screws. The cover may snap or screw onto

solder joints and “short” circuits. Pick up the

the base. Screw the modular jack to the wall. As with PC board with the foil side facing upwards toward

the cradle, if you are mounting on drywall, use drywall you. Carefully inspect the solder joints, these should screws. If the telephone service wires are not already look smooth, clean, and bright. If any of the solder

stripped and bent, strip 1⁄2′′ of insulation off of each wire joints look dull, dark, or blobby, then you should

and bend the stripped portion into a “U”. Loop the

remove the solder with a solder sucker or a solder

green wire around the “G” screw between the washer

wick and then resolder the joint all over again.

and the head of the screw. The loop should be in a

Now we will inspect the PC board for possible

clockwise direction. Insert the spade lug of the green short circuits. Short circuits can be caused from small wire from the modular connector under the washer and

solder blobs bridging the circuit traces or from cut

tighten the screw. Connect the red wire to the “R” screw component leads which can often stick to the circuit

in the same way.

board once they have been cut. A sticky residue from

solder will often trap component leads across the

If present, connect the black and yellow wires in the circuit traces. Look carefully for any bridging wires same way. If these are missing, merely connect the

across circuit traces.

black and yellow spade lugs to the “B” and “Y” screws.

This will keep them from shorting to the other wires.

Place the modular jack cover on the base. Plug in the Installing the telephone

telephone line cord. To locate the modular jack in the new location: Obtain the proper length of 4-wire

Select a convenient place for your phone. Place the

telephone cable. Install the modular jack, using the

telephone cradle against the wall and mark the center of 4-wire telephone cable in place of the telephone service the upper lobes of the two mounting holes. Screw in the wires. Run the 4-wire telephone cable to the old type two mounting screws (not provided) to about 1⁄4′′ of the hard wired jack. Strip 1⁄2′′ of insulation off the green mounting surface. Slide the cradle over the two screws telephone cable wire and bend the stripped portion into and then tighten the screws. The phone and cradle are a “U”. Loosen the screw holding the green telephone

very light. However, if you are mounting the cradle on service wire. Connect the two green wires and tighten 185

the screw. Fasten the red telephone service wire to the green telephone service wire is connected to the red

red telephone cable wire in the same way. Fasten the

modular jack wire and the red telephone service wire to remaining wires in the same way. If the black or yellow the green modular jack wire. You may instead purchase telephone service wires are missing, fasten the

an adapter which converts the old 4-connector jack to a telephone cable wire to the empty screw to keep it from modular jack. Once it has been installed, you can begin shorting to the other wires.

enjoying your newly completed telephone, and have

If your telephone service wiring terminates in a

great satisfaction in understanding how a telephone

4-connector jack, you may replace this jack in a manner works that you built it yourself. Your new telephone

similar to replacing the hard wired jack. Be sure that the should give you many years of trouble-free service.

Chapter Seventeen: Telephone Project

186

Chapter 18

Talking/Musical Telephone

Ringer

C8

22 μF, 35 V

Parts list

tantalum capacitor

D1

1N4758A 56 V Zener

Talking/Musical

diode

Telephone Ringer

D2

1N4148 silicon diode

R1, R2

33 K ohms, 1⁄ W,

4

5% resistpor

U1

4N25 NPN

opto¯coupler

R3

10 megohm, 1⁄ W,

4

5% resistor

U2

74LS161 counter IC

R4, R5, R7, R10

U3

74LS00 Quad NAND

10 K ohms, 1⁄ W,

gate

4

5% resistor

U4

ISD1016 Voice

R6

12 K ohms, 1⁄ W,

message chip

4

5% resistor

MOV

metal oxide

R8

470 K ohms, 1⁄ W,

varistor

4

5% resistor

P1

telephone line cord

R9

10 ohms, 1⁄ W,

4

S1

momentary pushbutton

5% resistor

S2

2¯position DIP

R11

2 K ohms, 1⁄ W,

4

switch

5% resistor

S3, S4

SPDT toggle

C1

22 μF, 250 V metal

switch

film capacitor

SPK

8¯ohm speaker

C2, C3

47 μF, 35 V

MIC

electret microphone

electrolytic capacitor

Misc

PC board, AC

C4

.1 μF, 50 V ceramic

adaptor, hardware,

capacitor

wire, enclosure, etc.

C5

1 μF, 35 V tantalum

Don’t listen to that annoying bell—build our talking

capacitor

telephone ringer and customize the way your phone

C6

.22 μF, 35 V

rings. Telephones ring and that’s about all there is to it.

polystyrene

Some phones buzz, beep, or chirp, but that is not very capacitor

exciting. With the advent of integrated circuits (ICs) C7

4.7 μF, 35 V

like the ISD-1016 Voice Messaging IC, you can build

tantalum capacitor

our talking telephone ringer and record personalized

187

Copyright © 2009 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Telephone

Ring detector

line

Microphone

Start

Reset

Message

Logic

storage

Figure 18-1

Telephone voice ringer (front view).

chip

Courtesy of Poptronix

Speaker

messages that will be played whenever someone calls

Counter

you; see Figure 18-1.

End of message

You will never have to listen to the same old bell again.

With the recording capabilities of the Talking/Musical Figure 18-2

Talking/musical ringer block diagram

Telephone Ringer you can include your own spoken

(Courtesy Poptronix)

messages, musical selections, your college fight song, or any other interesting sounds or phrases you can think side of U1 causes pin 5 to go low which signals a

of. You can also program several different messages that start-playback request from the ISD1016 messaging

play in sequence with each ring and the possibilities are chip, U4.

endless. The Talking/Musical Ringer does not interfere with normal telephone operation, it simply plugs into a The sensitivity of the ring-detection circuit is set

telephone jack, and requires an external 9-V DC wall

by R6. The 12 K resistor value was obtained assuming

power supply for power. When someone calls you, the

a nominal 100-volt incoming ring signal. If the ring

incoming ring signal triggers the message to be played voltage coming in on your phone line is lower than

on the project’s loudspeaker.

100 volts, you may need to increase R6 to a value

between 15 K and 30 K. Metal-oxide Varistor (MOV1)

protects the ringer from transient voltage spikes caused Circuit operation

by lightning-induced current on the telephone line.

Diode D1 protects the input LED of the opto-coupler

The diagram shown in Figure 18-2 is the block diagram from reverse voltage during the negative cycle of the of the Talking/Musical Telephone Ringer circuit.

AC ring signal. Diode D2 establishes a transient

When a ring signal appears across the telephone line, threshold to prevent the ringer from triggering

the ring detector sends a start signal to the message-when you pick up the phone or when dialing with a

storage chip. The counter and logic sections tell the rotary telephone.

message-storage chip which message to play based on

Pushbutton switch Sl has two functions: When S3 is

how many times the phone rings.

in PLAY position, S1 acts as a test button that permits Now take a look at the Talking/Musical ringer

you to play back the messages under manual control.

schematic diagram shown in Figure 18-3.

When S3 is in the RECORD position, pressing S1

enables the circuit recording function.

A 20 Hz ring signal of approximately 40 to l50 volts, present at Tip and Ring telephone line connections

The operation of U2 depends on the setting of

(green and red, respectively). This ringing signal voltage switch S4. When S4 is in the SINGLE position, one

is divided down by R1, R2, and R3. Current then flows message will be played each time the phone rings (U2

through C1 to pins 1 and 2 of U1, a 4N25 opto-coupler.

has no function in this case). When S4 is in the MULTI The opto-coupler isolates the rest of the circuitry from position, U2 operates as a counter circuit that counts the Chapter Eighteen: Talking/Musical Ringer the telephone line. The current flow through the input number of individual messages to be played. Up to five 188

Chapter Eighteen: Talking/Musical Ringer

+5 V

+5 V

9 10 28

M1

R1

C1

D1

U1

R6

1

C4

16

Green

1

5

23

2

Telephone

R3

20

3

+5

line

R2

D2

2

4

4

Red

C5

+

+

6

5

+5

R7 Single

S1

5

21

Multi

7 10 16

R4

U3:d

+5 V

25

1

2

12

C7

S4

11

14

U3:b

U4

4

+5 V

R5

1

13

3

6

+

19

3

U2

12

2

5

R11

24

R8

52-a

U3:a

17

R10

4

9

9

+

8

C6

Mic

52-b

MIC

+

C8

5

6

8

+

10

5 V

U3:C

1

3

+5 V

S3

14

U5

27

9 V

+

+

15

C2

Record

R9

2

C3

Adaptor

12

13 26

SPK

Figure 18-3

Talking/musical ringer. Courtesy of Poptronix

different messages can be sequenced with each

successive incoming ring signal. Settings for the

Construction

number of plays are shown in Table 18-1.

The author chose to use a single-sided PC board for

Quad NAND gate U3 works in conjunction with

most reliable long term results.

U2 to provide logic control for resetting U4 when the You can make your own PC board from scratch or use

proper number of playback messages has been reached.

pre-fab circuit board, many types of which are available The ISD1016 messaging chip (U4) stores up to

from your local RadioShack store. Before we begin

l6 seconds of high-quality audio. Audio for recording is building the Talking/Musical Telephone Ringer project, input to the chip via the electret microphone MIC, while let’s first find a clean, well-lit worktable or workbench.

playback occurs through the 8-ohm speaker SPK.

Next we will gather a small 20–30-W pencil tipped

Power to the circuit is provided via a 9 or l2-V DC

soldering iron, a length of 60/40 tin–lead solder, a small wall adapter. A 7805 regulator (U5) provides 5-V

canister of Tip Tinner, available at your local Radio regulated power to the rest of the circuitry.

Shack store, along with a few small hand tools. Try to locate small flat blade and Phillips screwdrivers. A pair of needle-nose pliers, a pair of tweezers along with a Table 18-1

magnifying glass, and a pair of end-cutters and we will Switch settings

begin constructing the project. Locate your schematic Number of Msgs

S4

S2a

S2b

diagram along with all of the components to build the project. Once all the components are in front of you, you 1

Single

X

X

can check them off against the project parts list to make 2

Multi

L

L

sure you are ready to start building the project. Now, locate 3

Multi

H

L

Tables 18-2 and 18-3, and place them in front of you.

4

Multi

L

H

Table 18-2 illustrates the resistor code chart and

5

Multi

H

H

how to read resistors, while Table 18-3, illustrates the 189

Table 18-2

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

No color

20%

Table 18-3

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

1.0

1R0

3,900

3.9

.0039

392

1.2

1R2

4,700

4.7

.0047

472

1.5

1R5

5,600

5.6

.0056

562

1.8

1R8

6,800

6.8

.0068

682

2.2

2R2

8,200

8.2

.0082

822

2.7

2R7

10,000

10

.01

103

3.3

3R3

12,000

12

.012

123

3.9

3R9

15,000

15

.015

153

4.7

4R7

18,000

18

.018

183

5.6

5R6

22,000

22

.022

223

6.8

6R8

27,000

27

.027

273

8.2

8R2

33,000

33

.033

333

10

100

39,000

39

.039

393

12

120

47,000

47

.047

473

15

150

56,000

56

.056

563

18

180

68,000

68

.068

683

22

220

82,000

82

.082

823

27

270

100,000

100

.1

104

33

330

120,000

120

.12

124

39

390

150,000

150

.15

154

47

470

180,000

180

.18

184

Chapter Eighteen: Talking/Musical Ringer 56

560

220,000

220

.22

224

190

Chapter Eighteen: Talking/Musical Ringer

Table 18-3—cont’d

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

68

680

270,000

270

.27

274

82

820

330,000

330

.33

334

100

.0001

101

390,000

390

.39

394

120

.00012

121

470,000

470

.47

474

150

.00015

151

560,000

560

.56

564

180

.00018

181

680,000

680

.68

684

220

.00022

221

820,000

820

.82

824

270

.00027

271

1,000

1

105

330

.00033

331

1,500

1.5

155

390

.00039

391

2,200

2.2

225

470

.00047

471

2,700

2.7

275

560

.00056

561

3,300

3.3

335

680

.00068

681

4,700

4.7

475

820

.00082

821

6.8

685

1,000

1.0

.001

102

10

106

1,200

1.2

.0012

122

22

226

1,500

1.5

.0015

152

33

336

1,800

1.8

.0018

182

47

476

2,200

2.2

.0022

222

68

686

2,700

2.7

.0027

272

100

107

3,300

3.3

.0033

332

157

157

Code = 2 significant digits of the capacitor value + number of zeros to follow 10 pF = 100

For values below 10 pF, use “R” in place of decimal e.g. 8.2 pF = 8R2

100 pF = 101

1,000 pF = 102

22,000 pF = 223

330,000 pF = 334

1 μF = 105

capacitor code chart which will aid you in constructing has a 20% tolerance value. If the resistor’s fourth band the project.

is silver then the resistor has a 10% tolerance value and Refer now to the resistor color code chart shown in

if the fourth band is gold then the resistor’s tolerance Table 18-2, which will help you identify the resistors in value will be 5%.

this project. Note that each resistor will have either Finally, we are ready to begin assembling the project, three or four color bands, which begin at one end of the so let’s get started. First, locate our first resistor R1.

resistor’s body. The first colored band represents the Resistor R1 has a value of 100 ohms and is a

resistor’s first digit, while the second color represents 5% tolerance type. Now look for a resistor whose first the second digit of the resistor’s value. The third colored color band is brown, black, brown, and gold. From the band represents the resistor’s multiplier value, and the chart you will notice that brown is represented by the fourth color band represents the resistor’s tolerance digit (1), and black is represented by (0). Notice that the value. If there is no fourth colored band then the resistor third color is brown and the multiplier is (10), so

191

10 × 10 = 100 ohms. Now place resistor R1 into its

these diodes on the circuit board. Place the four

proper location and solder it in place. Next, use a pair diodes on the circuit board and solder them in place.

of end-cutters to trim the excess resistor leads.

Then cut the excess component leads with your

Cut the excess component leads flush to the edge

end-cutters.

of the circuit board. Now locate the remaining resistors The Talking/Musical ringer circuit contains five

and place them in their respective locations on the

integrated circuits (ICs). IC U1 is an opto-coupler,

PC board. Solder the resistors in place and remember

while U2 is a 74LS161, U3 is a 74LS00 and U4 is

to trim the excess component leads with your

the voice chip. The regulator U5 is located in the

end-cutters.

power supply section of the circuit. ICs are often

Note that capacitors generally come from two major

static sensitive, so they must be handled with care.

groups or types. Non-polar types, such as the ones in Use a grounded anti-static wrist strap and stay seated this project, have no polarity and can be placed in either in one location when handling the ICs. Take out a

direction on the circuit board. The other type of

cheap insurance policy by installing IC sockets for

capacitors are called polarized types; these capacitors each of the ICs. In the event of a possible circuit failure, have polarity and have to be inserted on the board

it is much easier to simply unplug a defective IC than with respect to their polarity marking in order for the trying to unsolder 14 or 16 or more pins from a PC

circuit to operate correctly. On these types of capacitors, board without damaging the board. Integrated circuits you will observe that the components actually

have to be installed correctly if the circuit is going to have a plus or minus marking or a black or white

work properly. IC packages will have some sort of

band with a plus or minus marking on the body of

markings which will help you orient them on the

the capacitors.

PC board. An IC will have either a small indented

Next refer to Table 18-3; this chart helps to determine circle, a cutout, or notch at the top end of the IC

the value of small capacitors. Many capacitors are quite package. Pin 1 of the IC will be just to the left of the small in physical size, so manufacturers have devised a notch, or cutout. Refer to the manufacturer’s pin-out three-digit code which can be placed on the capacitor diagram, as well as the schematic, when installing these instead of the actual value. The code occupies a much parts. If you doubt you ability to correctly orient the ICs, smaller space on the capacitor and can usually fit

then seek the help of a knowledgeable electronics

nicely on the capacitor body, but without the chart the enthusiast to help you. Do not forget to install wire builder would have a difficult time determining the

jumpers at all locations marked “J.”, at the necessary capacitor’s value.

locations.

Now locate the capacitors from the component pile

Once the circuit board has been completed, take a

and try and locate capacitor C1, which should be

short break and then we will inspect the PC board for marked with either a 22 pF (223) or a 27 pF (227)

possible “cold” solder joints and “short” circuits.

value. Let’s go ahead and place C1 on the circuit board Pick up the PC board with the foil side facing

and then solder it place. Now take your end-cutters

upwards toward you. Carefully inspect the solder joints, and cut the excess capacitor leads flush to the

these should look smooth, clean, and bright. If any of edge of the circuit board. Once you have installed C1, the solder joints look dull, dark, or blobby, then you you can move on to installing the remaining

should remove the solder with a solder sucker or a

capacitors.

solder wick and then resolder the joint all over again.

The Talking/Musical Ringer project contains a

Now we will inspect the PC board for possible short

Zener diode at D1 and a single silicon diode at D2.

circuits. Short circuits can be caused from small solder These diodes also have polarity which must be observed blobs bridging the circuit traces or from cut component if the circuit is going to work correctly. You will notice leads which can often stick to the circuit board once that each diode will have a black or white colored band they have been cut. A sticky residue from solder

at one edge of the diode’s body. The colored band

will often trap component leads across the circuit

represents the diode’s cathode lead. Check your

traces. Look carefully for any bridging wires across

Chapter Eighteen: Talking/Musical Ringer schematic and parts layout diagrams when installing circuit traces.

192

Chapter Eighteen: Talking/Musical Ringer

Switches Sl, S3, and S4 were mounted on the front

panel of the enclosure, while the microphone and

speaker were mounted on the top of the enclosure.

Any plastic or metal enclosure that will accommodate

the PC board, switches, and speaker will suffice.

Drill the selected enclosure to provide mounting holes for the circuit board assembly, Sl, S3, S4, SPK, MIC, and access holes for the power cord and the telephone line cord. If you are using a metal enclosure, deburr all holes and insert rubber grommets for the AC line cord and the telephone cord. If you elect to use an external 9-V “wall wart” type power supply, you will have to

Figure 18-4

Telephone voice ringer (inside view)

mount a small coaxial jack on the rear panel of the

(Courtesy Poptronix)

chassis box.

Use about five or six inches of insulated wire

Once the unit is complete, plug the adapter into an AC

attached to each terminal to connect those components outlet and plug the telephone cord from the ringer into to the PC board. Once you have soldered all

an unused telephone jack. If you need to attach the unit components in place, you can test the circuit. With U4

to a jack that already has a phone connected to it,

still not installed in its socket, plug the AC adapter into you will need a duplex jack. It is a “Y” adapter that lets a wall outlet. Check for 5 V DC between pin 3 of U5

you plug two phones into one jack, permitting you to

and ground. If you do not obtain a proper reading, make use the voice ringer and the telephone at the same time.

sure the 9-volt adapter is indeed delivering 9 V DC

You may want to shut off the telephone’s internal ringer, (or more) when not connected to the ringer. If it is, so you can clearly hear the voice/musical ringer and its check the orientation of U5. Correct any wiring errors unusual message.

and/or replace any defective components before

proceeding.

Some recording tips

Once you obtain the proper +5-V reading from U5,

disconnect power from the ringer and install U4 in its To record multiple messages, perform the following:

socket. Power up the ringer again and place S4 in the 1.

Place S4 in the MULTI position.

SINGLE position and S3 in the RECORD position.

2.

Set S2- and S2(b) as listed in Table 18-1 for the

While pressing and holding Sl, speak a test message

number of messages you desire.

into the microphone. Then release Sl and place S3 into the PLAY position. A momentary pressing of S1 should

3.

Press and hold S1 to record the first message.

now result in the playback of your test message. If those 4.

Release Sl.

results are obtained, your ringer is ready to be mounted 5.

Press and hold S1 again to record the second

in an enclosure.

message.

Mount the circuit-board assembly in the enclosure

using 1⁄2′′ standoffs. Then mount all off-board

Table 18-1

components in their respective mounting holes. Pass the Switch settings

AC cord and the telephone cord through their rubber

Number of Msgs

S4

S2a

S2b

grommets and tie a knot in each one, about 5 inches

from the free ends inside the enclosure, to serve as

1

Single

X

X

strain relief for each cord. Strip the ends of each wire 2

Multi

L

L

and tin them with solder. Then solder the free ends in 3

Multi

H

L

their respective circuit board holes. Figure 18-4 shows 4

Multi

L

H

the author’s completed prototype installed in a metal 5

Multi

H

H

enclosure.

193

6.

Release Sl.

Since a standard ring signal is on for 2 s

and off for 2 s, you will want to make messages

7.

Repeat steps 5 and 6 for each additional message.

at least 2 s long to prevent successive triggering by 8.

Place S3 in the Play position for recording your last one ring cycle. This can easily be accomplished,

message.

even on short messages, by holding the

9.

Test the sequence by successively pressing Sl for

record button down for at least 2 s for each

each message.

message.

Chapter Eighteen: Talking/Musical Ringer

194

Chapter 19

Telephone Tollsaver

J1, J2

modular

Parts list

telephone jack (RJ11

type)

Tollsaver

PB1

pushbutton switch

R1

10 megohm, 1⁄ W

4

(chassis type)

5% resistor

S1, S2, S3, S4, S5, S6,

R2, R5, R6

1 K ohm,

S7

pushbutton

1

⁄ W 5% resistor

4

switches (PC¯mount)

R3

1 megohm, 1⁄ W

4

Misc

PC board, wire,

5% resistor

IC sockets, hardware,

R4

4.7 K ohm, 1⁄ W

4

plastic box, etc.

5% resistor

Have you checked your long distance telephone bill

C1

100 μF, 35 V

lately? Chances are you are paying way too much for

electrolytic capacitor

long-distance calls, even if you participate in a calling C2

68 μF, 35 V

plan. While some of those plans offer long-distance

electrolytic capacitor

calling at 15 cents a minute or less, you might be

paying a monthly fee. If you do not have a calling plan, C3

1 μF, 35 V

you could be paying as much as an exorbitant 28 cents electrolytic capacitor

a minute for long distance!

C4

2.2 μF, 35 V

electrolytic

The truth of the matter is that the cost to the

capacitor

consumer of long-distance calling is falling

dramatically. When you consider that the actual cost

D1, D2, D3

1N4004

to the carrier AT&T, MCI, Sprint, etc. is about 1 cent silicon diodes

per minute, it’s no wonder that competition is driving D4

1N5232B – 5.6 V

the price of telephone calls way down.

Zener diode

Over the past few years, “dial-around” services have

D5

1N5230B – 4.7 V

sprung up all over America. These services let you

Zener diode

make your calls at reduced rates. You simply dial a

Q1

2N3904 transistor

seven-digit code before the number that you are calling, Q2

BS170 – N

bypassing your regular long-distance carrier. The access

¯Channel

MOSFET

codes are easy to recognize; they usually start with the number 1010. Rates as low as 5 cents per minute with

U1

H11A5 optoislator IC

no monthly fee, no carrier switching, and no minimum

U2

HT¯9212A DTMF

calling time are presently available. These services are dialer IC

heavily advertised on TV and through the mail. These

XTL

3.579 MHz

providers can also be found by doing a search for

colorburst crystal

“dial-around service” on the Internet. If you are not 195

Copyright © 2009 by The McGraw-Hill Companies, Inc. Click here for terms of use.

taking advantage of these carriers, you are throwing

code) or international. Keep in mind, however, that only your money away.

one dialing sequence at a time can be stored.

The Tollsaver project can also be used as a special

purpose dialer for dialing fixed numbers on a regular Circuit description

basis, such as calling a taxi cab company, or the bus company or for older persons who regularly call a

The schematic diagram for the Tollsaver is shown in

care-giver or relative.

Figure 19-2. The Tollsaver is connected between a

The Tollsaver is a simple, easy-to-build electronic

telephone and the wall jack; J1 connects to the

dialing device that plugs into your telephone line, and telephone Sl and J2 goes to the wall jack. Since the

uses no batteries or AC power; see Figure 19-1.

telephone lines carry the DC current that powers

the Tollsaver, it is important that proper polarity

The Tollsaver is pre-programmed by you with the

between the red and green wires from the telephone

seven-digit code for your selected dial around service.

company be observed or the Tollsaver will not work.

When you want to make a long distance call, simply

Note also that proper polarity is maintained between

pick up the telephone handset and press a pushbutton on the two jacks: some older telephone equipment is

the Tollsaver; the stored access code is dialed. You then as polarity sensitive as the Tollsaver. The heart of

dial the telephone number that you want to call as usual.

the circuit is U2, a telephone-dialer chip that has

With the Tollsaver helping you route your call through redial capability. It contains a crystal controlled

the discount services, you will save serious money from oscillator circuit for generating dialing tones.

the first minute of calling.

Storage registers within the chip remember the

The Tollsaver, designed for telephone systems with

pre-programmed dial-around code.

tone dialing, has no effect on normal telephone use.

A set of four input and four output pins form a matrix It comes into play only when the telephone handset is for a 12- or 16-button keypad that can be scanned by

taken off-hook and the pushbutton is depressed. In fact, U2. Since using a full-blown keypad in the Tollsaver

the Tollsaver may also be used as a rapid dial device for seems like overkill, a series of discrete switches is used any discrete local, long distance (including the discount instead. Of those switches, S1–S7, only S1 and S2 are shown as being connected to U2 and are used instead.

Those switches are wired to U2 as the digits “1” and

“0” respectively—the two digits that are required to

access the various dial-around services. The other

switches are optional and can be wired into the circuit as any digit that you want. We will discuss that in

greater detail later in the construction section of this article. For now, we will just assume that there are

additional switches in the matrix along with S1 and

S2 that can be used for setting the stored number in the Tollsaver.

When the Tollsaver is first connected to the telephone line, C2 (a low-leakage electrolytic capacitor) charges up through R1 to about 5 V as limited by Zener diode

D4. That voltage is maintained at all times to retain the stored dial-around sequence code in U2’s memory as

long as the Tollsaver is connected to the telephone

line and is drawing current from it. The 5 μA that

the Tollsaver needs to work is well within the

limits imposed by the rules concerning the switched

Chapter Nineteen: Telephone Tollsaver Figure 19-1 Tollsaver circuit. Courtesy of Poptronix public-telephone network.

196

Chapter Nineteen: Telephone Tollsaver

J2 to

J1 to

telephone

telephone

line

set

Yellow

Black

+

Green

Red

Red

C1

D2

S3

S4

S5

S6

S7

1

2

See text

U1

D1

5

4

C4

+

R2

D5

R1

D

D3

+

G

Q1

S

+

Q2

C2

C3

R4

R6

R5

R3

D4

10

11

13

15

S1 “I”

U2

1

9 14

7

6

16 17

4

18

2

S2 “O”

S8

XTL

Figure 19-2

Tollsaver. Courtesy of Poptronix

When the telephone handset is picked up, current

on the phone, the voltage at pin 11 of U2 goes to a logic drawn by the phone flows through the light-emitting

one. With the telephone now on-hook, U2 is ready for

diode between pins 1 and 2 of Opto-isolator U1,

the next call.

switching on the transistor between pins 4 and 5.

The long-distance access code is programmed into

Current then flows through D2 and R2, charging C3 to

the Moneysaver the first time power is applied. When

about 5 V. That voltage is used to activate the circuit.

any telephone is picked up, S1–S7 are used to dial the Once C3 is charged, Q2 turns on, providing a zero

desired seven-digit access number that you want the

logic level to pin 1 of U2, the hook-switch sensing input.

Tollsaver to remember. After “dialing” the number

When U2 sees that input, it “wakes up” and starts

with S1–S7, simply hang up the telephone; that

scanning the switches. To dial out a long-distance access number is saved in U2’s redial register. As long as the code (more later on setting that), simply press S8. That Tollsaver is connected to a telephone line, it will

switch is wired into U2’s switch matrix as a “redial the remember that number.

last number” switch; the stored dial-around numbers are sequentially generated and appear at pin 13 of U2.

Circuit assembly

The tones are coupled by Q1 to the telephone line

through C4. Once the Moneysaver has finished dialing

Before we begin constructing the Tollsaver Project,

the access codes, you can then manually dial your call you will first need to find a clean, well-lit worktable or in the normal way; the call goes through the long-workbench. Next we will gather a small 25–30-W

distance carrier of your choice at the reduced rate.

pencil tipped soldering iron, a length of 60/40 tin–lead When the call is completed and the handset placed back solder, and a small canister of Tip Tinner, available at 197

your local RadioShack store; Tip Tinner is used to

band is silver then the resistor has a 10% tolerance

condition the soldering tip between solder joints. You value and if the fourth band is gold then the resistor’s drive the soldering tip into the compound and it cleans tolerance value will be 5%.

and prepares the soldering tip. Next grab a few small Finally, we are ready to begin assembling the project, hand tools; try to locate small flat blade and Phillips so let’s get started. The prototype project was

screwdrivers. A pair of needle-nose pliers, a pair of constructed on a single-sided printed circuit board or tweezers along with a magnifying glass, and a pair of PCB. With your PC board in front of you, we can now

end-cutters and we will begin constructing the project.

begin populating the circuit board. We are going to

Now locate your schematic diagram and parts layout

place and solder the lowest height components first, the diagram along with all of the components needed to

resistors and diodes. First, locate our first resistor R1.

build the project. Once all the components are in front Resistor R1 has a value of 10 megohms and is a 1⁄4 watt of you, you can check them off against the project parts 5% tolerance type. Now take a look for a resistor whose list to make sure you are ready to start building the first color band is brown, black, green, and gold. From project. The Tollsaver can be constructed on a small

the chart you will notice that brown is represented by printed circuit board.

the digit (1), and again the second band is black, which Locate Table 19-1 and place it in front of you.

is represented by (0). Notice that the third color is green Table 19-1 illustrates the resistor code chart which

and the multiplier is (100,000), so (1) (0) × 100,000 =

will help you to identify the resistors for the project.

1,000,000 or 1 megohm. Install resistor R1 in its

Note that each resistor will have either three or four respective location and then solder it in place on the color bands, which begin at one end of the resistor’s PC board. Now take a pair of end-cutters and trim the body. The first colored band represents the resistor’s excess resistor leads flush to the edge of the circuit first digit, while the second color represents the second board. Locate and install the remaining resistors in their digit of the resistor’s value. The third colored band correct positions on the PC board, and solder them in represents the resistor’s multiplier value, and the fourth place. Now use your end-cutters and remove the extra

color band represents the resistor’s tolerance value.

lead lengths.

If there is no fourth colored band then the resistor

Note that capacitors generally come from two major

has a 20% tolerance value. If the resistor’s fourth

groups or types. Non-polar types, such as the ones in Table 19-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

Chapter Nineteen: Telephone Tollsaver

No color

20%

198

Chapter Nineteen: Telephone Tollsaver

this project, have no polarity and can be placed in either Find the capacitors from the component pile and try

direction on the circuit board. The other type of

and locate capacitor C1, which should be marked

capacitors are called polarized types; these capacitors 100 μF. Now that you can read the resistor and

have polarity and have to be inserted on the board with capacitor charts, let’s go ahead and place R1 and C1

respect to their polarity marking in order for the circuit on the circuit board and solder them in place. Now take to operate correctly. On these types of capacitors, you your end-cutters and cut the excess component leads

will observe that the components actually have a plus or flush to the edge of the circuit board. Once you have minus marking or a black or white band with a plus or installed the first two components, you can move on

minus marking on the body of the capacitors.

to installing the remaining low profile components.

Now locate the capacitor chart shown in Table 19-2;

Next locate and install the remaining capacitors, first this will assist you installing the small capacitors which installing the low profile capacitors followed by the may have only a three-digit code marked on the

larger electrolytic capacitors. Use good quality

capacitors.

electrolytic or tantalum capacitors. Remember the larger Table 19-2

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

1.0

1R0

3,900

3.9

.0039

392

1.2

1R2

4,700

4.7

.0047

472

1.5

1R5

5,600

5.6

.0056

562

1.8

1R8

6,800

6.8

.0068

682

2.2

2R2

8,200

8.2

.0082

822

2.7

2R7

10,000

10

.01

103

3.3

3R3

12,000

12

.012

123

3.9

3R9

15,000

15

.015

153

4.7

4R7

18,000

18

.018

183

5.6

5R6

22,000

22

.022

223

6.8

6R8

27,000

27

.027

273

8.2

8R2

33,000

33

.033

333

10

100

39,000

39

.039

393

12

120

47,000

47

.047

473

15

150

56,000

56

.056

563

18

180

68,000

68

.068

683

22

220

82,000

82

.082

823

27

270

100,000

100

.1

104

33

330

120,000

120

.12

124

39

390

150,000

150

.15

154

47

470

180,000

180

.18

184

56

560

220,000

220

.22

224

68

680

270,000

270

.27

274

82

820

330,000

330

.33

334

100

.0001

101

390,000

390

.39

394

120

.00012

121

470,000

470

.47

474

150

.00015

151

560,000

560

.56

564

(Continued)

199

Table 19-2—cont’d

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

180

.00018

181

680,000

680

.68

684

220

.00022

221

820,000

820

.82

824

270

.00027

271

1,000

1

105

330

.00033

331

1,500

1.5

155

390

.00039

391

2,200

2.2

225

470

.00047

471

2,700

2.7

275

560

.00056

561

3,300

3.3

335

680

.00068

681

4,700

4.7

475

820

.00082

821

6.8

685

1,000

1.0

.001

102

10

106

1,200

1.2

.0012

122

22

226

1,500

1.5

.0015

152

33

336

1,800

1.8

.0018

182

47

476

2,200

2.2

.0022

222

68

686

2,700

2.7

.0027

272

100

107

3,300

3.3

.0033

332

157

157

Code = 2 significant digits of the capacitor value + number of zeros to follow 10 pF = 100

For values below 10 pF, use “R” in place of decimal e.g. 8.2 pF = 8R2

100 pF = 101

1,000 pF = 102

22,000 pF = 223

330,000 pF = 334

1 μF = 105

electrolytic capacitors have polarity which must be

circuit board. Place all the diodes on the circuit board observed if the circuit is work properly. Failure to install and solder them in place. Then cut the excess

the electrolytic capacitors correctly can damage the

component leads with your end-cutters.

component or other components when power is first

The Tollsaver circuit utilizes single NPN transistors applied to the circuit upon power-up. Install the

at Q1, and an FET transistor at Q2. Transistors generally capacitors in their correct positions on the PC board, have three leads, a Base lead, a Collector lead, and an and then solder them in place. Next trim the excess

Emitter lead. Refer to the schematic and you will notice component leads flush to the edge of the circuit board that there will be two diagonal leads pointing to a

using your end-cutters.

vertical line. The vertical line is the transistor’s base This project contains two silicon diodes at D2 and D3

lead and the two diagonal lines represent the collector and two Zener diodes at D4 and D5. These diodes also

and the emitter. The diagonal lead with the arrow on it have polarity which must be observed if the circuit is is the emitter lead, and this should help you install the going to work correctly. You will notice that each diode transistor on to the circuit board correctly. Go ahead will have a black or white colored band at one edge of and install the transistor Q1 on the PC board and

the diode’s body. The colored band represents the

solder it in place. The FET transistor at Q2 also has diode’s cathode lead. Check your schematic and parts

three leads but they are labeled differently. The FET

Chapter Nineteen: Telephone Tollsaver layout diagram when installing these diodes on the has a Drain marked (D), Source lead marked (S),

200

Chapter Nineteen: Telephone Tollsaver

and a Gate lead marked (G). FET transistors are very

overkill for a project like the Tollsaver. Switches S1–S7

sensitive to static electricity, so you must handle them take the place of the keypad to keep the assembly cost carefully using an anti-static wrist band which is

down. The only switches that must be installed are

grounded to an AC outlet. When handling the FET sit in S1 and S2; “1” and “0” are required to access any

one spot and do not move around in you chair or walk on dial-around service.

a carpet while installing this component. Locate the FET

You only need to install as many switches for S3–S7

and solder it place. Now, follow-up by cutting the excess as are needed for whatever number you would like to

component leads from Q1 and Q2 with your end-cutters.

program into the Tollsaver. Those switches are

The Tollsaver utilizes ICs and an opto-isolator.

hard-wired with short insulated jumpers so that they

ICs must be handled carefully and installed properly

appear to U2 as being part of a keypad matrix.

in order for the circuit to work perfectly. Use anti-static See Table 19-3 for a chart that lists the connections techniques when handling the IC to avoid damage

needed for each individual number.

from static electricity when moving about and installing Note that “1” and “0” are included in the chart

it. It is wise to install integrated circuit sockets as a for completeness; you do not need to wire those

cheap form of insurance against a possible circuit

digits since S1 and S2 are already hard-wired

failure at some later point in time. Install the IC

that way.

socket on the PC board and solder it in place.

For example, if you look closely at the photograph of ICs have to be installed correctly for the circuit

the prototype, you will see that S3 and S4 are wired for to work, so you must pay strict attention to inserting

“3” and “6” respectively; S5 is present but not wired.

them correctly into their sockets. Each integrated

If you look at Table 19-3, you will note that both of circuit has a locator either in the form of a small

those digits need a connection pin 3 of U2, and that is indented circle or a notch, or cutout at the top end of why two wires are inserted in the hole that connects

the IC package. Pin 1 of the IC will be just to the left to that pin. If you find yourself in a similar situation, of the locator. The opto-isolator will be housed in a be sure to use small-gauge wire! Switch S8 is a

small IC-like package with six pins. Identify the

panel-mounted pushbutton switch that activates the

pin-outs on the opto-isolator and then install it on the Tollsaver’s redial feature. It is wired to the PC board PC board. It is a good idea to use an integrated circuit with lengths of insulated wire.

socket for the opto-isolator as well as for the IC at U2.

Do not install the IC or opto-isolator at this point, only the IC sockets.

Now is a good time to take a short break. After the

Table 19-3

break we will inspect the circuit board for any possible Tollsaver pin-out table

“cold” solder joints or “short” circuits. Take a careful Digit

U1 – Pins

Connections

look at each of the PC solder joints, they should all look clean and shiny. If any of the solder joints look dull, 1

pin 1

pin 15

dark, or blobby, then you unsolder the joint, remove the 2

pin 2

pin 15

solder and then resolder the joint all over again. Next, 3

pin 3

pin 15

examine the PC board for any short circuits. Short

4

pin 1

pin 16

circuits can be caused from two circuit traces touching 5

pin 2

pin 16

each other due to a stray component lead that stuck to 6

pin 3

pin 16

the PC board from solder residue or from solder blobs 7

pin 1

pin 17

bridging the solder traces.

8

pin 2

pin 17

9

pin 3

pin 17

Switch wiring

0

pin 2

pin 18

0

pin 1

pin 18

As we mentioned before, although U2 is designed to

#

pin 3

pin 18

use a matrix keypad, the use of such a keypad would be 201

or greater. Set the meter to the 20-V DC range and

Final assembly

connect its leads across C2. With no ICs in place, apply power to J2 and see that C2 charges up to about 5 V

The Tollsaver was mounted in a small enclosure that has after a few minutes. If it does not, troubleshoot the appropriate holes for the telephone jacks at J1, J2, and circuit and repair the fault. Check the telephone-line switch S8. As an alternative, for J2 you can substitute a polarity as well as D2-D4, R1, and C2. Be sure that

length of 4-conductor telephone wire that terminates

C2 is a low-leakage capacitor. Disconnect the power

in a modular plug; that is what the author did. If you and insert the ICs into their sockets. Make sure that the use a jack, you will need a length of telephone cord

ICs have oriented correctly. Be sure that the chips are with modular jacks on each end. Center the circuit

seated properly with no pins bent under them.

board inside the enclosure and use four plastic standoffs Connect a telephone to J1 and leave the handset on

to mount the PC board inside the enclosure. The

hook. Then connect the meter across C2 as before.

Tollsaver is line powered, so no power supplies are

Connect J1 into a telephone wall jack and verify once needed. Now we are ready to connect up and test the

again that C2 charges up to about 5 volts after a couple Tollsaver.

of minutes. Measure the voltage across capacitor C3;

it should be zero.

Telephone line connection

Pick up the telephone handset; you should hear the

dial tone, and the voltage across C3 should rise to

The telephone line cable must be connected to the

about 5 V. Press the pushbuttons on the board to dial Tollsaver circuit with the proper polarity, or it will not the sequence code of your selected dial-around service.

work. Many telephone systems use a green wire and a

You should hear the tones in the handset, and the

red wire to carry the voice and ringing signals, with telephone line dial tone will be muted. Hang up the

green being the positive and red negative. Check your receiver and the Tollsaver is now initialized. Pick up the telephone line polarity with a DC voltmeter to be sure.

receiver again and listen for a dial tone. Press S8 briefly.

With no telephones off-hook, there should be about

The dial-around sequence should automatically be

50 V DC on the line.

repeated and the dial tone silenced. For a full test, If you find that the wiring is backwards, you can

dial a long-distance number using your telephone’s

correct that problem, if you know what you are doing.

keypad or dial. That call will use your selected

When in doubt, you can always hire a telephone line

long-distance carrier.

installer to make sure that the wiring is “up to snuff.”

If you need to reset U2 for any reason, disconnect the If you do not want to touch the wiring in your house, circuit from the telephone line and allow time for C2

you can always swap the wires from J2 to the PC board to discharge to less than one 1 volt. That will erase if your house is wired backwards.

the memory in U2, and it can be programmed as

With J2 connected to a telephone wall outlet, we are

described above.

ready to start testing the Moneysaver. If you are a bit If everything went well, the Tollsaver is working and nervous about plugging an untested Moneysaver into the ready for use. If the circuit does not work, then you will telephone line, you can simulate the telephone line on a have to remove it from the telephone line and recheck a workbench. Use a well-filtered 50-V power supply with few things. First make a visual check of the circuit

a 1,000-ohm, two-watt resistor in series. Connect the board. Look for short circuits or solder blobs or solder green wire from J2 to the positive terminal; the red wire bridges between PC traces. Look for cold solder joints goes to the negative terminal.

that look dull or dark. If you see any solder joints that look this way, then remove the solder from the joint and resolder the joint over again.

Circuit testing

Check all the ICs and make sure that they are

The only piece of test equipment that you will need

oriented correctly, then check to see if all the diodes Chapter Nineteen: Telephone Tollsaver is a voltmeter with a high input resistance-10 megohms have been installed correctly; be sure to check all of the 202

Chapter Nineteen: Telephone Tollsaver

electrolytic capacitors to make sure that they are all installed with respect to their proper polarity. Next, Using the tollsaver

check the two transistors to make sure that they have been installed correctly. If C3 does not charge up when Once the Tollsaver has been initialized as described in the the telephone handset is taken off the hook, then check testing section above, it must be left connected to the D2, R2, and C3.

telephone line at all times to preserve the stored sequence of digits. Should it be disconnected for any length of time, Once you know the Tollsaver is working correctly,

you will have to reprogram U1 with the correct sequence.

you can mount the circuit in a small plastic box. You Use the procedure for programming described above.

will need to install two RJ11 phone jacks on the case, as well as the pushbutton switches. Mount the PC board

With the Moneysaver properly programmed, each

atop four 1⁄4′′ plastic standoffs, and wire the switches to time you wish to make a long-distance call simply press the circuit board via five-inch lengths of insulated wires.

S8 after lifting the telephone handset, then dial the Plug the telephone line into (J2) on the Tollsaver, and telephone umber in the normal way. When you check

then plug your telephone set into the telephone jack

your next month’s telephone bill, you will be amazed at marked (J1).

how much money you have saved.

203

Chapter 20

Infinity Bug/Transmitter Project

C14

1 μF, 35 V

Parts list

tantalum capacitor

D1, D2, D3, D4

1N4004

Infinity Bug/Transmitter

silicon diode

R1, R2, R8, R15, R18

D5

8.2 volt Zener diode

22 K ohms, 1⁄ W,

4

5% resistor

D6, D7, D8, D9

1N4148

silicon diode

R3, R13

4.7 K ohm,

1

⁄ W, 5% resistor

D10

MCR100

4

¯6¯SCR

R4, R7, R10, R12

Q1, Q3, Q4

BC847

10 K ohm, 1⁄ W,

transistor

4

5% resistor

Q2, Q5

BC639 transistor

R6

15 K ohms, 1⁄ W,

4

U1

HEF40106BT – Hex

5% resistor

inverting Schmitt

R9

6.8 K ohms, 1⁄ W,

trigger IC

4

5% resistor

MIC

electret microphone

R11

120 ohms, 1⁄ W,

4

Misc

PC board,

5% resistor

IC socket, wire,

R14, R19

1 megohm, 1⁄ W,

4

hardware, standoffs,

5% resistor

enclosure, etc.

R16, R20

47 K ohms,

A kit of parts for this

1

⁄ W, 5% resistor

4

project is available

R17

2.2 megohm, 1⁄ W,

from:

4

5% resistor

Talking Electronics

C1, C4, C16

10 nF,

www.talkingelectronics.

35 V capacitor

com/

C2, C12

100nF, 35 V

The Infinity Bug/Transmitter is a remote telephone

C3, C5

47 nF, 35 V

listening device, which can listen-in via telephone and C6, C7, C9, C10, C13

will allow you to hear conversations from a remote

10 μF, 35 V

location unattended; see Figure 20-1. The Infinity Bug electrolytic

is connected across the phone-line of a distant phone, capacitor

and is line powered so no power supply is needed, since C8, C15

47 μF, 35 V

it derives its power from the phone line.

electrolytic capacitor

To use the Infinity Bug, the distant phone is

C11

22 nF, 35 V

dialed, and after having a conversation with

204

Copyright © 2009 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Chapter Twenty: Infinity Bug/Transmitter Project

the “line voltage” will drop to about 36 V, due to the current drawn by the bug. This will not upset the

operation of the phone system.

The diode bridge on the front-end of the circuit

protects the circuit from connecting the circuit to the line backwards.

The only two sections of the circuit that draw

current during quiescent conditions are the whistle-

detecting circuit made up of the BC 547 and its

Figure 20-1

Infinity bug circuit. Courtesy of Talking

surrounding components. This section draws less than

Electronics

0.25 mA. It is frequency sensitive and will not detect the 33 Hz ringing frequency. The “timing section,” of the person at the other end, the phone receiver will

the Infinity Bug is made using the 40106 a hex Schmitt be replaced. At this point you whistle into the

trigger IC.

receiver and the Infinity Bug will pick up the line

When a phone (that is connected to the same line as

quietly and begin listening-in using its high-gain

the Infinity bug) is picked up, the line voltage drops to amplifier, and will pick up the audio from the

about 12 V and the whistle-detecting circuit does not remote room.

see any voltage, as the 8.2 V Zener drops nearly all the The Infinity Bug/Transmitter does not have to

available voltage.

be next to the distant phone. It can be anywhere

Thus the circuit has a self-canceling feature. The

in the house, provided it is connected across the

principle of operation of the bug has been described

phone line of the distant phone. A timing circuit in

above and when the handset is put back on the phone,

the device will cancel after 3 min. To open the

the line voltage rises. This allows the person at the other Bug you need to whistle again. This can be repeated

end of the line to whistle. The tone produced by the

any number of times as needed. If the remote phone

whistle is passed through the 47 nF capacitor and a

is picked up, it cancels the Infinity Bug and goes

4.7 K ohm resistor to the base of the BC 547 transistor.

quiet.

The transistor amplifies the signal to produce a 2 V

p-p signal that is turned into a DC voltage by the

10 μF capacitor. This turns on the latch circuit, and the Circuit description

base of the BC 639 is raised to produce a voltage on

the emitter of about 4.5 V. The actual voltage on

The Infinity Bug consists of a number of circuit blocks, the emitter of the BC 639 is determined by the

plus components that perform very important tasks. The 120 ohm resistor in the emitter leg of a BC 547.

circuit diagram shown in Figure 20-2 illustrates the

The BC 547 is almost fully turned on by the 10 K

function of each of the components.

resistor between the collector and base. The 47 μF

The Infinity Bug connects across the phone line

capacitor on the base of the BC 639 holds the base

and takes very little current as most of the circuit is rigid to any AC signals so that the transistor operates not active when in the “waiting” state.

as an emitter follower. The transistor acts as an

impedance-matching stage as the phone-line has

This Infinity Bug is a called a “leech” device as it

relatively low impedance while the pre-amplifier

gets its operating current from the phone line. Some

section has quite a high impedance.

phone systems detect as little as 0.5 mA, and if more than 1 mA is drawn from the line, it remains engaged.

Finally, the electret microphone is connected

The voltage of a phone line varies from 42 to

to a microphone pre-amplifier stage consisting of

55 V, depending on the service-provider, and the

a BC 547 transistor, 1 M bias resistor, 4.7 K ohm

Infinity Bug will operate on this voltage range.

load and 22 nF input capacitor. Thus the audio section When the Infinity Bug is connected to the line,

consists of three stages in a very unusual arrangement.

205

D1

Phone

D4

line

C16

D3

D2

D5

Q

e

2

c

R7

b

R12

R13

D6

D10

R15

C3

A

K

R10

c

b

R6

G

Q3

R1

C12

+

e

R3

A

+

C1

C6

C9

C4

R5

D8

R14

R4

R2

c

R8

b

c

C5

Q

b

4

Q

C2

+

+

1

R11

e

C7

+

C11

M1

C10

R9

e

D9

C8

D7

+0

D12

A

R20

R16

U1:A

14

4

1

2

3

+

NC

Q5

R18

C14

7

U1:B

R17

+

R19

D11

+

C15

C13

Figure 20-2

Infinity transmitter. Courtesy of Talking Electronics This arrangement is necessary as the signal has

When the Infinity Bug is turned ON via a whistle,

to be delivered to the same line as the supply

the line voltage falls to about 12 V and the 47 μF

voltage, since the circuit derives power from the

capacitor in the timing circuit does not see any charging phone line.

voltage, as the 18 V Zener removes this voltage. The

In normal operation, the Infinity Bug turns off

47 μF is now slowly discharged via a 2.2 megohm

after about 3 min due to a timing circuit connected

resistor and when the voltage falls to below 2 V, the to one gate of a hex Schmitt trigger IC. The voltage

output of the gate goes HIGH. This HIGH is passed to

across the IC is set to 6.2 V via a Zener so the timing the base of a BC 639 via a 22 K resistor and 1 μF

can be controlled, as the lower threshold at which the electrolytic capacitor. The transistor removes voltage chip will change state is determined by the supply

from the latching circuit and the Infinity Bug drops off voltage. When the line voltage rises to 50 V, the 47 μF

the line. The 1 μF capacitor allows a pulse to activate capacitor in the timing circuit is rapidly charged via a the “turn-off” transistor.

47 K resistor that is connected to the rail via an 18 V

The 1 megohm resistor on the base discharges the

Zener. This puts a maximum of 6.2 V on the 47 μF

1 μF capacitor so that it is uncharged in readiness for capacitor as the input of the chip cannot rise above

the circuit timing out. The 1N4148 signal diode

the supply on the chip due to diodes on the input of

connected to the rail of the project is connected to a Chapter Twenty: Infinity Bug/Transmitter Project the gate.

22 K resistor and 100 nF capacitor. This arrangement

206

Chapter Twenty: Infinity Bug/Transmitter Project

detects the “ring voltage” (approx 150 V) and the Zener or workbench. Next we will gather a small 25–30-W

of the signal diode allows the 100 nF capacitor to charge pencil tipped soldering iron, a length of 60/40 tin–lead via the 22 K ohm resistor. All diodes have a maximum

solder, and a small canister of Tip Tinner, available at reverse voltage and the diode we have chosen has a

your local RadioShack store; Tip Tinner is used to

voltage of about 110 V. This voltage can be called its condition the soldering tip between solder joints. You

“Zener voltage.” Any voltage above this “Zener voltage”

drive the soldering tip into the compound and it cleans will pass through the diode. We have used this feature and prepares the soldering tip. Next grab a few small to keep the whistle-detect transistor turned on during the hand tools, try to locate small flat blade and Phillips time when the phone is “ringing.” More details on this screwdrivers. A pair of needle-nose pliers, a pair of project can be found at www.talkingelectronics.com/

tweezers along with a magnifying glass, and a pair of end-cutters and we will begin constructing the project.

Circuit assembly

Now locate your schematic diagram and parts layout

diagram along with all of the components needed to

Finally, we are ready to begin assembling the project, so build the project. Once all the components are in front let’s get started. The prototype project was constructed of you, you can check them off against the project parts on a single-sided printed circuit board or PCB. With

list to make sure you are ready to start building the your PC board in front of you, we can now begin

project. Now, locate Tables 20-1 and 20-2, and place

populating the circuit board. The kit offered in the parts them in front of you.

list utilizes surface mounted components in order to

Table 20-1 illustrates the resistor code chart and how construct a very small circuit board. The surface-mount to read resistors, while Table 20-2 illustrates the

components are generally the first to be soldered to the capacitor code chart which will aid you in constructing board. In this project kit offered, there are through-hole the project.

components and surface-mount components. If you add

Each resistor will have either three or four color

the surface-mount components first, make sure you do

bands, which begin at one end of the resistor’s body.

not “fill-in” any of the holes for the through-hole

The first colored band represents the resistor’s first components

digit, while the second color represents the second digit Before we begin constructing the Infinity Bug,

of the resistor’s value. The third colored band represents you will need to locate a clean, well-lit worktable

the resistor’s multiplier value, and the fourth color band Table 20-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

No color

20%

207

Table 20-2

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

1.0

1R0

3,900

3.9

.0039

392

1.2

1R2

4,700

4.7

.0047

472

1.5

1R5

5,600

5.6

.0056

562

1.8

1R8

6,800

6.8

.0068

682

2.2

2R2

8,200

8.2

.0082

822

2.7

2R7

10,000

10

.01

103

3.3

3R3

12,000

12

.012

123

3.9

3R9

15,000

15

.015

153

4.7

4R7

18,000

18

.018

183

5.6

5R6

22,000

22

.022

223

6.8

6R8

27,000

27

.027

273

8.2

8R2

33,000

33

.033

333

10

100

39,000

39

.039

393

12

120

47,000

47

.047

473

15

150

56,000

56

.056

563

18

180

68,000

68

.068

683

22

220

82,000

82

.082

823

27

270

100,000

100

.1

104

33

330

120,000

120

.12

124

39

390

150,000

150

.15

154

47

470

180,000

180

.18

184

56

560

220,000

220

.22

224

68

680

270,000

270

.27

274

82

820

330,000

330

.33

334

100

.0001

101

390,000

390

.39

394

120

.00012

121

470,000

470

.47

474

150

.00015

151

560,000

560

.56

564

180

.00018

181

680,000

680

.68

684

220

.00022

221

820,000

820

.82

824

270

.00027

271

1,000

1

105

330

.00033

331

1,500

1.5

155

390

.00039

391

2,200

2.2

225

470

.00047

471

2,700

2.7

275

560

.00056

561

3,300

3.3

335

680

.00068

681

4,700

4.7

475

820

.00082

821

6.8

685

1,000

1.0

.001

102

10

106

1,200

1.2

.0012

122

22

226

1,500

1.5

.0015

152

33

336

1,800

1.8

.0018

182

47

476

Chapter Twenty: Infinity Bug/Transmitter Project

208

Chapter Twenty: Infinity Bug/Transmitter Project

Table 20-2—cont’d

Three-digit capacitor codes

pF

nF

m F

CODE

pF

nF

m F

Code

2,200

2.2

.0022

222

68

686

2,700

2.7

.0027

272

100

107

3,300

3.3

.0033

332

157

157

Code = 2 significant digits of the capacitor value + number of zeros to follow 10 pF = 100

For values below 10 pF, use “R” in place of decimal e.g. 8.2 pF = 8R2

100 pF = 101

1,000 pF = 102

22,000 pF = 223

330,000 pF = 334

1 μF = 105

represents the resistor’s tolerance value. If there is no on the capacitor body, but without the chart the

fourth colored band then the resistor has a 20%

builder would have a difficult time determining the

tolerance value. If the resistor’s fourth band is silver capacitor’s value.

then the resistor has a 10% tolerance value and if the Note that capacitors generally come from two major

fourth band is gold then the resistor’s tolerance value groups or types. Non-polar types, such as the ones in will be 5%.

this project, have no polarity and can be placed in

We are going to place and solder the lowest height

either direction on the circuit board. The other type of components first, the resistors and diodes. First, locate capacitors are called polarized types, these capacitors our first resistor R1. Resistor R1 has a value of

have polarity and have to be inserted on the board

22 K ohms and is a 5% tolerance type. Now take a look with respect to their polarity marking in order for the for a resistor whose first color band is red, red, orange, circuit to operate correctly. On these types of

and gold. From the chart you will notice that red is

capacitors, you will observe that the components

represented by the digit (2), the second color band is actually have a plus or minus marking or a black or

red, which is represented by (2). Notice that the third white band with a plus or minus marking on the

color is orange and the multiplier is (1,000), so

body of the capacitors.

(2) (2) × 1,000 = 22,000 or 22 K ohms.

Now, we will install the capacitors for the project.

Go ahead and place R1 on the circuit board and

The kit offered uses surface-mount capacitors that are solder it in place. Now take your end-cutters and cut the not identified and are contained in a strip for this

excess component leads flush to the edge of the circuit project in the following order: Do not remove any of

board. Once you have installed the first resistor, you can the capacitors until they are required. Only remove one move on to installing the remaining ones. Solder them at a time and solder it to the board. First, locate

in place in their respective locations on the circuit capacitor C1, a 10 nF capacitor. Refer to Table 20-2

board, and follow up by trimming the excess component to find the three-digit code for the 10nf capacitor.

leads with you end-cutters.

Once identified, go ahead and install C1 and solder

Next refer to Table 20-2; this chart helps to determine it in place in its proper location. Next locate the

the value of small capacitors. Many capacitors are quite remaining small or low profile capacitors and install small in physical size, so manufacturers have devised a them in their respective locations on the PC board.

three-digit code which can be placed on the capacitor Solder these capacitors to the PC board and then

instead of the actual value. The code occupies a much remember to cut the excess component leads. Finally

smaller space on the capacitor and can usually fit nicely locate the electrolytic capacitors. The electrolytic

209

capacitors are generally larger capacitors and they will towards or away from the base lead. In the kit offered, have polarity marking on the side of the component.

the transistors are marked “1K” or “1G” Before

Look for a white or black band with a plus or minus

installing the two transistors refer to the parts

marking next to the colored band. Once you have

specification sheets as well as the parts layout diagram identified the electrolytic capacitors, refer to the

and the schematic. Be sure to orient the transistors prior schematic and parts layout diagrams to ensure that

to inserting them into the circuit board. If you are in you install the capacitors correctly. Electrolytic

doubt as to how to mount the transistors, have a

capacitors installed backwards can damage the

knowledgeable electronics enthusiasts help you. Now,

component and possibly damage the circuit when

insert the transistors on to the circuit board and solder power is first applied to the circuit.

them in place. Remember to cut the excess component

leads with your end-cutters, flush to the edge of the This project contains four silicon diodes, three Zener circuit board.

diodes, and an SCR or silicon controller rectifier.

Diodes always have some type of polarity markings,

The Infinity Transmitter/Bug uses a single

which must be observed if the circuit is going to work IC at U1. Prior to installing the IC, install an

correctly. You will notice that each diode will have a IC socket. An IC socket is low cost insurance in

black or white colored band at one edge of the diode’s the event of a circuit failure at some point in time.

body. The colored band represents the diode’s cathode It is much easier to simply unplug an IC from its

lead. Check your schematic and parts layout diagrams

socket and replace it rather than trying unsolder

when installing these diodes on the circuit board. Note 14 or 16 pins. ICs have to be installed correctly if

that the diodes are marked “A6.” The rectifier bridge the circuit is to work properly. You must orient the

diodes D1 through D4 are all 1N4004 silicon diodes

IC before inserting it into the socket. Take a look at the types. There are also three voltage/current diodes at D7, IC package. At the top end of the IC package, you will D8 and D9. Next locate and install the Zener diodes.

notice either a small indented circle, a cutout, or notch.

Note that all of the Zener diodes have different voltage This notch or cutout is the IC locator. Pin 1 of the

cut-off voltages, so pay particular attention, to install IC will be just to the left of the notch or cutout.

the correct Zener in its exact location. Finally, locate the Once certain of the orientation, install the IC in

single SCR. The SCR will have three leads, an Anode, a its socket.

Cathode and a Gate lead. Check the component

Finally, locate and install the electret microphone at specification sheet and then refer to both the schematic M1; it is installed at the junction of R14/R15 and C11.

and parts layout diagrams when installing the SCR.

The case of the electret microphone goes to the “-” on Once all the diodes and the SCR have been placed in

the board. This is the negative rail and runs along the their respective locations on the PC board, you can then bottom of the board. Solder the microphone in place

solder them in place. Finally, trim the excess component and remember to trim the excess lead lengths.

leads with your end-cutter flush to the edge of the

Once the circuit board has been completed, take a

circuit board.

short break and then we will inspect the PC board for The Infinity Transmitter/Bug utilizes five

possible “cold” solder joints and “short” circuits. Pick conventional NPN type transistors. Transistors are

up the PC board with the foil side facing upwards

generally three lead devices, which must be installed toward you. Carefully inspect the solder joints, these correctly if the circuit is to work properly. Careful should look smooth, clean, and bright. If any of the

handling and proper orientation in the circuit is critical.

solder joints look dull, dark, or blobby, then you

A transistor will usually have a Base lead, a Collector should remove the solder with a solder sucker or a

lead, and an Emitter lead. The base lead is generally a solder wick and then resolder the joint all over again.

vertical line inside a transistor circle symbol. The

Now we will inspect the PC board for possible short

collector lead is usually a slanted line facing towards circuits. Short circuits can be caused from small solder the base lead and the emitter lead is also a slanted line blobs bridging the circuit traces or from cut component facing the base lead but it will have an arrow pointing leads which can often stick to the circuit board once Chapter Twenty: Infinity Bug/Transmitter Project

210

Chapter Twenty: Infinity Bug/Transmitter Project

they have been cut. A sticky residue from solder will often trap component leads across the circuit traces.

Look carefully for any bridging wires across circuit

traces. Once this inspection is complete, we can move C1

on to installing the circuit board into some sort of

plastic enclosure.

The circuit is line powered so you will need no

R1

R2

external power supply or batteries. Now you will have D1

D2

to mount the circuit board inside of a plastic enclosure.

+

+

Lay the circuit board inside of a suitable plastic case, to B1

B2

check the fit. Locate some mounting standoffs and use Infinity

them to mount the circuit board inside of the case. Next, bug

24 V 45 V

you will have to connect the circuit to the phone line; this can be done using a length of 4-conductor phone

Figure 20-3

Infinity bug test circuit. Courtesy of

wire with a modular plug attached at one end of the

Talking Electronics

cable. The modular plug end can then simply plug into a telephone jack, and wire ends of the cable can connect to the circuit itself. You could also elect to hard-wire the less than 0.5 mA and only the whistle-detecting stage circuit directly to the phone line without the modular should be active. If you decide to measure the amplitude plugs if desired.

of the signal produced by the whistle-detecting stage at the collector of the transistor, you will need an

oscilloscope. The measured voltage should be about

Testing the infinity bug

2.5 V p-p. The DC voltage across the 10 μF electrolytic capacitor that provides a turn-on voltage for the latching To efficiently test the Infinity Bug you will need two circuit will rise to 0.6 V and the Infinity Bug will

phone lines, but if they are not available, the next best turn on.

solution is to build an Infinity Bug Test Circuit. The When the Infinity Bug is turned on, the emitter

470 ohm resistors are current-limit resistors and the voltage on the BC 639 transistor will be about 4.5 V.

LEDs indicate when the phone and Infinity Bug are

This voltage is created by the value of the 120 ohm

on the line.

resistor as it is the load resistor for the project. The The Infinity Bug can be tested with the following

4.5 V becomes the rail voltage for the audio stages

Test Circuit, as shown in Figure 20-3.

and the only way to test the audio stages is with an

Connect the Infinity Bug to the test circuit shown,

oscilloscope. Since the Infinity Bug is connected

and pick up the left-hand phone. Whistle into the

to a current-limited power supply (the 470 ohm resistor mouthpiece and the Bug will pick up the line and you

in the test power supply provides current limiting)

will be able to hear the ticking of a clock in the room.

you can use a jumper on the project with fear of

Pick up the second phone and the Bug will drop off the damaging anything.

line. Replace the second phone and whistle. The Infinity To test the audio stages, connect a jumper between

Bug will pick up the line again. Keep listening to the point “A” on the board and the base of the BC 639

Bug and it will drop off after about 2–3 min. Whistle amplifier transistor. You will be able to hear the

again and the Infinity Bug will pick up the line. Repeat faintest sounds in a room. If audio is not detected,

this again and if everything works perfectly, the Infinity measure the voltage on the collector of the first

Bug is fully tested.

audio transistor. It should be about 2 V. The second

What to do if the circuit does not work. The first

transistor should have about 4.5 V on the collector

thing to do is measure the current taken by the Infinity and 4 V on the emitter. The most common fault will

Bug when it is connected to the line. It should be

be a faulty connection to one of the surface-mount

211

components or a damaged transistor. You will need

is decreased, a squeal is also created. If the microphone an oscilloscope to detect the passage of audio through is removed, a squeal is also created. The circuit is

each of the stages.

somewhat complex as we are creating an audio signal

on the same lines that are supplying the voltage to

There are a number of critical components in the

the circuit.

circuit and the audio section is very important. The

current taken by the audio section causes the rail

In the event that the circuit does not function

voltage to drop to about 4.2 V when the bug is

at all, then you will have to disconnect the Infinity active. This voltage is determined mainly by the

Transmitter from the phone and carefully inspect the

120 ohm resistor in the emitter of the second stage.

circuit board to make sure you have not installed some The transistor is turned on by the 10 K resistor between components incorrectly. Commonly, electrolytic

the base and collector and the transistor is actually a capacitors, diodes, or transistors are installed backwards common-emitter device, although it appears to be an

or incorrectly causing the circuit to fail. Once you have emitter-follower. If the 120 ohm resistor is increased, detected the problem, you can go ahead and reconnect

the voltage on the section rises and creates a feedback the Infinity Transmitter to the phone line and retest squeal. If the 22 K ohm load resistor for the microphone the circuit.

Chapter Twenty: Infinity Bug/Transmitter Project

212

Chapter 21

Radio Phone Patch

Q1

2N3904 NPN

Parts list

transistor

U1

LM324 Op¯amp IC

Radio Phone Patch

U2

LM386 audio

R1

10 K ohms, 1⁄ W,

4

amplifier IC

5% resistor

T1

900 to 900 or

R2

100 ohm, 1⁄ W,

4

600 to 600 ohm – mini

5% resistor

transformer (Microtran

R3

10 K potentiometer

T2110)

R4

10 ohm, 1⁄ W,

4

S1, S3

SPDT toggle

5% resistor

switch

R5

1 K ohm

S2

SPST toggle switch

potentiometer

SPK

4¯8 ohm speaker

R6, R12, R13

10 K ohm,

B1

9

1

¯volt transistor

⁄ W, 5% resistor

4

radio battery

R7, R11

47 K ohms,

P1

4

1

¯pin telephone plug

⁄ W, 5% resistor

4

Misc

PC board, wire,

R8, R9

100 K ohms,

hardware, battery

1

⁄ W, 5% resistor

4

holder/clip,

R10

100k ohms, 1⁄ W,

4

enclosure, connectors.

5% resistor

For many years amateur radio enthusiasts have taken

C1, C8

10 μF, 35 V

advantage of the telephone to extend their voice

tantalum capacitor

communications beyond the physical location of his/her C2, C6, C11

2.2 μF, 35 V

transmitter and receiver. Such an arrangement is called a tantalum capacitor

Telephone Patch, and the Federal Communications

C3

.01 μF, 35 V disc

Commission has authorized this procedure to be used

capacitor

within the Amateur Radio and the Citizens band radio

C4

1,000 pF, 15 V

frequencies. As with all radio communications, strict tantalum capacitor

rules specified by the FCC must be followed, and the

telephone patch equipment interfaced with the telephone C5, C12

.22 μF, 35 V

network must meet the requirements of the FCC Rules

tantalum capacitor

and Regulations. The Radio Phone Patch described here C7

100 μF, 15 V

is a simple and easy to build circuit which will provide tantalum capacitor

the means to connect and operate an amateur radio or

C9, C10

.1 μF, 35 V

CB radio transceiver with the telephone network

ceramic capacitor

(see Figure 21-1).

213

Copyright © 2009 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Circuit description

Take a look at the schematic shown in Figure 21-2. The Radio Phone Patch consists of two sections of a quad

operational amplifier chip, an audio power amplifier, and an isolation transformer which connects the

amplifier circuitry to the telephone line. The primary of T1 is connected to the telephone line through series

capacitor C2. This provides DC blocking so that only

audio frequencies are impressed upon the transformer

Figure 21-1

Telephone phone patch circuit. Courtesy

winding. The circuit composed of R1, R2, C1, and Q1

of Cengage Learning

is a holding circuit which provides a DC path for the telephone line current, which is necessary to hold the The Radio Phone Patch circuit operates from a

line in operation when the telephone set is on the hook.

common 9-V transistor battery, and should have an

The AC impedance of this circuit is very high, due to operating life equivalent to that provided by any of the the action of C1 which does not permit any audio

small handheld radios. An additional feature of this

frequencies to be impressed upon the base of Q1.

telephone patch is a monitoring circuit which permits This prevents the holding circuit from loading down

the radio operator to hear both sides of the telephone the line, and preserves the impedance matching

conversation.

action of T1.

S1

XMIT

Radio mike

TIP

+ C2

R7

+

R5

M

T1

R1

RX

Q1

Z

C3

−

C6

Normal

C4

1

Phone

R6

S3

+

C5

UI:A

line

+

Patch

C1

R2

+

3

−

R13

Ring

OFF S2

R8

+

ON

+

+

C7

C8

B1

R10

R9

Mike

2

6

+ C11

in

−

Radio

Radio

5

+

C10

set

SPK

U2

3

R11

+

R3

+ C9 SPK

Monitor

volume

R4

4

R14

− 13

U1:B

C12

14

RX Volume

+

11

12

Chapter Twenty-One: Radio Phone Patch Figure 21-2 Radio phone patch. Courtesy of Cengage Learning 214

Chapter Twenty-One: Radio Phone Patch

When the Radio Phone Patch is operated in transmit

The circuitry for the Radio Phone Patch is shown in

mode, S1 connects the transformer winding to

Figure 21-2 and was constructed on a printed circuit

operational amplifier U1 through the transmit volume

board measuring 2-3 / 4′′ × 4-3 / 4′′ and may be inserted into control, R5. U1(A) has a gain of about 5, which provides the cabinet of a radio transceiver or can be housed in a sufficient drive to the microphone input of the radio separate chassis box placed next to your radio

transceiver through the NORMAL/PATCH switch. Thus,

transceiver

any audio signals present on the telephone line will be Once all the components are in front of you, you can

fed to the microphone input circuit of the radio

check them off against the project parts list to make sure transceiver when the circuit is operated in transmit mode.

you are ready to start building the project. Now, locate During receiving mode, S1 is thrown to the receive

Tables 21-1 and 21-2, and place them in front of you.

position. Audio information received by the radio

Table 21-1 illustrates the resistor code chart and how to transceiver and fed to its speaker is also impressed upon read resistors, while Table 21-2 illustrates the capacitor the input of operational amplifier U1(B) through the

code chart which will aid you in constructing the project.

receive volume control, R14. U1(B) has a gain of

Refer now to Table 21-1, which introduces the

about 5, and drives the transformer winding through

resistor color chart that will help you identify resistors.

R10. Thus, in receive mode, any audio signals received Each resistor will have either three or four color bands, by the radio transceiver will be impressed upon the

which begin at one end of the resistor’s body. The first telephone line through T1.

colored band represents the resistor’s first digit, while The use of a monitoring audio amplifier in the Radio

the second color represents the second digit of the

Phone Patch permits hanging up the phone once the call resistor’s value. The third colored band represents the is initiated. The monitor amplifier will reproduce both resistor’s multiplier value, and the fourth color band sides of the conversation and its volume can be set to a represents the resistor’s tolerance value. If there is no satisfactory level by means of the monitor volume

fourth colored band then the resistor has a 20%

control R3. U2 is a low power amplifier which will

tolerance value. If the resistor’s fourth band is silver drive a small speaker.

then the resistor has a 10% tolerance value and if the Power for the circuit is provided by a common 9-V

fourth band is gold then the resistor’s tolerance value transistor radio battery. Current drain on the battery will will be 5%.

depend upon the level of volume provided by the monitor Finally, we are ready to begin assembling the project, speaker, and will be in the 20-mA range at low volumes.

so let’s get started. The prototype was constructed on a single-sided printed circuit board or PCB. With your PC

Circuit assembly

board in front of you, we can now begin populating the circuit board. We are going to place and solder the

Before we begin constructing the Radio Phone Patch, you lowest height components first, the resistors and diodes.

will need to locate a clean, well-lit worktable or

First, locate our first resistor R1. Resistor R1 has a workbench. Next we will gather a small 25–30-W pencil value of 10 K ohms and is a 5% tolerance type. Now

tipped soldering iron, a length of 60/40 tin–lead solder, take a look for a resistor whose first color band is

and a small canister of Tip Tinner, available at your local brown, black, orange, and gold. From the chart you will RadioShack store; Tip Tinner is used to condition the notice that brown is represented by the digit (1), the soldering tip between solder joints. You drive the

second color band is black, which is represented by (0).

soldering tip into the compound and it cleans and prepares Notice that the third color is orange and the multiplier is the soldering tip. Next grab a few small hand tools; try (1,000), so (1) (0) × 1,000 = 10,000 or 10 K ohms.

to locate small flat blade and Phillips screwdrivers.

Go ahead and locate where resistor R1 goes on the

A pair of needle-nose pliers, a pair of tweezers along with PC and install it, next solder it in place on the PC board, a magnifying glass, and a pair of end-cutters and we will and then with a pair of end-cutters trim the excess

begin constructing the project. Now locate your schematic component leads flush to the edge of the circuit board.

diagram and parts layout diagram along with all of the Next locate the remaining resistors and install them

components needed to build the project.

in their respective locations on the main controller

215

Table 21-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

No color

20%

Table 21-2

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

1.0

1R0

3,900

3.9

.0039

392

1.2

1R2

4,700

4.7

.0047

472

1.5

1R5

5,600

5.6

.0056

562

1.8

1R8

6,800

6.8

.0068

682

2.2

2R2

8,200

8.2

.0082

822

2.7

2R7

10,000

10

.01

103

3.3

3R3

12,000

12

.012

123

3.9

3R9

15,000

15

.015

153

4.7

4R7

18,000

18

.018

183

5.6

5R6

22,000

22

.022

223

6.8

6R8

27,000

27

.027

273

8.2

8R2

33,000

33

.033

333

10

100

39,000

39

.039

393

12

120

47,000

47

.047

473

15

150

56,000

56

.056

563

18

180

68,000

68

.068

683

22

220

82,000

82

.082

823

27

270

100,000

100

.1

104

33

330

120,000

120

.12

124

39

390

150,000

150

.15

154

47

470

180,000

180

.18

184

Chapter Twenty-One: Radio Phone Patch

216

Chapter Twenty-One: Radio Phone Patch

Table 21-2—cont’d

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

56

560

220,000

220

.22

224

68

680

270,000

270

.27

274

82

820

330,000

330

.33

334

100

.0001

101

390,000

390

.39

394

120

.00012

121

470,000

470

.47

474

150

.00015

151

560,000

560

.56

564

180

.00018

181

680,000

680

.68

684

220

.00022

221

820,000

820

.82

824

270

.00027

271

1,000

1

105

330

.00033

331

1,500

1.5

155

390

.00039

391

2,200

2.2

225

470

.00047

471

2,700

2.7

275

560

.00056

561

3,300

3.3

335

680

.00068

681

4,700

4.7

475

820

.00082

821

6.8

685

1,000

1.0

.001

102

10

106

1,200

1.2

.0012

122

22

226

1,500

1.5

.0015

152

33

336

1,800

1.8

.0018

182

47

476

2,200

2.2

.0022

222

68

686

2,700

2.7

.0027

272

100

107

3,300

3.3

.0033

332

157

157

Code = 2 significant digits of the capacitor value + number of zeros to follow 10 pF = 100

For values below 10 pF, use “R” in place of decimal e.g. 8.2 pF = 8R2

100 pF = 101

1,000 pF = 102

22,000 pF = 223

330,000 pF = 334

1 μF = 105

PC board. Solder the resistors to the board, and

on the capacitor body, but without the chart the builder remember to cut the extra lead with your end-cutters.

would have a difficult time determining the capacitor’s Next refer to Table 21-2; this chart helps to determine value.

the value of small capacitors. Many capacitors are quite Note that capacitors generally come from two major

small in physical size, so manufacturers have devised a groups or types. Non-polar types, such as the ones in three-digit code which can be placed on the capacitor this project, have no polarity and can be placed in either instead of the actual value. The code occupies a much direction on the circuit board. The other type of

smaller space on the capacitor and can usually fit nicely capacitors are called polarized types, these capacitors 217

have polarity and have to be inserted on the board with The Radio Phone Patch circuit also contains

respect to their polarity marking in order for the circuit two ICs. ICs are often static sensitive, so they must to operate correctly. On these types of capacitors, you be handled with care. Use a grounded anti-static wrist will observe that the components actually have a plus strap and stay seated in one location when handling the or minus marking or a black or white band with a plus ICs. Take out a cheap insurance policy by installing

or minus marking on the body of the capacitors.

IC sockets for each of the ICs. In the event of a

Capacitors must be installed properly with respect to possible circuit failure, it is much easier to simply polarity in order for the circuit to work properly. Failure unplug a defective IC than trying to unsolder 14 or

to install electrolytic capacitors correctly could cause 16 pins from a PC board without damaging the board.

damage to the capacitor as well as to other components ICs have to be installed correctly if the circuit is going in the circuit when power is first applied.

to work properly. IC packages will have some sort of

markings which will help you orient them on the

Now look for the capacitors from the component

PC board. An IC will have either a small indented

stack and locate capacitor C1, labeled 10 μF. Go ahead circle, a cut-out, or notch at the top end of the

and place C1 on the circuit board and solder it in place.

IC package. Pin 1 of the IC will be just to the left of Now take your end-cutters and cut the excess

the notch or cut-out. Refer to the manufacturer’s pin-out component leads flush to the edge of the circuit board.

diagram, as well as the schematic, when installing these Note that there are a number of small capacitors in the parts. Accidental reversal of pin insertion can cause the circuit that may not be labeled with their actual value, integration to fail. If you doubt your ability to correctly so you will have to check Table 21-2, to learn how to orient the ICs, then seek the help of a knowledgeable use the three-digit capacitor code. Capacitor C4, for electronics enthusiast.

example is a .001 μF capacitor but you may have to

look for a three-digit code marked (102). There are a Next, locate transformer T1 and place it on the circuit number of electrolytic capacitors in the circuit and

board. Any small isolation transformer with 900 to 900

placing them in the circuit with respect to their proper or 600 to 600 ohms will work fine for this circuit. Use polarity is essential for proper operation of the circuit.

the transformer tabs to hold the transformer in place Once you have installed these components, you can

then solder the transformer leads to the PC board,

move on to installing the remaining capacitors.

remembering to trim the excess leads.

The Radio Phone Patch utilizes a single conventional

Once the main Radio Phone Patch circuit board has

transistor at Q1. Transistors are generally three lead been completed, take a short break and then we will

devices, which must be installed correctly if the circuit inspect the PC board for possible “cold” solder joints is to work properly. Careful handling and proper

and “short” circuits. Pick up the PC board with the foil orientation in the circuit is critical. A transistor will side facing upwards toward you. Carefully inspect the usually have a Base lead, a Collector lead, and an

solder joints, these should look smooth, clean, and

Emitter lead. The base lead is generally a vertical line bright. If any of the solder joints look dull, dark, or inside a transistor circle symbol. The collector lead is blobby, then you should remove the solder with a solder usually a slanted line facing towards the base lead and sucker or a solder wick and then resolder the joint all the emitter lead is also a slanted line facing the base over again. Now we will inspect the PC board for

lead but it will have an arrow pointing towards or away possible short circuits. Short circuits can be caused from from the base lead. Now, identify the two transistors, small solder blobs bridging the circuit traces or from cut referring to the manufacturer’s specification sheets as component leads which can often stick to the circuit

well as the schematic and parts layout diagrams when

board once they have been cut. A sticky residue from

installing the two transistors. If you have trouble

solder will often trap component leads across the circuit installing the transistors, get the help of an electronics traces. Look carefully for any bridging wires across

enthusiast with some experience. Install the transistors circuit traces.

in their respective locations and then solder them in Once this inspection is complete, we can move on to

place. Remember to trim the excess component leads

installing the circuit board into an aluminum enclosure.

with your end-cutters.

Locate a suitable enclosure to house the circuit board.

Chapter Twenty-One: Radio Phone Patch

218

Chapter Twenty-One: Radio Phone Patch

Arrange the circuit board and the transformer on the

the speaker to the ground terminal of the printed circuit bottom of the chassis box. Now, locate four 1 / 4′′

board. Using two wires of different color will help in standoffs, and mount the PC board between the

avoiding misconnections.

standoffs and the bottom of the chassis box. If you

The connections to the telephone line should be made

selected a conventional relay you will have to mount it using a standard 4-prong telephone plug, or the new

on the chassis and wire it to the PC board. If you

modular connector which is now standard equipment

selected a non-PC board transformer then you will have with many telephone companies. Either of these types

to mount the transformer to the base of the chassis box of connectors is readily available from electronics

and wire it to the circuit board. Locate a 9-V battery supply houses, as well as those outlets which sell

holder and mount it to the bottom of the chassis box.

telephones to the general public. Before making a

You could also elect to use a small “wall wart” 9-V

connection between the printed circuit and telephone

power supply to power the circuit if desired.

plug, check the polarity of the telephone line with a DC

Operating controls for the circuit R3, R5, R14, S1,

voltmeter. Once you have done this you will be able to and S3 are shown mounted on the printed circuit board.

properly connect the Radio Phone Patch to the

This method of construction is left as an option to the telephone line. Note: Do not connect the Radio Phone

builder. You may want to locate these controls on the Patch to the telephone line unless you are placing it in front of the panel on the enclosure, so you may elect to operation. If the unit is left connected to the line it will use standard chassis mounted controls instead.

prevent normal operation of the telephone.

Next you will have to install an RJ11 phone jack or a 2-position terminal strip on the front panel of the chassis to bring the phone into the chassis box. Do not forget to Operation

install a power switch; this is shown as S2, and can be mounted on the front panel of the chassis box. Finally, The three operating volume controls in the Radio Phone you will have to mount the NORMAL/PATCH switch

Patch can be adjusted while the unit is in operation. As (S3) on the front panel, as well as TRANSMIT/RECEIVE

a start, set each control to mid-position. If your

switch (S1) to the front panel of the enclosure.

telephone is the type which uses a rotary dial you will have to dial the number you are calling before you

connect the Radio Telephone Patch to the telephone

Installation

line. If your telephone line is equipped for Touch Tone dialing, you can connect the Radio Phone Patch to the When connecting the Radio Phone Patch to your radio

telephone line either before you dial, or after. Once you transceiver, follow the directions shown in the

have dialed the number and connected the Radio Phone

schematic diagram. There are two connections which

Patch to the telephone line, you can hang up the

must be made to the radio transceiver, not including

telephone whenever it is no longer needed for

ground wires. These are the microphone input jack and communication. The holding circuit of the Radio Phone the speaker terminals. You may wish to purchase a

Patch will keep the telephone line in operation.

microphone plug and jack which match those

Set the NORMAL/PATCH switch, S3, to the Patch

components on your radio transceiver. This will permit position. The only other operating switch will be the you to make the connections to the radio without

TRANSMIT/RECEIVE switch, S1, which will have to

disturbing either the original microphone cable or the be operated manually as you transmit the telephone

connections to the jack within the radio. Use shielded conversation and receive the reply from the radio

microphone wire for the microphone connections. Note

transceiver. Since your radio transceiver also has a

that when S3 is set to the normal position, the

Transmit/Receive button on the microphone, you will

microphone will be connected to the radio transceiver in have to operate these switches in unison.

the usual manner, permitting normal operation. When

making the connection to the speaker of the radio

If you have a modulation indicator on your radio

transceiver, you may use a twisted pair of light gauge transceiver, you can use it to give you an approximate stranded wires. Be sure to connect the grounded side of indication of the proper setting of the transmit volume 219

control, R5. Otherwise you will have to rely on

terminated, be sure to disconnect the Radio Phone Patch information provided by the remote party receiving the from the telephone line. Failure to do this will result in radio broadcast as to whether or not the level of

an inoperative telephone.

modulation is sufficient.

Before placing the Radio Phone Patch on the air, read Before adjusting the receive volume control, R14, set and obey the following rules which are spelled out

your radio transceiver’s volume control for a

under FCC rules: (a) You may connect your radio

comfortable volume setting. Use the squelch control to transmitter to a telephone if you comply with all of the eliminate receiver noise when no signal is present. By following: (1) You, or someone authorized to operate

speaking into your telephone handset, you can ask the under your license, must be present at your radio station party at the other end of the telephone line if the

and must: (i)Manually make the connection (the

received volume from the radio transceiver is sufficient.

connection must not be made by remote control);

This will enable you to adjust R14 for proper volume on (ii) Supervise the operation of the transmitter during the the telephone line signal.

connection; (iii) Listen to each communication during Once the receive and transmit volume controls are set the connection; and (iv) Stop all communications if

to a satisfactory volume level for both parties, you can there are operations in violation of these rules. (2) Each hang up your telephone and use the monitor feature of communication during the telephone connection must

Radio Phone Patch to hear both sides of the

comply with all of these rules. (3) You must obey any conversation as you operate the receive/transmit

restriction that the telephone company places on the

switches. Set the monitor volume control, R3, for a

connection of a radio transmitter to a telephone. (b) The comfortable volume setting. After you have used your

radio transmitter you connect to a telephone must not be Radio Phone Patch for the first time, you can leave the shared with any other radio station. (c) If you connect three volume control settings as they are. The next time your radio transmitter to a telephone, you must use

you operate the unit they will probably need little or no a phone patch device which has been registered with

readjustment. When the telephone patch conversation is the FCC.

Chapter Twenty-One: Radio Phone Patch

220

Chapter 22

Telephone Phone Intercom

C10

10 μF, 35 V

Parts list

electrolytic capacitor

U1

Teltone 8870

Telephone Phone

¯01

Touch Tone Decoder

Intercom

(C.P. Claire Co.)

R1

600 ohms, 1⁄ W,

4

U2

MC14049 hex

5% resistor

inverting buffer

R2, R3

100 K ohm, 1⁄ W,

4

U3

MC14013B dual D

5% resistor

¯type

flip-flop

R4

300 K ohm, 1⁄ W,

4

U4

LM555N timer

5% resistor

U5

LM7805 – 5

R5, R6, R10, R11, R13

¯V

regulator

56 K ohms, 1⁄ W,

4

5% resistor

Q1, Q2, Q3

MPSA14

transistor

R7

10 ohms, 1⁄ W,

4

5% resistor

D3, 34, 37, 38

1N4148

silicon diodes

R8

220 K ohm, 1⁄ W,

4

5% resistor

31, D2, D5

1N4004

silicon diode

R9

10 K ohm, 1⁄ W,

4

5% resistor

LED1

red LED

R12

560 ohm, 1⁄ W,

BR1

silicon diode

4

5% resistor

bridge

C1

.01 μF, 200 volts

BZ

Piezo buzzer

ceramic disc capacitor

XTL

3.58 MHz crystal

C2, C4, C5, C6, C7

RY1

4PDT relay 12 V,

.01 μF, 50 volts

1¯amp coil –

ceramic disc capacitor

communications relay

C3

.1 μF, 35 V ceramic

T1

600/600 ohm audio

capacitor

isolation transformer

C8

22 μF, 16 V

J1, J2

RJ11 phone jacks

tantalum

Misc

PC board, IC

C7

.1 μF, 50 V ceramic

sockets, wire,

disc capacitor

12 V¯ 500 mA

C9

1,000 μF, 16 V

plug¯in transformer,

electrolytic capacitor

enclosure, etc.

221

Copyright © 2009 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Alert Module

labor installing wires. Responding to demand, many

R1

2.2 megohm,1⁄ W, 5%

manufacturers have incorporated the intercom as an

4

added feature in their telephones. However, even

R2, R4, R8

220 K ohm,

replacing your existing equipment is an expense that

1

⁄ w, 5%

4

usually outweighs the justification.

R3

10 megohms, 1⁄ W, 5%

4

The home phone intercom project, shown in

R5

56 K ohm, 1⁄ W, 5%

4

Figure 22-1, may be used concurrently with any

R6

33 K ohm, 1⁄ W, 5%

4

touch-tone phone system, and it provides features that R7

680 K ohm, 1⁄ W, 5%

make it practical, easy to use, and inexpensive. Because 4

it connects to your existing telephone equipment, there R9, R10

100 K ohm,

1

are no unsightly boxes to clutter up your desk.

⁄ W, 5%

4

R11

300 K ohm, 1⁄ W, 5%

4

C1

.01 μF, 500 V

How it works

ceramic disc capacitor

To engage the intercom at any time, all you have to do C2

1 μF, 16 V

is pick up any phone and press the “#” key that causes electrolytic capacitor

one or more alert nodules to sound an alarm, signaling C3

.1 μF, 35 V ceramic

other people in the home to pick up a phone. If you

capacitor

answer a call that comes in for someone else, pressing U1

Teltone 8870¯01

the “#” key will place the call on hold and the alarm Touch Tone decoder

will sound on the alert modules, signaling someone

(C.P. Claire Co.)

else in the home to pick up the phone. That someone

Q1, Q2, Q4

MPSA14

else may then release the call on hold by pressing the transistor

Q3

2N5401 transistor

D1, D2, D3

1N4004

silicon diode

D4, D5

1N4148 silicon

diode

XTL

3.58 MHz color

burst crystal

BZ

piezo buzzer

B1

9¯volt battery

PL1

4¯wire modular

phone plug

Misc

PC board,

IC sockets, wire,

battery clip/holder,

enclosure, etc.

Use your home telephones as a home intercom system.

It is quick and easy to add an intercom feature to your existing home telephones. Intercoms have been around

for many years, providing a valuable tool in

communications for home and industry. Unfortunately

Figure 22-1

Phone intercom components. Courtesy of

these systems either require added hardware or hours of Chapter Twenty-Two: Telephone Phone Intercom

Poptronix

222

Chapter Twenty-Two: Telephone Phone Intercom

“#” key or talk to you in private before answering the thereby energizing the audible alarm. The alarm will

call. Since the system is voice operated (VOX), the

remain on for as long as the “#” key is depressed.

intercom will disengage and return to normal operation Pin 6 of U2 is now low which sends a clock pulse to

after approximately 30 s.

U3. That transfers the high at U3 pin 2 to the output at The home phone intercom takes advantage of a

pin 1, which energizes the relay through Q1, R5, and

device called a “network interface.” Installed in most U2. The trigger input of U4, also being low, starts the newer homes over the past 10 years; despite the

VOX-timer U4. The clock pulse to U3 is delayed

complicated name it is simply a connector box that

slightly by R7 and C2 until the output of U4 pin at 3

separates the outside phone line from your internal

has enough time to remove the reset signal at U3

wiring (see Figure 22-2).

pin 4. When the “#” is released, pin 11 of U3 goes high Since a network interface is used by the phone company and toggles the output of U3 pin 13 to a low state,

to determine whether problems are internal or external, a preventing the alarm to sound during the next

substantial premium service charge may be imposed if you depression of the “#” key (manual turn off).

do not have one. Therefore, it is highly recommended that If conversation continues, U4 is prevented from time-one be installed even if not for this project.

out through C7 and Q2. If conversation stops for more than 30 s, C4 charges to the threshold voltage at U4 pin 6

and pin 3 return to a low state. That places a high on the Theory of operation

reset pin (pin 4) and the set pin (pin 8) of U3, which turns off RYl, returning the system to the standby mode. Any Glance at the Intercom Controller board in Figure 22-3

calls in process are held by maintaining central office loop and at the schematic depicted in Figure 22-4.

current through R1, while in intercom mode.

In the standby mode, relay RY1 is not energized and the only connection to the phone line is the coupling-capacitor Alert module

C1. The Teltone 8870-01 (U1) is a telephone tone decoder whose BCD output is dependent on which tones are

An Alert module is placed at every room near the room’s present at pin 9 (see decoder diagram in Figure 22-5).

telephone. The Alert module is illustrated in Figure 22-6

The two most significant bits (pins 16 and l7) will

and in the schematic at Figure 22-7; it plugs into any only be high during a “#” key depression. The high on home phone jack, and can be powered by either a

pin 7 of U4 and pin 4 of U2 allow Q3 to turn on,

7.2-V rechargeable Ni-Cd or 9-V alkaline battery.

Junction

RD

GR

block

Yellow

YEL

BL

Incoming

line

Green

Network

interface

To connector

BL

J1 main control

Red

module

RD

YEL

Black

To connector

GR

J2 on main

control module

To house wiring

Figure 22-2

Network interface

223

Telephone tones are decoded by U1 as previously

discussed. A “#” key activation will activate the alarm.

Diode D1 is important in that it protects U1 and the rest of the semiconductors from damage when the AC

ringing voltage is present on the phone line. If you are using a rechargeable battery charging current is supplied through R3 during on-hook conditions.

Circuit assembly

Before we begin constructing the Telephone Phone

Intercom, you will need to locate a clean, well-lit

Figure 22-3

Telephone intercom main circuit board.

worktable or workbench. Next we will gather a small

Courtesy of Poptronix

25–30-W pencil tipped soldering iron, a length of

However the circuit is only active during an off-hook 60/40 tin–lead solder, and a small canister of Tip Tinner, condition to conserve the battery during normal

available at your local RadioShack store; Tip Tinner is operation. (There are approximately 50 V on the

used to condition the soldering tip between solder

phone line). That allows base current to flow through joints. You drive the soldering tip into the compound R1 which turns on Q1 and holds Q2 in an off state

and it cleans and prepares the soldering tip. Next grab a preventing power to U1 and the audible alarm. When

few small hand tools, try to locate small flat blade and the line voltage falls, as evident in an off-hook

Phillips screwdrivers. A pair of needle-nose pliers, a pair condition, Q2 turns on, thereby placing U1 in the

of tweezers along with a magnifying glass, and a pair of standby mode.

end-cutters and we will begin constructing the project.

J2-1

+5 V

Yellow

Yellow

RY 1-b

J1-1

GRN

+5 V

J1-2

GRN

C1

C2

RY1-a

C11

C3

RY1-c

R1

R5

C5

T1

18

+5 V

+

10

1

17

D1

4

16 R4

R6

BZ

+5 V

IN

R7

J2-3

3

U1

R3

15

U5

R2

1

U2:c

U2:b

RY-D

RED

2

D3

6

+

5

13

7

5

4

GND

C9

+

D2

C10

9

14

8

D7

+

Q3

+

5 V

5 V

D4

6

7

8

R12

XTL

BR1

C6

11

D6

RY1

13

R11

D5

R10

LED1

U3:b

9

+5 V

12 V AC

U2:a

R8

Q1

2

14 5

8

10

4

9

3

2

3

RED

2

Q2

U4

U3:a

J1-3

3

7

R13

U2:e

C4

15

1

10

9

1

5

C8 +

R9

14 12

11

4

C7

7

6

U2:d

U2:f

J2-4

J1-4

Black

Black

Chapter Twenty-Two: Telephone Phone Intercom Figure 22-4 Phone intercom main controller schematic. Courtesy of Poptronix 224

Chapter Twenty-Two: Telephone Phone Intercom

VDD

VSS

VREF

INH -OZ only

−

Bias

PD

+

Circuit

Chip ref

-OZ only

High

Q1

group

Chip Chip

filter

power bias

Code

Q2

Zero

Digital

converter

crossing

detection

IN+

and

Dial

+

detectors

algorithm

latch

Q

tone

3

IN−

−

filter

Low

group

Q4

filter

GS

Clock

St

Steering

Gt

logic

OSC1

OSC2

St/GT

ESt

StD

OE

Figure 22-5

Teltone M-8870-01/02. Courtesy of Teletone

Now locate your schematic diagram and parts layout

diagram along with all of the components needed to

build the project.

The Home Phone Intercom controller is built on one

PC board, and the alert modules are built on separate boards for each telephone location. Determine the

number of alert modules you will need including the

master control unit. The modules are loud enough to

cover approximately 1,000 square feet each, even when placed behind furniture. It is recommended that one

module be installed in a central location on each phone of your house.

Once all the components are in front of you, you can

check them off against the project parts list to make sure you are ready to start building the project. Now, locate Tables 22-1 and 22-2, and place them in front of you.

Table 22-1 illustrates the resistor code chart and how to read resistors, while Table 22-2 illustrates the capacitor code chart which will aid you in constructing the project.

Finally, we are ready to begin assembling the project, so let’s get started. The prototype project was

constructed on a single-sided printed circuit board or PCB. With your PC board in front of you, we can now

begin populating the circuit board. We are going to

Figure 22-6

Telephone intercom remote ring board.

place and solder the lowest height components first,

Courtesy of Poptronix

such as the resistors and the diodes.

225

9 V

R10

+

−

Green

C1

D3

+

D1

D2

R9

R10

R3

R5

R1116

R7

D4

2

3

R1

e

17

Q3

BZ

14

b

18

R4

U1

13

C3

c

10

D5

Q1

R6

+

R8

c

C2

c

b

7

b

1

e

Q2

e

4

Q4

8

R2

−

XTL

5

6

9

Red

Figure 22-7

Alert module. Courtesy of Poptronix

Refer now to Table 22-1 which depicts the resistor

The third colored band represents the resistor’s multiplier color codes; this chart will help you identify each resistor value, and the fourth color band represents the resistor’s before you mount them on the PC board. Note that each tolerance value. If there is no fourth colored band then resistor will have either three or four color bands, which the resistor has a 20% tolerance value. If the resistor’s begin at one end of the resistor’s body. The first colored fourth band is silver then the resistor has a 10% tolerance band represents the resistor’s first digit, while the second value and if the fourth band is gold then the resistor’s color represents the second digit of the resistor’s value.

tolerance value will be 5%.

Table 22-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

Chapter Twenty-Two: Telephone Phone Intercom

No color

20%

226

Chapter Twenty-Two: Telephone Phone Intercom

Table 22-2

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

1.0

1R0

3,900

3.9

.0039

392

1.2

1R2

4,700

4.7

.0047

472

1.5

1R5

5,600

5.6

.0056

562

1.8

1R8

6,800

6.8

.0068

682

2.2

2R2

8,200

8.2

.0082

822

2.7

2R7

10,000

10

.01

103

3.3

3R3

12,000

12

.012

123

3.9

3R9

15,000

15

.015

153

4.7

4R7

18,000

18

.018

183

5.6

5R6

22,000

22

.022

223

6.8

6R8

27,000

27

.027

273

8.2

8R2

33,000

33

.033

333

10

100

39,000

39

.039

393

12

120

47,000

47

.047

473

15

150

56,000

56

.056

563

18

180

68,000

68

.068

683

22

220

82,000

82

.082

823

27

270

100,000

100

.1

104

33

330

120,000

120

.12

124

39

390

150,000

150

.15

154

47

470

180,000

180

.18

184

56

560

220,000

220

.22

224

68

680

270,000

270

.27

274

82

820

330,000

330

.33

334

100

.0001

101

390,000

390

.39

394

120

.00012

121

470,000

470

.47

474

150

.00015

151

560,000

560

.56

564

180

.00018

181

680,000

680

.68

684

220

.00022

221

820,000

820

.82

824

270

.00027

271

1,000

1

105

330

.00033

331

1,500

1.5

155

390

.00039

391

2,200

2.2

225

470

.00047

471

2,700

2.7

275

560

.00056

561

3,300

3.3

335

680

.00068

681

4,700

4.7

475

820

.00082

821

6.8

685

1,000

1.0

.001

102

10

106

1,200

1.2

.0012

122

22

226

1,500

1.5

.0015

152

33

336

1,800

1.8

.0018

182

47

476

2,200

2.2

.0022

222

68

686

(Continued)

227

Table 22-2—cont’d

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

2,700

2.7

.0027

272

100

107

3,300

3.3

.0033

332

157

157

Code = 2 significant digits of the capacitor value + number of zeros to follow 10 pF = 100

For values below 10 pF, use “R” in place of decimal e.g. 8.2 pF = 8R2

100 pF = 101

1,000 pF = 102

22,000 pF = 223

330,000 pF = 334

1 μF = 105

Now, locate our first resistor R1. Resistor R1 has a

Many capacitors are quite small in physical size, so

value of 600 ohms and is a 5% tolerance type. Now take manufacturers have devised a three-digit code which

a look for a resistor whose first color band is blue, can be placed on the capacitor instead of the actual

black, brown, and gold. From the chart you will notice value. The code occupies a much smaller space on the

that blue is represented by the digit (6), the second color capacitor and can usually fit nicely on the capacitor band is black, which is represented by (0). Notice that body, but without the chart the builder would have a

the third color is brown and the multiplier is (10), so difficult time determining the capacitor’s value.

(6) (0) × 10 = 600 ohms.

Now look for the capacitors from the component

Go ahead and locate where resistor R1 goes on the PC

stack and locate capacitors C1 and C2, they are small and install it, next solder it in place, and then with a pair of capacitors labeled (103). Refer to the Table 22-2 to find end-cutters trim the excess component leads flush to the code (103) and you will see that it represents a capacitor edge of the circuit board. Next locate the remaining

value of .01 μF. Go ahead and place C1 and C2 on the

resistors and install them in their respective locations on the circuit board and solder them in place on the circuit main controller PC board. Solder the resistors to the board, board. Now take your end-cutters and cut the excess

and remember to cut the extra lead with your end-cutters.

component leads flush to the edge of the circuit board.

Once you have installed these components, you can

Note that capacitors generally come from two major

move on to installing the remaining capacitors.

groups or types. Non-polar types, such as the ones in this project, have no polarity and can be placed in either The main Telephone Intercom board contains five

direction on the circuit board. The other type of

silicon diodes. Diodes, as you will remember, will always capacitors are called polarized types, these capacitors have some type of polarity markings, which must be

have polarity and have to be inserted on the board with observed if the circuit is going to work correctly. You will respect to their polarity marking in order for the circuit notice that each diode will have a black or white colored to operate correctly. On these types of capacitors, you band at one edge of its body. The colored band represents will observe that the components actually have a plus or the diode’s cathode lead. Check your schematic and parts minus marking or a black or white band with a plus or layout diagrams when installing these diodes on the

minus marking on the body of the capacitors.

circuit board. Place all the diodes on the circuit board in Capacitors must be installed properly with respect to their respective locations and solder them in place. Diode polarity in order for the circuit to work properly. Failure bridge BR1 on the right side of the schematic can be

to install electrolytic capacitors correctly could cause installed now. After soldering in the diodes and the diode damage to the capacitor as well as to other components bridge, remember to cut the excess component leads with Chapter Twenty-Two: Telephone Phone Intercom in the circuit when power is first applied.

your end-cutters, flush to the edge of the circuit board.

228

Chapter Twenty-Two: Telephone Phone Intercom

The Telephone Intercom main board utilizes three

LED, in order to have the LED protrude through the

conventional transistors. Transistors are generally three enclosure box. Solder the LED to the PC board and then lead devices, which must be installed correctly if the trim the excess leads.

circuit is to work properly. Careful handling and proper Now, locate the crystal at XTL and install it in its proper orientation in the circuit is critical. A transistor will location between pins 7 and 8 of U1. Next, locate the piezo usually have a Base lead, a Collector lead, and an

buzzer at BZ which is connected to the collector of Q3.

Emitter lead. The base lead is generally a vertical line Locate and install the mini transformer at T1, which is inside a transistor circle symbol. The collector lead is connected to the input of U5. Finally go ahead and install usually a slanted line facing towards the base lead and the 4PDT communications relay. If you purchased a PC

the emitter lead is also a slanted line facing the base lead board relay you can install it on the PC board, but if you but it will have an arrow pointing towards or away from purchased a conventional relay you will have to mount it the base lead. Now, identify the two transistors, referring on the chassis and wire it to the circuit board.

to the manufacturer’s specification sheets as well as the Once the main Intercom Controller circuit board has

schematic and parts layout diagrams when installing the been completed, take a short break and then we will

two transistors. If you have trouble installing the

inspect the PC board for possible “cold” solder joints and transistors, get the help of an electronics enthusiast with

“short” circuits. Pick up the PC board with the foil side some experience. Install the transistors in their respective facing upwards toward you. Carefully inspect the solder locations and then solder them in place. Remember to

joints, these should look smooth, clean, and bright. If any trim the excess component leads with your end-cutters.

of the solder joints look dull, dark, or blobby, then you The main Intercom Controller circuit also contains

should remove the solder with a solder sucker or a solder five ICs. ICs are often static sensitive, so they must be wick and then resolder the joint all over again. Now we handled with care. Use a grounded anti-static wrist strap will inspect the PC board for possible short circuits. Short and stay seated in one location when handling the

circuits can be caused from small solder blobs bridging integrated circuits. Take out a cheap insurance policy the circuit traces or from cut component leads which can by installing IC sockets for each of the ICs. In the event often stick to the circuit board once they have been cut.

of a possible circuit failure, it is much easier to simply A sticky residue from solder will often trap component unplug a defective IC, than trying to unsolder 14 or

leads across the circuit traces. Look carefully for any 16 pins from a PC board without damaging the board.

bridging wires across circuit traces.

ICs have to be installed correctly if the circuit is going Once the inspection is complete, we can move on to

to work properly. IC packages will have some sort of

installing the circuit board into an aluminum enclosure.

markings which will help you orient them on the

Locate a suitable enclosure to house the circuit board.

PC board. An IC will have either a small indented

Arrange the circuit board and the transformer on the

circle, a cutout, or notch at the top end of the

bottom of the chassis box. Now, locate four 1 / 4 inch IC package. Pin 1 of the IC will be just to the left

standoffs, and mount the PC board between the

of the notch, or cutout. Refer to the manufacturer’s

standoffs and the bottom of the chassis box. If you

pin-out diagram, as well as the schematic when

selected a convention relay you will have to mount it on installing these parts. If you doubt your ability to

the chassis and wire it to the PC board. Mount the

correctly orient the ICs, then seek the help of a

transformer to the base of the chassis box and wire it to knowledgeable electronics enthusiast.

the circuit board.

The Intercom Controller circuit utilizes a single LED

Mount a coaxial power jack on the rear panel of the

at LED1, which also must be oriented correctly if the chassis box for the AC power supply at BR1’s input.

circuit is to function properly. An LED has two leads, a The 12 V AC power supply could be a low cost “wall

cathode and an anode lead. The anode lead will usually wart” type power supply. Mount the status LED on the

be the longer of the two leads and the cathode lead will front panel if desired. Next you will have to install an usually be the shorter lead, just under the flat side edge RJ11 phone jack or a 2-position terminal strip on the of the LED; this should help orient the LED on the PC

front panel of the chassis to bring the phone into the board. You may want to lead about 1 / 2 lead length on the chassis box. Now you are ready to connect the main

229

controller to the phone line, but before we do, you will need to construct the desired number of Alert Modules.

Installation and check out

Determine where your network interface is by locating Alert module construction

the area where the phone line enters the house. In some cases, the device is mounted on the outside. It is a wall Next refer to the Alert Module schematic shown in

box with a short wire loop connecting to a modular

Figure 22-7. First, install all the resistors on the PC

jack. Refer back to Figure 22-2 on how to install a

board then solder them in place and trim the excess

network interface if it is not already present. During the component leads with you end-cutters. Next install all of next few steps, your phone system will be inoperative the capacitors on the Alert Module and then solder them until installation is complete.

in place on the PC board. Next install the four silicon Disconnect the short wire from the jack on the

diodes, remembering they are polarity sensitive, so care network interface. Connect that wire to J1 on the main must be taken to install them correctly on the PC. Now control module. Make sure all phones on the same

locate the four transistors and install them on the PC

extension are on-hook, and connect the controller to a board. Refer to the schematic, parts layout diagram, and l2-V AC source. Pick up a telephone receiver and press manufacturer’s specification sheets when installing them.

the “#” key. The alarm will sound and the LED should

Transistors must be installed properly the first time, so be on. You will also be able hear yourself talk through that they are damage free when power is first applied to the handset. Hang up the phone. The LED should remain the circuit. Now install the piezo buzzer at BZ; it is on for approximately 30 s before turning off.

connected between the collector of Q4 and resistor R7.

Connect the remaining wire from the main control

Finally, install an IC socket for the touch-tone decoder module to the jack on the network interface. Pick up the at U1. Locate the touch-tone decoder chip, and insert it receiver again and initiate a call to determine normal into the socket, paying particular attention to the

operation. If you are unable to dial out, the red and positioning notch when inserting the IC into its socket, green wires (tip and ring) have been reversed

in order to avoid damage to the IC upon power up.

somewhere in the system. Remember that positive

The values for resistors R3 and R10 depend on what

phone line voltage must be present at J2 pin 2. It may type of battery you are using. Use l0 megohms for R3

be necessary to toggle the “#” key once or twice to get and 82 ohms for R10 for a 9-V alkaline battery. If a

everything going when the system is first installed or rechargeable battery is used, change the value of R3 to after a power failure. Install the alert modules and

82 K and R10 to l0 ohms.

determine the correct polarity by measuring a positive voltage at the anode of D1. Reverse the wires in the

The Alert Modules will need to be placed in a

module if it turns out to be necessary. If a rechargeable suitable enclosure next to a phone jack in each desired battery is used, you should allow it to charge for at least room installation. A small plastic box can be used to 24 hours before activating the system.

mount each of the Alert Modules. Make sure you have

enough room for the 9-V battery and the buzzer. You

Now, you can test each of the Alert Modules in each

will want to either install a modular phone jack on the location and you are ready to begin using your new

enclosure or you will need to make up a cable with a

Telephone Intercom system. The Telephone Intercom

modular phone plug between the circuit and the phone

will become your favorite phone accessory, saving your line for each of the Alert Modules. Once the Alert

voice and many footsteps, or having to yell or walk

Modules are installed in their cases, with batteries

around the house trying to let someone know a phone

connected, you will be ready to connect each one to the call is for them. The Telephone Intercom will serve you phone line and test the modules.

for many years as a faithful servant around the house.

Chapter Twenty-Two: Telephone Phone Intercom

230

Chapter 23

Speaker-Phone Project

C28

.1 μF disc, 50 V

Parts list

(104)

C2, C4, C6, C7, C8,

Speaker-Phone

C17, C22, C23

.47 μF,

R1, R6, R14, R20

50 V electrolytic

10 K ohm, 1⁄ W,

4

capacitor

5% resistor

C5, C11, C15, C19, C20,

R2

1 K ohm, 1⁄ W,

4

C21, C29

2.2 μF,

5% resistor

50 V electrolytic

R3, R9, R13, R19

capacitor

4.7 K ohm, 1⁄ W,

4

C16, C26

47 μF, 50 V

5% resistor

electrolytic capacitor

R4 alternate R10

C24

220 μF, 50 V

270 ohm, 1⁄ W,

4

electrolytic capacitor

5% resistor

C12, C25, C27

470 μF

R5

68 K ohm, 1⁄ W,

4

or 330 μF, 50 V

5% resistor

electrolytic capacitor

R7, R12

47 K ohm,

U1

MC34118 28¯pin DIP

1

⁄ W, 5% resistor

4

Speaker¯phone IC

R8

820 ohm, 1⁄ W,

4

U2

LM386 8¯pin DIP

5% resistor

audio amplifier IC

R10

100 ohm, 1⁄ W,

4

D5

6.2 volt zener diode

5% resistor

D1, D2, D3, D4, D6,

R11, R15, R16, R17

D7

1N4002 black

100 K ohm, 1⁄ W,

4

epoxy rectifier

5% resistor

diode

R18

10 K potentiometer

MK1

miniature

(PC board type)

microphone element

C1

100 pF disc, 50 V

T1, T2

1,000¯to¯8 ohm

(100 or 101)

audio transformer

C9, C10, C13, C14

.01 μF

S1, S2

PC mount DPDT

disc, 50 V (103)

push¯switch

C3, C18

.05 or .047 μF

J1

modular RJ¯11

disc, 50 V (473)

telephone line jack

231

Copyright © 2009 by The McGraw-Hill Companies, Inc. Click here for terms of use.

J2

subminiature

The Speaker-Phone Project shown in Figure 23-1

phone/speaker jack

gives you full, state-of-the-art speaker-phone technology.

SPK

8¯ohm¯3” speaker

First, it is a complete stand alone telephone for

Misc

PC board, IC

incoming calls. Use some other phone or dialer right

sockets, wire, battery

along with it only if you have a frequent need to initiate holder, battery clip,

those unique Speaker-phone-style calls. Otherwise, you enclosure, hardware, etc

can use your speaker-phone to answer all incoming

calls, handling them while you work or play.

Kit available from:

A pair of speaker-phone units can make a great

Ramsey Electronics

hands-free intercom system for which you will imagine 590 Fishers Station Drive

dozens of practical applications. You will figure out how Victor, NY 14564

to set them up so they can serve as intercoms and

convenient speaker-phones.

585¯924¯4560

The Speaker-Phone Project efficiently replaces a cluster of add-on phone gadgets to give you what you really

How does a speaker-phone work?

want in the shop or office: The ability to answer

incoming calls and continue what you are doing while

You must be able to turn the speaker up to normal room talking from anywhere in the room.

volume, and the microphone circuit must be sensitive

enough for you to speak from anywhere in a small room.

The Speaker-Phone Project is great for family and

How would you do it? Remember: No switches, just two

conference calling, or you can connect two speaker-phones wires, and no squealing “feedback”! To put it very simply, together for a completely hands-free intercom; this is the speaker-phone is “smart”: it knows when to be idle, ideal for linking the shop with the rest of the house.

when to transmit, when to receive, when to mute, when Imagine how handy it would be to simply answer back

to attenuate, and what to do about background noise.

from anywhere in your shop without stopping what you

It even recognizes the difference between steady

are doing. It’s like linking two rooms together. The great background noise and the phone line’s dial tone. The

features of this project include the circuit: (1) Needs no Speaker-phone block diagram, illustrated in Figure 23-2, battery when connected to the phone line. (2) Can be

was designed around a high-tech Motorola MC65118

simply connected to the phone line by itself without

Speaker-phone IC.

using an extra telephone. For intercom use, a regular 9-V battery powers the unit. It includes built-in electret Motorola explains the MC34118 this way: The

microphone; just add your choice of speaker.

fundamental difference between the operation of a

speaker-phone and a handset is that of half-duplex

versus full-duplex.

The handset is full duplex, since conversation can

occur in both directions (transmit and receive)

simultaneously. A Speaker-phone has higher gain levels in both paths, and attempting to converse full duplex results in oscillatory problems due to the loop that exists within the system. The loop is formed by the receive

and transmit paths, the hybrid, and the acoustic coupling (speaker to microphone.)

The most practical solution used to date is to design the speaker-phone to function in a half-duplex mode,

i.e. only one person speaks at a time, while the other Figure 23-1

Speaker-phone. Courtesy of Ramsey

listens. To achieve this requires a circuit which can Chapter Twenty-Three: Speaker-Phone Project Electronics detect who is talking, switch on the appropriate path 232

Chapter Twenty-Three: Speaker-Phone Project

VCC

VB

VB

2 BAL

RMF

RHF

TXO

MC1

TX Atten

Tip

RM1

MC0

TX1

RH1

HT1

Phone line

−

−

11

+

10

9

8

7

+

Ring

VB

23 TL11

R

R

MIC

TL12 17

C

14

+

VB

5

−

VCC

+

Mute

VB

HT0+

12

VCC

VCC

CPT

Background

16

noise mon

Background

AGC

CPR

noise mon

27

TL02

RL01

18

Atten

19

25

control

24

RL02

Level dectetors

Level detectors

TL01

VCC

4

VB

CD

R

400

3

R

28

13

Filter

Bias

20 RL12 VIC

RX0

2

21

1

GND

VB

RX1 26 RL11

+1

22

F0

F1

VB

15

RX

Vol

Atten

−+

15

Dial tone

MV

Speaker

detector

VB

amp

Figure 23-2

MC34118 Block diagram. Courtesy of Motorola Inc

(transmit or receive), and switch off (attenuate) the circuit to the phone line’s two wires. There is nothing other path. In this way, the loop gain is maintained less hi-tech about calling these two wires “tip” and “ring.”

than unity. When the talkers exchange function, the

That is our inheritance from manual switchboard days.

circuit must quickly detect this, and switch the circuit Tip and ring referred to parts of the plug and patch cord appropriately. By providing speech level detectors, the sets handled by the operator. As mentioned, S1(A)

circuit operates in hands-free mode, eliminating the

performs the same function as a conventional telephone need for a push-to-talk switch. The MC34118 provides

“hook” switch. As soon as S1 is pressed in, the central the necessary level detectors, attenuators, and switching office equipment is able to sense that the Speaker-phone control for a properly operating Speaker-phone. The

is connected to the line or “loop.”

Speaker-phone IC also provides background noise

The phone line carries both audio energy (AC) and

monitors which make the circuit insensitive to room as DC voltage. T1 and T2 couple the audio signals to U1’s well as line noise, hybrid amplifiers for interfacing to hybrid amplifiers (pins 5 and 6). In telephone

Tip and Ring, i.e. the phone line connections.

terminology, “hybrid” is a circuit that divides a single transmission channel into two, one for each direction.

Circuit description

Diodes D1-D4 are arranged to make the input

insensitive to DC polarity; the circuit gets correct

The Speaker-phone schematic diagram, in Figure 23-3 also DC polarity no matter which way the phone line is

provides a complete diagram of the MC34118’s functions.

connected! IC U2 is a self-contained audio amplifier

How self-evident the circuit functions seem to you

capable of outputs up to 400 mW, quite sufficient to

depends on your level of electronics experimenting or drive quality speakers to room volume. The LM386

learning. Here are the highlights of what makes the SP1

audio amplifier is connected directly to a speaker for tick. S1(A) and a jumper from B to A connect the

conversation listening.

233

+6 V

R1

C5

R2

C1

RJ11

R4

C3

T1

T2

C6

R3

C2

D6 D7

D

C4

A

J1

MIC

E

C9

R6

R7

R8

C

Telephone

C7

C8

R5

R9

C10

jack

11

16

17

9

8

23

7

6

S2

5

D1

D2

+6

12

Mute

+6 R9

18

4

C13

R11

C11 16

C12

U1

D3

2

D4

19

D5

C16

C15

C14

10

1

S1:B

+

C17

Intercom OSE

R13

22

R10

−

battery input

28

3

R12 14

27

25

24

13

21

26

C21

C19

15

C20

C18

R18

C23

C25

R14

C23

R15

+6 V

U2

R16

6

C27

C22

SPK

3

+

5

2

−

7

+

C24

J2

C26

R17

Figure 23-3

Speaker-phone circuit. Courtesy of Ramsey Electronics Switch S2 simply activates the microphone amplifier

condition the soldering tip between solder joints. You muting feature built into the Speaker-phone IC. Pin 12

drive the soldering tip into the compound and it cleans is ordinarily low (0 voltage) for normal operation. The and prepares the soldering tip. Next grab a few small microphone input circuitry is set up to accommodate both hand tools; try to locate small flat blade and Phillips self-powered microphones and those which require a small screwdrivers. A pair of needle-nose pliers, a pair of DC voltage for proper operation. Hands-free intercom

tweezers along with a magnifying glass, and a pair of operation is the same as half-duplex Speaker-phone

end-cutters and we will begin constructing the project.

operation except that a source of DC voltage is required.

Now locate your schematic diagram and parts layout

This is made easy by S1(B) and a jumper from A to C.

diagram along with all of the components needed to

Perhaps the easiest overview of the circuit would be

build the project.

the following pin by pin notes on the MC34118

Once all the components are in front of you, you can

(see Table 23-1).

check them off against the project parts list to make sure you are ready to start building the project. Now, Circuit assembly

locate Tables 23-2 and 23-3, and place them in front of you. Table 23-2 illustrates the resistor code chart and Before we begin constructing the Speaker-phone, you

how to read resistors, while Table 23-3 illustrates the will need to locate a clean, well-lit worktable or

capacitor code chart which will aid you in constructing workbench. Next we will gather a small 25–30-W

the project.

pencil tipped soldering iron, a length of 60/40 tin–lead Finally, we are ready to begin assembling the project, solder, and a small canister of Tip Tinner, available at so let’s get started. The prototype was constructed on a Chapter Twenty-Three: Speaker-Phone Project your local RadioShack store; Tip Tinner is used to single-sided printed circuit board or PCB. With your

234

Chapter Twenty-Three: Speaker-Phone Project

Table 23-1

colored band then the resistor has a 20% tolerance

Speaker-phone IC pin descriptions

value. If the resistor’s fourth band is silver then the resistor has a 10% tolerance value and if the fourth band IC Pin Descriptions

is gold then the resistor’s tolerance value will be 5%.

1.

Filter output

We are going to place and solder the lowest height

2.

Filter input

components first, the resistors and diodes. First, locate 3.

Chip disable (not used in SP1design)

our first resistor R1. Resistor R1 has a value of 10 K

4.

Vcc (DC supply voltage)

ohms and is a 5% tolerance type. Now take a look for a 5.

Hybrid amplifier output #2

resistor whose first color band is brown, black, orange, 6.

Hybrid amplifier output #1

and gold. From the chart you will notice that brown is 7.

Input to hybrid amplifier #1

represented by the digit (1), the second color band is black, which is represented by (0). Notice that the

8.

TX attenuator output

third color is orange and the multiplier is (1,000), so 9.

TX attenuator input

(1) (0) × 1,000 = 10,000 or 10 K ohms.

10.

Microphone amplifier output

Go ahead and locate where resistor R1 goes on the

11.

Microphone amplifier input

PC and install it, next solder it in place on the PC board, 12.

Mute input (mike amplifier muted by + DC at pin 12)

and then with a pair of end-cutters trim the excess

13.

Volume control input

component leads flush to the edge of the circuit board.

14.

Response time to switch between transmit and receive

Next locate the remaining resistors and install them in established by R15 and C21

their respective locations on the main controller PC

15.

Supplies bias to volume control, filtered by C24

board. Solder the resistors to the board, and remember 16.

Time constant for TX BNM set by R11 and C16

to cut the extra lead with your end-cutters.

17.

Input to TX level detector on mike/speaker side

Note that capacitors generally come from two major

18.

Output of TX level detector and input to TX BNM

groups or types. Non-polar types, such as the ones in 19.

Output of RX level detector on mike/speaker side

this project, have no polarity and can be placed in either 20.

Input to RX level detector on mike/speaker side

direction on the circuit board. The other type of

21.

Input to RX attenuator and dial tone detector

capacitors are called polarized types, these capacitors 22.

Output of RX attenuator

have polarity and have to be inserted on the board with 23.

Input to transmit level detector on line side

respect to their polarity marking in order for the circuit 24.

Output of transmit level detector on line side

to operate correctly. On these types of capacitors, you 25.

Output of RX level detector on line side, also input to will observe that the components actually have a plus or minus marking or a black or white band with a plus or RX BNM

minus marking on the body of the capacitors.

26.

Input to RX level detector on line side

Capacitors must be installed properly with respect to 27.

Time constant for RX BNM set by R16, C26

polarity in order for the circuit to work properly. Failure 28.

Ground for entire IC.

to install electrolytic capacitors correctly could cause damage to the capacitor as well as to other components in the circuit when power is first applied.

PC board in front of you, we can now begin populating the circuit board. Now refer to the resistor color code Many capacitors are quite small in physical size, so

chart shown in Table 23-2. You will note that each

manufacturers have devised a three-digit code which

resistor will have either three or four color bands, which can be placed on the capacitor instead of the actual

begin at one end of the resistor’s body. The first colored value. The code occupies a much smaller space on the

band represents the resistor’s first digit, while the capacitor and can usually fit nicely on the capacitor second color represents the second digit of the resistor’s body, but without the chart the builder would have a

value. The third colored band represents the resistor’s difficult time determining the capacitor’s value.

multiplier value, and the fourth color band represents Now look for the lowest profiles capacitors from the

the resistor’s tolerance value. If there is no fourth component stack and locate capacitor C1, labeled (100) 235

Table 23-2

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

No color

20%

Table 23-3

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

1.0

1R0

3,900

3.9

.0039

392

1.2

1R2

4,700

4.7

.0047

472

1.5

1R5

5,600

5.6

.0056

562

1.8

1R8

6,800

6.8

.0068

682

2.2

2R2

8,200

8.2

.0082

822

2.7

2R7

10,000

10

.01

103

3.3

3R3

12,000

12

.012

123

3.9

3R9

15,000

15

.015

153

4.7

4R7

18,000

18

.018

183

5.6

5R6

22,000

22

.022

223

6.8

6R8

27,000

27

.027

273

8.2

8R2

33,000

33

.033

333

10

100

39,000

39

.039

393

12

120

47,000

47

.047

473

15

150

56,000

56

.056

563

18

180

68,000

68

.068

683

22

220

82,000

82

.082

823

27

270

100,000

100

.1

104

33

330

120,000

120

.12

124

39

390

150,000

150

.15

154

Chapter Twenty-Three: Speaker-Phone Project 47

470

180,000

180

.18

184

236

Chapter Twenty-Three: Speaker-Phone Project

Table 23-3—cont’d

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

56

560

220,000

220

.22

224

68

680

270,000

270

.27

274

82

820

330,000

330

.33

334

100

.0001

101

390,000

390

.39

394

120

.00012

121

470,000

470

.47

474

150

.00015

151

560,000

560

.56

564

180

.00018

181

680,000

680

.68

684

220

.00022

221

820,000

820

.82

824

270

.00027

271

1,000

1

105

330

.00033

331

1,500

1.5

155

390

.00039

391

2,200

2.2

225

470

.00047

471

2,700

2.7

275

560

.00056

561

3,300

3.3

335

680

.00068

681

4,700

4.7

475

820

.00082

821

6.8

685

1,000

1.0

.001

102

10

106

1,200

1.2

.0012

122

22

226

1,500

1.5

.0015

152

33

336

1,800

1.8

.0018

182

47

476

2,200

2.2

.0022

222

68

686

2,700

2.7

.0027

272

100

107

3,300

3.3

.0033

332

157

157

Code = 2 significant digits of the capacitor value + number of zeros to follow 10 pF = 100

For values below 10 pF, use “R” in place of decimal e.g. 8.2 pF = 8R2

100 pF = 101

1,000 pF = 102

22,000 pF = 223

330,000 pF = 334

1 μF = 105

or 100 pF. Note that there are a number of small

There are a number of electrolytic capacitors in the

capacitors in the circuit that may not be labeled with circuit and placing them in the circuit with respect to their actual value, so you will have to check Table 23-2

their proper polarity is essential for proper operation of to learn how to use the three-digit capacitor code. Go the circuit. Once you have located the larger electrolytic ahead and place C1 on the circuit board and solder it in capacitors install them in their respective locations and place. Now take your end-cutters and cut the excess

solder them in place. Finally trim the excess component component leads flush to the edge of the circuit board.

leads.

Next, locate the remaining low profile capacitors and The Speaker-Phone Project contains a number of

install them on the printed circuit board, then solder them silicon diodes and a Zener diode. Diodes, as you will in place. Remember to trim the extra component leads.

remember, always have some type of polarity markings, 237

which must be observed if the circuit is going to work and T2. Notice the red marking on one side of the top correctly. You will notice that each diode will have a insulator on each unit. These marked sides must be

black or white colored band at one edge of its body. The pointed toward the center of the board, as shown by the colored band represents the diode’s cathode lead. Check dark sides for T1 and T2 on the PC board drawing. For your schematic and parts layout diagrams when

each transformer (they are identical units), a total of six installing these diodes on the circuit board. Place all the solder connections should be made. The outer two tabs diodes on the circuit board in their respective locations are soldered to common ground for mechanical rigidity.

and solder them in place. The diode bridge on the right Install both transformers then solder the leads to the side of the schematic can be installed now. After

PC board, remembering to trim the excess leads.

soldering the diodes and the diode bridge in place in Next locate and install the electret microphone MK1.

their respective locations, remember to cut the excess The electret microphone will have either two or three component leads with your end-cutters, flush to the

leads. The ground lead is often obvious and is

edge of the circuit board. Note, if you plan to using the connected to the body of the microphone. Observe the

project as a telephone speaker-phone, install Zener

correct polarity, then go ahead and install the

diode D5 (small gray body with black band). The

microphone on the PC board. Now, locate the On-off

banded end marks the cathode and must be oriented as

switch at S1 and the Mute switch at S2; the prototype illustrated. If you plan to use your speaker-phone only project used DPST pushbutton switches, but you could

as a duplex intercom, do not install D5. Place it in a elect to use toggle switches for these if you cannot

safe place for possible future use.

locate the pushbutton switches. Finally, locate and

The main speaker-phone circuit also contains two

install the subminiature phone jack at J1, the modular ICs. The main speaker-phone chip at U1 is the 28 pin

phone jack at J1, and the potentiometer at R18 on the Motorola MC34118 chip. IC number U2 is an

edges of the circuit board. Solder these components to LM386 audio amplifier chip. ICs are often static

the circuit board.

sensitive, so they must be handled with care. Use

Once the main Speaker-phone circuit board has been

a grounded anti-static wrist strap and stay seated

completed, take a short break and then we will inspect in one location when handling the ICs. Take out a

the PC board for possible “cold” solder joints and

cheap insurance policy by installing IC sockets for

“short” circuits. Pick up the PC board with the foil side each of the ICs. In the event of a possible circuit

facing upwards toward you. Carefully inspect the solder failure, it is much easier to simply unplug a defective joints, these should look smooth, clean, and bright. If IC, than trying to unsolder 14 or more pins from a

any of the solder joints look dull, dark, or blobby, then PC board without damaging the board. Integrated

you should remove the solder with a solder sucker or a circuits have to be installed correctly if the circuit is solder wick and then resolder the joint all over again.

going to work properly. IC packages will have some

Now we will inspect the PC board for possible short

sort of markings which will help you orient them on

circuits. Short circuits can be caused from small solder the PC board. An IC will have either a small indented blobs bridging the circuit traces of from cut component circle, a cutout, or notch at the top end of the IC

leads which can often stick to the circuit board once they package. Pin 1 of the IC will be just to the left of

have been cut. A sticky residue from solder will often the notch or cutout. Refer to the manufacturer’s

trap component leads across the circuit traces. Look

pin-out diagram, as well as the schematic when

carefully for any bridging wires across circuit traces.

installing these parts. Accidental reversal of pin

Once this inspection is complete, we can move on to

insertion can cause the integration to fail. If you

installing the circuit board into an aluminum enclosure.

doubt your ability to correctly orient the ICs, then

Locate a suitable enclosure to house the circuit board.

seek the help of a knowledgeable electronics

Arrange the circuit board and the transformer on the

enthusiast.

bottom of the chassis box. Now, locate four 1 / 4′′

Next, locate transformers T1 and T2 and place them

standoffs, and mount the PC board between the

on the circuit board. Both transformers are miniature standoffs and the bottom of the chassis box. If you

100 to 8 ohm types. Examine the audio transformers, T1

selected a conventional relay you will have to mount it Chapter Twenty-Three: Speaker-Phone Project

238

Chapter Twenty-Three: Speaker-Phone Project

on the chassis and wire it to the PC board. If you

“transmit” there will be a short delay or “pumping”

selected a non-PC board transformer then you will have effect as you move from talking to listening. Do not

to mount the transformer to the base of the chassis box forget to “hang up” when you are finished.

and wire it to the circuit board. Locate a 9-V battery holder and mount it to the bottom of the plastic box and Initiating speaker-phone calls

solder the battery clip wire to the circuit board.

While the MC34118 IC makes provision for adding a

Speaker-phone setup and

DTMF tone dialer, for the simplest and least expensive approach, rate an ordinary telephone set as part of our use—phone mode

Speaker-phone installation. The average electronics buff is well aware that suitable phones are abundant at

Connect up the telephone line to the Speaker-phone

negligible cost, often with memory and other handy

circuit, install the 9-V battery, plug in an 8-ohm speaker features. Simply connect the auxiliary phone and your to the output jack J2, and you will be ready to test the speaker-phone to the phone line with a commonly

speaker-phone for the first time. First, set both S1 and S2

available dual-modular adapter, or use a dual wall jack, to their “out” or off position. Set the volume control to a etc. Use the auxiliary phone for dialing, incoming rings mid-range point. Next, test the modular phone cord you and situations where you prefer a handset. Enjoy the

intend to use with the speaker-phone, even if it is brand Speaker-phone for efficient, hands-free communication.

new. Do this simply by trying it on another telephone.

Be sure to hang up the auxiliary phone after turning on Then, connect the cord between the speaker-phone’s

your Speaker-phone.

telephone jack at J1 and a working, correctly-wired phone jack. (Defective modular plugs, cords, or jacks are a major cause of telephone malfunction.) If you have not yet

Optimizing your speaker-phone

connected your external speaker, then connect a speaker to the circuit board. For decent audio quality, use a speaker There are three variables to be considered in any

at least 3′′ in diameter. A properly enclosed speaker will line-powered Speaker-phone installation: The first

sound better and louder than a speaker lying naked on a concern is the positioning of the speaker in relation to workbench.

the microphone. Next, you must consider your distance Now press S1 to the “in” (On) position. You should hear from the telephone switching complex which supplies

a normal dial tone. Adjust volume control as desired. If line voltage. (If the voltage is marginal because you are you do not get a dial tone, recheck all your work, starting on a distant point of the phone company “loop,”

with the phone line and speaker wires. With S1 still on, tap supplementary battery power may be needed for this or the microphone and you should hear the sound in the

any other Speaker-phone.) You must also consider the

speaker. Speak in a normal tone of voice near the

basic “talk power” of the party on the other end. Let’s microphone, and the dial tone should drop out when you consider the three details. First, if your Speaker-phone speak and return when you are quiet. With S2 (Mute/Hold) works perfectly from the moment you set it up, then

pressed IN, you should still hear the dial tone, but the you are in great shape. Otherwise, consider the

microphone should not respond even to a loud yell.

following: In general, some degree of acoustical

Finally, turn S1 to the OFF position; this is the

separation must be provided between microphone and

equivalent of putting a phone handset back “on the

speaker. Put simply, they should not “point” at each

hook.” If everything above checks out, you are ready for other, or there will be some form of oscillation or erratic your first speaker-phone conversation. Ask someone to operation. Some experimenting may be needed.

call you. When you hear the ringing (on any other

Usually, telephone line voltage is sufficient for good phone), you can answer the call by pressing S1. You

Speaker-phone performance. However, the available

should be able to carry on a normal chat while you are voltage is determined by the distance of your location anywhere in an average-sized room. Be aware that since from the central office and local factors. The easiest way the Speaker-phone is switching between “receive” and

to determine if a supplementary battery is needed is just 239

to try it out. Please study the section Installing Optional speaker positioning is more subtle; greatly reduced

Battery before making any type of battery connection. If speaker volume, erratic switching action, possibly with the battery improves performance, then continue using it a slight ringing sound.

for that particular location. It is switched in and out of the circuit by the “B” section of S1.

Intercom operation

Finally, you may encounter situations where the

person on the other end is just not speaking loud

Two Speaker-phone units may be used as a hands-free

enough for positive SP1 switching between receive and half-duplex wired intercom system. This offers many

transmit. This can be caused either by the other party’s handy problem-solving applications for home and

use of a poor-quality phone or just because they are

business alike. If you have the practical application, we speaking too softly. You may need to ask them to try a see no reason why additional units could not be put “on different phone, or just to speak up, or to speak more line.” Phone-line Speaker-phone operation need not be directly into their handset microphone; or redial for a sacrificed in such local intercom installations. If you better connection.

successfully built one or more Speaker-phones, you

probably already have some handy switching ideas. We

will leave those to your ingenuity.

Notes on speaker placement

To set up two Speaker-phone circuits for hands-free

In general, the Speaker-phone’s speaker audio will

intercom service, just do the following: First, solder a sound best if the speaker is of reasonably good size and jumper from A to B. Interconnect both units with a

quality and is properly enclosed or “baffled.” It should modular phone extension cord, or any other 2-wire pair face the same direction as the microphone or away from practical for your setup. Interconnection of further units it, not directly at it. Remember that it is a basic function is up to user testing and experimenting. In general, keep of the Speaker-phone to detect incoming audio and

all “tip” and “ring” lines common to each other.

quickly attenuate the microphone circuit. Therefore,

The Speaker-phone is designed using the latest

audio feedback of the familiar “squealing” kind is not a Motorola chip-set and should serve you and your family common occurrence. The feedback resulting from poor

for many years into the future.

Chapter Twenty-Three: Speaker-Phone Project

240

Chapter 24

Telephone Scrambler

C13, C15

470 μF, 35 V,

Parts list

electrolytic capacitor

U1

74HC86 – quad

Telephone Scrambler

2¯input exclusive

R1

2.2 megohms, 1⁄ W,

4

OR gate

5% resistors

U2, U7

74HC161 –

R2, R3

470 ohms, 1⁄ W,

4

synchronous 4¯bit

5% resistors

binary counter

R4, R5

100 ohms, 1⁄ W,

4

U5, U6

TP3054N codec

5% resistors

(National)

R6, R7

22 K ohms, 1⁄ W,

4

U8

LM7905; −5 V

5% resistors

regulator

R8, R10, R14, R15, R17

U9

LM7805; +5 V

1 K ohms, 1⁄ W,

4

regulator

5% resistors

Q1

2N3565 or 2N3904 NPN

R12

8.2 K ohms, 1⁄ W,

4

transistor

5% resistors

S1, S2

DPDT switch

R13

1 K ohm

J1, J2

RJ¯11 –

potentiometer

4¯conductor modular

R16

10 K potentiometer

phone jack

R18, R19, R20

10 K ohms,

J3

1

⁄ inch coaxial

8

1

⁄ W, 5% resistors

4

power jack

R21

33 K ohms, 1⁄ W,

4

XTL

3 MHz crystal

5% resistors

(2.5–4 MHz¯ usuable)

C1

22 pF, 35 V,

Misc

PC board, wire,

NPO capacitor

6–14 V, 100 ma power

C2, C3

82 pF, 35 V,

supply, IC sockets,

NPO capacitor

enclosure, etc

C4, C5, C11, C14,

There are many situations when you wish you had a

C16

.01 μF, 35 V disc

Telephone Scrambler for privacy or security. The

military has long been known for using sophisticated

C6, C9, C10

1 μF, 35 V,

voice-scrambling systems, but there is a definite need for electrolytic capacitor

less costly ones in everyday life, in order to discourage C7, C8

10 μF, 35 V

the casual eavesdropper. The voice-encryption systems, electrolytic capacitor

or the voice scrambler described here inverts the

C12

470 pF, 35 V, disc

frequency spectrum of the speech, either side of a

241

Copyright © 2009 by The McGraw-Hill Companies, Inc. Click here for terms of use.

will be made intelligible only with the correct

descrambler.

This method of speech scrambling is accomplished

by mixing the audio input to be scrambled with a carrier tone, as shown in Figure 24-2.

The mixing process is carried out with a balanced

modulator, which results in a double-sideband

Figure 24-1

Telephone scrambler system. Courtesy of

suppressed-carrier signal. The two resulting sidebands Poptronix

are the lower sideband audio frequencies in the voice range (about 150–3,000 Hz) and upper sideband

reference frequency to scramble the audio, and reinverts frequencies (about 3,000–7,000 Hz).

it to descramble the speech, see Figure 24-1.

Since most voice circuits are designed for frequencies Although the system is intended primarily to scramble in the lower sideband range, the upper sideband is filtered telephone conversations, it is not limited to that.

out. The lower sideband contains frequencies that are The device can also scramble tape recordings, which

similar to the original voice frequencies, but it has an Output

spectrum

from mixer

Lower

Upper

sideband

sideband

300 Hz

5700 Hz

Scrambled

Balanced mixer

audio output

300 Hz

spectrum

LPF

Audio input

0–2700 Hz

150 –2700 Hz

Upper

sideband

rejected

DSC

3000 Hz

Scrambling

Lower

Upper

sideband

sideband

150 Hz

5850 Hz

Unscrambled

audio output

spectrum

300 Hz

LPF

300 Hz

2850 Hz

0–2700 Hz

Upper

Scrambled

sideband

audio input

rejected

DSC

3000 Hz

300–2850 Hz

Chapter Twenty-Four: Telephone Scrambler Figure 24-2 Scrambler block diagram. Courtesy of Poptronix 242

Chapter Twenty-Four: Telephone Scrambler

inverted spectrum. Assuming a 3,000-Hz carrier signal, more than double the highest audio frequency (2,700 Hz).

an input signal of 500 Hz will produce a 2,500-Hz

Every second eight-bit digitized audio sample has its sign output, and a 1-KHz signal will produce a 2-KHz output.

bit inverted while being fed to a digital-to-analog

The spectral energy of a human voice is more

converter. That has the effect of inverting the spectrum of concentrated at the ends of the voice spectrum, mainly the analog output signal after conversion from the

the 300–l,000 Hz range, and somewhat less in the

digitized audio. The signal is then fed to a bandpass filter 2,000–2,500 Hz range. The resulting output will therefore to remove switching components, leaving the final audio have a very high pitched sound, and be unintelligible. It signal as one that corresponds to the input signal, except can, however, be carried over normal telephone lines

that its spectrum is folded around one fourth of the

without being understood by eavesdroppers.

sampling frequency or 1,465 Hz.

A digital voice-scrambling method is used in the

In Figure 24-3 it can be seen that a 1-KHz sine-wave

circuit because it requires fewer parts than an analog sampled as shown, with even- numbered samples inverted, system, needs no adjustment, and requires no switching.

results in a lower-frequency sine-wave (b). The process Because the descrambling process is the inverse of the also works in reverse; if the lower-frequency waveform scrambling process, the same circuit can be used for

(2-b) is sampled at the same points, and alternate samples both functions. The encryption system has two channels inverted, the original waveform can be regenerated.

for full-duplex operation, which allows easy two-way

communication. Note that two complete systems at each end of a phone line are required for two people to carry Circuit description

on a scrambled conversation.

An audio input signal is first filtered with an active The voice scrambler/descrambler schematic is

switched-capacitor bandpass filter to limit the frequency illustrated in Figure 24-4. Two National Semiconductor range to between 150 and 2,700 Hz. The signal is then TP3054 coder/decoder, or codec chips,—form the heart

digitized with a sampling rate of 5.86 KHz, which is

of the telephone scrambler circuit.

Frequency = 1/τ Cycles per second

+

4

12

1

7

9

Time

2

10

1 KHz

6

Sample

Sine

3

5

11

wave

13

8

Time

Freq = 1/τ

τ Cycles per second

Figure 24-3

Sampled 1-KHZ sine wave. Courtesy of Poptronix

243

+5 V

+5 V

14

10

U2:b

9

4

C5

11

8

5

3

5

C4

C

LD 9

A

C

13

12

4

U3

7

1

6

U1:b

U4

B

ET

CL

D

13

14

9

U2:a

3

10

10

9

11

8

A

ED

4

5

ET

LD

1

16

7

16

10

12

U1:a

CL

VCC

ED

VCC

3

6

15

8

15

2

2

CLK

CD

CLK

CD

1.5 mHz 750 kH

GND

GND

R4

C2

C1

XTC

C3

7

2

2

Jump

R1

C12

+5 V

1

3

U9

+5 V

4

6–14 V AC

D1

+

3

C13

C14

5

11

12

75 mA

2

CLK

Q

CLK

D

1

U7:a

6

13

U7:b

9

Q

a

2

8

D

Q

Pwr

U8

−5 V

in

D2

C15

C16

+

+5 V

U1:D

U1:C

+5 V

4

5

12

5

12

R2

1

R3

6

TSX

8

8

TSX

6

DR

9

U6

5

9

3

2

6 11

U5

+

DX 11

R9

DX

10

10

CLKS

R11

14

C7

14

4

−5 V

4

15

VBB

VBB

15

2

2

GND

GND

R10

R8

7

7

Audio

R16

R15

R5

R13

3 Audio

R6

out

C9 R17

R14

R7

C10

out

Audio 16

Audio

16

+5 V

in

in

VCC

RX

+

+

Level

XMIT

1

1

level

+

Incoming audio

C8

C11

R18

from phone

To

handset

R21

Scram

R19

Normal

S1

C6

R20

J1

Q1

+

R12

Mic hot

S2

J2

Audio in

RX hot

Figure 24-4

Phone scrambler schematic. Courtesy of Poptronix

The two integrated circuits, U5 and U6, contain all of and fed about 75 mA of isolated, low voltage AC

the necessary A/D and D/A converters, switched-capacitor from a wall-mounted transformer Do not connect the

filters, and associated tuning and control circuitry.

unit to the AC line without such a suitable isolating The scrambler’s “ground” must be isolated with

transformer

respect to true earth ground. Therefore the PC board of Most of the rest of the circuit is clock and control

Chapter Twenty-Four: Telephone Scrambler the scrambler should be mounted on insulated standoffs circuitry that supports the two codecs. The clock signal 244

Chapter Twenty-Four: Telephone Scrambler

is generated by an oscillator made up of 3-MHz crystal

+12 V

XTL and U1:a and U1:b. The 3-MHz signal is divided

in half by U2:a to produce the main 1.5-MHz clock

+

signal, and U2:b again divides by 2 to produce an

470 μF

optional clock frequency of 750 KHz. That signal is

Audio

10 K

input

further divided down by U3 and U4 to produce 5.86- and 3

6

470 μF

2.93-KHz signals. The D-type flip-flop at U4 produces a 5

+

2 Lm386w

2.93-KHz pulse train that is used for bit-sign inversion.

Speaker

4

The 5.86-KHz pulse shifts a serial data stream, eight 10 Ω

clock pulses wide, from the codec’s A/D converter to

the D/A converter. Data from an A/D converter (pin l1

of U5 or U6) is fed to U1:d or U1:c, respectively.

.1 μF

These Exclusive OR gates act as inputs, and are held

high, or as straight-through non-inverting buffers if the Figure 24-5

Audio amplifier

opposite input is held low. By applying a 2.93 KHz

pulse on one input, alternate data-stream sign bits

telephone circuit. Resistor Rl3 sets the sound level at (which occur at a 5.86 KHz rate) are inverted.

the telephone receiver and Rl is set for optimum

Therefore, the data from pin 11 of U5 (or U6) that is reception at the other end of the telephone line.

fed back to the D/A converter section (pin 6) has every other sample reversed in sign. That has the

Figure 24-6 shows two more possible applications

aforementioned effect of inverting the frequency

using the Telephone Scrambler circuit; 6-a shows how

spectrum of the reconstructed analog signal.

the system can be used to make scrambled audio

recordings, and 6-b shows how a radio transceiver can The circuitry required to interface the voice-encryption be fitted with this device.

system to a telephone to the scrambler circuitry is

shown on the bottom right of the schematic. Resistor

Rl7 couples audio from amplifier Q1 to U5. Transistor Scrambler

Q1 provides about 10 dB voltage gain.

Mic input

In

Ch1 Out

Modular jacks J1 and J2 connect Sl and S2 via

Microphone

jumpers that are configured for your particular

Out Ch2

In

Earphone

telephone set. Because direct insertion of the device in a Descrambler

output

Casette

telephone line would not be feasible without a lot of Headphones

recorder

switching due to ringing and signaling considerations, it is necessary to install this device in the handset line.

Speaker

This way, only the microphone and earphone have to be A

considered. The TP3054 transistor can drive a 600 ohm load (the impedance of a telephone line) directly if

telephones are not being used; simply use the input and Scrambler

output pins of each codec directly. To have the chip

Mic input

In

Ch1 Out

drive a loudspeaker a small audio amplifier such as that Microphone

Radio

transceiver

shown in Figure 24-5 is required.

Out Ch2

In

Note that when using a microphone to input audio to

Speaker

Descrambler

output

the codec, some microphones have internal audio

Headphones

amplifiers and can produce well over one volt of audio.

Those microphone outputs can be input directly to the Speaker

codec. Low-output microphones require amplification.

B

A switching network (S1 and S2) is added on the

PC board to switch the scrambler in or out of the

Figure 24-6

Scrambler recording. Courtesy of Poptronix

245

(Bear in mind that in services such as amateur radio, it solder the lowest height components first, the resistors is illegal to use encryption. so check FCC rules to verify and diodes. First, locate our first resistor R1. Resistor R1

the legality for any intended application.)

has a value of 2.2 megohms and is a 1 / 4 W 5% tolerance type. Now take a look for a resistor whose first color band is red, red, green, and gold. From the chart you will Circuit assembly

notice that red is represented by the digit (2), and again the second band is red, which is represented

Before we begin constructing the Telephone Scrambler, by (2). Notice that the third color is green and the

you will need to locate a clean, well-lit worktable or multiplier is (100,000), so (2) (2) × 100,000 = 2,200,000

workbench. Next we will gather a small 25–30 W

or 2.2 megohm. Place R1 on the PC board in its

pencil tipped soldering iron, a length of 60/40 tin–lead respective location and solder it in place. Then take a pair solder, and a small canister of Tip Tinner, available at of end-cutters and trim the excess resistor leads flush to your local RadioShack store; Tip Tinner is used to

the edge of the circuit board. Now locate the remaining condition the soldering tip between solder joints. You resistors and install them in their proper locations on the drive the soldering tip into the compound and it cleans PC board. Solder them all in place and then remember to and prepares the soldering tip. Next grab a few small trim the excess leads with your end-cutters.

hand tools, and try to locate small flat blade and

Note that capacitors generally come from two major

Phillips screwdrivers. A pair of needle-nose pliers, a groups or types. Non-polar types, such as the ones in pair of tweezers along with a magnifying glass, and a this project, have no polarity and can be placed in either pair of end-cutters and we will begin constructing the direction on the circuit board. The other type of

project. Now locate your schematic diagram and parts

capacitors are called polarized types, these capacitors layout diagram along with all of the components needed have polarity and have to be inserted on the board with to build the project. Once all the components are in

respect to their polarity marking in order for the circuit front of you, you can check them off against the project to operate correctly. On these types of capacitors, you parts list to make sure you are ready to start building the will observe that the components actually have a plus or project. The Telephone Scrambler can be constructed

minus marking or a black or white band with a plus or on a double-sided printed circuit board. Because the

minus marking on the body of the capacitors.

PC board does not have plated-through holes, first install through-board jumpers at all locations marked with an Now locate the capacitor chart shown in Table 24-2;

“X,” and solder them on both sides of the board. All

this chart will help you identify small capacitors which component leads that pass through a hole with copper

may be marked with only a three-digit code instead of on both sides must also be soldered on both sides.

an actual value.

Table 24-1 illustrates the resistor code chart and how Locate the capacitors from the component pile and

to read resistors. Note that each resistor will have either try and locate capacitor C1, which should be marked

three or four color bands, which begin at one end of the 22 p or 22 pF, or from the capacitor chart you may see resistor’s body. The first colored band represents the 220 marked on the capacitor body. Now take your

resistor’s first digit, while the second color represents the end-cutters and cut the excess component leads flush to second digit of the resistor’s value. The third colored the edge of the circuit board. Once you have installed band represents the resistor’s multiplier value, and the the first capacitor, you can move on to installing the fourth color band represents the resistor’s tolerance remaining capacitors onto the circuit board; solder them value. If there is no fourth colored band then the resistor in place and then remember to trim the excess leads.

has a 20% tolerance value. If the resistor’s fourth band is Next locate and install the remaining capacitors, first silver then the resistor has a 10% tolerance value and if installing the low profile capacitors followed by the the fourth band is gold then the resistor’s tolerance value larger electrolytic capacitors. Use good quality

will be 5%.

electrolytic or tantalum capacitors. Remember the larger With your PC board in front of you, we can now begin

electrolytic capacitors have polarity which must be

populating the circuit board. We are going to place and observed if the circuit is to work properly. Failure to Chapter Twenty-Four: Telephone Scrambler

246

Chapter Twenty-Four: Telephone Scrambler

Table 24-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

No color

20%

Table 24-2

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

1.0

1R0

3,900

3.9

.0039

392

1.2

1R2

4,700

4.7

.0047

472

1.5

1R5

5,600

5.6

.0056

562

1.8

1R8

6,800

6.8

.0068

682

2.2

2R2

8,200

8.2

.0082

822

2.7

2R7

10,000

10

.01

103

3.3

3R3

12,000

12

.012

123

3.9

3R9

15,000

15

.015

153

4.7

4R7

18,000

18

.018

183

5.6

5R6

22,000

22

.022

223

6.8

6R8

27,000

27

.027

273

8.2

8R2

33,000

33

.033

333

10

100

39,000

39

.039

393

12

120

47,000

47

.047

473

15

150

56,000

56

.056

563

18

180

68,000

68

.068

683

22

220

82,000

82

.082

823

27

270

100,000

100

.1

104

33

330

120,000

120

.12

124

39

390

150,000

150

.15

154

47

470

180,000

180

.18

184

(Continued)

247

Table 24-2—cont’d

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

56

560

220,000

220

.22

224

68

680

270,000

270

.27

274

82

820

330,000

330

.33

334

100

.0001

101

390,000

390

.39

394

120

.00012

121

470,000

470

.47

474

150

.00015

151

560,000

560

.56

564

180

.00018

181

680,000

680

.68

684

220

.00022

221

820,000

820

.82

824

270

.00027

271

1,000

1

105

330

.00033

331

1,500

1.5

155

390

.00039

391

2,200

2.2

225

470

.00047

471

2,700

2.7

275

560

.00056

561

3,300

3.3

335

680

.00068

681

4,700

4.7

475

820

.00082

821

6.8

685

1,000

1.0

.001

102

10

106

1,200

1.2

.0012

122

22

226

1,500

1.5

.0015

152

33

336

1,800

1.8

.0018

182

47

476

2,200

2.2

.0022

222

68

686

2,700

2.7

.0027

272

100

107

3,300

3.3

.0033

332

157

157

Code = 2 significant digits of the capacitor value + number of zeros to follow 10 pF = 100

For values below 10 pF, use “R” in place of decimal e.g. 8.2 pF = 8R2

100 pF = 101

1,000 pF = 102

22,000 pF = 223

330,000 pF = 334

1 μF = 105

install the electrolytic capacitors correctly can damage You will notice that each diode will have a black or

the component or other components when power is first white colored band at one edge of the diode’s body.

applied to the circuit upon power-up. Install the

The colored band represents the diode’s cathode lead.

capacitors in their correct positions on the PC board, Check your schematic and parts layout diagrams when

and then solder them in place. Next trim the excess

installing these diodes on the circuit board. Place all the component leads flush to the edge of the circuit board diodes on the circuit board and solder them in place. Then using your end-cutters.

cut the excess component leads with your end-cutters.

The Phone Scrambler project contains two silicon

The telephone Scrambler circuit utilizes single NPN

diodes. These diodes also have polarity which must

transistors at Q1. Transistors generally have three leads, Chapter Twenty-Four: Telephone Scrambler be observed if the circuit is going to work correctly.

a Base lead, a Collector lead and an Emitter lead.

248

Chapter Twenty-Four: Telephone Scrambler

Refer to the schematic and you will notice that there U4, pins 5 and l2 of U5, and U6. Check for 2.93-KHz

will be two diagonal leads pointing to a vertical line.

pulse train at pin 1 U1:c and pin 4 of U1:d. Due to the The vertical line is the transistor’s base lead and the two short pulse width (250 nanoseconds), it might be difficult diagonal lines represent the collector and the emitter.

to see these pulses with an economy model oscilloscope.

The diagonal lead with the arrow on it is the emitter If all checks out, apply a 0.5-V peak-to-peak,

lead, and this should help you install the transistor on to 1-KHz tone to the junction of R17 and C9:a; a 2 KHz

the circuit board correctly. Go ahead and install

tone should be produced by U5. Now temporarily

transistor Q1 on the PC board and solder it in place.

connect pin 3 of U5 to the junction of C10 and Rl4

Now follow-up by cutting the excess component leads

using a 100 K resistor. Pin 3 of U6 should produce the from Q1 and Q2, with your end-cutters.

original 1-KHz tone.

The Scrambler utilizes a number of ICs. ICs must

Next apply an audio signal from a tape deck or

be handled carefully and installed properly in order

radio with about 2 V peak-to-peak to the junction of

for the circuit to work perfectly. Use anti-static

Rl7 and C9. Listen to the output at pin 3 of U5; it

techniques when handling the ICs to avoid damage

should sound “scrambled.” Now listen to the output of from static electricity when moving about and

channel 2. It should be normal, but note that the high installing it. It is wise to install IC sockets as a cheap and low frequencies might sound somewhat attenuated

form of insurance against a possible circuit failure at due to the narrow band-width of the system.

some later point in time. Install the IC sockets on the PC board and solder them in place. Each integrated

Adapting a phone

circuit has a locator either in the form of a small

indented circle, or a notch, or cut-out at the top end Note that this unit cannot be connected directly to the of the IC package. Pin 1 of the IC will be just to the phone lines. It will handle speech audio, but not pass left of the locator. Go ahead and install the ICs into ringing signals or rotary dialing pulses. It will also their respective IC sockets.

distort dialing tones. You must use only a phone whose Now is a good time to take a short break. After the

handset has accessible microphone and receiver

break we will inspect the circuit board for any possible connections. You cannot use a unified telephone (where

“cold” solder joints or “short” circuits. Take a careful the dial or pad is built into the handset). The handset look at each of the PC solder joints, they should all look should preferably have an elecret microphone. However, clean and shiny. If any of the solder joints look dull, carbon microphones (found in older phones) can be

dark, or blobby, then you unsolder the joint, remove the used, if necessary, but R19 should be changed to about solder and then resolder the joint all over again. Next, 1 K, and R20 may have to be increased if excessive

examine the PC board for any short circuits. Short

audio from a carbon microphone over-drives Q1,

circuits can be caused from two circuit traces touching causing distortion.

each other due to a stray component lead that stuck to Depending on the phone you have, you must make

the PC board from solder residue or from solder blobs the proper jumper connections on the PC board near JI bridging the solder traces.

and J2. A Radio Shack telephone model No. ET-l7l (cat Before the ICs are inserted in their sockets, apply 6 to No. 43-374) was used in the prototype. You must

l2 V AC to the junction of D1 and D2 and ground.

identify the following things on your phone(s).

Check for 5 V at pin 4 of U5 and U6, and pin l6 of U2, U3, and U4, and pin 14 of U1. Next, verify −5 V at pin 1.

The handset microphone and earpiece connections

1 of U5 and U6. If these voltages check out, insert the 2.

The type of microphone (electret, dynamic, or carbon) ICs into their sockets.

3.

Microphone polarity if it is the electret type

4.

The base connections.

Testing

There are usually four wires that connect a telephone Verify that a 5-V peak-to-peak 1.5-MHz signal exists at handset to its base. If you cannot visually identify the pin 2 of U3. Check for a 5.8 KHz pulse train at pin 15 of wires after disassembling the handset, try connecting 249

a 1.5-V battery to alternate pairs of wires on the

The telephone base connections can to be determined

handset until you hear a click in the earpiece. Mark

from the positions of the handset leads at the modular these as the receiver leads; there should be between

connector. When you have all of the telephone

50 and l,000 ohms between them. The other two leads

connections identified, install the jumpers

are for the microphone.

on the PC board near jacks J1 and J2. Once you

Check for short circuits between both of the receiver know the signal positions at jacks J1 and J2 for your leads and the microphone leads with an ohmmeter on a

phone, install four jumpers per jack to properly route high resistance range. A low resistance or a short between the signals.

any two leads indicates that they are the ground leads for The finished board can be mounted in a suitable case.

the microphone and receiver. If the microphone works, The case pictured allows the telephone to be placed on all is well; if not, reverse the microphone connections.

top of the scrambler without taking up any extra space.

This will identify the microphone’s hot and ground

With a pair of scrambler phones in hand, you are ready leads. Once you have identified all of the handset

to start talking. All you need now is someone to talk to, leads, note their positions on the modular connector.

and a confidential topic to discuss.

Chapter Twenty-Four: Telephone Scrambler

250

Chapter 25

Telephone Tattletale

C7

47 μF, 15 V

Parts list

electrolytic capacitor

C8, C9, C10

.01 μF,

Telephone Tattletale

15 V ceramic capacitor

R1, R2, R3

10 K ohms,

D1, D2, D3, D4

1N2069

1

⁄ w, 5% resistor

4

silicon diode

R4

1.5 megohms, 1⁄ W,

4

D5

1N2070 silicon diode

5% resistor

D6, D7, D8

1N4148

R5, R8

1 megohm, 1⁄ W,

4

silicon diode

5% resistor

U1

CD4002B dual 4

R6

390 K ohms, 1⁄ W,

¯input

4

NOR gate IC

5% resistor

U2, U3

CD4081B quad

R7

22 ohms, 1⁄ W,

4

2

5% resistor

¯input AND gate IC

U4, U7, U8, U9

LM555

R9, R10, R11

100 K ohms,

timer IC

1

⁄ W, 5% resistor

4

U5

CD4040B 12 stage

R13

2.2 K ohms, 1⁄ W,

4

binary counter IC

5% resistor

U6

CD4011B quad 2

R14

150 ohms, 1⁄ W,

¯input

4

NAND gate IC

5% resistor

Q1

MPSA42 300 volt NPN

R15

39 K ohms, 1⁄ W,

4

silicon transistor

5% resistor

Q2

2N3904 NPN silicon

R16

15 K ohms, 1⁄ W,

4

transistor

5% resistor

LED1

red LED

R17

680 ohms, 1⁄ W,

4

5% resistor

T1

transformer – 115 V

primary/6.3 V @

C1

1,000 μF, 15 V

300 mA secondary

electrolytic capacitor

Z1

Varistor

C2

.47 μF, 15 V

ceramic capacitor

F1

fuse 1¯ampere

C3

.22 μF, 15 V

S1

SPST toggle or slide

ceramic capacitor

switch

C4, C5, C6

.1 μF,

S2, S3, S4

normally

200 V ceramic or mylar

open sensors

251

Copyright © 2009 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Misc

PC board, wire,

you that one of the switches has been tripped. The

IC sockets, terminal

number of beeps indicates which switch, and you have

strips, enclosure, etc.

the option of taking action or not as you see fit.

Do you ever wonder what’s happening at your home or

Tattletale will continue to report to you for about a business while you are away? Does the thought of

minute. Then it will hang up, ready to answer when you break-in, fire, or other calamity worry you? If so,

call again. You may check Tattletale’s status as often as Tattletale, shown in Figure 25-1, is just what you need.

you like.

This remarkable device is able to report to you, no

matter how far away you are, on the condition of your Circuit details

home or business. All it takes is one phone call. With Tattletale at your service, you will be able to monitor up The Tattletale phone monitor circuit is illustrated in to three possible emergency situations and have your

Figure 25-2. The Tattletale circuit contains two sections.

telephone report back to you when you call. Tattletale is The first part is the logic section composed of U1

completely automatic and easily activated each time you through U8. The remainder of the circuitry is used to leave your home or business. A convenient LED

answer the telephone call and place the tones on the

indicator provides visual indication that Tattletale is telephone line. Each of these sections is discussed in armed and ready to answer that inquiring call.

detail. The logic section of the circuit starts with a NOR

Emergency situations such as fire, break-in, heating

gate U1:a, which is used as a detector to determine if any system failure, and flood can be easily monitored by

of the sensing switches has been tripped. If all sensing connecting three independent normally open switches or switches are normal, U3:a is enabled and the second

thermostats to Tattletale’s three sensing terminals.

output of U5 (pin 7) is coupled through U3:a and U1:b Normally closed switches can also be used by making a to trigger one-shot multi-vibrator U7. Should any of the simple circuit modification. The type of emergency

sensing switches be activated, U3:a is disabled and one which Tattletale can monitor is limited only by your

of the succeeding outputs of U5 will trigger U7 in a

imagination.

similar manner.

Operation of this unit is very simple. It is activated by Integrated circuit U8 is an astable multi-vibrator

throwing the power switch on before you leave the

operating at a frequency of about 3 Hz. The output of premises. When you wish to check on the condition of

U8 clocks U5, a binary counter. The first output of U5

the sensing switches you call your number, and

(pin 9) is one half the clock frequency and each

Tattletale answers immediately. You will hear a series of succeeding output has a period which is twice as long as tones or beeps. One beep every couple of seconds

the preceding stage. The start of the reset pulse

indicates that all is well; two, three, or four beeps tells generated by U7 is determined by the output signal

from U5 that is permitted to pass through AND gates

U2 and U3, in accordance with the status of the sensing switches. In this way the count length of U5 is

controlled by the switches, and the signal at pin 9 of U5

will contain 1, 2, 3, or 4 pulses. These pulses are used to enable U9, a tone generator operating at a frequency of about 2,000 Hz. Since U7 holds U8 and U5 in reset

condition for one or two seconds each time it is

triggered, the tones generated by U9 are perceived by you to be in a group of 1, 2, 3, or 4 bursts.

In order to answer a telephone call, the circuit has

been designed to respond to the 90-volt, 20-Hz ringing Figure 25-1

Tattletale circuit board. Courtesy of

signal. U6:a and U6:b are connected in a latch circuit Cengage Learning

or flip-flop configuration, which has two stable states.

Chapter Twenty-Five: Telephone Tattletale

252

U3:A

1

14 3

2

7

6

U2:B

U1:B

9

4

8

R4

14

R1

5

4

10

2

3

S2

2

3

11

U7

13

5

7

5

U2:A

4

12

7

6

1

2

S3

1

R2

3

1

4

6

U3:B

C2

14

U1:A

12

5

13

7 11 U3:D

S4

4

8

R5

R3

3

2

3

2 4 13 12 14 15 1

U8

7

16

5

9 7 6 5

U5

6

1

10

8

S1

U3:C

F1

C3

11

9

D2

10

8

U6:C

P1

D1

10

9

8

D9

C1

R15

R7

C10

R17

Q1

D3

+

C4

D6

R9

14

U6:a

4

8

R12

4

8

R11

R13

2

2

3

3

T1

D4

1

3

D5

U4

7

U9 7

D7

5

R8

C6

2

Telephone

21

U6:A

R18

line

6

R

5

6

R16

1

1

Q2

14

+

4

R10

5

C9

6

7

C7

D8

C5

C8

U6:B

Figure 25-2

Tattletale circuit. Courtesy of Cengage Learning

253

e

l

a

t

e

l

t

t

a

T

e

n

o

h

p

e

l

e

T

:

e

v

i

F

-

y

t

n

e

w

T

r

e

t

p

a

h

C

When power is first applied to the circuit the logic level build the project. Once all the components are in front at the output (pin 4) of U6:b will be high. This applies of you, you can check them off against the project parts forward bias to Q2, switching it on and illuminating

list to make sure you are ready to start building the LED1 to indicate that the circuit is armed and ready.

project. Now, locate Tables 25-1 and 25-2, and place

The ringing signal which appears across the telephone them in front of you.

fine is applied to pin 1 of U6:a through C4 and R8.

Table 25-1 illustrates the resistor code chart and how This signal causes the latch circuit to change state. The to read resistors, while Table 25-2 illustrates the

negative-going output at pin 4 of U6:b then triggers

capacitor code chart which will aid you in constructing one shot multi-vibrator U4. The output at pin 3 of U4

the project.

then goes positive. The forward bias of Q1 causes this Refer now to Table 25-1 which illustrates the resistor transistor to conduct, connecting R14 across the

color code chart which will help you identify the

telephone line and answers the call. Since U4 has a time resistor values. Each resistor will have either three or period of about a minute, the circuit will hold the

four color bands, which begin at one end of the

telephone line for that time interval and then “hang up.”

resistor’s body. The first colored band represents the The negative-going waveform at pin 3 of U4 is used to resistor’s first digit, while the second color represents reset the latch circuit back to the armed mode so that it the second digit of the resistor’s value. The third colored is ready to answer another telephone call. The LED is band represents the resistor’s multiplier value, and the also illuminated again. During the time that Q1 is

fourth color band represents the resistor’s tolerance conducting, the tone bursts from U9 are fed to the base value. If there is no fourth colored band then the resistor of Q1. Thus, these tone bursts, which contain the audio has a 20% tolerance value. If the resistor’s fourth band information indicating the status of the sensing

is silver then the resistor has a 10% tolerance value and switches, are impressed upon the telephone line.

if the fourth band is gold then the resistor’s tolerance value will be 5%.

Construction

So let’s get started, now we are ready to begin

assembling the project. The prototype project was

The Tattletale project was constructed on a single-sided constructed on a single-sided printed circuit board or printed circuit board as illustrated. The prototype

PCB. With your PC board in front of you, we can now

circuit board used in this project measured about

begin populating the circuit board. We are going to

3-1⁄ × 4-1⁄′′. You may also construct this circuit on place and solder the lowest height components first, the 4

2

a perfboard, hard wiring the connections. Layout is

resistors and the diodes. First locate our first resistor R1.

not critical.

Resistor R1 has a value of 10 K ohms and is a 5%

Before we begin building the Tatttletale project, you tolerance type. Now take a look for a resistor whose

will need to locate a clean, well-lit worktable or

first color band is brown, black, orange, and gold. From workbench. Next we will gather a small 25–30-W

the chart you will notice that brown is represented by pencil tipped soldering iron, a length of 60/40 tin–lead the digit (1), and again the second band is black, which solder, and a small canister of Tip Tinner, available at is represented by (0). Notice that the third color is your local RadioShack store; Tip Tinner is used to

orange and the multiplier is (100), so (1) (0) × 100 =

condition the soldering tip between solder joints. You 10,000 ohms.

drive the soldering tip into the compound and it cleans Now, place resistor R1 on the circuit board in its

and prepares the soldering tip. Next grab a few small respective location, then solder it in place. Follow up by hand tools, and try to locate small flat blade and Phillips using a pair of end-cutters to trim the excess component screwdrivers. A pair of needle-nose pliers, a pair of leads flush to the edge of the circuit board. Next locate tweezers along with a magnifying glass, and a pair of the remaining resistors and place them on the circuit end-cutters and we will begin constructing the project.

board at their correct locations and solder them in place.

Now locate your schematic diagram and parts layout

Take your end-cutters and cut the excess component

diagram along with all of the components needed to

leads, flush to the edge of the circuit board.

Chapter Twenty-Five: Telephone Tattletale

254

Chapter Twenty-Five: Telephone Tattletale

Table 25-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

No color

20%

Table 25-2

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

1.0

1R0

3,900

3.9

.0039

392

1.2

1R2

4,700

4.7

.0047

472

1.5

1R5

5,600

5.6

.0056

562

1.8

1R8

6,800

6.8

.0068

682

2.2

2R2

8,200

8.2

.0082

822

2.7

2R7

10,000

10

.01

103

3.3

3R3

12,000

12

.012

123

3.9

3R9

15,000

15

.015

153

4.7

4R7

18,000

18

.018

183

5.6

5R6

22,000

22

.022

223

6.8

6R8

27,000

27

.027

273

8.2

8R2

33,000

33

.033

333

10

100

39,000

39

.039

393

12

120

47,000

47

.047

473

15

150

56,000

56

.056

563

18

180

68,000

68

.068

683

22

220

82,000

82

.082

823

27

270

100,000

100

.1

104

33

330

120,000

120

.12

124

39

390

150,000

150

.15

154

47

470

180,000

180

.18

184

(Continued)

255

Table 25-2—cont’d

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

56

560

220,000

220

.22

224

68

680

270,000

270

.27

274

82

820

330,000

330

.33

334

100

.0001

101

390,000

390

.39

394

120

.00012

121

470,000

470

.47

474

150

.00015

151

560,000

560

.56

564

180

.00018

181

680,000

680

.68

684

220

.00022

221

820,000

820

.82

824

270

.00027

271

1,000

1

105

330

.00033

331

1,500

1.5

155

390

.00039

391

2,200

2.2

225

470

.00047

471

2,700

2.7

275

560

.00056

561

3,300

3.3

335

680

.00068

681

4,700

4.7

475

820

.00082

821

6.8

685

1,000

1.0

.001

102

10

106

1,200

1.2

.0012

122

22

226

1,500

1.5

.0015

152

33

336

1,800

1.8

.0018

182

47

476

2,200

2.2

.0022

222

68

686

2,700

2.7

.0027

272

100

107

3,300

3.3

.0033

332

157

157

Code = 2 significant digits of the capacitor value + number of zeros to follow 10 pF = 100

For values below 10 pF, use “R” in place of decimal e.g. 8.2 pF = 8R2

100 pF = 101

1,000 pF = 102

22,000 pF = 223

330,000 pF = 334

1 μF = 105

Next we will identify and install the capacitors for the will observe that the components actually have a

project. Note that capacitors generally come from two plus or minus marking or a black or white band

major groups or types. Non-polar types, such as the

with a plus or minus marking on the body of the

ones in this project, have no polarity and can be placed capacitors.

in either direction on the circuit board. The other type Many capacitors are quite small in physical size, so

of capacitors are called polarized types, these capacitors manufacturers have devised a three-digit code which

have polarity and have to be inserted on the board with can be placed on the capacitor instead of the actual

respect to their polarity marking in order for the circuit value. The code occupies a much smaller space on the

Chapter Twenty-Five: Telephone Tattletale to operate correctly. On these types of capacitors, you capacitor and can usually fit nicely on the capacitor 256

Chapter Twenty-Five: Telephone Tattletale

body, but without the chart the builder would have a

PC board. Solder the LEDs to the PC board and then

difficult time determining the capacitor’s value.

trim the excess leads.

Next, locate the capacitors from the component pile. It The Tattletale circuit also utilizes two transistors at is easier to first install the lowest profile components Q1 and Q2. Transistors generally have three leads, a

before installing the larger components. With that in mind Base lead, a Collector lead and an Emitter lead. Refer to we are going to install the smaller profile capacitors the schematic and you will notice that there will be two first—capacitors C2 and C3 and so forth. Capacitor C2 is diagonal leads pointing to a vertical line. The vertical marked .47 μF, while C3 is labeled .22 μF. Locate

line is the transistor’s base lead and the two diagonal these two capacitors first, and refer to Table 25-2, which lines represent the collector and the emitter. The

will help identify the smaller capacitors, which may have diagonal lead with the arrow on it is the emitter lead, the three-digit codes on them. Use your schematic and and this should help you install the transistor onto the parts layout diagrams to find where C2 and C3 are

circuit board correctly. Note that the collector-to-emitter located. After installing these two capacitors, you can voltage rating of Q1 must be at least 300 volts to

move and solder them in place, remembering to trim the withstand the 90-volt rms ringing signal from the

excess component leads. Next find the remaining small telephone line. Refer to the manufacturer’s specification physical sized capacitors and locate them on the circuit sheets as well as the schematic and parts layout

board, then solder them in place. Trim the extra leads as diagrams when locating and mounting the transistors.

necessary. Finally locate the larger electrolytic capacitors, Go ahead and install the transistors on the PC board and such as C1 and C7. These capacitors are polarity

solder them in place, then follow-up by cutting the

sensitive and must be oriented correctly for the circuit to excess component leads.

work properly. Failure to install them correctly could The Tattletale project requires a number of ICs.

damage the components and could potentially damage

ICs must be installed correctly in order for the circuit to the entire circuit when first powered up. Install the function properly. It is recommended that you construct electrolytic capacitors, solder them in place, then trim the the circuit using integrated circuit sockets as a low cost excess leads.

form of insurance in the event of a circuit failure. It is This project contains eight silicon diodes at D1 through much easier to simply unplug an IC rather than trying to D8. These diodes also have polarity which must be

successfully unsolder a 16-pin IC and install a new one.

observed if the circuit is going to work correctly. You will Install the IC sockets but do not install the integrated notice that each diode will have a black or white colored circuits at this time.

band at one edge of the diode’s body. The colored band represents the diode’s cathode lead. Check your schematic Sensor switches

and parts layout diagrams when installing these diodes on the circuit board. Note that diodes D1 through D4 are The Tattletale circuit was designed for normally open 1N4001 silicon diodes in the power supply bridge circuit, type sensors or sensor switches, however, if one or more while diode D9 is a 1N4004, which must also have a

of your sensing switches needs to be a normally closed 300-V rating since it is across the telephone line input.

type, you may use it by adding an inverter to the circuit The remaining diodes D6, D7, and D8 are all 1N4148

to reverse the logic. Note that U6 has one spare section small signal diodes. Place all the diodes on the circuit which is not used. This section may be utilized for

board and solder them in place. Then trim the excess

implementation of a normally closed sensing switch.

component leads with your end-cutters.

Figure 25-3 illustrates the circuit modification using a The Tattletale circuit uses two LEDs, which also must normally closed switch (S5) and U6(d) in place of S2.

be oriented correctly if the circuit is to function

Notice that R1 which is normally connected to pins 2

properly. Remember that LEDs have two leads, a

and 3 of U1 is now placed at the input of U6:d (pins 12

cathode and an anode lead. The anode lead will usually and 13). S5, a normally closed switch, is used in

be the longer of the two leads and the cathode lead will place of S2. Due to the inverting action of U6(d),

usually be the shorter lead, just under the flat side edge pins 2 and 3 of U1 will be at zero logic level when no of the LED; this should help orient the LED on the

emergency exists. If your requirement for Tattletale is to 257

CD4011B

CD4002B

S5

13

2

11

1

9 V

3

12

4

5

10 K

Figure 25-3

Normally closed sensor option

use more than one normally closed switch, another chip up the PC board with the foil side facing upwards

such as CD40118 or CD4069B may be added to the

toward you. Carefully inspect the solder joints, these circuit. Remember, when you use one section of a

should look smooth, clean, and bright. If any of the

CD40118 as an inverter, you must connect both inputs

solder joints look dull, dark, or blobby, then you should together. CMOS digital chips should never have input

remove the solder with a solder sucker or a solder wick terminals which are left floating.

and then resolder the joint all over again.

Tattletale’s logic circuit has not been designed to

Now we will inspect the PC board for possible short

differentiate between two or more sensing switches,

circuits. Short circuits can be caused from small solder when they are simultaneously activated. In this circuit S2

blobs bridging the circuit traces or from cut component has priority over S3 and S4, and S3 has priority over S4.

leads which can often stick to the circuit board once they For this reason you should use S2 for your most urgent have been cut. A sticky residue from solder will often emergency situation, followed by S3 and then S4.

trap component leads across the circuit traces. Look

carefully for any bridging wires across circuit traces. It is To make the connection to the telephone line it is

much easier to correct a problem at this stage rather than suggested that you obtain a standard modular plug and trying to troubleshoot a non-working circuit later. Once cord which is available from any outlet selling telephone this task is complete, we can move on to installing the accessories. The use of a quick disconnect plug is required circuit board into some sort of plastic enclosure.

by FCC regulations and makes it easy to connect and

disconnect Tattletale from your phone line at any time.

Locate a suitable metal chassis box to house the

Tattletale project. The prototype circuit board contained It is important that the polarity of your telephone

all the components including the transformer. Center the connection is correct as indicated on the schematic. If circuit board inside the chassis box and use four 1⁄ inch you use the red and green wires of your modular cord

4

standoffs to lift and mount the PC board to the bottom of set, the polarity should be correct. If you have any

the chassis box. You will want to mount the power switch doubt about the polarity of your telephone line, verify it and LED on the front panel of the chassis box. The

by checking it with any DC voltmeter capable of

power line cord should exit the rear panel of the chassis measuring 50 V. The black and yellow wires of the

through a grommet. You should install a panel mounted telephone cord are not used. For a professional touch fuse holder at the rear panel of the box. Depending upon you may wish to mount the circuit board in a suitable your particular needs you could elect to mount a

enclosure. Place the LED and S1 where they may easily 6-position terminal strip on the front panel to accept be seen. To make the connections to the sensing

connections to the input sensors. You will also need

switches use a terminal strip containing four screw

to supply a 2-conductor phone line cord in order to

connections. Once you have installed Tattletale you may connect the Tattletale to the phone line. One method

leave it connected to the telephone line and use power of solving this problem would be to install cord with switch S1 to turn it on and off. The LED will indicate a modular telephone plug attached to one end and

when Tattletale is activated.

hard-wired to the circuit at the other end. You could Once the circuit board has been completed, take a

install a modular jack on the chassis box and then

short break and then we will inspect the PC board for simply use a telephone jumper cable with a modular

Chapter Twenty-Five: Telephone Tattletale possible “cold” solder joints and “short” circuits. Pick plug at both ends.

258

Chapter Twenty-Five: Telephone Tattletale

You can check the one-shot action of U4 by

Tattletale testing

momentarily shorting pin 2 of U4 to ground while

examining the output at pin 3. Pin 3 should read about Before placing any of the ICs in their sockets apply

9 volts when you trigger U4 at pin 2, remain so for

115 V AC power to the primary of T1 and measure the

about a minute, and then return to zero volts. When you voltage across C1. This voltage should be about 9-volts are satisfied that the U6 and U4 circuitry are operating DC, with polarity as indicated in the schematic. With the properly, proceed with the next check.

negative lead of the voltmeter connected to the negative Set sensing switch S4 to the closed position; S2 and

side of C1, check each IC socket for the presence of

S3 should be left in the open position. Apply AC-line

+9 volts at the power supply input terminals. These

power to the circuit and check pin 9 of U5 for four

terminals are pin 8, 14, and 16 for 8, 14-, and 16-pin ICs discrete pulses, repeating every second or two. Next, respectively. If you read the correct voltages, disconnect close S3 and check for three pulses at pin 9 of U5. Then the AC power from the unit and allow time for C1 to

close S2; the number of pulses should now be two. With discharge. If incorrect voltages are obtained, troubleshoot all sensing switches open, there should be just one pulse the circuit until you obtain the correct voltage readings.

every second or two.

You may now insert the integrated circuit chips into

If you do not get the specified response, you can

their sockets. Be careful to orient them properly. All check the counter chain by temporarily removing U7

integrated circuits have some sort of markings which

from its socket and shorting pin 11 of U5 to ground.

indicate the positioning information. Most ICs will have This will enable U5 to count continuously since it will either a small indented circle, a cutout, or notch at the now be clocked by U8. You can then follow the

top end of the IC package. Pin 1 will be just to the left waveforms produced by U5 through the AND gates of

of the notch, or cutout; this information will help you to U2 and U3 to the trigger input terminal (pin 2) of U7.

position the component correctly in the circuit. Use the IC layout information diagram as well as the schematic U7 can be checked manually for its one-shot action by to help orient the IC correctly. If you have any doubts in momentarily shorting pin 2 to ground and examining the your ability to install the integrated circuits, have a one second pulse at pin 3. Pin 3 should go to about

knowledgeable electronics enthusiast help you. It is

9 volts for about a second and then return to zero. U9 can recommended that the circuit builder use IC sockets for be checked for 2,000-Hz astable operation by temporarily this project as a low cost insurance policy against future removing U3 and connecting pins 4 and 8 of U9 together.

circuit failure. It is much easier to simply unplug a You should obtain a 2,000-Hz square wave at pin 3 of

defective IC, rather than trying to unsolder 14 or 16 pins U9. If the unit passes these tests remove any temporary successfully without damaging the circuit board.

connections and insert the ICs into their sockets.

To check the circuit waveforms it is best if you use an With AC power off connect Tattletale to the telephone oscilloscope. If an oscilloscope is not available, you may line using the modular connector. Turn the AC power

use a voltmeter with an input resistance of at least

on; the LED should be lighted. Make an operational

1 megohm to check DC levels and slow-moving

check. Call your number from another telephone which

waveforms.

is not connected to the same line. You should get an

immediate answer in the form of one beep every

The first part of the checkout is the call answering

second. Stay on the line. Tattletale should disconnect circuit. Turn AC Power on; the LED should light. Take a after about a minute. You can further check the

piece of wire and momentarily short pin 1 of U6 to

operation of the unit by closing one of the sensing

ground. The LED should extinguish and remain so for

switches and verifying that the proper number of pulses about a minute, then it should automatically light again.

is produced when you call. This completes the checkout If you do not get this response check the flip-flop circuit of your unit and you may place it in service.

of U6:a and U6:b by examining pin 4 of U6 as you

momentarily short to ground first pin 1 then pin 6 of For protection against break-in you may use any of

U6. This action should cause the logic level at pin 4 to the readily available magnetically or mechanically

first go high, then low.

operated door and window switches. It is also possible 259

to use a continuous closed circuit composed of foil

To detect a flood you can purchase or construct a

placed around the periphery of glass panes. Remember, simple float switch which is activated when water enters a continuous loop of foil such as this constitutes a

the protected area. For an extra early warning it would be normally closed circuit and you will need to implement prudent to locate the float switch in a well or depression the circuit modification of Figure 25-3.

such as the bottom of the sump where a pump is located.

To detect fire, heating system, refrigeration, and/or air Be sure that water is not permitted to touch any of the conditioning failure it is easiest to install a suitable electrical connections of your switch. Now that Tattletale thermostat in the affected area. For heating system

is ready to operate, do not forget to turn it on when you failure, use a thermostat whose contacts close on a fall leave the premises. The LED indicator will provide

in temperature. For fire, or refrigeration, and air

assurance that your unit is armed and ready to answer conditioning failure use a thermostat with contacts that your call. Be sure to turn the unit off again when you close on a rise in temperature.

return so that you do not miss your incoming calls.

Chapter Twenty-Five: Telephone Tattletale

260

Chapter 26

DTMF Telephone Controller Project

C1

.22 μF, 200 V

Parts list

capacitor

C2

10 μF, 200 V

DTMF Telephone Controller

capacitor

R1

10 K ohm, 1⁄ W,

4

C3

C

5% resistor

A

- timing

component U5(see text)

R2

150 K ohm, 1⁄ W,

4

set for 60 sec

5% resistor

C4, C6, C8, C9

1 μF,

R3

82 K ohm, 1⁄ W,

4

35 V capacitor

5% resistor

C5

CB - timing

R4

RA - timing

component U6(see text)

component U5 (see

set for 5 sec

text) set for 60 s

C7

C

R5

R

C

- timing

B

- timing

component U7(see text)

component U6 (see

set for 5 sec

text) set for 5 s

C10

.1 μF, 35 V disc

R6, R9

4.7 K, 1⁄ W,

4

capacitor

5% resistor

R7

R

Q1, Q2, Q3, Q4

BC547

D

- timing

component U7(see text)

NPN transistor

set for 5 s

Q5, Q6, Q7, Q8

BC547

R8

R

NPN transistor

C

- timing

component U7(see text)

U1

MT8870 Touch¯Tone

set for 5 s

decoder

R10

390 K, 1⁄ W,

4

U2

7447 IC¯BCD

5% resistor

7¯segment decoder

R11, R12, R13, R14

U3

74154 IC - 4 to 16

330 ohm, 1⁄ W,

4

line decoder

5% resistor

U4

MCT2E opto¯coupler

R15, R16, R17

330 ohm,

1

U5, U6, U7

NE555 Timer

⁄ W, 5% resistor

4

IC

R18, 19

4.7 K, 1⁄

W,

4

5% resistor

U8, U12

7408 - Quad

2¯input AND gate IC

R20, R21, R22, R23

4.7 K, 1⁄

W,

U9, U10

7474 -

4

5% resistor

D¯Flip¯Flop IC

261

Copyright © 2009 by The McGraw-Hill Companies, Inc. Click here for terms of use.

U11

74126 - Quad

tones at the same time. These two tones are taken

3¯state buffer IC

from a row frequency and a column frequency.

U13

7404 - Hex

The resultant frequency signal is called “Dual Tone

inverter IC

Multiple Frequency.” A DTMF signal is the algebraic

sum of two different audio frequencies. Each of the low U14

LM7805 regulator IC

and high frequency groups comprise four frequencies

XTL

3.58 MHZ crystal

from the various keys present on the telephone keypad; DSP

7

two different frequencies, one from the high frequency

¯segment display

(see text)

group and another from the low frequency group

are used to produce a DTMF signal to represent the

RLY1, RLY2

5¯V reed

pressed key.

relay

The frequencies were originally chosen so that they

RLY3, RLY4, RLY5

5¯V

were not harmonically related to each other. The

reed relay

frequencies associated with touch-tone keys on the

The DTMF Telephone Controller is ideal for remote

telephone encoder keypad are shown in Table 26-1.

control applications around your home, office, shop,

When you send these DTMF signals to the telephone

or barn. You can remotely control almost any device

exchange, the telephone exchange identifies these

with this controller project. The DTMF Telephone

signals and makes the connection through computers

Controller unit continually monitors your phone

and switching circuits to the person you are calling.

line and looks for the proper user touch-tone sequences to remotely control devices around your home or

When you press the digit 5 on a telephone keypad it

office (see Figure 26-1).

generates a resultant tone signal which is made up of frequencies 770 and 1336 Hz. Pressing digit 8 will

Once it is heard, the user may select which of the

produce the tone taken from tones 852 Hz and 1336 Hz.

trigger relays to turn on or off. Now you can call home In both the cases, the column frequency 1336 Hz is the and, when your answering machine picks up, control

same. These signals are digital signals which are

lights, security systems, or just about any number of symmetrical with the sinusoidal wave.

other custom applications! The DTMF controller offers full control from any telephone anywhere in the world!

The Telephone remote controller system board

Circuit description

utilizes the Dual Tone Multi Frequency Tone (DTMF)

encoding or touch-tone dialing technology, which was

The Telephone Controller consists of eight sub-circuit invented by the Bell System many years ago. When you

blocks, beginning with the ring detector, a DTMF

press a numeric button in the telephone keypad, the

decoder, 4-16 line decoder/demultiplexer, some

keypad starts up two oscillators and generates two

D-flip-flops, display driver, relay driver circuits, and power supply, etc. The overall DTMF Telephone

Controller schematic is shown in Figure 26-2.

Table 26-1

Touch tone frequency chart

High Frequency Group

Low

1,209 Hz

1,330 Hz

1,447 Hz

Frequency

697 Hz

1

2

3

Group

770 Hz

4

5

6

852 Hz

7

8

9

Chapter Twenty-Six: DTMF Telephone Controller

941 Hz

0

0

#

Figure 26-1

DTMF controller

262

Chapter Twenty-Six: DTMF Telephone Controller

9–12 V DC

VCC

U14

In

R11

X7

C10

N/O

RL1

10

18 17

7

U1

3 14 15 9 10 11

N/C

12

XTL

16

4

13

R10

U2

R17

8

5

DSP

R1

8

16

6

2

1

7

2

11

+

C1

12

R2

Telephone

13

3

14

line

R18

A3

A2

A1

A0

1

connection

15

R3

20

21

22

23

12 19

18

4 5

6 9

C2

24

U3

VCC

4

Q11

Q10

Q4 Q3 Q2 Q1

1

+5 V

U4

VCC

StD

11

10

4

3

2

1

5

3

1

RL1

R19

5

2

U13

U13

U13

U13

6

4

2

Q1

R18

12

9

5

2 U5

2

3

13

12 10

9

5

4

2

1

13

C4

U11

U11

U11

U11

4

U8

U8

U8

U8

Q2

5

10

4

1

8

7

8

6

11

3

7 11

8

6

3

7 6 1

B

R4

C3

Q3

D

CL

D

CL

D

CL

D

CL

R9

4

8

R6

12

11

2

3

12

11

2

3

7

2

− 8

6

−

− 8 U9:B

6 U9:A

−

U6

9

5

9

5

Q

Q

Q

Q

U10:B

Q

U10:A

Q

Q

Q

6

7

3

14101314

14101314

5

1

C5

7

C6

VCC

VCC

RL5

VCC

RL4

VCC

RL3

VCC

RL2

VCC

+5 V VCC

Q4

8

R9

R7

Q8

Q7

Q6

Q5

7

R23

R22

R21

R20

4

R8

U7

StD

6

3

13

12

10

9

5

4

2

1

2 5

+

14

C7

U12

U12

U12

U12

1

C9

7

11

8

6

3

C8

+5 V

VCC

B

Figure 26-2

Touch tone controller

263

Our discussion will begin with the ring detection circuit other NE555 timer chips at U6 and U7 also have their

and then progress through the entire circuit, describing timing components listed as Rb, Rc .... and Cb, Cc .... , the circuit in detail.

you must also compute the optimum timing components

for these two ICs.

Ring detector circuit

Signal decoding section

The ring detector circuit essentially “picks up the phone”

automatically after a set period of time. This circuit After passing through the ring detector, the circuit is ready identifies the ringing signal sent from the telephone to receive a DTMF signal from the remote telephone or exchange. On getting the ringing signal this circuit

touch-tone encoder. The MT8870 DTMF decoder chip is

connects the controller unit to the telephone line. The the heart of the Telephone Controller. The decoder chip incoming AC ringing signal is bypassed by resister R3

takes DTMF signal coming via the telephone line and

and capacitor C2 and is then applied to the opto-coupler converts that signal into a respective 4-bit BCD number MCT2E at U4. Note that this opto-coupler is a 6 pin IC.

output obtained from pins 11 to 14; see the block diagram The opto-coupler is made up of an internal LED and a

in Figure 26-3 and Truth Table 26-2.

transistor. When the internal LED glows, the light falls The oscillator frequency of the decoder is controlled on the emitter-collector junction of the transistor. This by a 3.85 MHz crystal. The MT-8870 is a full DTMF

transistor becomes forward biased and the output is

receiver that integrates both band split filter and decoder obtained at the emitter of the transistor. On applying the functions into a single 18-pin DIP. Its filter section uses signal to the anode of the opto-coupler, grounding the switched capacitor technology for both the high and low cathode, on the positive cycle of the signal the LED

group filters and for dial tone rejection. Its decoder uses glows; as a result +5 V output is obtained at the emitter digital counting techniques to detect and decode all 16

of the opto-coupler at pin number 4 of U4.

DTMF tone pairs into a 4-bit code. External component The ring detector circuit is built around a monostable count is minimized by provision of an on-chip

multi-vibrater constructed around timer IC 555, at U5.

differential input amplifier, clock generator, and latched When a negative going pulse is applied to its triggering tri-state interface bus. Minimal external components

input at pin 2, the output of the IC goes high. This output required include a low-cost 3.579545 MHz crystal, a

is available at pin 3 of this IC. This will remain high for timing resistor, and a timing capacitor. The MT-8870-02

the time period designed by the RC combination,

can also inhibit the decoding of fourth column digits.

depending on values of resister RA and capacitor CA.

The MT-8870 operating functions include a band split

A high signal on pin 3 of this timer IC biases the transistor filter that separates the high and low tones of the received Q2 in the relay driver circuit which in turn switches ON

pair, and a digital decoder that verifies both the frequency the relay. This relay puts a resistance loop of about and duration of the received tones before passing the 220 ohms across the telephone line. This resistance loop resulting 4-bit code to the output bus. The low and high coming on-line causes the telephone line voltage to drop group tones are separated by applying the dual-tone

from 50 to 12 V. This is the same as lifting the receiver signal to the inputs of two 6th order switched capacitor of the telephone handset (hook-off state). This timing band pass filters with bandwidths that correspond to the circuit is designed for a period of 60 seconds, calculated bands enclosing the low and high group tones.

by the formula: Td = 1.1 RA CA.

The filter section of the DTMF controller

After the timing period the output of this IC goes low incorporates notches at 350 and 440 Hz, providing

which in turn switches OFF the transistor T2. By

excellent dial tone rejection. Each filter output is

varying the values of the RA and CA the ON period of

followed by a single-order switched capacitor section the monostable multi-vibrator is changed according to that smooths the signals prior to limiting. Signal

the formula given above. In the relay driver circuit a limiting is performed by high gain comparators that

resister is used to provide the necessary base current to provide hysteresis to prevent detection of unwanted

the transistor so that it can bias properly. Note that the low-level signals and noise. The MT-8870 decoder uses Chapter Twenty-Six: DTMF Telephone Controller

264

Chapter Twenty-Six: DTMF Telephone Controller

VDD

VSS

VREF

INH

Bias

PWDN

circuit

VREF buffer

Chip

Q1

bias

High

Code

Chip pwr

Digital

filter group

converter

detection

Q

and

2

algorithm

In +

Dial

latch

Zero crossing

tone

Q3

In

detectors

−

filter

GS

Low

Q

filter group

4

St

Steering

To all chip blocks

GT

logic

OSC1

OSC2

St/GT

ESt

StD

TOE

Figure 26-3

Touch tone decoder block diagram

a digital counting technique to determine the

registered, the receiver checks for valid signal duration frequencies of the limited tones and to verify that they (referred to as character-recognition-condition). This correspond to standard DTMF frequencies. When the

check is performed by an external RC time constant

detector recognizes the simultaneous presence of two

driven by ESt. A short delay to allow the output latch to valid tones (known as signal condition), it raises the settle, and the delayed steering output flag (StD) goes Early Steering flag (ESt). Any loss of signal condition high, signaling that a received tone pair has been

will cause ESt to fall. Before a decoded tone pair is registered. The contents of the output latch are made Table 26-2

MT8870 Truth table

BCD Outputs Q3–Q0

Keys

Q3

Q2

Q1

Q0

Device

1

0

0

0

1

1

2

0

0

1

0

2

3

0

0

1

1

3

4

0

1

0

0

4

5

0

1

0

1

5

6

0

1

1

0

6

7

0

1

1

1

7

8

1

0

0

0

8

9

1

0

0

1

9

0

1

0

1

0

10

265

available on the 4-bit output bus by raising the three the 74154 the needs to get inverted to get a logical high state control input (OE) to logic high. The inhibit mode output. This inversion is carried out by TTL hex inverter is enabled by a logic high input to pin 5 (INH). It

IC 7404. This IC inverts the data on its input terminal inhibits the detection of 1633 Hz.

and gives inverted output.

The output code will remain the same as the previous

The SM74154 integrated circuit is a 4-16 line

detected code. On the M-8870 models, this pin is tied decoder; it takes the 4 line BCD input and selects

to ground (logic low). The input arrangement of the

respective output, one among the 16 output lines. It is MT-8870 provides a differential input operational

active low output IC so when any output line is selected amplifier as well as a bias source (VREF) to bias the it is indicated by an active low signal; the rest of the output inputs at mid-rail. Provision is made for connection of a lines will remain active high. This 4-line-to-16-line feedback resistor to the op-amp output (GS) for gain

decoder utilizes TTL circuitry to decode four binary-coded adjustment. The internal clock circuit is completed with inputs into one of sixteen mutually exclusive outputs the addition of a standard 3.579545 MHz crystal. The

when both the strobe inputs, G1 and G2, are low.

input arrangement of the MT-8870 IC provides a

The de-multiplexing function is performed by using the differential input operational amplifier as well as a bias 4 input lines to address the output line, passing data source (VREF) to bias the inputs at mid-rail. Provision from one of the strobe inputs with the other strobe input is made for connection of a feedback resistor to the

low. When either strobe input is high, all outputs are op-amp output (GS) for gain adjustment.

high. These de-multiplexers are ideally suited for

The DTMF Controller utilizes three NE555 timer

implementing high-performance memory decoders. All

chips. The NE555 integrated circuit is a timing chip that inputs are buffered and input clamping diodes are

is capable of producing accurate timing pulses. This IC

provided to minimize transmission-line effects and

is used as a multi-vibrator. By using this IC we can

thereby simplify system design; see the

construct two types of multi-vibrator, monostable and multiplexer/demultiplexer diagram in Figure 26-4 and

astable. The monostable multi-vibrator produces a

truth Table 26-3.

single pulse when a triggering pulse is applied to its triggering input. The astable multi-vibrator produces a train of pulses depending on the resister-capacitor

combination wired around it.

Inputs

Outputs

With a monostable operation, the time delay

is controlled by one external resistor and one

Pins

24

23

22

21

20

19

18

17

16

15

14

13

Pins

capacitor connected between Vcc-Discharge (R), and

A

B

C

D

G2 G1 15

14

13 12

11

Threshold-Ground (C). With an astable operation, the

VCC

frequency and pulse width are produced by two external resistors and one capacitor connected between

Vcc-Discharge (R), Discharge-Threshold (R), and

Threshold-Ground (C). In integrated circuit U5, the first NE555 is driven by the ring detector and control the

74154

phone line connection. The second NE555, at U6 drives the 74126 chips and the third NE555 chip is driven by the touch-tone decoder chip’s StD line.

As previously mentioned, the output of the

Touch-Tone decoder is then fed to the 4-16 line decoder 0

1

2

3

4

5

6

7

8

9

10

GND

IC74154. This IC takes the BCD number and decodes.

Pins

1

2

3

4

5

6

7

8

9

10

11

12

Pins

According to that BCD number it selects the active low Outputs

output line from 1 to 16 which is decimal equivalent of the BCD number present at its input pins. The output of Figure 26-4

74154 Decoder chip

Chapter Twenty-Six: DTMF Telephone Controller

266

Table 26-3

CSN74154 Decoder truth table

G1

G2

D

C

B

A

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

L

L

L

L

L

L

L

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

L

L

L

L

L

H

H

L

H

H

H

H

H

H

H

H

H

H

H

H

H

H

L

L

L

L

H

L

H

H

L

H

H

H

H

H

H

H

H

H

H

H

H

H

L

L

L

L

H

H

H

H

H

L

H

H

H

H

H

H

H

H

H

H

H

H

L

L

L

H

L

L

H

H

H

H

L

H

H

H

H

H

H

H

H

H

H

H

L

L

L

H

L

H

H

H

H

H

H

L

H

H

H

H

H

H

H

H

H

H

L

L

L

H

H

L

H

H

H

H

H

H

L

H

H

H

H

H

H

H

H

H

L

L

L

H

H

H

H

H

H

H

H

H

H

L

H

H

H

H

H

H

H

H

L

L

H

L

L

L

H

H

H

H

H

H

H

H

L

H

H

H

H

H

H

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L

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L

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H

H

H

H

H

H

H

H

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L

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H

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H

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L

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L

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L

H

H

H

H

H

H

H

H

H

H

L

H

H

H

H

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L

L

H

L

H

H

H

H

H

H

H

H

H

H

H

H

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L

H

H

H

H

L

L

H

H

L

L

H

H

H

H

H

H

H

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H

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H

H

L

H

H

H

L

L

H

H

L

H

H

H

H

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H

H

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H

H

H

H

H

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L

H

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L

L

H

H

H

L

H

H

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H

H

H

H

H

H

H

H

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H

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L

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L

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H

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H

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H

H

H

H

H

H

H

L

L

H

X

X

X

X

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

L

X

X

X

X

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

X

X

X

X

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

267

r

e

l

l

o

r

t

n

o

C

e

n

o

h

p

e

l

e

T

F

M

T

D

:

x

i

S

-

y

t

n

e

w

T

r

e

t

p

a

h

C

buffer, an LM74126, contains four independent gates

Number display section

each of which performs a non-inverting buffer function.

The outputs have the 3-STATE feature. When control

This section of the circuit displays the received device signal is at high state, the outputs are nothing but the code from the telephone line dialed from remote

data present at its input terminals. When control signal section. This section consists of a BCD to seven

is at low state, the outputs are held at high impedance segment decoder, the SM74LS47 and a seven segment

state. So no output will be available at the output

common anode display, at DSP. The DM74LS47 chip

terminal. The LM7474 is a conventional D-flip-flop IC.

accepts four lines of BCD (8421) input data from the

This IC consists of two D flip-flops. These flip-flops are decoder chip and generates their complements internally used to latch the data that present at its input terminal.

and decodes the data with seven AND/OR gates having

Each flip-flop has one data, one clock, one clear, one open-collector outputs to drive indicator segments

preset input terminals.

directly. Each segment output is guaranteed to sink

After making confirmation of current status of the

24 mA in the ON (LOW) state and withstand 15 V in

device to alter the status of that device, you have to the OFF (HIGH) state with a maximum leakage current

change the mode of the tri-state buffer by making the of 250 mA. Auxiliary inputs provided blanking, lamp

control input high. This is done by pressing the “#” key.

test and cascadable zero-suppression functions. The

When this key is pressed the output of the 4-16 line

display driver IC has 10 pins, two of these pins are

decoder goes low. This gives a triggering pulse to the common for all LEDs and remaining are another

monostable multi-vibrator which is built around the U6.

polarity terminals of the LED. When common anode

This will keep the output high for about 5 seconds.

seven segment display is used, two common terminal

Working of the monostable multi-vibrator already

pins are connected to +5 V or logic high state and

discussed. In this time interval the output of the tri state another terminal are kept at logic low state, allowing the buffer will be the signal at its input terminal.

respective LED to glow.

Now the device code of the chosen relay whose status

is to be altered is again pressed. The output of the

Device control section

tri-state buffer is latched by using a D flip-flop. This D flip flop is used in the toggle mode. For each positive The Device Control Section consists of device status

going edge of the clock a pulse will trigger the flip flop.

check unit, device switching unit, device status

After a period of 5 s the output of the U6 goes low

feedback unit, relay driver circuit and beep tone

and puts the tri state buffer in the high impedance

generator unit. Before switching On/Off any device,

state. Therefore to change the status of any other

there can be confusion about its present status of the device to be done after the output of U6 goes low,

outputs. This section handles the device status. The

again “#” key is pressed to make the tri-state buffer inverted output of 4-16 line decoder and the output of act as input–output state and the respective code of the respective flip-flop are fed to the independent block of device is pressed.

AND gates at U8 and U12 using 7408. If the device is

already in the ON state, then we will hear a beep sound.

Device feedback section

The outputs of each AND gate are connected to the

beep tone generator unit by using a transistor. This beep After changing the present status of the device, you can generator unit produces a short duration beep indicating confirm the operation that you performed. The DTMF

than the device is already in switched ON state. If

Controller unit will now give the feedback tone after device is in OFF state then no beep will be heard.

switching ON any device. This status feedback circuitry, utilizes a dual input AND gate, the output of the flip Device switching section

flop and a tri state buffer to provide the input for the feedback. When the both inputs are high that indicates This Device Switching section consists of a tri-state buffer that the device is switched ON, then the output of the Chapter Twenty-Six: DTMF Telephone Controller at U11 and two flip-flops at U9 and U10. The tri-state AND gate goes logic high state. This output is fed

268

Chapter Twenty-Six: DTMF Telephone Controller

to the beep generator unit through switching a transistor.

Until you press the key the feedback tone is heard.

Power supply section

This feedback tone is heard only when the device is

switched ON. After switching OFF the device, this tone In order for the DTMF Controller to operate, the circuit is not heard.

must have a power supply and a permanent back up

power supply. This is achieved by using a 5 V regulated power supply from a voltage regulated IC 7805. This

Beep tone generator section

5 V source is connected to all ICs and relays, and the IC

gets a backup from a 9 V battery.

The beep tone generator unit produces a beep tone

of audible frequency. This unit is constructed using

a 555 timer chip. Here it is wired as an astable

Assembling the DTMF controller

multi-vibrator with a few external components like

resister and capacitor, required along with the timer Before we begin constructing the DTMF Controller, you 555 chip set. This frequency comes in the audible

will need to locate a clean, well-lit worktable or

range between 40 to 650 Hz. It should be less than

workbench. Next we will gather a small 25–30-W

650 Hz otherwise it will mix up with the DTMF tone.

pencil tipped soldering iron, a length of 60/40 tin–lead When it is less than 650 Hz the frequency which causes solder, and a small canister of Tip Tinner, available at the false triggering is filtered-off by the external

your local RadioShack store; Tip Tinner is used to

structure of DTMF decoder IC at U1.

condition the soldering tip between solder joints. You drive the soldering tip into the compound and it cleans and prepares the soldering tip. Next grab a few small Relay driver circuit

hand tools; try to locate small flat blade and Phillips screwdrivers. A pair of needle-nose pliers, a pair of In order to switch the appliances On or Off, small

tweezers along with a magnifying glass, and a pair of PC board type relays were used. Since the output of the end-cutters and we will begin constructing the project.

D flip flop is normally +5 V or it is the voltage of logic Now locate your schematic diagram and parts layout

high state, we cannot use this output to run the device diagram along with all of the components needed to

or appliances. Therefore here we use relays which

build the project.

can handle a high voltage of 230 V or more, and a

Once all the components are in front of you, you can

high current in the rate of 10 A to energize the

check them off against the project parts list to make electromagnetic coil of the relays +5 V is sufficient.

sure you are ready to start building the project. Now, Here we use the transistors to energize the relay coil.

locate Tables 26-4 and 26-5, and place them in front of The output of the D flip-flop is applied to the base of you. Table 26-4 illustrates the resistor code chart and the transistor Q5–Q8 via a resistor. When the base

how to read resistors, while Table 26-5 illustrates the voltage of the transistor is above 0.7 V the emitter-base capacitor code chart which will aid you in constructing (EB) junction of the transistor becomes forward biased.

the project.

As a result the transistor goes into saturation, thus Refer now to the resistor color code chart in

switching ON the transistor. Switching the transistor Table 26-4, which will help you identify the resistor values ON, thus activates the relay. When the output of

for the project. Note that each resistor will have either D flip-flop goes low the base voltage drops below 0.7 V

three or four color bands, which begin at one end of the and as a result the device also switches OFF.

resistor’s body. The first colored band represents the The DTMF controller is a relatively compact unit

resistor’s first digit, while the second color represents with four 5-A relay outputs, each with its own screw

the second digit of the resistor’s value. The third colored terminals. The DTMF controller requires 9–12 V DC at

band represents the resistor’s multiplier value, and the 300 mA, which can be obtained from a small “wall

fourth color band represents the resistor’s tolerance cube” or “wall-wart” power supply, available through

value. If there is no fourth colored band then the resistor a local RadioShack store or parts supplier outlet.

has a 20% tolerance value. If the resistor’s fourth band 269

Table 26-4

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

No color

20%

Table 26-5

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

1.0

1R0

3,900

3.9

.0039

392

1.2

1R2

4,700

4.7

.0047

472

1.5

1R5

5,600

5.6

.0056

562

1.8

1R8

6,800

6.8

.0068

682

2.2

2R2

8,200

8.2

.0082

822

2.7

2R7

10,000

10

.01

103

3.3

3R3

12,000

12

.012

123

3.9

3R9

15,000

15

.015

153

4.7

4R7

18,000

18

.018

183

5.6

5R6

22,000

22

.022

223

6.8

6R8

27,000

27

.027

273

8.2

8R2

33,000

33

.033

333

10

100

39,000

39

.039

393

12

120

47,000

47

.047

473

15

150

56,000

56

.056

563

18

180

68,000

68

.068

683

22

220

82,000

82

.082

823

27

270

100,000

100

.1

104

33

330

120,000

120

.12

124

39

390

150,000

150

.15

154

47

470

180,000

180

.18

184

Chapter Twenty-Six: DTMF Telephone Controller

270

Chapter Twenty-Six: DTMF Telephone Controller

Table 26-5—cont’d

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

56

560

220,000

220

.22

224

68

680

270,000

270

.27

274

82

820

330,000

330

.33

334

100

.0001

101

390,000

390

.39

394

120

.00012

121

470,000

470

.47

474

150

.00015

151

560,000

560

.56

564

180

.00018

181

680,000

680

.68

684

220

.00022

221

820,000

820

.82

824

270

.00027

271

1,000

1

105

330

.00033

331

1,500

1.5

155

390

.00039

391

2,200

2.2

225

470

.00047

471

2,700

2.7

275

560

.00056

561

3,300

3.3

335

680

.00068

681

4,700

4.7

475

820

.00082

821

6.8

685

1,000

1.0

.001

102

10

106

1,200

1.2

.0012

122

22

226

1,500

1.5

.0015

152

33

336

1,800

1.8

.0018

182

47

476

2,200

2.2

.0022

222

68

686

2,700

2.7

.0027

272

100

107

3,300

3.3

.0033

332

157

157

Code = 2 significant digits of the capacitor value + number of zeros to follow 10 pF = 100

For values below 10 pF, use “R” in place of decimal e.g. 8.2 pF = 8R2

100 pF = 101

1,000 pF = 102

22,000 pF = 223

330,000 pF = 334

1 μF = 105

is silver then the resistor has a 10% tolerance value and resistors and the diodes. First, locate our first

if the fourth band is gold then the resistor’s tolerance resistor R1. Resistor R1 has a value of 10 K ohms and value will be 5%.

is a 5% tolerance type. Now take a look for a resistor Finally we are ready to begin assembling the project, whose first color band is brown, black, and orange.

so let’s get started. The prototype project was

From the chart you will notice that brown is represented constructed on a single-sided printed circuit board or by the digit (1), the second color band is black, which is PCB. With your PC board in front of you, we can now

represented by (0). Notice that the third color is orange, begin populating the circuit board. We are going to

so the multiplier is (100), so (1) (0) × 100 = 10,000

place and solder the lowest height components first, the ohms or 10 K ohms.

271

Go ahead and locate where resistor R1 goes on the

to the edge of the circuit board. Once you have installed PC and install it. Next solder it in place on the

these components, you can move on to installing the

PC board, and then with a pair of end-cutters trim the remaining capacitors.

excess component leads flush to the edge of the

The DTMF Telephone Controller utilizes eight

circuit board. Next locate the remaining resistors and conventional transistors. Transistors are generally three install them in their respective locations on the main lead devices, which must be installed correctly if the controller PC board. Solder the resistors to the

circuit is to work properly. Careful handling and proper board, and remember to cut the extra lead with your

orientation in the circuit is critical. A transistor will end-cutters.

usually have a Base lead, a Collector lead, and an

Next refer to Table 26-5; this chart helps to determine Emitter lead. The base lead is generally a vertical line value of small capacitors. Many capacitors are quite

inside a transistor circle symbol. The collector lead is small in physical size, so manufacturers have devised a usually a slanted line facing towards the base lead and three-digit code which can be placed on the capacitor the emitter lead is also a slanted line facing the base instead of the actual value. The code occupies a much lead, but it will have an arrow pointing towards or away smaller space on the capacitor and can usually fit nicely from the base lead. Now, identify the two transistors, on the capacitor body, but without the chart the builder referring to the manufacturer’s specification sheets as would have a difficult time determining the capacitor’s well as the schematic and parts layout diagrams when

value.

installing the two transistors. If you have trouble

installing the transistors, get the help of an electronics Capacitors must be installed properly with respect to enthusiast with some experience. Install the transistors polarity in order for the circuit to work properly. Failure in their respective locations and then solder them in to install electrolytic capacitors correctly could cause place. Remember to trim the excess component leads

damage to the capacitor as well as to other components with your end-cutters.

in the circuit when power is first applied.

The DTMF Controller circuit is a number of ICs.

Note that capacitors generally come from two

ICs are often static sensitive, so they must be

major groups or types. Non-polar types, such as the

handled with care. Use a grounded anti-static

ones in this project, have no polarity and can be

wrist strap and stay seated in one location when

placed in either direction on the circuit board. The other handling the ICs. Take out a cheap insurance

type of capacitors are called polarized types, these

policy by installing IC sockets for each of the ICs.

capacitors have polarity and have to be inserted on the In the event of a possible circuit failure, it is much board, with respect to their polarity marking in order easier to simply unplug a defective IC, than trying

for the circuit to operate correctly. On these types of to unsolder 14 or 16 pins from a PC board without

capacitors, you will observe that the components

damaging the board. ICs have to be installed correctly actually have a plus or minus marking or a black or

if the circuit is going to work properly. IC packages white band with a plus or minus marking on the

will have some sort of markings which will help

body of the capacitors.

you orient them on the PC board. An IC will have

Now look in the component stack for the capacitors

either a small indented circle, a cutout, or notch,

and locate capacitor C1; it is a rather large capacitor at the top end of the IC package. Pin 1 of the IC

labeled .22 μF, 250 v -NP. The NP refers to

will be just to the left of the notch, or cutout.

non-polarized. This large capacitor is placed across

Refer to the manufacturer’s pin-out diagram, as

the telephone line and will have to be a 250 V type.

well as the schematic when installing these parts.

When installing the remaining capacitors, refer to the If you doubt your ability to correctly orient the ICs, Table 26-5 to find the three-digit code on the smallest then seek the help of a knowledgeable electronics

capacitors, if you do not see the actual value printed on enthusiast to help you.

them. Go ahead and place the capacitors on the circuit Next, you will need to identify the opto-isolator

board and solder them in place. Now take your

which is installed at U4. It is a 6-pin device

end-cutters and cut the excess component leads flush

which looks like a small DIP IC. It should

Chapter Twenty-Six: DTMF Telephone Controller

272

Chapter Twenty-Six: DTMF Telephone Controller

have a located mark to help you identify pin number

“wall wart” type power supply. You can mount the

one, usually at the top left of the IC. Go ahead and

status 7-segment number display (DSP) on the circuit

install the opto-isolator on the PC using an 8-pin DIP

board or on the front panel if desired. If you mount the IC socket.

DSP display on the circuit board, you will have to cut The DTMF Controller circuit utilizes a single

out a “window” on the chassis, so that when the PC

7-segment common anode LED display at DSP, which

board is mounted up to the panel the display can shine also must be oriented correctly if the circuit is to

out the small window. Next you will have to install an function properly. The 7-segment display has 10 pins.

RJ11 phone jack or a 2-position terminal strip on the Out of this, two pins are common for all LEDs and

front panel of the chassis to bring the phone into the remaining are other polarity terminals of the LED.

chassis box. You will most likely want to mount a

When common anode seven segment display is used,

10-position screw terminal block on the rear panel to two common terminal pins are connected to +5 V or

allow connections to the control relays. Install a

logic high state and other terminals are kept at logic power On-Off switch on the front panel.

low state. Then respective LED glows. You may

Now you are ready to connect the main controller

want to lead about 1 / 4′′ lead length on the LED, in order to the phone line, and apply power to the DTMF

to have the LED protrude through the enclosure box.

Telephone Controller board; and begin testing of

Solder the LED to the PC board and then trim

the circuit.

the excess leads.

Once the DTMF Telephone Controller circuit board

Testing the DTMF controller

has been completed, take a short break and then we will inspect the PC board for possible “cold” solder joints Once the DTMF Controller has been installed in the

and “short” circuits. Pick up the PC board with the foil chassis box and connected to the telephone line and

side facing upwards toward you. Carefully inspect the power supply, you will be ready to begin testing the

solder joints, these should look smooth, clean, and

DTMF Controller circuit. Now switch the On-Off

bright. If any of the solder joints look dull, dark, or switch so that the telephone line is connected to

blobby, then you should remove the solder with a solder telephone interfacing unit.

sucker or a solder wick and then resolder the joint all over again. Now we will inspect the PC board for

Now place a call to your Telephone Controller

possible short circuits. Short circuits can be caused from set using a remote telephone set or mobile phone.

small solder blobs bridging the circuit traces or from cut The signal goes to the telephone exchange

component leads which can often stick to the circuit

and the exchange sends a ringing signal to your

board once they have been cut. A sticky residue from

set through the phone line. The ring detector unit

solder will often trap component leads across the circuit detects the ringing signal and makes the output of

traces. Look carefully for any bridging wires across

the U5 to high state so that local control section

circuit traces.

of then connected to the telephone for a time

interval of 60 s.

Once this task is complete, we can move on to

Now follow the steps below to test the proper

installing the circuit board into an aluminum enclosure.

sequence of the DTMF Controller. First, press the

Locate a suitable enclosure to house the circuit board respective code of the device whose status is to be

within the enclosure. Arrange the circuit board on the checked. The dialed number of the device is displayed bottom of the chassis box. Now, locate four 1 / 8 inch on seven segment display. If the device is already

standoffs, and mount the PC board between the

switched ON then you will hear a short duration beep

standoffs and the bottom of the chassis box.

tone from beep tone generator unit. Now press the “#”

Mount a coaxial power jack on the rear panel of the

button on the keypad and again press the device number chassis box for the small AC “wall-cube” power supply, which is displayed; now the device is switched OFF and which is connected to the input of the regulator at U14.

you will not hear the feedback tone indicating that the The 9–12 V dc power supply could be a low cost

device is switched OFF.

273

Finally, repeat the first step once again. In step one Applications

you will not hear the beep tone because the device is switched OFF during above step two. Repeat step two.

The DTMF Telephone Controller is a very useful

Now you will hear the feedback tone because the device project with many possible home or office switching

is switched ON. After 60 s the local control unit will applications. Using a standard telephone as a remote

be disconnected from the telephone line so that your

encoder and the conventional telephone system, and you money is saved.

can construct useful control projects. Have fun!

Chapter Twenty-Six: DTMF Telephone Controller

274

Chapter 27

The BASIC STAMP Microcontroller

A handful of telephone related projects in the latter part language is designed around standard BASIC and

of this book illustrates how a microcontroller, which is commands terms as such as PULSOUT or SERIN

a small microprocessor, can be used to perform the

which are hardware-driven commands. The beauty of

major functions of or control a complete system. The

the BASIC STAMP series microcontrollers is that you

projects in this book revolve around the Parallax BASIC

have the power to tell it exactly what to do, without STAMP 2 microcontroller. The Parallax controllers can going through any extra processes. This means high

perform many functions, are quite flexible, and are

reliability and no guesswork. Using PBASIC allows you relatively low in cost. Parallax probably offers the most to save valuable time because the learning curve is very support of any microcontroller supplier, so you can get short and the sample codes and resources are

started quickly and easily.

abundantly available from www.parallax.com. Parallax

The BASIC STAMP microcontroller is a single-board

offers free editors, manuals, and forums for help with computer that runs the Parallax PBASIC language

programming the BASIC STAMP series as well as the

interpreter in its microcontroller. The developer’s code new Propeller series of microcontrollers.

is stored in an EEPROM, which can also be used for

To begin using the BASIC STAMP controller, you

data storage. The PBASIC language has easy-to-use

would first connect the hardware sensors or switches to commands for basic I/O, like turning devices on or off, the BASIC STAMP pins, then you simply download the

interfacing with sensors, etc. More advanced commands Windows STAMP Editor 2.5 or above. After downloading

allow the BASIC STAMP module to interface with

the editor, you install the editor program. Next you open other integrated circuits, communicate with each other, up the editor program and call-up the program of choice and operate in networks.

or type in the code you wish to program into the BASIC

The program code entered into the BASIC STAMP is

STAMP controller. Connect up a programming cable

tokenized or compressed and stored within the STAMP’s between your personal computer or laptop and the

EEPROM memory. This memory is non-volatile, meaning

STAMP controller. Next, you apply power to the BASIC

it retains its program even without power. Every time the STAMP controller. You will have to configure the editor BASIC STAMP receives power, it starts running its code program to communicate serially to the STAMP so you

starting with the first executable line. This EEPROM can will have to establish communications between the PC

be rewritten immediately, without any lengthy erase cycle and the STAMP by setting protocols such as COM port

or procedure, by simply downloading the code from the and speed and bits. Once that is down you can press RUN

STAMP editor again. Each location in the EEPROM is

from the drop down tabs and the program should be

guaranteed for 10,000,000 write cycles before it wears out loading in to the STAMP controller.

for the BS 2. The BASIC STAMP microcontroller is also On the BASIC STAMP 2 modules from within the

available in a few other configurations such as the BS 2e, editor and with your PBASIC program on the screen,

BS 2sx, BS 2p, and BS 2pe. EEPROM is guaranteed for

CTRL-M (Windows software) to view the memory map

100,000 write cycles before it wears out.

screens. In the DOS software, the first screen shows

Programming the BASIC STAMP 2 series

your RAM space, the second screen shows an expanded

microcontrollers is performed in PBASIC which is a

view of the program (EEPROM) space and the third

very simple yet powerful language that allows anyone to screen shows a detailed view of the program space. Press program a microcontroller. The foundation of the

the spacebar to alternate between the three screens.

275

Copyright © 2009 by The McGraw-Hill Companies, Inc. Click here for terms of use.

In the Windows software, all EEPROM and RAM are

shown on one window.

The BASIC STAMP 1 was the first of the STAMP

series, using a mini version of BASIC or BASIC tokens in order to program the microcontroller. The BASIC

STAMP 1C features a 256 byte EEPROM for program

memory and runs at 4 mhz, performing 2,000

instructions per second. The STAMP 1 is programmed

via the parallel port of a personal computer. All of the projects in this STAMP 2 communications project book

will use the STAMP 2 microprocessor which sports a

2,048 byte EEPROM and runs at 20 μHz, performing

4,000 instructions per second. The STAMP 2 runs much

faster and has a number of extra commands, such as

SHIFTIN/SHIFTOUT and XOUT and will hold larger

programs than the original STAMP 1. Table 27-1

Figure 27-1

BASIC STAMP 2 microcontroller.

illustrates the differences between the BASIC STAMP 1

Courtesy of Parallax, Inc

and the BASIC STAMP 2.

The STAMP 2 is a very versatile and popular

The BASIC STAMP 2 is available in two different

microprocessor building block which can be used to

types in a DIP package or the SOIC style package. The develop many different electronic systems, as shown in original BASIC STAMP 2 is a PIC chip with a PBASIC2

Figure 27-1 and in the block diagram shown in

interpreter running at 20 MHz. The STAMP 2 has 16

Figure 27-2.

pins for input/output applications and can talk directly to Table 27-1

STAMP microcontroller comparison chart

Product

BS-1-1C / STAMP 1

BS2-1C / STAMP 2

Package

14-Pin SIP

24-Pin DIP

Package size

1.4′′ x .6′′ x.1′′

1.2′′ × .6′′ × .4′′

Environment

32–158 degrees F

40–185 degrees F

Processor speed

4 mHz

20 mHz

Program execution speed

~2,000 instructions/s

~4,000 instructions/s

RAM size

16 bytes-2-I/O, 14 variable

32 bytes 6-I/O, 26 variable

Scratch pad RAM

N/A

N/A

EEPROM program size

256 bytes, 80 instructions

2 K bytes, 500 instructions

Number of I/O pins

8

16 + 2 dedicated serial

Voltage requirement

5–15 Vdc

5–15 Vdc

Current draw @ 5 V

1 mA-Run/25 μA sleep

3 mA-Run/50 μA sleep

Source/sink current per I/O

20 mA/25 mA

20 mA/25 mA

Source/sink current per unit

40 mA/50 mA

40 mA/50 mA per 8-I/O pins

PBASIC Commands

32

42

PC program Interface

serial w/BS1 serial adaptor

serial port 9600 baud

Windows text Editor

STAMPw.exe

STAMPw.exe

Chapter Twenty-Seven: BASIC STAMP

276

Chapter Twenty-Seven: BASIC STAMP

4.7 K

4.2 Brown-out

Resistor

Dual NPN

PNP

requeator

pack

Transistor

Transistor

pack

pack

+9–12 V DC

1

24

SOUT

VIN

2

23

SIN

G

VSS

V

OUT

ATN

3

22

RES

IN

A

NC

4

GND

VSS

WP

GND

21

VDD

SCL

SD

VDD +5 V

OM

EEPR

OUT

GND

GND

NC

LM29365V

24LCI6B/SN

NC

NC

NC

VSS

P0

5

20

P15

6

15

P1

+

P14

15 μF

20 MHZ RES

P2

7

18

P13

10 K

P3

8

17

P12

1

28

VSS

RES

2

27

VSS

X1

P4

9

3

26

VDD

16

X0

P11

4

25

VDD

P15

5

24

SDA

P14

6

23

SCC

P13

22

7

P5

RX

10

P12

15

P10

8

21

TX

P11

9

20

P0

P10

10

19

P1

P9

11

PBASIC 2/52

18

P2

P8

P6

P1C16C 57C – 20/55

11

12

17

14

P9

P3

P7

13

16

P4

P6

14

15

VSS

P5

P7

12

13

P8

Figure 27-2

BASIC STAMP 2 (Original)

277

a serial port from a personal computer for programming.

Parallax which sells the STAMP 2 products offers this in a 24 pin carrier board version which is a self contained STAMP 2 with onboard regulator and brow-out protection.

The original STAMP 2 module is offered for about $49.

Many first time hobbyists choose the STAMP 2 and a

carrier board, the Board of Education or Homework

series prototype systems to begin designing and

programming their own new projects. The original

STAMP 2 is illustrated with its programming cable in

Figure 27-3.

The BASIC STAMP 2 is very easy to utilize. Simply

connect a 9-V battery to pin 24 and a programming cable to pins 1 through 4 and you are ready to begin. Open up the free STAMP 2 editor, load a program from your

computer to the BASIC STAMP 2 and your STAMP 2

will come to life. The original BASIC STAMP 2 utilizes Figure 27-4

BASIC STAMP 2 Alternative

a small 24-pin carrier board which houses the main

processor chip, memory, regulators, etc.

Another approach to obtaining the STAMP 2 is to

chip, a 16C57C-HS/P PIC, and a 28 pin DIP style

build your own “alternative” STAMP 2; in this

STAMP 2 as seen in Figure 27-4.

configuration you obtain the 28 pin DIP interpreter chip The lower cost 28 pin PIC BASIC interpreter chips,

and a few extra support or “glue” components and you

the PBASIC2C/P, requires a few external support chips can save some money by assembling your own

and occupies a bit more real estate but the cost is

Alternative STAMP 2.

significantly lower. The BASIC STAMP 2 costs $49,

The “alternative” STAMP 2 configuration revolves

while “rolling your own” version will cost about half or around the lower cost BASIC STAMP 2 Interpreter

$11 for the STAMP alternative plus $8 or so for the

−

9 V

+

1

SOUT

VIN

24

PC serial port

2

SIN

VSS

23

3

ATN

RES

22

1

4

VSS

VDD

21

DSR

6

5

P0

P15

20

2

.1

RX

μF

6

P1

P14

19

RTS

7

7

P2

P13

18

3

TX

8

P3

P12

17

8

.1 μF

9

P4

P11

16

4

DTR

10

P5

P10

15

9

11

P6

P9

14

5

GND

12

P7

P8

13

Chapter Twenty-Seven: BASIC STAMP Figure 27-3 BASIC STAMP 2 (BS2-1C) programming cable 278

Chapter Twenty-Seven: BASIC STAMP

extra support components. The 28 pin BASIC STAMP 2

projects is to use “perf-board” type construction, using interpreter chip requires a few external support

point to point wiring. This type of construction is a little components, a 24LC6B memory chip, a MAX232 serial

more permanent but can be modified more easily than if interface chip and a ceramic resonator. The MAX232

you were to construct your own printed circuit board.

requires four 1 uf capacitors, a diode and a resistor, and Printed circuit boards are generally used when design is provides a conventional serial I/O which is used to

complete or finalized and debugged.

program the microprocessor. The STAMP 2

The design of the alternate STAMP 2 requires you to

“alternative” circuit is depicted in Figure 27-5.

supply your own 5 volt regulator in order to power the Whereas the original BASIC STAMP 2 contains

BASIC interpreter, memory, and serial communications

all the associates microprocessor components on the

chip. You can supply the regulator with 9–12 V DC via 24-pin carrier board the alternative STAMP utilizes

a “wall wart” power supply or build your own power

discrete components wired to the large 28-pin

supply.

16C57C-HS/P microprocessor chip.

A heat sink on the regulator is advisable, in order to You can build the alternative STAMP 2 on an

dissipate heat properly. When constructing the

experimenter board; with this method you can insert

alternative STAMP 2, be sure to observe the correct

components and the chips, and wire the circuit together polarity when installing the four 1 μF electrolytic

using jumper wires. In this method your designs are fluid capacitors and the diode at D1. Note that the switch S1

and can be changed until you complete and debug your

is used to reset the microprocessor if one of the

project. A second method to building your STAMP 2

programs stalls. The alternative STAMP 2 has 16 in/outs

+5 V

+5 V

9-Pin serial

8

3

2

U2

R1

2 XTL

6

DSR

7

1

3

1

5

Reset

7

RTS

6

26 27

6

4

S1

7

U1

5

GND

12

P8 P9 P10 P11P12 P13 P14 P15

13

+5 R2

4

DTR

28

25

R3

U3

24

9

8

23

8

3

TXD

22

R4

21

11

14

20

9

2

RXD

19

+5 V

D1

10

7

18

17

16

1

+ C4

C3

16

+

2

3

+

15

6

4

C5

14

5

C2

13

+

15

1

12

11

4

10

2

+5 V

+

Out

In

+12 V

C1

U4

+

+

+5 V

C7

C6

GND

P7 P6

P5 P4 P3 P2 P1 P0

Figure 27-5

Alternative STAMP 2

279

9-Pin

PB-9

1

MAX232

6

2

DTR

13

U3

STAMP 2

3

TXD

8

7

4

RXD

14

U1

5

XTL

GND

GND

U2

Figure 27-6

Alternative STAMP 2 Programming cable

but the pinouts are different from the original STAMP 2.

The BASIC STAMP 2 is also available in the OEM

The alternative STAMP 2 provides P0 through P15

plug-in board version which uses the 16C57C-HS/P

at the interpreter chip pins 10 through 25. A simple

chip as shown in Figures 27-7 and 27-8.

trick is to add 10 to the functional designation. The The OEM BASIC STAMP 2 is available as a kit or in

MAX232 chip at U3 allows the PIC processor to

a pre-wired version for around $38. The OEM version is communicate to your personal computer, so that you

designed to be a plug-in computer for a commercial

can download your programs via the serial port of your product. The entire BASIC STAMP 2 and support

PC (see Figure 27-6).

components are on the PC board with a 20 pin header at Chapter Twenty-Seven: BASIC STAMP Figure 27-7 BASIC STAMP OEM controller. Courtesy of Parallax, Inc 280

Chapter Twenty-Seven: BASIC STAMP

+VCC

LM2940-5

VIN

U2

3

1

1

8

VIN

VOUT

2

7

Resonator

3

+

30 mHZ

6

GND

4

2

5

XTL

24LC16B

4.7 K

28

10 K

1

10 K

10 K

2

U1

27

4.7 K

3

26

J2

4

25

Stamp 2/P

1

5

24

6

6

23

2

2N3904

7

22

8

21

7

Q1

Q3

9

20

3

8

10

19

4

11

18

MN13811

2N3906

12

17

9

3

2

5

13

16

U3

14

15

DB9

1

PIC16C57C-HS/P

Q2

2N3904

.1 μF

.1 μF

20

19

18

17

16 15 14

13

12 11

10 9

8

7

6 5

4

3

2 1

Figure 27-8

BASIC STAMP 2 OEM/Industrial

proper pin-outs for both input and output pins

the bottom of the board. The pinouts for the OEM

because they are different between the original BASIC

STAMP 2 are again a little different than the original STAMP 2, the alternative STAMP 2 and the OEM

STAMP 2 but lend themselves to all STAMP 2

STAMP 2.

applications; this is a good alternative to the original BASIC STAMP 2. The OEM STAMP 2 contains the

Parallax, the supplier of the STAMP microcontroller

STAMP 2 chip, a regulator, low voltage detector chip, a products, has been around from the early 1990s and has 20 mHZ resonator, a memory chip, three transistors, two a very large and dedicated following; and for very good resistor packs, and a few capacitors all on the PC board.

reasons. Parallax supplies a complete line of processors, You can readily substitute the BASIC OEM module for

sensors, support chips as well as good on-line

any of the projects in this book or for any BASIC

documentation, manuals, example codes, and forums for STAMP 2 project. You must be careful to observe the

each of their products; see www.parallax.com

281

Chapter 28

DTMF Touch-Tone

Generator/Decoder Display

S1

SPST toggle switch

Parts list

S2

SPST pushbutton

switch (normally open)

Touch¯Tone

PC type

Generator/Dialer

P1

DB¯9, 9 pin female

U1

CM8880 Touch¯tone

RS¯232 connector

encoder/decoder IC

Misc

circuit board,

U2

BASIC STAMP 2 9

headers, wire, jack,

(original)

plugs, etc.

U3

LM 7805 5 V

Touch¯Tone

regulator IC

Decoder/Display

U4

LM358 Op¯amp

U1

CM8880 Touch¯tone

R1

100 K ohm 1⁄ W

4

encoder/decoder IC

resistor

U2

BASIC STAMP 2

R2, R5

10 K ohm 1⁄ W

4

(original)

resistor

U3

LM 7805 5 V

R3

390 K ohm 1⁄ W

regulator

4

resistor

R1, R2, R5

100 K ohm

R4

3.3 K ohm 1⁄ W

1

⁄ W resistor

4

4

resistor

R3

37.5 K ohm 1⁄ W

4

R6

10 K ohm

resistor

potentiometer

R4

60 K ohm 1⁄ W

4

R7

22 K ohm 1⁄ W

resistor

4

resistor

R6

390 K ohm 1⁄ W

4

C1

.1 μF 250 V

resistor

polyester capacitor

R7

10 K ohm 1⁄ W

4

C2, 23, C7,

.1 μF

resistor

35 volt disc capacitor

C1, C2

.1 μF 250 V

C4

2.2 μF 35 V

polyester capacitor

electrolytic capacitor

C3, CD4, C5

.1 μF

C5, C6

10 μF 35 V

35 volt disc capacitor

electrolytic

C6

10 μF, 35 V

capacitor

electrolytic capacitor

XTL

3.579 color burst

XTL

3.579 color burst

crystal

crystal

282

Copyright © 2009 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Chapter Twenty-Eight: DTMF Touch-Tone Generator

S1

SPST toggle switch

Table 28-1

S2

SPST pushbutton

Touch tone or DTMF frequency tones

switch (normally open)

1209

1336

1477

1633

LX

LCD module Scott

697

1

2

3

A

Edwards ILM¯216

770

4

5

6

B

(www.seetron.com)

852

7

8

9

C

P1

DB¯9, 9 pin female

941

0

0

#

D

RS¯232 connector

Misc

circuit board,

on a phone line or radio circuit and display the numbers headers, wire, etc.

on an LCD panel.

Dual Tone Multifrequency or DTMF tone signaling has

Both Touch-Tone Generator and decoder/display

been around since the late 1950s and 1960s. The DTMF

projects use the STAMP 2 microprocessor and the new

signaling system originated from the Grand Old

CM8880 DTMF encoder/decoder chip, and a 20 pin

Ma Bell. The beauty of this signal system is that two in-line DIP package. This Encoder/Decoder chip can be non-resonant tones are transmitted simultaneously and easily interfaced to the STAMP 2 controller and can be can be sent over land lines or wire or radio systems

used to both generate and decode Touch-Tone tones.

between and through various repeater systems around

The chip only requires about six external components

the country. The DTMF system is very reliable in that to form a complete encoder/decoder. The CM8880 chip

two tones must be decoded at once, so that false outputs uses a ubiquitous 3.579 color burst crystal for its

are very unlikely. The DTMF system was and still is a oscillator. The chip produces a binary output on pins very powerful method of signaling and control for the D0 through D3, which directly connects to the

phone system as well as for ham radio operators to

STAMP 2 controller (see Table 28-2). The Est and StGt, control remote repeater systems or remote base

i.e. pins 18 and 19 respectively, form a time constant to transmitters over long distances. Touch-Tone

frequencies are illustrated in Table 28-1.

In the past, Touch-Tone frequencies had to be

Table 28-2

generated and decoded by discrete tone generators

DTMF binary and decimal values

and tone decoders. Encoders and decoders were

Binary Value

Decimal Value

Keypad Symbol

quite complex. Today DTMF encoding and decoding

can be accomplished by a single 20 pin integrated

0000

0

D

circuit chip.

0001

1

1

In this chapter, we will take a look at two different 0010

2

2

projects. The first project is a simple Touch-Tone

0011

3

3

Generator which can be used to send DTMF signals

0100

4

4

through a telephone line or radio transceiver. The

0101

5

5

second project uses the CM8880 to decode DTMF tones

0110

6

6

0111

7

7

1000

8

8

1001

9

9

1010

10

0

1011

11

0

1100

12

#

1101

13

A

1110

14

B

1111

15

C

Figure 28-1

DTMF decoder display

283

Table 28-3

Table 28-4

Control bits CS, RW, and RS0 status

Functions of control register A

CS

RW

RS0

Description

Bit

Name

Function

0

0

0

Active: write data (i.e. send DTMF)

0

Tone out

0 = tone generator disabled

0

0

1

Active: write instructions to CM8880

1 = tone generator enabled

0

1

0

Active: read data (i.e. receive DTMF)

1

Mode control

0 = send and receive DTMF

0

1

1

Active: read status from CM8880

1 = send DTMF, receive call

1

0

0

inactive

progress tone (DTMF bursts

1

0

1

inactive

lengthened to 104 ms)

1

1

0

inactive

2

Interrupt 0

= make controller check for

1

1

1

inactive

enable

DTMF rec’d

1 = interrupt controller via pin 13

determine a valid signal duration time in which to

when DTMF rec’d

accept a tone pair.

3

Register 0

= next instruction write goes

Three additional bits are used to select the modes of select

to CRA

the CM8880. The (CS) or chip select pin, the (RW) or

1 = next instruction write goes

read/write pin and the (RS0) or resister select pin;

to CRB

Table 28-3 depicts all the combinations of the three

control pins.

mode select the CM8880 chip. Pins 14 through 17 are

The CM8880 is only active when CS equals 0. The

data output pins which send the binary representation of RW bit determines the data direction; 1 = read and

the number received by the decoder portion of the chip.

0 = write, and the RS bit determines whether the

The Touch-Tone Generator uses pin 8 of the CM8880 to

transaction involves data (DTMF tones) or internal

send the analog audio signal to be amplified by U4.

functions, i.e. 1= instructions/status and 0 = data.

The output of the IC amplifier is couple via C6 to a

Before you can use the CM8880, you have to set it up.

microphone input of a radio transceiver or wire circuit.

The device has two control registers; A and B. In the If you have a walkie talkie or mobile radio you could beginning of the program listing you will notice the set-up use this circuit to send tones over radio to a remote of the registers; also refer to Tables 28-4 and 28-5.

receiver with a second CM8880 set up as a decoder to

translate the remote tones into control functions

(see the Radio Decoder project). In the Touch-Tone

Generator program shown below, you will notice the

Touch-Tone Generator

project

Table 28-5

Functions of control register B

Our first project in this chapter is a Touch-Tone Generator, run by the BASIC STAMP 2 microprocessor shown in

Bit

Name

Function

Figure 28-2.

0

BURST

0 = output DTMF bursts of 52 or 104 ms

The Touch-Tone Generator can be used to send

1 =1 output DTMF as long as enabled

Touch-Tone signals through a radio or wire circuit. This 1

Test

0 = normal operating mode

circuit can be interfaced directly to a telephone line or to 1 = present test timing bit on pin 13

the microphone input of a radio so that you could send 2

Single/

0 = output dual (real DTMF) tones

DTMF tones over telephone or radio circuits to control Dual

1 = output separate row or column tones

things remotely. The Touch-Tone Generator utilizes the 3

Column/

0 = if above = 1 select row tone

STAMP 2 to animate the CM8880 encoder/decoder chip.

Chapter Twenty-Eight: DTMF Touch-Tone Generator

Row

1 = if above = 1 select column tone

Note that pins 9, 10, and 11 are used to enable and

284

Chapter Twenty-Eight: DTMF Touch-Tone Generator

Programming

cable

DB–9

+5 V

7 6 5 4 3 2

+5 V

1

20

C2

IN

VDD

+

2

19

IN− STGT

C3

3

18

CS

EST

R8

1

24

R1

U1

4

17 R3

TX

VREF

2

23

RX

U2

5

16

VSS

3

22

ATW

6

15

21

OSC1

4 GND

XTL

7

14

5

20

OSC2

P15

C1

P0

8

13

19

6

RSET

Tone

P1

P14

7

18

9

12 R4

+5

P2

P13

S2

R/W

F2

R2

8

17

10

11

R5

P3

P12

CS

RSO

9

16

P4

P11

10

15

P5

P10

11

14

P6

P9

12

13

P7

P8

U4

+V

C4

R7

R6

6

8

C5

−

7

S1

5

Audio

+5 V

+ 9 V DC

Out

+

In

4

U3

Out

+

+

C6

C7

Figure 28-2

Touch-Tone Generator

phone number 459-0623. Simply substitute your own The STAMP 2 animates the control pins on pins 9,

phone number or tone sequence for your particular

10, and 11, and accepts the binary output of the

application.

CM8880 via pins 14 through 17. The LCD panel is

driven by the BASIC STAMP 2 on Pin P7. The program

accepts numbers and displays them sequentially, and if Touch-Tone

the delay between characters is too long then the display will show a <space> until another stream is decoded.

decoder/display project

Power switch S1 applies 5 V to the STAMP 2 via the

5 V regulator at U3. Momentary pushbutton S2 is the

Our second project utilizes the CM8880 DTMF

system reset button, which is used in the event of a

encoder/decoder and the STAMP 2 to form a

system “lock-up.”

Touch-Tone Decoder Display project. This decoder

will allow you to monitor Touch-Tone signals,decode

the phone numbers dialed, and display the number on

Circuit assembly

a serial LCD display. This project can be placed across the phone line to capture phone numbers, or it could be Before we begin constructing the Touch-Tone

used with a radio transceiver to monitor access tones Generator/Decoder, you will need to locate a clean,

sent “over the air” and display the captured numbers on well-lit worktable or workbench. Next we will gather a the display. The Touch-Tone Decoder project uses the

small 25–30 W pencil tipped soldering iron, a length

CM8880 in the decoder mode. The tone signals are

of 60/40 tin–lead solder, and a small canister of Tip received via C1 and C2, using the balanced input

Tinner, available at your local RadioShack store;

network shown in Figure 28-3.

Tip Tinner is used to condition the soldering tip

285

Programming

DB-9

C1

R1

cable

+5 V DC

7 6 5 4 3 2

+5 V

Phone

line

C3

1

20

C2

R2

2

19

C4

R9

U1

R5 3

18

R3

1

24

R4

4

17

R6

TX

2

23

RX

U2

5

16

3

22

ATN

Stamp

6

15

4

21

GND

2

7

14

5

20

P0

P15

Reset

XTL

6

19

13

8

P1

P14

R8

7

18

9

12

+5

P2

P13

S2

8

17

R7

P3

P12

10

11

9

16

P4

P11

10

15

P5

P10

11

14

P6

P9

12

13

P7

P8

LCD-Disp

+5 V

Out

S1

IN

+9 volts DC

+5 V

IN

U3

+

+

C5

C6

Figure 28-3

DTMF Decoder/display

between solder joints. You drive the soldering tip into Table 28-6 illustrates the resistor code chart and how the compound and it cleans and prepares the soldering to read resistors, while Table 28-7 illustrates the

tip. Next grab a few small hand tools; try to locate

capacitor code chart, which will aid you in constructing small flat blade and Phillips screwdrivers. A pair of the project.

needle-nose pliers, a pair of tweezers along with a

Refer now to the resistor color code chart in Table 28-6, magnifying glass, and a pair of end-cutters and

which will help you identify the resistor values. Note we will begin constructing the project. Now locate

that each resistor will have either three or four color your schematic diagram and parts layout diagram

bands, which begin at one end of the resistor’s body.

along with all of the components needed to build

The first colored band represents the resistor’s first the project.

digit, while the second color represents the second digit The Touch-Tone Generator/Decoder can be built on a

of the resistor’s value. The third colored band represents 4′′ × 5′′ single sided glass epoxy circuit board. There the resistor’s multiplier value, and the fourth color band are slight variations in the two circuits. You could build represents the resistor’s tolerance value. If there is no a single Touch-Tone encoder/decoder circuit that will fourth colored band then the resistor has a 20%

perform both functions if desired, incorporating all the tolerance value. If the resistor’s fourth band is silver components; note the component designations are a bit then the resistor has a 10% tolerance value and if the different. You could build the Touch-Tone Decoder and fourth band is gold then the resistor’s tolerance value simply add the additional components around U4 for

will be 5%.

Touch-Tone output generation.

Finally, we are ready to begin assembling the project, Once all the components are in front of you, you

so let’s get started. The prototype project was

can check them off against the project parts list to

constructed on a single-sided printed circuit board or make sure you are ready to start building the project.

PCB. With your Touch-Tone Decoder PC board in front

Now, locate Tables 28-6 and 28-7, and place them in

of you, we can now begin populating the circuit board.

CChapter Twenty-Eight: DTMF Touch-Tone Generator front of you.

We are going to place and solder the lowest height

286

Chapter Twenty-Eight: DTMF Touch-Tone Generator

Table 28-6

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

No color

20%

Table 28-7

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

1.0

1R0

3,900

3.9

.0039

392

1.2

1R2

4,700

4.7

.0047

472

1.5

1R5

5,600

5.6

.0056

562

1.8

1R8

6,800

6.8

.0068

682

2.2

2R2

8,200

8.2

.0082

822

2.7

2R7

10,000

10

.01

103

3.3

3R3

12,000

12

.012

123

3.9

3R9

15,000

15

.015

153

4.7

4R7

18,000

18

.018

183

5.6

5R6

22,000

22

.022

223

6.8

6R8

27,000

27

.027

273

8.2

8R2

33,000

33

.033

333

10

100

39,000

39

.039

393

12

120

47,000

47

.047

473

15

150

56,000

56

.056

563

18

180

68,000

68

.068

683

22

220

82,000

82

.082

823

27

270

100,000

100

.1

104

33

330

120,000

120

.12

124

39

390

150,000

150

.15

154

47

470

180,000

180

.18

184

56

560

220,000

220

.22

224

(Continued)

287

Table 28-7—cont’d

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

68

680

270,000

270

.27

274

82

820

330,000

330

.33

334

100

.0001

101

390,000

390

.39

394

120

.00012

121

470,000

470

.47

474

150

.00015

151

560,000

560

.56

564

180

.00018

181

680,000

680

.68

684

220

.00022

221

820,000

820

.82

824

270

.00027

271

1,000

1

105

330

.00033

331

1,500

1.5

155

390

.00039

391

2,200

2.2

225

470

.00047

471

2,700

2.7

275

560

.00056

561

3,300

3.3

335

680

.00068

681

4,700

4.7

475

820

.00082

821

6.8

685

1,000

1.0

.001

102

10

106

1,200

1.2

.0012

122

22

226

1,500

1.5

.0015

152

33

336

1,800

1.8

.0018

182

47

476

2,200

2.2

.0022

222

68

686

2,700

2.7

.0027

272

100

107

3,300

3.3

.0033

332

157

157

Code = 2 significant digits of the capacitor value + number of zeros to follow 10 pF = 100

For values below 10 pF, use “R” in place of decimal e.g. 8.2 pF = 8R2

100 pF = 101

1,000 pF = 102

22,000 pF = 223

330,000 pF = 334

1 μF = 105

components first, the resistors and diodes. First,

excess component leads flush to the edge of the circuit locate our first resistor R1. Resistor R1 has a value of board. Next locate the remaining resistors and install 100,000 ohms and is a 5% tolerance type. Now take a

them in their respective locations on the main controller look for a resistor whose first color band is brown,

PC board. Solder the resistors to the board, and

black, yellow, and gold. From the chart you will notice remember to cut the extra lead with your end-cutters.

that brown is represented by the digit (1), the second Note that capacitors generally come from two major

color band is black, which is represented by (0). Notice groups or types. Non-polar types, such as the ones in that the third color is yellow and the multiplier is

this project, have no polarity and can be placed in either (10,000), so (1) (0) × 10,000 = 100,000 or 100 K ohms.

direction on the circuit board. The other type of

Go ahead and locate where resistor R1 goes on

capacitors are called polarized types; these capacitors the PC and install it; next solder it in place on the have polarity and have to be inserted on the board with Chapter Twenty-Eight: DTMF Touch-Tone Generator PC board, and then with a pair of end-cutters trim the respect to their polarity marking in order for the circuit 288

Chapter Twenty-Eight: DTMF Touch-Tone Generator

to operate correctly. On these types of capacitors, you indented circle, a cutout, or notch at the top end

will observe that the components actually have a plus or of the IC package. Pin 1 of the IC will be just to

minus marking or a black or white band with a plus

the left of the notch, or cutout. Refer to the

or minus marking on the body of the capacitors.

manufacturer’s pin-out diagram, as well as the

Capacitors must be installed properly with respect to schematic, when installing these parts. If you

polarity in order for the circuit to work properly. Failure doubt your ability to correctly orient the ICs, then

to install electrolytic capacitors correctly could cause seek the help of a knowledgeable electronics enthusiast damage to the capacitor as well as to other components to help you.

in the circuit when power is first applied.

When installing the BASIC STAMP 2 microcontroller

Many capacitors are quite small in physical size, so

be sure to handle it very carefully, using anti-static manufacturers have devised a three-digit code which

precautions. The BASIC STAMP 2 module has a copper

can be placed on the capacitor instead of the actual

foil dot in the top center of the carrier board; also note value. The code occupies a much smaller space on the

that the largest chip on the microcontroller board is at capacitor and can usually fit nicely on the capacitor the bottom of the carrier board. This information should body, but without the chart the builder would have a

help in orienting the BASIC STAMP 2 module. Be slow

difficult time determining the capacitor’s value.

and careful when installing the BS2, as it represents a significant cost and you do not want to damage it by

Now look for the capacitors from the component

installing it incorrectly.

stack and locate capacitors C3 and C4, they are small sized capacitors labeled (104) or .1 μF. Refer to

Now let’s finish up the circuit board, locating the

Table 28-7 to find code (104) and you will see that it crystal at XTL and installing it in its proper location represents a capacitor value of .1 μF. Capacitors C1 and between pins 6 and 7 of U1. Install a 4-position header C2 are also .1 μF but are larger in size and voltage

for the programming pins 1, 2, 3, and 4 on the BASIC

requirements. Go ahead and place these first four

STAMP 2 controller. Install the printed circuit board capacitors on the circuit board and solder them in place.

type momentary pushbutton reset switch at S2. If you

Now take your end-cutters and cut the excess

are building the Touch-Tone Generator, you will want

component leads flush to the edge of the circuit board.

to install the PC board type potentiometer at R6 and

Once you have installed these components, you can

provide two terminals for the audio output from the

move on to installing the remaining capacitors at C5, audio amplifier chip at U4.

C6, and C7, which are an electrolytic types, so be sure An LM7805 5-V regulator was used to step-down

you observe the correct polarity when installing these.

the voltage to 5-V for the BASIC STAMP 2, the

Touch-Tone decoder chip, and the Op-Amp at U4.

Both the Touch-Tone Generator and the Decoder

Be sure to orient the regulator correctly in order for projects contain ICs. The Touch-Tone encoder utilizes the circuit to work properly. Check the manufacturer’s the Touch-Tone encoder/decoder chip as well as the

specification sheet for proper pin-outs of the regulator LM358 Op-Amp, while the Touch-Tone decoder uses

before installing it.

only the Touch-Tone encoder/decoder chip. ICs are

often static sensitive, so they must be handled with

If you are building the Touch-Tone Decoder circuit

care. Use a grounded anti-static wrist strap and stay you will have to wire up the serial LCD module to the seated in one location when handling the ICs. Take

BASIC STAMP 2 circuit. The ground wire of the LCD

out a cheap insurance policy by installing IC sockets will go to the system ground, the LCD’s power lead

for each of the ICs. In the event of a possible circuit will go to the +5 V system power, and the serial signal failure, it is much easier to simply unplug a defective lead of the LCD will go to pin 12 or P7 on the

IC than trying to unsolder 20 or 24 pins from a PC

STAMP 2 module.

board without damaging the board. ICs have to

Once the Touch-Tone Encoder or Touch-tone Decoder

be installed correctly if the circuit is going to work circuit board has been completed, take a short break and properly. IC packages will have some sort of

then we will inspect the PC board for possible “cold”

markings which will help you orient them on

solder joints and “short” circuits. Pick up the PC board the PC board. An IC will have either a small

with the foil side facing upwards toward you.

289

Carefully inspect the solder joints, these should look Make a directory for the Touch-Tone Encoder

smooth, clean, and bright. If any of the solder joints and Touch-Tone Decoder programs. Type in or

look dull, dark, or blobby, then you should remove the download the two programs into the directory. Go to

solder with a solder sucker or a solder wick and then www.paralax.com and locate the Windows BASIC

resolder the joint all over again. Now we will inspect STAMP Editor 2.5 or above from the DOWNLOADS

the PC board for possible short circuits. Short circuits section of the website. Install the STAMP 2 editor

can be caused from small solder blobs bridging the

program. From the STAMP 2 editor program, open up

circuit traces or from cut component leads which can

either the Touch-Tone Generator (dial.bs2) or Touch-Tone often stick to the circuit board once they have been cut.

Decoder (dtmf_rcv.bs2) program. In the Touch-Tone A sticky residue from solder will often trap component Generator program you will notice that there is a

leads across the circuit traces. Look carefully for any simulated telephone number listed. You will need to

bridging wires across circuit traces.

change the sample phone number to the desired phone Next, you will need to locate or build a 9 volt

number. With power applied to your circuit and the

DC power supply in order to power the DTMF

programming cable connected, between the

encoder/decoder circuits. You can elect to build a

programming computer and BASIC STAMP 2,

power supply or try to locate a “wall wart” power

go to the RUN tab on the toolbar in the editor program supply from a surplus electronic supplier, to provide and press RUN and download either the Touch-Tone

9-V to the regulator at U3.

Encoder or Decoder program into your circuit board

depending upon which circuit you built. Once the

The Touch-Tone encoder or decoder circuit board can

program is installed into the BASIC STAMP 2,

be mounted in a small plastic enclosure box to protect you can begin using your new Touch-Tone

it. Use four plastic standoffs to mount the circuit board Generator/Decoder circuits.

to the base plate of the plastic or metal enclosure box.

Install a coaxial power jack for your 9-V DC

Building the Touch-Tone encoder or generator, will

power supply. Install an audio output jack if you are allow you to dial a phone number or generate control

constructing the Touch-Tone Generator circuit. If you tones which can be sent through your telephone line or are building the Touch-Tone Decoder circuit, you will radio equipment. In operation you would use the

want to mount the LCD on the top or front of the

STAMP 2 frequency output or Freqout command to

enclosure, along with the power switch at S1. You will send DTMF tones out of the circuit.

also need to install a four position jack on the enclosure Building the Touch-Tone decoder will permit you to

for the programming cable connections.

decode phone numbers dialed on your phone line, so

Now you are ready to test out your Touch-Tone

you could monitor the phone line or you could use the Encoder or Decoder circuit. Programming the STAMP 2

Touch-Tone decoder to “read” tone from a radio receiver controller is achieved using the TX, RX, ATN, and

which ham operators use to control objects or repeater ground pins 1 though 4. Connect up the programming

systems.

cable between your personal computer and the 4-pin

The Radio DTMF Encoder/Decoder circuits can be

programming pins on the BASIC STAMP 2

used for many different applications; we only illustrated microcontroller. Now connect your 9-volt “wall-wart”

two but your imagination can think up many more.

power supply to the circuit, and you are ready to begin Once you become more familiar with programming the

programming and testing the Touch-Tone

BASIC STAMP 2, the encoder and decoder programs

Generator/Decoder circuits.

will lend themselves to many user modifications!

Chapter Twenty-Eight: DTMF Touch-Tone Generator

290

Chapter Twenty-Eight: DTMF Touch-Tone Generator

Touch-Tone Generator/dialing program

‘DIAL.BS2

‘ Program: DIAL.BS2 (BS2 sends DTMF tones via the 8880)

‘ This program demonstrates how to use the CM8880 as a DTMF tone

‘ generator. All that is required is to initialize the 8880 properly,

‘ then write the number of the desired DTMF tone to the 8880s

‘ 4¯bit bus.

‘ The symbols below are the pin numbers to which the 8880s

‘ control inputs are connected, and one variable used to read

‘ digits out of a lookup table.

RS

con 4

‘ Register¯select pin (0 = data).

RW

con 5

‘ Read/Write pin (0 = write).

CS

con 6

‘ Chip-select pin (0 = active).

digit

var nib

‘ Index of digits to dial, 1-15.

‘ This code initializes the 8880 for dialing by writing to its

‘ internal control registers CRA and CRB. The write occurs when

‘ CS (pin 6) is taken low, then returned high. See the accompanying

‘ article for an explanation of the 8880s registers.

OUTL = 127

‘ Pins 0-6 high to deselect 8880.

DIRL = 127

‘ Set up to write to 8880 (pins 0-6 outputs).

OUTL = %00011011

‘ Set up register A, next write to register B.

high CS

OUTL = %00010000

‘ Clear register B; ready to send DTMF.

high CS

‘ This for/next loop dials the seven digits of my fax number. For

‘ simplicity, it writes the digit to be dialed directly to the output

‘ pins. Since valid digits are between 0 and 15, this also takes RS,

‘ RW, and CS low—perfect for writing data to the 8880. To complete

‘ the write, the CS line is returned high. The initialization above

‘ sets the 8880 for tone bursts of 200 ms duration, so we pause

‘ 250 ms between digits. Note: in the DTMF code as used by the phone

‘ system, zero is represented by ten (1010 binary) not 0. That is why

‘ the phone number 459¯0623 is coded 4,5,9,10,6,2,3.

for digit = 0 to 6

lookup digit,[4,5,9,10,6,2,3], OUTL

‘ Get digit from table.

high CS

‘ Done with write.

pause 250

‘ Wait to dial next digit.

next

end

Touch-Tone decoding/display program

DTMF_RCV.BS2

‘ Program: DTMF_RCV.BS2 (Receives/displays DTMF using 8880 with BS2)

‘ This program demonstrates how to use the 8880 as a DTMF decoder. As 291

‘ each new DTMF digit is received, it is displayed on an LCD Serial

‘ Backpack screen. If no tones are received within a period of time

‘ set by sp_time, the program prints a space (or other selected character)

‘ to the LCD to record the delay. When the display reaches the right¯hand

‘ edge of the screen, it clears the LCD and starts over at the left edge.

RS

con 4

‘ Register¯select pin (0 = data).

RW

con 5

‘ Read/Write pin (0 = write).

CS

con 6

‘ Chip¯select pin (0 = active).

dtmf

var

byte

‘ Received DTMF digit.

dt_Flag

var

bit

‘ DTMF¯received flag.

dt_det

var

INL.bit2

‘ DTMF detected status bit.

home_Flag

var

bit

‘ Flag: 0 = cursor at left edge of LCD.

polls

var

word

‘ Number of unsuccessful polls of DTMF.

LCDw

con 16

‘ Width of LCD screen.

LCDcol

var

byte

‘ Current column of LCD screen for wrap.

LCDcls

con 1

‘ LCD clear¯screen command.

I

con 254

‘ LCD instruction toggle.

sp_time

con 1500

‘ Print space this # of polls w/o DTMF.

n24n

con $418D

‘ Serout constant: 2400 baud inverted.

‘ This code initializes the 8880 for receiving by writing to its

‘ internal control registers CRA and CRB. The write occurs when

‘ CS (pin 6) is taken low, then returned high.

OUTL = %01111111

‘ Pin 7 (LCD) low, pins 0 through 6 high.

DIRL = %11111111

‘ Set up to write to 8880 (all outputs).

OUTL = %00011000

‘ Set up register A, next write to register B.

high CS

OUTL = %00010000

‘ Clear register B; ready to send DTMF.

high CS

DIRL = %11110000

‘ Now set the 4¯bit bus to input.

high RW

‘ And set RW to “read.”

serout 7,n24n,[I,LCDcls,I]

‘ Clear the LCD screen.

‘ In the loop below, the program checks the 8880’s status register

‘ to determine whether a DTMF tone has been received (indicated by

‘ a ‘1’ in bit 2). If no tone, the program loops back and checks

‘ again. If a tone is present, the program switches from status to

‘ data (RS low) and gets the value (0-15) of the tone. This

‘ automatically resets the 8880’s status flag.

again:

high RS

‘ Read status register.

low CS

‘ Activate the 8880.

dt_flag = dt_det ‘ Store DTMF¯detected bit into flag.

high CS

‘ End the read.

if dt_Flag = 1 then skip1

‘ If tone detected, continue.

polls = polls+1

‘ Another poll without DTMF tone.

if polls < sp_time then again

' If not time to print a space, poll.

if LCDcol = LCDw then skip2

‘ Don’t erase the screen to print spaces.

dtmf = 16

‘ Tell display routine to print a space.

Chapter Twenty-Eight: DTMF Touch-Tone Generator

gosub Display

‘ Print space to LCD.

292

Chapter Twenty-Eight: DTMF Touch-Tone Generator

skip2:

polls = 0

‘ Clear the counter.

goto again

‘ Poll some more.

skip1:

‘ Tone detected:

polls = 0

‘ Clear the poll counter.

low RS

‘ Get the DTMF data.

low CS

‘ Activate 8880.

dtmf = INL & %00001111

‘ Strip off upper 4 bits using AND.

high CS

‘ Deactivate 8880.

gosub display

‘ Display the data.

goto again

‘ Do it all again.

Display:

if LCDcol <LCDw then skip3

‘ If not at end of LCD, do not clear screen.

serout 7,N24N,[I,LCDcls,I]

‘ Clear the LCD screen.

LCDcol = 0

‘ And reset the column counter.

skip3:‘ Look up the symbol for

the digit.

if LCDcol=0 AND dtmf=16 then ret ‘ No spaces at first column.

lookup dtmf,[“D1234567890*#ABC¯”] ,dtmf

serout 7,N24N,[dtmf]

‘ Write it to the Backpack display.

LCDcol = LCDcol + 1

‘ Increment the column counter.

ret:

return

293

Chapter 29

Caller-ID/Blocker Project

C7, C11

1 μF 50 V

Parts list

electrolytic capacitor

C8, C9

30 pF 35 V

Caller¯ID/Blocker

disc capacitor

R1, R2, R3

10 K ohm

C10, C12

1 μF 50 V

1

⁄ watt resistor

2

disc capacitor

R4

18 K ohm 1⁄ W

4

MOV

300 V metal

resistor

oxide varistor

R5

15 K ohm 1⁄ W

4

D1, D2, D4

1N4004

resistor

silicon diodes

R6

270 K ohm 1⁄ W

4

D5

1N4001 silicon diode

resistor

DS1, DS2, DS3

LED

R7

4.7 megohm 1⁄ W

4

DS4, DS5

LED

resistor

Q1

2N2222 NPN transistor

R8

10 megohm 1⁄ W

4

U1

Motorola MC 145447

resistor

Caller¯ID chip

R9

22 K ohm 1⁄ W

4

U2

BASIC STAMP 2

resistor

(original)

R10

470 ohm 1⁄ W

4

U3

LM7805 5 V

resistor

regulator

R11, R12, R13, R14

XTL

3.579 color burst

1 K ohm 1⁄ W

4

crystal

resistor

K1

5 volt reed relay

R15, R16

10 K ohm

SPST

1

⁄ W resistor

4

LCD

serial LCD display

R17, R18, R19

10 K ohm

www.seetron.com

1

⁄ W resistor

4

SW1, SW2, SW3

momentary

C1, C2

.2 μF 400 V

pushbutton switch

mylar capacitor

(normally open)

C3, C4

470 pF 400 V

SW4, SW5

momentary

mylar capacitor

pushbutton switch

C5

.2 μF 50 V disc

(normally open)

capacitor

Misc circuit board,

C6

1 μF 50 V disc

power supply, wire,

capacitor

connectors, etc.

294

Copyright © 2009 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Chapter Twenty-Nine: Caller-ID/Blocker Project

Unwanted calls are highly interruptive and very

BASIC STAMP 2. The Ring detect output of the

annoying. Why not screen your incoming calls?

Caller-ID chip is fed to P18 of STAMP 2. The ring

Everyone knows those pesky unsolicited callers always detect signal determines that the circuit should “pick up”

phone you when you are indisposed or just sitting down or initiate. Once the ring signal is detected, the STAMP

for dinner. Screen your calls from unwanted phone

2 pulls in the relay at K1. Indicator DS5 confirms that callers or bill collectors, or your ex-wife/husband. The the relay has pulled in. The indicator at DS4 is a monitor Caller-ID/Blocker project, shown in Figure 29-1, will LED; it stays on normally and then toggles off when the allow you to identify up to 10 incoming telephone calls Caller-ID program is running. The indicator at DS3 is a and display the phone numbers on an LCD display. The

troubleshooting LED; it goes high after the data has

Caller-ID unit will also allow you to block incoming calls.

been read out from the LCD display unit. The last

The Caller-ID project centers around the infamous

indicator at DS2 is driven by P0. This LED is also for BASIC STAMP 2 microprocessor, a Motorola

troubleshooting; it goes high after the data has been Caller-ID chip, and a handful of external components, successfully read into from the MC145447.

shown in Figure 29-2.

There are four function or operational input switches The Caller-ID connects across your phone line with

on STAMP 2 pins P9 through P12; we will discuss the

the ring and tip connections. A Metal Oxide Varistor functional operations later. Function A is activated by a (MOV) is placed across the phone line to limit high

normally open pushbutton switch at SW4. Function B

voltage “spikes” from damaging your circuit. Capacitors is operated through SW3 at P11. Function C is

C2 and C4 are the phone line inputs to the Caller-ID

implemented by SW1 at STAMP 2 pin P9. The RUN or

chip shown in the block diagram in Figure 29-3.

START pushbutton is started by SW2 when the circuit

is first energized. Note, all pushbutton switches are tied The ring and tip phone line inputs are fed to an to high to 5 V and when pressed the switches go to

op-amp and then to a band pass filter, followed by a

ground upon activation. The Caller-ID display is

demodulator and valid data detector. The output of the connected to the STAMP 2 via pin P15. The LCD

valid data detector is the Caller-ID data information. An display is a single wire serial “backpack” style from additional two capacitors, C1 and C2, are placed across Scott Edwards Electronics at www.seetron.com.

the line ahead of a diode bridge, which is used to rectify the ringing voltage. This ringing detect signal is then Power to the Caller-ID chip and the STAMP 2 is a

inputted to the ring detect pins on the Motorola

supplied by a 5 V regulator at U3. On the MC145447,

MC145447 Caller-ID chip, pins 3 an 4. The ring detect power is applied to pin 16, while pin 21 is used on the network is formed by resistors R3, R4, R5, and R6

STAMP 2. A system reset switch is shown at SW5,

along with C5. The ubiquitous 3.579 Mhz color burst

a normally open pushbutton switch. A 9 to 12 V

crystal forms the basic reference oscillator. The output

“wall-wart” power supply can be used to power the

at pin 7 of the Caller-ID chip drives an NPN transistor, Caller-ID circuit ahead of the regulator at U3.

which in turn drives the data indicator LED at DS1. The Alternatively, a 9-V transistor radio battery could be Caller-ID data is next coupled to the P19 pin on the

used but a power supply is recommended.

Circuit assembly

Before we begin constructing the Telephone Caller-ID

project, you will need to locate a clean, well-lit

worktable or workbench. Next we will gather a small

25–30-W pencil tipped soldering iron, a length of

60/40 tin–lead solder, and a small canister of Tip Tinner, available at your local RadioShack store; Tip Tinner is used to condition the soldering tip between solder

Figure 29-1

Caller ID front panel. Courtesy of

joints. You drive the soldering tip into the compound J Gary Sparks

and it cleans and prepares the soldering tip. Next grab a 295

296

+V

R10

Phone line

+V

+

C6

V

Serial LCD

Tip

Q1

C3

R1

+

+

DS1

C1

R9

16

D1-D4

Mov

1

15

T1

DO

2

U1

R1

DB9

+V

C10

3 RD11

7 6 5 4 3 2 J1

4

C4

R2

12

RD12

R/D

C2

5

1

24

R19 S5

2

U2

23

−

6

10

3

22

R3

1RT

OS-1

4

21

Ring

7

9

X1

5

BS2 20

1PU

OS-0

6

19

Phone line

7

18

R4

8

8

17

9

16

R8

+V

R11

R12

R13

10

15

R18

11

14

S4

R5

12

13

R16

R17

C5

C8

C9

R7

S1

S3

K1

R6

R14

S2

C7

DS2

DS3

DS4

+V

D5

DS5

−

(−)

Output

C11

C12

Input

+

+

+

U3

+

+5 V

Out

In

9–12 V DC

Figure 29-2

Caller ID project circuit

Chapter Twenty-Nine: Caller-ID/Blocker Project

Tip

−

202

BPF

VAG

Demod

Ring

+

Raw data

out

Cooke data

Ring det in 1

out

Ring

Ring det in 2

detect

circuit

Ring time

Valid

Carrier

data

detect

detect

Ring detect

out

Internal

Power up

power up

Clock

Clock select

gen

OSC in

OSC out

VDD

VSS

Figure 29-3

MC145447 Caller-ID chip

few small hand tools; try to locate small flat blade and Note that each resistor will have either three or four Phillips screwdrivers. A pair of needle-nose pliers,

color bands, which begin at one end of the resistor’s a pair of tweezers along with a magnifying glass, and a body. The first colored band represents the resistor’s pair of end-cutters and we will begin constructing the first digit, while the second color represents the second project. Now locate your schematic diagram and parts

digit of the resistor’s value. The third colored band layout diagram along with all of the components needed represents the resistor’s multiplier value, and the fourth to build the project.

color band represents the resistor’s tolerance value.

The Caller-ID circuit was built on a small single

If there is no fourth colored band then the resistor has a sided glass epoxy circuit board. You can elect to

20% tolerance value. If the resistor’s fourth band is construct you own PC board or you could assemble the

silver then the resistor has a 10% tolerance value and circuit on a STAMP 2 carrier board if desired. The

if the fourth band is gold then the resistor’s tolerance circuit board was then placed in a 4 × 6′′ plastic box.

value will be 5%.

Finally, we are ready to begin assembling the project, Once all the components are in front of you, you can

so let’s get started. As mentioned earlier, the prototype check them off against the project parts list to make project was constructed on a single-sided printed circuit sure you are ready to start building the project. Now, board or PCB; with your PC board in front of you, we

locate Tables 29-1 and 29-2, and place them in front

can now begin populating the circuit board. We are

of you.

going to place and solder the lowest height components Table 29-1 illustrates the resistor code chart and

first, the resistors and diodes. First, locate our first how to read resistors, while Table 29-2 illustrates the resistor R1. Resistors R1, R2, and R3 are 10,000 ohms, capacitor code chart which will aid you in constructing 1⁄2 W with a 5% tolerance. Now look for three resistors the project.

whose first color band is brown, black, orange, and

Refer now to the resistor color code chart in

gold. From the chart you will notice that brown is

Table 29-1, which will help you identify the resistor values.

represented by the digit (1), the second color band is 297

Table 29-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

No color

20%

Table 29-2

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

1.0

1R0

3,900

3.9

.0039

392

1.2

1R2

4,700

4.7

.0047

472

1.5

1R5

5,600

5.6

.0056

562

1.8

1R8

6,800

6.8

.0068

682

2.2

2R2

8,200

8.2

.0082

822

2.7

2R7

10,000

10

.01

103

3.3

3R3

12,000

12

.012

123

3.9

3R9

15,000

15

.015

153

4.7

4R7

18,000

18

.018

183

5.6

5R6

22,000

22

.022

223

6.8

6R8

27,000

27

.027

273

8.2

8R2

33,000

33

.033

333

10

100

39,000

39

.039

393

12

120

47,000

47

.047

473

15

150

56,000

56

.056

563

18

180

68,000

68

.068

683

22

220

82,000

82

.082

823

27

270

100,000

100

.1

104

33

330

120,000

120

.12

124

39

390

150,000

150

.15

154

47

470

180,000

180

.18

184

Chapter Twenty-Nine: Caller-ID/Blocker Project 56

560

220,000

220

.22

224

298

Chapter Twenty-Nine: Caller-ID/Blocker Project

Table 29-2—cont’d

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

68

680

270,000

270

.27

274

82

820

330,000

330

.33

334

100

.0001

101

390,000

390

.39

394

120

.00012

121

470,000

470

.47

474

150

.00015

151

560,000

560

.56

564

180

.00018

181

680,000

680

.68

684

220

.00022

221

820,000

820

.82

824

270

.00027

271

1,000

1

105

330

.00033

331

1,500

1.5

155

390

.00039

391

2,200

2.2

225

470

.00047

471

2,700

2.7

275

560

.00056

561

3,300

3.3

335

680

.00068

681

4,700

4.7

475

820

.00082

821

6.8

685

1,000

1.0

.001

102

10

106

1,200

1.2

.0012

122

22

226

1,500

1.5

.0015

152

33

336

1,800

1.8

.0018

182

47

476

2,200

2.2

.0022

222

68

686

2,700

2.7

.0027

272

100

107

3,300

3.3

.0033

332

157

157

Code = 2 significant digits of the capacitor value + number of zeros to follow 10 pF = 100

For values below 10 pF, use “R” in place of decimal e.g. 8.2 pF = 8R2

100 pF = 101

1,000 pF = 102

22,000 pF = 223

330,000 pF = 334

1 μF = 105

black, which is represented by (0). Notice that the third Note that capacitors generally come from two major

color is orange and the multiplier is (1,000), so

groups or types. Non-polar types, such as the ones in (1) (0) × 1,000 = 10,000 or 10 K ohms.

this project, have no polarity and can be placed in either Go ahead and locate where resistors R1, R2, and R3

direction on the circuit board. The other type of

are located on the PC and install them, next solder them capacitors are called polarized types, these capacitors in place on the PC board, and then with a pair of

have polarity and have to be inserted on the board with end-cutters trim the excess component leads flush to the respect to their polarity marking in order for the circuit edge of the circuit board. Next locate the remaining

to operate correctly. On these types of capacitors, you resistors and install them in their respective locations on will observe that the components actually have a plus or the main controller PC board. Solder the resistors to the minus marking or a black or white band with a plus or board, and remember to cut the extra lead with your

minus marking on the body of the capacitors.

end-cutters.

Capacitors must be installed properly with respect to 299

polarity in order for the circuit to work properly. Failure solder them in place on the PC board. Remember to cut to install electrolytic capacitors correctly could cause the excess component leads with your end-cutters, flush damage to the capacitors as well as to other components to the edge of the circuit board.

in the circuit when power is first applied.

The Caller-ID circuit utilizes a single conventional

Many capacitors are quite small in physical size, so

transistor at Q1, which is connected to the D0 or

manufacturers have devised a three-digit code which

pin 15 of U1. Transistors are generally three lead

can be placed on the capacitor instead of the actual

devices, which must be installed correctly if the circuit value. The code occupies a much smaller space on the

is to work properly. Careful handling and proper

capacitor and can usually fit nicely on the capacitor orientation in the circuit is critical. A transistor will body, but without the chart the builder would have a

usually have a Base lead, a Collector lead, and an

difficult time determining the capacitor’s value.

Emitter lead. The base lead is generally a vertical line Now look for the capacitors from the component

inside a transistor circle symbol. The collector lead is stack and locate capacitors C6, C10, and C11, small

usually a slanted line facing towards the base lead and capacitors labeled (104). Refer to Table 29-2 to find the emitter lead is also a slanted line facing the base code (104) and you will see that it represents a capacitor lead but it will have an arrow pointing towards or away value of .1 μF. Go ahead and place C6, C10, and C11 on from the base lead. Now, identify the two transistors, the circuit board and solder them in place. Next locate refer to the manufacturer’s specification sheets as well the 30 pF disc capacitors, they will most likely be

as the schematic and parts layout diagrams when

marked (33). Install these capacitors in their respective installing the two transistors. If you have trouble

locations. Now take your end-cutters and cut the excess installing the transistors, get the help of an electronics component leads flush to the edge of the circuit board.

enthusiast with some experience. Install the transistors Once you have installed these components, you can

in their respective locations and then solder them in move on to installing the remaining low profile

place. Remember to trim the excess component leads

capacitors.

with your end-cutters.

Next locate the larger capacitors and electrolytic

The Caller-ID circuit contains ICs. ICs are

capacitors. Note that C1, C2, C3, and C4 are low

often static sensitive, so they must be handled

value capacitors but large in size since they are high with care. Use a grounded anti-static wrist strap

voltage capacitors placed across the phone line. Install and stay seated in one location when handling the ICs.

these four capacitors and then solder them in place on Take out a cheap insurance policy by installing IC

the PC board. Finally locate the electrolytic capacitors.

sockets for each of the ICs. In the event of a possible Make note of their polarity and install them with respect circuit failure, it is much easier to simply unplug a to their proper polarity, this is importance if the circuit defective IC, than trying to unsolder 14 or 16 pins

is to work correctly. Solder the electrolytic capacitors in from a PC board without damaging the board. ICs

place and then trim the excess lead lengths with your have to be installed correctly if the circuit is going to end-cutters.

work properly. IC packages will have some sort of

markings which will help you orient them on the PC

The Caller-ID project contains five silicon diodes.

board. An IC will have either a small indented circle, Diodes, as you will remember, will always have some

a cut-out, or notch at the top end of the IC package.

type of polarity markings, which must be observed if

Pin 1 of the IC will be just to the left of the notch or the circuit is going to work correctly. You will notice cut-out. Refer to the manufacturer’s pin-out diagram, that each diode will have a black or white colored band as well as the schematic when installing these parts.

at one edge of the diode’s body. The colored band

If you doubt you ability to correctly orient the ICs, represents the diode’s cathode lead. Check your

then seek the help of a knowledgeable electronics

schematic and parts layout diagrams when installing the enthusiast.

diodes on the circuit board. The diode bridge consisting of diodes D1 through D4 is at the input of the circuit, The Caller-ID project also contains an IC regulator

located on its left side. Diode D5 is located at pin 8 of at U3 as well as the BASIC STAMP 2 microprocessor

Chapter Twenty-Nine: Caller-ID/Blocker Project U2. Place the diodes in their correct locations and then at U1. Take a look at the BASIC STAMP 2 module.

300

Chapter Twenty-Nine: Caller-ID/Blocker Project

On the top-middle of the STAMP 2 module you will

see a copper dot. Also note that the largest IC on the carrier board will be at the bottom; this will help you orient the BASIC STAMP module on the circuit board.

Be sure to use a large 24 pin IC socket when installing the BASIC STAMP 2 module. When installing the

regulator, be sure to properly identify the input and output before installing the component on the

PC board. Check the PC layout or manufacturer’s

specifications before installing U3, to avoid damage

to the circuit.

The Caller-ID circuit utilizes five LEDs, which also

must be oriented correctly if the circuit is to function properly. An LED has two leads, a cathode and an

Figure 29-4

Caller-ID inside view. Courtesy of

anode lead. The anode lead will usually be the longer of J Gary Sparks

the two leads and the cathode lead will usually be the shorter lead, just under the flat side edge of the LED; Locate a suitable enclosure to house the Caller-ID

this should help orient the LED on the PC board. You

circuit board within the enclosure. Use four plastic

may want to lead about 1⁄2 lead length on the LED, in standoffs to mount the circuit board to the bottom plate order to have the LED protrude through the enclosure

of the enclosure. If you selected a convention relay you box. Solder the LEDs to the PC board and then trim the will have to mount it on the chassis and wire it to the excess leads.

PC board.

Now, locate the crystal at XTL and install it in its

Mount a coaxial power jack on the rear panel of the

proper location between pins 9 and 10 of the Caller-ID

chassis box, in order to plug in a small “wall-wart”

chip at U1. Next locate and install the SPST, normally 9-V DC power supply at input of the regulator. Mount

open reed relay at K1, which is connected to pin 8 of the five status LEDs on the front panel of the enclosure the STAMP 2. Finally, locate the metal oxide varistor box. Next you will have to install an RJ11 phone jack or (MOV) protector at the input of the telephone line.

a 2-position terminal strip on the front panel of the Once the Caller-ID circuit board has been completed,

chassis to bring the phone into the chassis box. Locate take a short break and then we will inspect the PC board all four momentary pushbutton function switches and

for possible “cold” solder joints and “short” circuits.

arrange to mount them on the front panel of the

Pick up the PC board with the foil side facing upwards enclosure. Mount a DB-9 serial connector on the rear

toward you. Carefully inspect the solder joints, these panel which will be used to connect the programming

should look smooth, clean, and bright. If any of the

cable between the Caller-ID circuit and your personal solder joints look dull, dark, or blobby, then you should computer or laptop. Finally, install the LCD panel on remove the solder with a solder sucker or a solder wick the front panel of the enclosure box. Handle the LCD

and then resolder the joint all over again. Now we will panel very carefully and do not press too hard on the inspect the PC board for possible short circuits. Short LCD front while handling the LCD in order to avoid

circuits can be caused from small solder blobs bridging damaging it. The LCD will have three wires which will the circuit traces or from cut component leads which

need to be connected to the Caller-ID circuit. You will can often stick to the circuit board once they have been have to connect the 5-V power lead to a +5-V bus on

cut. A sticky residue from solder will often trap

the circuit board. The LCD also must have a ground

component leads across the circuit traces. Look

connection and finally the serial signal wire from the carefully for any bridging wires across circuit traces.

LCD must be connected to pin 20 of the BASIC

Once the inspection is complete, we can move on to

STAMP 2 module.

installing the circuit board into an aluminum enclosure Now you will need to make a directory on your

(see Figure 29-4).

computer labeled CallerID. Next you will need to

301

download the Windows BASIC STAMP Editor

Table 29-3

version 2.5 or above from www.parallax.com. The

Momentary pushbutton switch functions

program can be found under the DOWNLOADS

Function A

Function B

Function C

pull-down button. Install the Windows editor program

on your computer and then open the program and type

Read

Blocked

Store

press once

in or load the CallerID.bs2 program into the editor Options

X

press C then A

program. Now connect the programming cable between

Erase

X

press C then B

the Caller-ID circuit and your personal computer. Apply power to the Caller-ID circuit and we are ready to

download the CallerID.bs2 program into the BASIC

Function B as you did for Function A and note the

STAMP 2 module.

blocked numbers run from #11–20. The blocked

Operation of the Caller-ID project begins when the

number will be stored at the memory location of the last phone starts ringing. The ring detector tells the STAMP

read-out number as cycled from Function B. The

2 to wake-up and begin accepting data from the Caller-number which is stored into the blocked memory will

ID chip. Upon power-up the LCD reads “Waiting,” then

be the last one read out as cycled by Function A.

the STAMP 2 program reads in the Caller-ID or CID

In order to erase a number which has been blocked,

data, in multiple data message format (MDMF). This

you will need to hold down the Function C button until format presents the number and name of the originating the LED on pin 2 goes out, then momentarily press the call. Note, the SDMF formats send only the telephone

Function B button. Notice that zeros will replace the numbers and will not work with this program in its

blocked number.

present form. The program for this project displays the To turn on the call blocking feature; you will need

originating number on the LCD screen and stores up to to hold down the Function C button until the LED on

10 numbers in the EEPROM. The system will overwrite

pin 2 goes out. Next momentarily press the Function

the oldest numbers displayed as new ones are received.

A button. The LCD display will cycle through “Call

In order to see past numbers, you will need to press the Blocking Off,” “Inhibit Blocked Calls,” “Connect Not

Function A button once, or several times during a delay Blocked Calls” for each push of the Function C and the loop, to cycle back through the past read-ins. Table 29-3

Function A buttons. The last two options are nearly

illustrates the functions of the pushbuttons used on the the same except: (1) when there is an error in data read, Caller-ID unit.

the first will allow the call to go through, the second The program will store up to 10 numbers in to the

will also allow the call to go through but only (2) when EEPROM as numbers which are considered “blocked”.

there is a call from a blocked number, only the first ring To store a number in the EEPROM simply press

will get heard (until the CID data has been processed) Function C and hold the button for about a second until while the second will not ring at all; (3) when there is a the LED pin 2 is out. To see what numbers are blocked call from a not blocked number, the second will silence cycle through the blocked numbers by depressing

the first ring.

Chapter Twenty-Nine: Caller-ID/Blocker Project

302

Chapter Twenty-Nine: Caller-ID/Blocker Project

‘CallerID.BS2 by J. Gary Sparks

‘THIS PROGRAM READS IN AND STORES CALLER¯ID DATA FROM A MC145447, STORES

‘NUMBERS WHICH ARE DESIGNATED ‘BLOCKED’, READS OUT NUMBERS ON A SERIAL

‘BACKPACK LCD, DECIDES TO BLOCK THE CALL IF A ‘BLOCKED NUMBER’ HAS CALLED

‘*************************NOTES****************************

‘read in first world length; if #, read in #;if not # store an OTH(er)

‘

and fill rest of ram with ascii spaces

‘I did a test and the first (hex) word length was dec 39 for a #

‘

and dec 16 for out of area; I DISCARDED THIS OPTION SINCE

‘

SOMETIMES ONLY THE NUMBER IS SENT AND THIS CONFUSES THE PROGRAM

‘

PLUS THE STAMP SEEMED TOO SLOW TO DECIDE ON THE WORD LENGTH AND

‘

THEN WAIT FOR AN (02)

‘read direct from MC145447

‘relay is on at first

‘fctc 0 (delay) ¯> fcta 0 ¯> fcta 1 ¯> fctc 1 =

‘

cycle through blocking options

‘fctc 0 (delay) store cid # in blked # register

‘fctc 0 (delay) ¯> fctb 0 ¯> fctb 1 ¯> fctc 1 = store 00s in blked numbers

‘

to erase a number

‘fctc must be held down for a delay to prevent accidents

‘start storing info with mem addr 12

‘pin 15 is lcd output line

‘pin 14 is data input line

‘pin 13 is here we will come, data to be sent, line

‘IF PIN 13 = 0, NRD, a ring has been detected, not ring detect

‘IF PINS 12 OR 11 OR 9 = 0 = FCTA or FCTB or FCTC

‘pin 12 is functiona input line, look at data, normally 1

‘pin 11 is functionb input line, look at blocked #s, normally 1

‘if pin 10 = 0 reset mem loc 0 (stored data), mem loc 1 (blocked #s)

‘

and come up in blocking off via nb,bi

‘tie pin 10 (skip) high with resistor and be able to jump to ground

‘

the very first time only to set address counters to initial values

‘pin 9 is functionc input line, store a blocked #, normally 1

‘if you shut down or you reload the program you can save stored info

‘THIS HAS FOR...NEXT EEPROM OUTPUT LOOP, SHOWS #: ########## via FUNCTION

‘

LIMIT 20 STORED NUMBERS

‘SEE CONSTANT DEFINITION BELOW: DTLMT IS FOR 10 STORED #S, NUMBERED 1-10

‘

BLLMT IS FOR 10 BLOCKED #S, NUMBERED 11-20

‘READ OUT BLOCKED NUMBERS VIA FUNCTIONB, PIN 11

‘READ OUT CID NUMBERS VIA FUNCIONA, PIN 12

‘STORE NUMBERS TO BLOCK VIA FUNCTIONC, PIN 9

‘pin 0 is led for read in complete—test purposes only

‘pin 1 is led for read out complete—test purposes only

‘pin 2 is led for function subroutine in operation, use a led

‘pin 3 is for relay

‘output “WAITING” on power up, if error, after set blocking

‘*******************************************************************

303

‘*****************************SET IN/OUT***********************************

input 14: input 13: input 12

input 11: input 10: input 9

‘in lines

low 0: low 1

‘out lines; set 2, 3 later

‘*************************************************************************

‘***************************DECLARE******************************************

‘these are the ram spots that are read into

a

var

byte

b

var

byte

c

var

byte

d

var

byte

e

var

byte

f

var

byte

g

var

byte

h

var

byte

i

var

byte

j

var

byte

k

var

byte

‘l

var

byte

‘input lines

nrd

var

in13

‘not Ring Detect from MC145447

fcta

var

in12

‘function a

fctb

var

in11

‘function b

skp

var

in10

‘ground on very first power up to initialize

fctc

var

in9

‘function c

‘constants

dtst

con

12

‘this is the start address for data

dtlmt

con

111

‘the add. of the final data byte, 10 #s, 12¯111

bllmt

con

211

‘the add. of the final blk no byte, 10#s, 112¯211

cidad

con

0

‘this is the adr. of CID reception and storage

‘and first read out

blnad

con

1

‘this is the adr. of the blocked number

‘read in and read out

cidro

con

2

‘this is the adr. of the CID rdout when sequencing

bi

con

3

‘this is the adr. of 1 inhibits blked call

nb

con

4

‘this is the adr. of 1 connects line when not blked

‘call

‘more variables

x

var

byte

‘scratch pad

y

var

byte

‘hold addresses, etc.

z

var

byte

‘scratch pad

qa

var

byte

‘used in “test if # is blocked”

qb

var

byte

qc

var

byte

‘*****************************************************************************

Chapter Twenty-Nine: Caller-ID/Blocker Project

‘THIS WILL RESET DATA COUNTERS AND BLOCKING IF PIN 10 IS LOW

304

Chapter Twenty-Nine: Caller-ID/Blocker Project

if skp = 1 then start1

‘if pin 12 is high don’t reset

write cidad,dtst

‘will be adr. of CID rcption

write blnad,dtlmt+1

‘will be adr. of blkd nos.

write bi,0: write nb,0

‘come up with blocking off

‘THIS IS THE SET¯RESET SEGMENT FOR THE LCD

start1: pause 1000

‘let lcd settle

serout 15,396+$4000,[254,1]

‘cls

pause 1000

serout 15,396+$4000,[“WAITING”] ‘at start, if error,

‘after set blocking

‘THIS IS THE MAIN HOLD LOOP

‘GO TO THE BEGINNING OF SERIN¯ING THE DATA IF PIN13 = 0

‘OR GO TO A FUNCTION SUBROUTINE IF PINS 12 OR 11 OR 9 = 0

start2: high 2: high 3

‘set led, relay each time

start2a:if nrd = 0 then start3x

‘nrd = 0, data soon

if fcta = 0 then fnctn

‘function switch pressed

if fctb = 0 then fnctn

if fctc = 0 then zz

‘put in delay to prevents oops

goto start2a

‘loop

zz:

pause 2000

‘to prevent accidents

if fctc = 1 then start2a

‘oops has been prevented

goto fnctn

‘COME HERE FROM ABOVE IF NRD HAS BEEN LOW

‘IF “CONNECT NOT BLOCKED” IS SET TURN OFF RELAY

‘NOTE HOW THIS WORKS IN CONJUNCTION WITH

‘ “TEST TO SEE IF THE NUMBER IS A BLOCKED ONE AND HOW BLOCKING IS SET”

‘ LATER

start3x:read nb,z

‘check if “connect not blocked” is set

if z = 1 then goon

‘if it is on, low 3

goto start3

‘if “connect not blocked” not set, do nil

goon:

low 3

‘THIS IS THE MAIN READ¯IN SECTION OF THE PROGRAM

‘the first CID info is hex 80 to denote MDMF, the format this program

‘is written for; wait for that

‘1. then read in the next byte which will be large if full data is sent

‘2. or small if is “out of area” or “private”

‘after waiting hex 80, read in word¯length and then decide whether

‘3. to wait for hex 02 = number parameter or to go to reason for absence

‘4. see “notes to myself” for how I got 28, half¯way between 16 and 39

‘1-4 HAS BEEN CHANGED; THE STAMP APPEARS NOT TO BE FAST ENOUGH FOR RELIABLE

‘OPERATION OF THIS FEATURE OF THE EARLIER PROGRAM CID23.BS2

start3: low 2

‘indicator led

serin 14,813,6000,start1,[WAIT (128)]

‘wait hex 80

305

serin 14,813,1000,nonum,[WAIT (02),a,b,c,d,e,f,g,h,i,j,k]

‘read in word¯length, then the number

‘the word¯length will be dumped

goto anum

nonum: b = “O”:c = “T”:d = “H”

‘OTH for other

e = “ ”:f = “ ”:g = “ ”:h = “ ”:i = “ ”:j = “ ”:k = “ ”

‘set spaces in other variables

anum:

high 0

‘got this far

‘THIS IS THE MAIN OUTPUT SECTION OF THE PROGRAM

serout 15,396+$4000,[254,1]

‘cls

serout 15,396+$4000,[b,c,d,“ ”,e,f,g,“ ”,h,i,j,k] ‘output high 1

‘got this far

‘HERE WE STORE DATA IN EEPROM

read cidad,y

‘define y

gosub st

‘store via subroutine

if y = dtlmt+1 then far1 ‘dtlmt¯dtst+1/10 #s, start with dtst again goto far2

‘ADDR. COUNTER ALWAYS NEXT INPUT

far1: write cidad,dtst ‘new cycle

goto test

far2: write cidad,y

‘save how far the memory has been used+1

goto test

‘*****************************************************************************

‘SUBROUTINE

st:

write y,b

‘STORE THE DATA IN EEPROM

y = y+1

write y,c

y = y+1

write y,d

y = y+1

write y,e

y = y+1

write y,f

y = y+1

write y,g

y = y+1

write y,h

y = y+1

write y,i

y = y+1

write y,j

y = y+1

write y,k

y = y+1

‘ready for next one

return

Chapter Twenty-Nine: Caller-ID/Blocker Project

‘*****************************************************************************

306

Chapter Twenty-Nine: Caller-ID/Blocker Project

‘TEST TO SEE IF THE NUMBER IS A BLOCKED ONE AND HOW BLOCKING IS SET

test:

qc = bllmt¯dtlmt¯10

‘amount of blocked mem. - 10

for qa = 0 to qc step 10 ‘IS # BLOCKED?

for qb = 1 to 10 step 1

‘compare

read dtlmt+qa+qb,y

‘compare

read cidad,x

‘compare

read x+qb−11,z

‘compare

if y = z then here1

‘compare

goto here2

‘compare

here1:

next

‘compare

goto test0

‘was a blocked #

here2:

next

‘compare

goto fnctaQ

‘it wasn’t a blocked #, go on

test0:

read bi,y

if y = 0 then fnctnQ

‘INHIBIT BLOCKED off, go on

low 3

‘if bi is 1 inhibit

goto fnctnQ

‘go on

‘NOTE HOW THESE DECISIONS WORK IN CONJUNCTION WITH EARLIER:

‘

“IF ‘CONNECT NOT BLOCKED’ IS SET TURN OFF RELAY”

‘********************************************************************

‘STAY AS LONG AS RINGING

fnctaQ:

high 3

‘turn on relay

fnctnQ:

x = 0

‘scratchpad = 0

goto stay2

‘avoid a reset

stay1:

x = 0

stay2:

if nrd = 0 then

stay1 ‘do nothing as long as ringing

pause 50

‘stopped ringing

x = x+1

‘add 1 every 50 ms

if x < 100 then stay2

'if less than 5 sec keep testing

low 0: low 1

'reset 0, 1

goto start2

‘********************************************************************

'THE FUNCTION SWITCH COMES HERE

'fncta:

high 3

'turn on 3 if need be

fnctn:

low 2

'COME HERE FROM FUNCTION, blip led

pause 250

'debounce

if fcta = 0 then so1

‘go to stored output

if fctb = 0 then so3

if fctc = 0 then mem1

‘goto holding for function c

pause 250

‘debounce more

‘

low 0

‘reset LEDs that confirmed earlier work

‘

low 1

goto start2

‘HERE IS THE STORED OUTPUT

307

‘STORED NUMBERS

so1:

read cidad,y

‘y is addr. of next store, in cidad

if y < > dtst then so2

‘reset cidad for highest data addr.

y = dtlmt+1

‘if recycling

so2:

gosub socid

‘OUTPUT DATA STORE IN EEPROM

write cidro,y

‘THIS WILL BE USED IN STORING READ

‘WHERE¯LEFT¯OFF INTO BLKED # MEM

if y < =

dtst then resty1

‘reset y when first # is done

goto hold1

resty1: y = dtlmt+1

goto hold1

‘BLOCKED NUMBERS

so3:

read blnad,y

goto so5

so4:

y = y+10

if y< = bllmt then so5

y = dtlmt+1

so5:

gosub sobln

write blnad,y

goto hold2

‘************************************************************************

‘THIS SUBROUTINE OUTPUTS THE DATA STORED IN EEPROM

socid:

y = y-10

sobln:

serout 15,396+$4000,[254,192]

‘down a line; come here for

z = y-2

‘consecutive stored output

z = z/10

‘get entry # digit(s)

serout 15,396+$4000,[dec z, “: ”] ‘this is entry #

for z = y to y+9

‘OUTPUT EEPROMED DATA HERE

read z,x

serout 15,396+$4000,[x]

next

serout 15,396+$4000,[“ ”]

‘get rid of past

return

‘*************************************************************************

‘WHAT TO DO NEXT IN FUNCTION MODE

hold1:

if fcta = 0 then hold1

hold2:

if fctb = 0 then hold2

pause 100

‘debounce

z = 0

hold4:

z = z+1

‘do again if another fcta = 0

pause 10

‘within one second

if fcta = 0 then so2

if fctb = 0 then so4

if z = 100 then fnctn

‘return to function to reset leds and go

goto hold4

‘back to main wait loop

‘STORE A BLOCKED # OR STORE 0S

Chapter Twenty-Nine: Caller-ID/Blocker Project

308

Chapter Twenty-Nine: Caller-ID/Blocker Project

mem1:

pause 100

‘debounce

mem2:

if fctb = 0 then do1

‘store 0s if fctb = 0

if fcta = 0 then do2

if fctc = 0 then mem2

‘to erase

goto on1

do1:

b = 48:c = 48:d = 48:e = 48:f = 48:g = 48:h = 48:i = 48:j = 48:k = 48

goto on2

‘set zeros

on1:

read cidro,y

‘from last read out

read y,b

‘GET #S INTO b, c, d, etc.

y = y+1

read y,c

y = y+1

read y,d

y = y+1

read y,e

y = y+1

read y,f

y = y+1

read y,g

y = y+1

read y,h

y = y+1

read y,i

y = y+1

read y,j

y = y+1

read y,k

‘

y = y+1

‘unnecessary

on2:

read blnad,y

‘to blocked data at point last looked at

gosub st

‘store it

pause 100

‘debounce

sit1:

if fctc = 0 then sit1

sit2:

if fctb = 0 then sit2

goto fnctn

‘THIS SETS WHETHER THE PROGRAM SHOULD BLOCK CALLS OR NOT

do2:

serout 15,396+$4000,[254,1] ‘cls

pause 100

‘debounce

read bi,z

‘read setting

if z = 0 then tgl1

write bi,0: write nb,1

‘settings

serout 15,396+$4000,[“connect not”,254,192,“blocked calls”]

goto sit3

tgl1:

read nb,z

if z = 0 then tgl2

write bi,0: write nb,0

‘settings

serout 15,396+$4000,[“call blocking”, 254,192,“is off”]

309

goto sit3

tgl2:

write bi,1: write nb,0

‘settings

serout 15,396+$4000,[“inhibit blocked”, 254,192,“calls”]

sit3:

if fcta = 0 then sit3

sit4:

if fctc = 0 then sit4

goto start1

Chapter Twenty-Nine: Caller-ID/Blocker Project

310

Chapter 30

Page-Alert

J3

10 pin female header

Parts list

J4

10 position screw

terminal

Page¯Alert

Misc

PC board, wire,

R1, R2

240 ohm 1⁄ W

2

standoffs, chassis

resistor

box, etc.

R3, R4, R5, R6, R7

Switch/sensor Module

10 K ohm 1⁄ W resistor

4

R1, R3

20 K ohm 1⁄ W

4

R8, R9

330 ohm 1⁄ W

resistor

4

resistor

R2, R4

10 K ohm 1⁄ W

4

R10

1 K ohm 1⁄ W,

resistor

4

5% resistor

C1

.01 μF 25 volt disc

C1, C2

.1 μF 35 V

capacitor

electrolytic capacitor

D1, D2

1N914 silicon

C3

35 μF 35 V

diode

electrolytic capacitor

Q1

2N2222 NPN

C4

5 μF, 35 V

transistor

electrolytic capacitor

Misc

Sensors,

D1

red LED

PC board, wire,

V1

Sidactor P3002AB¯ND

hardware, header,

U1

Cermetek CH1817D

etc.

¯DAA

module

Temperature/voltage

U2

BASIC STAMP 2

Level Module

microcontroller

R1, R3

2 K ohm 1⁄ W

(original)

4

resistor

U3

LM7805 regulator (5 V)

R2

50 K ohm

S1

On¯Off power switch

potentiometer

– toggle switch

R5

1 megohm 1⁄ W

S2

On

4

¯Off power switch

resistor

– toggle switch

R4, R6

10 K ohm 1⁄ W

RY1

On¯Off power switch

4

resistor

– toggle switch

J1

RJ11 PC mount

R7

10 megohm 1⁄ W

4

telephone jack

resistor

J2

4 pin programming

R8

3.3 K ohm 1⁄ W

4

header

resistor

311

Copyright © 2009 by The McGraw-Hill Companies, Inc. Click here for terms of use.

C1

.1 μF 25 V disc

capacitor

C2

.01 μF 25 V disc

capacitor

U1

LM393 comparator IC

S1

Resistive sensor,

thermistor, etc.

Misc

PC board, header,

wire, hardware, etc.

Figure 30-1

Page-Alert circuit board

Page-Alert

which will activate the Page-Alert. The Temperature/

The Page-Alert is a low cost microprocessor controlled Voltage level module can be utilized to monitor

alarm reporting system, which can monitor up to four

temperature fluctuations or voltage level changes

different alarm conditions and immediately report them depending upon the configuration, and report the

to your numerical pager (see Figure 30-1).

problem to your pager.

The Page-Alert can be used to protect your home,

The Page-Alert utilizes your existing telephone line, office, shop, or vacation home while you are away. The so it incurs no additional monthly phone bills, which are Page-Alert can be configured to monitor voltage levels, generally required by alarm companies. Simply plug in temperature, movement, doors, windows, and electronic the power supply and connect it to a regular phone line equipment such as computer failures (see block diagram and connect up at least one sensor and you are ready to in Figure 30-2). The Page-Alert can free you to be two remotely monitor just about any alarm condition.

places at once!

Upon receiving a call from your Page-Alert, you can

The optional enhancement modules such as the

elect to respond yourself, or call a neighbor, friend, or Pyro-electric Motion Module can be used to sense

co-worker to solve the problem. You could also elect

“body heat” up to 30′ away and provide an output

to notify the police if desired.

Phone

line

Phone

Page alert

Power

Window sensor

Floor mat

sensor

Door switch

Gate alarm

Chapter Thirty: Page-Alert Figure 30-2 Page-Alert block diagram 312

Chapter Thirty: Page-Alert

DB-9F

+5 V

D1

7 6 5 4 3 2

R8

J1

D2

P1

S1

+5 V

D1

Lamp

RESE1

Siren

1

R9

24

+9 V

U2

VDD

2

GND 23

R7

S2

N/O

3

RY1

22

Basic

R10

4

R/S

R6

Stamp

21

R5

R4

R3

5

+5

N/C

P0

20

II

R1

P15

Ring

6 P1

19

7

P14 18

V1

P2

P13

8

17

P3

P12

9

R2

16

Tip

P4

10

P11 13

P5

11

P10 14

Telephone

P6

Tip

12

P9 13

line

P7

P8

U1

1

9

IN 1

IN 2

IN 3

IN 4

2

8

Ring

XM(+) +5 V

7

1

ON

3

6

C2

+9 V

XM(−)

4

R1

5

C1

J3-1

J3-10

DAA

+5 V

Out

IN

CH1817

U3

(Bottom)

J4-1

J4-10

+

+

+12 V DC

Input

C3

CA

Figure 30-3

Page-Alert circuit diagram

The Page-Alert multichannel alarm reporting

“BASIC” language. The BS2 has 16 input/output lines

system centers around the BASIC STAMP 2 (BS2)

which can be seen in Table 30-1, which describes the

microcomputer at U2, as shown in Figure 30-3.

pinouts of the BS2 microcontroller, including the

The BS2 microcomputer is a small but powerful

serial port connections to your programming computer.

computer capable of up to 4,000 instructions per

The BS2 microcomputer is generally used for specific

second. The BS2 micro-computer consists of the main

or dedicated control application.

processor, memory, reset, regulators, and touch tone/

The Page-Alert scans up to four alarm input channels

X-10 generator circuits all combined in a 24 pin chip simultaneously. All four channels are configured as

carrier. The BS2 computer runs on an interpreted

normally open inputs, with 10 K ohm resistors across

Table 30-1

Basic STAMP 2 microprocessor pinouts

Pin

Name

Function

Description

1

SOU

Serial out

temporarily connects to PC’s (Rx)

2

SIN

Serial out

temporarily connects to PC’s (Tx)

3

ATN

Attention

temporarily connects to PC’s (DTR)

4

VSS

Ground

temporarily connects to PC’s ground

5

P0

User I/O 0

user ports which can be used for inputs

6

P1

User I/O 1

or outputs:

7

P2

User I/O 2

(Continued)

313

Table 30-1—cont’d

Basic STAMP 2 microprocessor pinouts

Pin

Name

Function

Description

8

P3

User I/O 3

Output mode: Pins will source from VDD. Pins should

9

P4

User I/O 4

not be allowed to source more than 20 ma, or sink more than 10

P5

User I/O 5

25 ma. As groups, P0–P7 and P8–P15 should not be

11

P6

User I/O 6

allowed to source more than 40 ma, or sink 50 ma.

12

P7

User I/O 7

13

P8

User I/O 8

Input mode: Pins are floating(less than 1 μa. leakage) 14

P9

User I/O 9

The logic threshold is approx. 1.4 V.

15

P10

User I/O 10

16

P11

User I/O 11

Note: to realize low power during sleep, make sure that no 17

P12

User I/O 12

pins are floating, causing erratic power drain. Either drive 18

P13

User I/O 13

them to VSS or VDD, or program them as outputs that do 19

P14

User I/O 14

not have to source current.

20

P15

User I/O 15

21

VDD

Regulator out

Output from 5 V regulator (VIN powered). Should not be allowed to source more than 50 ma, including P0–P15 loads.

22

RES

Power in

Power input (VIN not powered). Accepts 4.5–5.5 V. Current consumption is dependent on run/sleep mode and I/O.

23

VSS

Reset I/O

When low, all I/Os are inputs and program execution is suspended. When high, program executes from start. Goes low when VDD is less than 4 V or ATN is greater than 1.4 V.

Pulled to VDD by a 4.7 K resistor. May be monitored as a brown-out/reset indicator. Can be pulled low externally (i.e. button to VSS) to force a reset. Do not drive high.

24

VIN

Ground

Ground. Located next to Vin for easy battery backup.

Regulator In

Input to 5 V regulator. Accepts 5.5–15 V. If power is applied directly to VDD, pin may be left unconnected.

the inputs at pins P0 through P3. The inputs to the

DAA module, allowing the phone to go “off hook.”

Page-Alert are brought out to the screw terminals at

The microprocessor now begins the dialing sequence

J4 for easy connections to the outside world.

to call your pager.

Inputs P0 through P3 are used as input channels;

The BS2 microprocessor contains a touch-tone

P4 through P7 are not used in this project. The output generator which is utilized to dial your pager and also of the microcontroller at P9 is utilized to drive the generate the identifier codes. Pin 15 or P10 on the BS2

Data Access Arrangement module (DAA) at U1. The

is used to drive the audio signal from the touch-tone Cermetek DAA is a Telco approved telephone interface, output to the TX (+) pin on the DAA, which dials the

which should be used to couple and isolate electronic phone. The TX (−) pin on the DAA is connected to

circuits to the phone line. It provides the correct

ground via a .1 disc capacitor. Pin 7 of the DAA is the input/output level interfacing, relay, and protection 5 V power connection, while pin 9 is the ground

circuits needed for interfacing (see Figure 30-4).

connection. The RCV and RI pins on the DAA are not

Once an alarm input is triggered, the Page-Alert

used here. Pins 1 and 2 of the DAA are connected to

Chapter Thirty: Page-Alert activates pin 14, which in turn drives the OH pin in the the phone line’s ring and tip lines via the Sidactor

314

Chapter Thirty: Page-Alert

CH1817

soldering tip into the compound and it cleans and

VCC

GND

prepares the soldering tip. Next grab a few small hand tools; try to locate small flat blade and Phillips

Tip

screwdrivers. A pair of needle-nose pliers, a pair of Surge

tweezers along with a magnifying glass, and a pair of and

Isolation

protection

Ring

end-cutters and we will begin constructing the project.

circuit

Now locate your schematic diagram and parts layout

diagram along with all of the components needed to

build the project.

XMIT

Off-hook

Once all the components are in front of you, you can

Hydrid

switch

2W/4W

RCV

check them off against the project parts list to make converter

Ring det

sure you are ready to start building the project. Now, R1

locate Tables 30-2 and 30-3, and place them in front of you. Table 30-2 illustrates the resistor code chart and how to read resistors, while Table 30-3 illustrates the OH

capacitor code chart which will aid you in constructing Figure 30-4

DAA Telephone interface module

the project.

Refer now to the resistor color code chart shown in

protection device, followed by two 100 ohm resistors

Table 30-2, which will help you identify the resistor which are used couple the DAA to the RJ11 phone plug.

values. Note that each resistor will have either three or four color bands, which begin at one end of the

A reset function is provided at pin 22 of U2, and is

resistor’s body. The first colored band represents the connected via R5 to pin 21(VDD). This pin is a “brown resistor’s first digit, while the second color represents out” detector and reset device. A reset push button is the second digit of the resistor’s value. The third colored connected between pin 22 and ground. A bypass

band represents the resistor’s multiplier value, and the capacitor is coupled across the power leads at pins 23

fourth color band represents the resistor’s tolerance and 24. The power input on pin 24 can accept 5 to

value. If there is no fourth colored band then the resistor 15 V DC, which powers the internal regulators in

has a 20% tolerance value. If the resistor’s fourth band the BS2. Pin 21 is the 5 V system power pin from the

is silver then the resistor has a 10% tolerance value and regulator.

if the fourth band is gold then the resistor’s tolerance The regulator at U3 is used to power the Page-Alert

value will be 5%.

system. A 12 DC “wall wart” power cube can be used to Finally, we are ready to begin assembling the

provide input power to the Page-Alert board at J4-2.

project, so let’s get started. The prototype project was The regulator provides 5 V to pin 21 of the BS2

constructed on a 21⁄2 × 41⁄4′′ single-sided printed circuit controller at U2. The 5 V source is also utilized to

board or PCB. With your PC board in front of you,

provide power to the sensor daughter boards which can we can now begin populating the circuit board.

be plugged into the female header at J3.

We are going to place and solder the lowest height

components first, the resistors and diodes. Let’s locate Circuit assembly

our first two resistors R1 and R2. Resistors R1 and R2

each have a value of 100 ohms and are a 5% tolerance

Before we begin constructing the Page-Alert, you will type. Now take a look for a resistor whose first color need to find a clean, well-lit worktable or workbench.

band is brown, black, brown, and gold. From the

Next we will gather a small 25–30 W pencil tipped

chart you will notice that brown is represented by

soldering iron, a length of 60/40 tin–lead solder, and a the digit (1), the second color band is black,

small canister of Tip Tinner, available at your local which is represented by (0). Notice that the third color RadioShack store; Tip Tinner is used to condition the is brown and the multiplier is (10), so (1) (0) × 10 =

soldering tip between solder joints. You drive the

100 ohms.

315

Table 30-2

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

No color

20%

Table 30-3

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

1.0

1R0

3,900

3.9

.0039

392

1.2

1R2

4,700

4.7

.0047

472

1.5

1R5

5,600

5.6

.0056

562

1.8

1R8

6,800

6.8

.0068

682

2.2

2R2

8,200

8.2

.0082

822

2.7

2R7

10,000

10

.01

103

3.3

3R3

12,000

12

.012

123

3.9

3R9

15,000

15

.015

153

4.7

4R7

18,000

18

.018

183

5.6

5R6

22,000

22

.022

223

6.8

6R8

27,000

27

.027

273

8.2

8R2

33,000

33

.033

333

10

100

39,000

39

.039

393

12

120

47,000

47

.047

473

15

150

56,000

56

.056

563

18

180

68,000

68

.068

683

22

220

82,000

82

.082

823

27

270

100,000

100

.1

104

33

330

120,000

120

.12

124

39

390

150,000

150

.15

154

47

470

180,000

180

.18

184

Chapter Thirty: Page-Alert 56

560

220,000

220

.22

224

316

Chapter Thirty: Page-Alert

Table 30-3—cont’d

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

68

680

270,000

270

.27

274

82

820

330,000

330

.33

334

100

.0001

101

390,000

390

.39

394

120

.00012

121

470,000

470

.47

474

150

.00015

151

560,000

560

.56

564

180

.00018

181

680,000

680

.68

684

220

.00022

221

820,000

820

.82

824

270

.00027

271

1,000

1

105

330

.00033

331

1,500

1.5

155

390

.00039

391

2,200

2.2

225

470

.00047

471

2,700

2.7

275

560

.00056

561

3,300

3.3

335

680

.00068

681

4,700

4.7

475

820

.00082

821

6.8

685

1,000

1.0

.001

102

10

106

1,200

1.2

.0012

122

22

226

1,500

1.5

.0015

152

33

336

1,800

1.8

.0018

182

47

476

2,200

2.2

.0022

222

68

686

2,700

2.7

.0027

272

100

107

3,300

3.3

.0033

332

157

157

Code = 2 significant digits of the capacitor value + number of zeros to follow 10 pF = 100

For values below 10 pF, use “R” in place of decimal e.g. 8.2 pF = 8R2

100 pF = 101

1,000 pF = 102

22,000 pF = 223

330,000 pF = 334

1 μF = 105

Go ahead and locate where resistors R1and R2 are

capacitors are called polarized types, these capacitors placed on the PC and install them, next solder them in have polarity and have to be inserted on the board with place on the PC board, and then with a pair of end-cutters respect to their polarity marking in order for the circuit trim the excess component leads flush to the edge of the to operate correctly. On these types of capacitors, you circuit board. Next locate the remaining resistors and will observe that the components actually have a plus install them in their respective locations on the main or minus marking or a black or white band with a

controller PC board. Solder the resistors to the board, and plus or minus marking on the body of the capacitors.

remember to cut the extra lead with your end-cutters.

Capacitors must be installed properly with respect to Note that capacitors generally come from two major

polarity in order for the circuit to work properly. Failure groups or types. Non-polar types, such as the ones in to install electrolytic capacitors correctly could cause this project, have no polarity and can be placed in either damage to the capacitors as well as to other components direction on the circuit board. The other type of

in the circuit when power is first applied.

317

Next refer to Table 30-3; this chart helps to determine facing towards the base lead and the emitter lead is also the value of small capacitors. Many capacitors are quite a slanted line facing the base lead but it will have an small in physical size, so manufacturers have devised a arrow pointing towards or away from the base lead.

three-digit code which can be placed on the capacitor Now, identify the two transistors, and refer to the

instead of the actual value. The code occupies a much manufacturer’s specification sheets as well as the

smaller space on the capacitor and can usually fit

schematic and parts layout diagrams when installing

nicely on the capacitor body, but without the chart the the two transistors. If you have trouble installing the builder would have a difficult time determining the

transistors, get the help of an electronics enthusiast capacitor’s value.

with some experience. Install the transistors in their Now look for the capacitors from the component

respective locations and then solder them in place.

stack and locate capacitors C1 and C2, they are small Remember to trim the excess component leads with

capacitors labeled (104). Refer to Table 30-3 to find your end-cutters.

code (104) and you will see that it represents a capacitor The Page-Alert circuit also contains two ICs.

value of .1 μF. Go ahead and place C1 and C2 on the

ICs are often static sensitive, so they must be

circuit board and solder them in place. Now take your handled with care. Use a grounded anti-static

end-cutters and cut the excess component leads flush to wrist strap and stay seated in one location when

the edge of the circuit board. Once you have installed handling the integrated circuits. Take out a cheap

these components, you can move on to installing the

insurance policy by installing IC sockets for each of remaining capacitors. Finally locate the two electrolytic the ICs. In the event of a possible circuit failure, it is capacitors at C3 and C4 and go ahead and install them much easier to simply unplug a defective IC, than

on the PC board, remembering these capacitors have

trying to unsolder 14 or 16 pins from a PC board

polarity and it must be observed if the circuit is to without damaging the board. ICs have to be installed

work correctly. The minus terminals of the capacitors correctly if the circuit is going to work properly. IC

are connected to ground.

packages will have some sort of markings which will

help you orient them on the PC board. An IC will have The Page-Alert project contains a single silicon

either a small indented circle, a cutout, or notch at the diode, placed across the relay RY1. Diodes, as you will top end of the IC package. Pin 1 of the IC will be just remember, will always have some type of polarity

to the left of the notch, or cutout. Refer to the

markings, which must be observed if the circuit is going manufacturer’s pin-out diagram, as well as the

to work correctly. You will notice that each diode will schematic, when installing these parts. If you doubt

have a black or white colored band at one edge of the your ability to correctly orient the ICs, then seek the diode’s body. The colored band represents the diode’s help of a knowledgeable electronics enthusiast.

cathode lead. Check your schematic and parts layout

diagrams when installing these diodes on the circuit

The DAA module has 9 pins which protrude through

board. Place the diode on the circuit board in its

the bottom of the module. You can solder the module

respective location and solder it in place on the

directly to the PC, but be careful to install it correctly.

PC board. After soldering in the diodes and the

Note, pins 1 and 9 are across from each other and pins diode bridge, remember to cut the excess component

4 and 5 are across from each other and there is a gap leads with your end-cutters, flush to the edge of the between pins 2 and 3 on the same side of the module.

circuit board.

The Page-Alert employs two LEDs at D1 and D2,

The Page-Alert utilizes three conventional transistors.

which also must be oriented correctly if the they are to Transistors are generally three lead devices, which must function properly. An LED has two leads, a cathode and be installed correctly if the circuit is to work properly.

an anode lead. The anode lead will usually be the longer Careful handling and proper orientation in the circuit is of the two leads and the cathode lead will usually be the critical. A transistor will usually have a Base lead, a shorter lead, just under the flat side edge of the LED; this Collector lead, and an Emitter lead. The base lead is should help orient the LED on the PC board. You may

generally a vertical line inside a transistor circle

want to lead about 1⁄2 lead length on the LED, in order Chapter Thirty: Page-Alert symbol. The collector lead is usually a slanted line to have the LED protrude through the enclosure box.

318

Chapter Thirty: Page-Alert

Solder the LEDs to the PC board and then trim the

Table 30-4

excess leads.

Accessory daughter board I/O connections

The prototype utilized a mini PC board SPDT relay

J3 – 10 Pin header – power and I/O

at RY1. Study the relay pin-outs carefully before

J4 – 10 Pin header – sensor daughter boards

attempting to install the relay on the PC board. You

will want to make sure that you can properly identify Pin

Pinout Description

the relay coil leads as well as the relay pole outputs 1

+5 volt power pin

before installing the relay on the PC board and

2

System ground

soldering it in place.

3

IN1 input pin

Once the main Page-Alert board has been completed,

4

IN2 input pin

take a short break and then we will inspect the PC board 5

IN3 input pin

for possible “cold” solder joints and “short” circuits.

6

IN4 input pin

Pick up the PC board with the foil side facing upwards 7

No connection

toward you. Carefully inspect the solder joints, these 8

No connection

should look smooth, clean, and bright. If any of the

solder joints look dull, dark, or blobby, then you should 9

+9 volt power

remove the solder with a solder sucker or a solder wick 10

No connection

and then resolder the joint all over again. Now we will inspect the PC board for possible short circuits. Short circuits can be caused from small solder blobs bridging shown at pin1, while the TX line is at pin2. A DTR line the circuit traces or from cut component leads which

is provided at pin 3, and the ground is at pin 4.

can often stick to the circuit board once they have been To program your Page-Alert, you simply apply

cut. A sticky residue from solder will often trap

power to the screw terminals at J3/J4 and connect the component leads across the circuit traces. Look

Page-Alert via the serial cable to your personal

carefully for any bridging wires across circuit traces.

computer. Next, go to www.parallax.com and download

the Windows BASIC STAMP Editor version 2.5 or above.

Open up the editor program and type in or download the Using the Page-Alert

palert.bs2 program into the editor. Once the palert.bs2

program appears on your computer screen, you will have Note the 10 position screw terminal strip at J4 which is to enter your pager’s number into the first phone number connected to a 10 pin female header at J3. The 10 pin position and then you must enter the second number or header J3 is used to accept the Motion Module, or the identifier into the program. With the power connected up TVM add-on modules, or other expansion devices.

to the Page-Alert board and the programming cable

Table 30-4 illustrates the pinouts for the screw terminal connected, you can RUN the palert.bs2 program from the strip and the 10 pin header connections.

editor and it will load the program into the BASIC

Once the Page-Alert has been completed, recheck the

STAMP computer on the Page-Alert board.

component placement and your solder connections. You

Now you are ready to utilize the Page-Alert. You can

are now ready to power your Page-Alert unit. Locate a connect a normally open alarm switch/sensor between

12 V DC power supply which will be used to power

each input terminal and the 5 V terminal on the screw your Page-Alert. You can readily elect to utilize the terminal, for up to four channels. You can use any type ubiquitous 12 V DC “wall wart” to power your

of normally open alarm switch or sensor. Door or

Page-Alert; usually, these power supplies are quite

window switches could be used as well as any other

economical. The Page-Alert prototype was housed in an sensor with a normally open set of contacts. You could economical 4 × 5′′ plastic Pactec enclosure.

also elect to build the Switch/Sensor Module, which

The Page-Alert is initially programmed via pins 1

will allow you to connect normally open and normally

through 4. These pins are the serial input/output

closed switches or sensors to the Page-Alert. Additional connections used to program the BS2. The RX line is

modules are described in Chapter 31.

319

In order to test activate the Page-Alert, you could

DIRH = %11111111

also substitute a normally open pushbutton to start the new_io_state = %00000000

Page-Alert unit. Once activated, the Page-Alert should old_io_state = %00000000

come to life! First, the status lamp will begin to flicker to indicate the program has started. Next, the OH line for flash = 1 to 3

on the DAA is activated and the phone line goes

high LEDPin

“off hook.” Next the microprocessor begins

pause 1500

touch-tone dialing your pager’s phone number.

low LEDpin

The microprocessor then waits for a short interval,

pause 1500

and the triggered alarm channel’s ID or identifier is next

sent to your numerical pager.

main:

high LEDPin

Once alerted via your pager, you can respond

new_io_state = INL

yourself or you can elect to call a friend, neighbor, co-pause 100

worker, or even the police depending upon the severity low LEDPin

of the problem. The Page-Alert uses your existing

pause 100

phone line, so there is no additional phone cost to use it.

if new_io_state < > %00000000 then

The Page-Alert can be used as a self contained silent dial_pager

alarm using the Switch/Sensor Module or the Motion

after_io1:

Sensor Module described in the next chapter. The

old_io_state = new_io_state

Page-Alert can also be used with a multi-channel

goto main

alarm control box; in this way the Page-Alert becomes delay_and_scan:

the phone dialer for the alarm control box.

old_io_state = new_io_state

The Page-Alert is a low cost means to free you and

for timer = 1 to recall_delay

alert you to intruders, or equipment failures of

high LEDPin

impending doom. Why not have some fun? Build one!

new_io_state = INL

pause 500

PAGE¯ALERT PROGRAM

low LEDPin

pause 500

‘Palert.BS2

if new_io_state < > old_io_state

‘identify variables

then dial_pager

flash

VAR byte

old_io_state = new_io_state

new_io_state

VAR byte

next

old_io_state

VAR byte

goto after_io1

call_state

VAR byte

io

VAR byte

dial_pager:

timer

VAR byte

if new_io_state = %00000000 then main

high LEDPin

‘identify constants

high OHPin

OHPin

CON 9

high Siren

TxPin

CON 10

high Lamp

Siren

Con 12

pause 500

Lamp

Con 13

LEDPin

CON 15

dtmfout TxPin,500, 500, [8]

recall_delay

CON 120

pause 200

dtmfout TxPin,400, 200, [7,9,9,6,

‘initialize variables and program

6,5,8]

init:

sleep 6

Chapter Thirty: Page-Alert

DIRL = %00000000

gosub send_msg

320

Chapter Thirty: Page-Alert

goto delay_and_scan

Normally open sensors or switch contacts are shown

send_msg:

at S1, S2, and S3. Normally closed switches or alarm

io = new_io_state

sensors are shown S4, S5, S6, and S7. Any number of

‘debug ibin8 io, cr

normally closed or normally open switches can be used dtmfout TxPin, 300, 200, [5,5,io.bit0,

in this input circuit. Two 1N914 diodes, an NPN

io.bit1,io.bit2,io.bit3,11]

transistor, and a few resistors form the heart of this pause 1000

detector. You could elect to build one of these input low OHPin

circuits for each of the BASIC STAMP 2 input pins if low LEDPin

desired. The output of this input converter circuit provides pause 30000

a 5 volt signal to the input of the STAMP 2 upon an alarm low Siren

signal. A few of these detector circuits could be built on a low Lamp

single circuit board to create a multi-channel alarm system pause 100

using your Tele-Alert system. The alarm sensor daughter return

board is simply plugged into the main Tele-Alert board end

through the set of header pins on each of the boards.

Circuit assembly

Alarm Switch/Sensor

Module

Before we begin constructing the Switch/Sensor board, you will need to locate a clean, well-lit worktable or workbench. Next we will gather a small 25–30 W pencil Normally open/normally closed

tipped soldering iron, a length of 60/40 tin–lead solder, input sensor board

and a small canister of Tip Tinner, available at your local RadioShack store; Tip Tinner is used to condition the The Switch/Sensor Module can be used to connect any

soldering tip between solder joints. You drive the

number of alarm sensors to the input of the Tele-Alert soldering tip into the compound and it cleans and prepares system. Using the Alarm Sensor Module you can easily

the soldering tip. Next grab a few small hand tools; try to turn your Tele-Alert into a portable burglar alarm system, locate small flat blade and Phillips screwdrivers. A pair which can be used to call you and let you know someone of needle-nose pliers, a pair of tweezers along with

has violated a particular space that you have protected.

a magnifying glass, and a pair of end-cutters and we will The diagram in Figure 30-5 depicts a clever method

begin constructing the project. Now locate your schematic of utilizing both normally open and normally closed

diagram and parts layout diagram along with all of the input sensors or alarm switches, using a simple circuit.

components needed to build the project.

Daughter board

+5 V

connector

P3-1

S1

S3

D2

R1

Q1

R2

S2

R3

+

Output

S4

D1

C1

R4

P3-10

S5

S6

S7

Figure 30-5

Switch/sensor module

321

The Switch/Sensor Board is built on single sided

Note that capacitors generally come from two major

PC board. Once all the components are in front of you, groups or types. Non-polar types, such as the ones in you can check them off against the project parts list to this project, have no polarity and can be placed in either make sure you are ready to start building the project.

direction on the circuit board. The other type of

Now, locate Tables 30-2 and 30-3, and place them in

capacitors are called polarized types, these capacitors front of you. Table 30-2 illustrates the resistor code have polarity and have to be inserted on the board with chart and how to read resistors, while Table 30-3

respect to their polarity marking in order for the circuit illustrates the capacitor code chart which will aid

to operate correctly. On these types of capacitors, you you in constructing the project.

will observe that the components actually have a plus or minus marking or a black or white band with a plus

Refer now to the resistor color code chart shown in

or minus marking on the body of the capacitors.

Table 30-2, which will help you identify the resistor Capacitors must be installed properly with respect to values for the project. Note that each resistor will have polarity in order for the circuit to work properly. Failure either three or four color bands, which begin at one end to install electrolytic capacitors correctly could cause of the resistor’s body. The first colored band represents damage to the capacitors as well as to other components the resistor’s first digit, while the second color

in the circuit when power is first applied.

represents the second digit of the resistor’s value. The third colored band represents the resistor’s multiplier Next refer to Table 30-3, this chart helps to determine value, and the fourth color band represents the resistor’s value of small capacitors. Many capacitors are quite

tolerance value. If there is no fourth colored band then small in physical size, so manufacturers have devised a the resistor has a 20% tolerance value. If the resistor’s three-digit code which can be placed on the capacitor fourth band is silver then the resistor has a 10%

instead of the actual value. The code occupies a much tolerance value and if the fourth band is gold then the smaller space on the capacitor and can usually fit

resistor’s tolerance value will be 5%.

nicely on the capacitor body, but without the chart the builder would have a difficult time determining the

Finally, we are ready to begin assembling the project, capacitor’s value.

so let’s get started. The prototype project was

constructed on a single-sided printed circuit board or Now look for the capacitors from the component

PCB. With your PC board in front of you, we can now

stack and locate capacitor C1; it is a small capacitor begin populating the circuit board. We are going to

labeled (103). Refer to the Table 30-3 to find code (103) place and solder the lowest height components first,

and you will see that it represents a capacitor value of the resistors and the diodes. First, locate our first

.1 μF. Go ahead and place these capacitors on the circuit resistor R1. Resistor R1 has a value of 20,000 ohms and board and solder them in place. Now take your

is a 5% tolerance type. Now take a look for a resistor end-cutters and cut the excess component leads flush to whose first color band is red, black, orange, and gold.

the edge of the circuit board. Once you have installed From the chart you will notice that red is represented by these components, you can move on to installing the

the digit (2), the second color band is black, which is remaining capacitors. Save the larger electrolytic

represented by (0). Notice that the third color is orange capacitors for mounting last. The electrolytic capacitors and the multiplier is (1,000), so (2) (0) × 1,000 = 20,000

will have a plus or minus sign or a black or white color or 20 K ohms.

band. Be sure to orient the electrolytic capacitors

Go ahead and locate where resistor R1 goes on the

correctly when placing them on the PC board.

PC and install it, next solder it in place on the PC board, The Alarm Switch/Sensor board contains two silicon

and then with a pair of end-cutters trim the excess

diodes. Diodes, as you will remember, will always have component leads flush to the edge of the circuit board.

some type of polarity markings, which must be

Next, locate the remaining resistors and install them in observed if the circuit is going to work correctly. You their respective locations on the main controller

will notice that each diode will have a black or white PC board. Solder the resistors to the PC board, and

colored band at one edge of the diode’s body. The

remember to cut the extra component leads with your

colored band represents the diode’s cathode lead. Check Chapter Thirty: Page-Alert end-cutters.

your schematic and parts layout diagrams when

322

Chapter Thirty: Page-Alert

installing these diodes on the circuit board. Place the connect up normally closed sensors and switches in

diodes on the circuit board in their respective locations series at S4, S5, S6, and S7. If you installed a

and solder them in place on the PC board. After

10-position header on the bottom of the Switch/Sensor soldering in the diodes and the diode bridge, remember Module then you can simply plug in the module’s

to cut the excess component leads with your

P3 connector into the Page-Alert’s J3 connector on the end-cutters, flush to the edge of the circuit board.

Page-Alert board. You can add as many switches of

The Switch/Sensor Board uses a single transistor at

either type, however, with too many switches configured circuit’s output which interfaces with the main Tele-in series and parallel in this fashion you will not be able Alert board. Transistors generally have three leads, a to trace the actual alarm sensor very easily. In order to Base lead, a Collector lead and an Emitter lead. Refer to pinpoint the sensors more easily, you may want to

the schematic and you will notice that there will be two consider building a four channel output Switch/Sensor diagonal leads pointing to a vertical line. The vertical Module instead of a single channel board as shown.

line is the transistor’s base lead and the two diagonal The Alarm Switch/Sensor board is a great addition to

lines represent the collector and the emitter. The

the Page-Alert or Tele-Alert system.

diagonal lead with the arrow on it is the emitter lead, and this should help you install the transistor on to the circuit board correctly. Go ahead and install the

transistor on the PC board and solder it in place, then Temperature/Voltage level

follow-up by cutting the excess components leads.

module

If your Switch/Sensor board only has a single

channel as shown in the schematic, then the output

The Temperature/Voltage Level Module board is a

header only needs a signal output and ground.

versatile addition to the Tele-Alert microprocessor

The single channel output from the Alarm Sensor board alarm controller (see Figure 30-6).

can be sent to the BS2 at input P0. If you elected to The Temperature/Voltage Level Module is a single

build a multi-channel Switch/ Sensor board then the

channel module that will permit you to monitor

additional channels would be sent to STAMP inputs

temperature level changes either upwards or

P1, P2, P3, and P4.

downwards, or allow you to measure voltage level

Once the Alarm Sensor circuit board has been

changes by setting a user threshold control.

completed, take a short break and then we will inspect The Temperature/Voltage Level or TVM board

the PC board for possible “cold” solder joints and

consists of a single LM393 comparator integrated

“short” circuits. Pick up the PC board with the foil side circuit and a handful of components, which is illustrated facing upwards toward you. Carefully inspect the solder in the schematic of Figure 30-7.

joints, these should look smooth, clean, and bright.

If any of the solder joints look dull, dark, or blobby, then you should remove the solder with a solder sucker or a solder wick and then resolder the joint all over again. Now we will inspect the PC board for possible

“short” circuits. Short circuits can be caused from small solder blobs bridging the circuit traces or from cut

component leads which can often stick to the circuit

board once they have been cut. A sticky residue from

solder will often trap component leads across the circuit traces. Look carefully for any bridging wires across

circuit traces.

Once your Switch/Sensor board is complete and

ready to go, simply attach your normally open sensors or switches in parallel at S1, S2, and S3. You can also Figure 30-6

Page-Alert TVM temperature board

323

+9 V

Daughter board

R5

connector

R7

R1

P3-1

R4

+5 V

C1

R2

+

2

8

R8

−

1

393A

R3

+9 V

+

U1

3

4

+

9 V

S1

C2

P3-10

IN 1

R6

To page – alert

Tele – alert

Figure 30-7

Temperature-voltage module (TVM)

The circuit begins with S1, a resistive sensor and R6.

system being monitored, adjust the threshold control, The thermistor or temperature sensors at S1 and R6

and you are ready to go.

form a voltage divider to ground. In this configuration you are able to monitor upward temperature changes.

If the position of S1 and R6 are reversed, then you are Circuit Assembly

able to monitor decreasing temperature changes. The

thermistor outputs at pin 3 of U1(A) represents the plus Before we begin constructing the TVM board, you will

(+) inputs to the comparator circuits. The resistor

need to locate a clean, well lit worktable or workbench.

network at R12 acts as the threshold control on the

Next we will gather a small 25–30 W pencil tipped

minus (−) inputs of the comparator. The output of the soldering iron, a length of 60/40 tin–lead solder, and a comparator at pin 1 produces a (high) output when the small canister of Tip Tinner, available at your local threshold is sensed.

RadioShack store; Tip Tinner is used to condition

The TVM Module can also be used to monitor

the soldering tip between solder joints. You drive the voltage level changes by eliminating the Thermistor S1

soldering tip into the compound and it cleans and

and resistor R6 and replacing them with “scaling”

prepares the soldering tip. Next grab a few small hand resistors instead. Scaling resistors will now represent tools; try to locate small flat blade and Phillips

voltage dividers consisting of two resistors at each input screwdrivers. A pair of needle-nose pliers, a pair of channel. Ratios such as 100 K to 1 K for R1/R2 or 1 K

tweezers along with a magnifying glass, and a pair of to 100 ohms for R3/R4 would be used as input scalers.

end-cutters and we will begin constructing the project.

The higher value resistor would replace the thermistors Now locate your schematic diagram and parts layout

while the lower value resistor would go to ground. Note, diagram along with all of the components needed to

capacitors C1 and C3 provide noise reduction, when

build the project.

using external inputs. To measure voltage level changes, Once all the components are in front of you, you can

Chapter Thirty: Page-Alert you simply connect the input wire IN1 to the circuit or check them off against the project parts list to make 324

Chapter Thirty: Page-Alert

sure you are ready to start building the project. Now, Remember that when voltage level detection is desired, locate Tables 30-2 and 30-3, and place them in front of scaling resistors are use in place of the thermistors as you. Table 30-2 illustrates the resistor code chart and mentioned earlier. Next locate the remaining resistors how to read resistors, while Table 30-3 illustrates the and install them in their respective locations on the capacitor code chart which will aid you in constructing main controller PC board. Solder the resistors to the the project.

PC board, remembering to cut the extra component

leads with your end-cutters.

Refer now to the resistor color code chart shown in

Table 30-2, which will assist you in identifying the

Note that capacitors generally come from two major

resistor values for the project. Note that each resistor groups or types. Non-polar types, such as the ones in will have either three or four color bands, which begin this project, have no polarity and can be placed in either at one end of the resistor’s body. The first colored band direction on the circuit board. The other type of

represents the resistor’s first digit, while the second capacitors are called polarized types, these capacitors color represents the second digit of the resistor’s value.

have polarity and have to be inserted on the board with The third colored band represents the resistor’s

respect to their polarity marking in order for the circuit multiplier value, and the fourth color band represents to operate correctly. On these types of capacitors, you the resistor’s tolerance value. If there is no fourth will observe that the components actually have a plus or colored band then the resistor has a 20% tolerance

minus marking or a black or white band with a plus or value. If the resistor’s fourth band is silver then the minus marking on the body of the capacitors.

resistor has a 10% tolerance value and if the fourth band Capacitors must be installed properly with respect to is gold then the resistor’s tolerance value will be 5%.

polarity in order for the circuit to work properly. Failure to install electrolytic capacitors correctly could cause Finally, we are ready to begin assembling the project, damage to the capacitors as well as to other components so let’s get started. The prototype project was

in the circuit when power is first applied.

constructed on a single-sided printed circuit board or Many capacitors are quite small in physical size, so

PCB. With your PC board in front of you, we can now

manufacturers have devised a three-digit code which

begin populating the circuit board. We are going to

can be placed on the capacitor instead of the actual

place and solder the lowest height components first, the value. The code occupies a much smaller space on the

resistors and diodes. First, locate our first resistors R1

capacitor and can usually fit nicely on the capacitor and R3. Both resistors have a value of 2,000 ohms

body, but without the chart the builder would have a

and are a 5% tolerance type. Now take a look for a

difficult time determining the capacitor’s value.

resistor whose first color band is red, black, red, and gold. From the chart you will notice that red is

Now look for the capacitors from the component

represented by the digit (2), the second color band

stack and locate capacitor C1; it is a small capacitor is black, which is represented by (0). Notice that the labeled (104). Refer to Table 30-3 to find code (104) third color is red and the multiplier is (100), so

and you will see that it represents a capacitor value of (2) (0) × 100 = 2,000 or 2 K ohms.

.1 μF. Now locate capacitor C2; it may be labeled (103) Go ahead and locate where resistor R1 goes on the

or .01 μF. Go ahead and place these capacitors on the PC and install it, next solder it in place on the PC board, circuit board and solder them in place. Now take your and then with a pair of end-cutters trim the excess

end-cutters and cut the excess component leads flush to component leads flush to the edge of the circuit board.

the edge of the circuit board. Once you have installed Note, for initial testing S1/R6 should not be inserted.

these components, you can move on to installing the

When later installing the thermistors or scaling resistors, remaining capacitors. Save the larger electrolytic

be sure to observe carefully the placement of S1/R6,

capacitors for mounting last. The electrolytic capacitors depending upon the temperature direction you desire to will have a plus or minus sign or a black or white color measure or if you want to sense voltage levels. Trim

band. Be sure to orient the electrolytic capacitors

Potentiometer R2 is used to set the threshold values

correctly when placing them on the PC board.

for either temperature or voltage level sensing. The

The resistive temperature or photocell can be placed at trim-pots are located at the top of the circuit board.

S1 for sensing or you could elect to use the circuit to 325

detect voltage level changes by connecting a low voltage being remotely monitored are connected to these pins #8

input to the terminal labeled IN1. The LM393A is a dual and #9, i.e. inputs IN1 and IN2 respectively.

comparator, so you could easily fabricate a dual channel Once the TVM circuit board has been completed,

TVM board with two outputs. Simply build two of the

take a short break and then we will inspect the PC board circuits shown on a single daughter board.

for possible “cold” solder joints and “short” circuits.

The pinouts at the edge of the TVM board are

Pick up the PC board with the foil side facing upwards described below and are shown in Table 30-4.

toward you. Carefully inspect the solder joints, these At the top of the board the first solder pad used is pin should look smooth, clean, and bright. If any of the

#2 which is for the 9 V reference connection for the

solder joints look dull, dark, or blobby, then you should inputs at IN1 and trim potentiometer R2. Pin #3 is used remove the solder with a solder sucker or a solder wick for the system ground connection. Pins #4 and #5 are

and then resolder the joint all over again. Now we will used for the two TVM outputs to the Tele-Alert board.

inspect the PC board for possible short circuits. Short Solder pads 6 and 7 are not used, while solder pads

circuits can be caused from small solder blobs bridging 8 and 9 are reserved for inputs IN1 and IN2 to the

the circuit traces or from cut component leads which

comparators. The last pin at position 10 is used to

can often stick to the circuit board once they have

supply 5 V to the comparator.

been cut. A sticky residue from solder will often

trap component leads across the circuit traces.

Once the board has been completed, you will need to

Look carefully for any bridging wires across

place the 10 pin header on the component side of the

circuit traces.

PC board and solder it on the foil side of the PC board.

The 10 pin header allows connection with the Page-Alert Your Temperature/Voltage Level Module is now

or Tele-Alert boards. The 10 pin header on the TVM

complete and ready to go. It is advised that you test board then can be inserted into the 10 pin female header your new TVM board before you connect it to the main

(second inside header) on the main Page-Alert or

Tele-Alert board. The TVM board was designed to

Tele-Alert board once you are ready. Note that pins #8

incorporate a 10-position header pin set which can be and #9 are inputs to the comparator and these pins should used to simply plug the TVM board into the Page-Alert be either clipped or bent so as not to be inserted into the or Tele-Alert Board at J3.

Tele-Alert board. The voltage level inputs from the circuit Testing the TVM board

Table 30-4

Accessory daughter board I/O connections

You could elect to construct a multi-channel TVM

board by incorporating up to four of the circuits shown J3 – 10 Pin header – power and I/O

onto to a single TVM PC board. Connect a scope or

J4 – 10 Pin header – sensor daughter boards

multi-meter to the channel 1 output on the TVM board.

Next, connect the plus (

Pin

Pinout description

+) lead from a 5 volt power

supply to pins #2 and #10, then connect the minus (−) 1

+ 5 volt power pin

lead from the power supply to the system ground at

2

System ground

pin #3. For this initial testing, resistors R1/R2 and 3

IN1 input pin

R3/R4 are not inserted. Now, locate an adjustable low 4

IN2 input pin

voltage power supply. Connect the plus lead (+) from

5

IN3 input pin

the adjustable supply to the input at IN1 or pin #8,

and connect the minus (

6

IN4 input pin

−) lead to the system

ground at pin #3. Be sure the adjustable power

7

No connection

supply is initially adjusted for 0 V before applying

8

No connection

terminals at the edge of the TVM board.

9

+ 9 volt power

Now, turn on the first 5 V power supply and slowly

Chapter Thirty: Page-Alert 10

No connection

advance the adjustable power supply voltage from

326

Chapter Thirty: Page-Alert

zero to one or two volts. You may have to set the

move on to testing channel 2 in the same manner.

threshold to set the trip point at which you will

Once the TVM board has been tested and you have

begin to see an output on the scope. Once the

decided if you wish to have temperature or voltage

comparator is tripped the scope reading should change level sensing you can insert the input resistors S1/R2

from 0 to 5 V. Once channel 1 has been tested, you can or the scalers.

327

Chapter 31

Tele-Alert Project

XTL

20 MHz ceramic

Parts list

resonator

T1

600–600 ohm audio

Tele¯Alert

transformer

R1, R2, R3, R12

J1, J2

10 position male

4.7 K ohm 1⁄ W resistor

4

header jacks

R4, R5, R6, R7

10 K ohm

1

J3

3 position male

⁄ W resistor

4

header jacks

R8, R9, R10, R11

10 K ohm 1⁄ W resistor

J4, J5

4 position male

4

header jack

R13

330 ohm 1⁄ W

4

resistor

U1

PIC 16C57

microprocessor

R14

620 ohm 1⁄ W

4

resistor

U2

24LC16B EEPROM memory

R15

1 K ohm 1⁄ W

U3

MAX232 Serial com

4

resistor

chip

R16

150 ohm 1⁄ W

4

U4

PVT412L MOS relay

resistor

U5

LM7805 5 volt DC

R17

130 V rms MOV

regulator

C1

10 μF 35 V

Misc

PC board, wire,

electrolytic capacitor

IC sockets, standoffs,

C2, C7, C8, C9

.1 μF

chassis box, etc.

35 V capacitor

PIR Motion Module

C3, C4, C5, C6

1 μF

R1

47 K ohms 1⁄ W

35 V electrolytic

4

resistor

capacitor

C10

.001 μF 35 V

R2

200 K ohm trim

capacitor

potentiometer

C11

.1 μF 250 V mylar

R3

3.9 K ohm 1⁄ W

4

capacitor

resistor

C12

47 μF 35 V

R4

56 K ohm 1⁄ W

4

electrolytic capacitor

resistor

D1

1N914 silicon diode

R5

10 K ohm 1⁄ W

4

D2, D3

3.9 V zener

resistor

diode

R6

1 megohm trim

D4

LED

potentiometer

328

Copyright © 2009 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Chapter Thirty-One: Tele-Alert Project

R7

10 K ohm 1⁄ W

U1

LM358 dual op

4

¯amp

resistor

MIC

electret microphone

C1, C4, C7

100 nF 35 V

Misc

PC board, 10 pin

electrolytic capacitor

header, IC sockets,

C2

220 pF 35 V mylar

wire, hardware, etc.

capacitor

C3, C5

10 μF 35 V

Tele-Alert

electrolytic capacitor

C6

.1 μF 35 V disc

The Tele-Alert is a unique new low cost multi-channel capacitor

microprocessor controlled remote event/alarm reporting C8

4.7 nF 35 V disc

system which will immediately notify you anywhere

capacitor

in the country of any event via your cell phone;

Q1

2N2222 transistor

see Figure 31-1.

LED

red LED

The Tele-Alert can monitor up to four different alarm or event conditions from a host of different types of U1

78L05 5 V

regulator

U2

PIR controller chip

KC778B

PIR

PIR sensor RE200B

F1, F2

PIR Fresnel

lens¯wide/narrow beam

Misc

PC board, header,

IC socket, wire,

hardware, etc.

kit available:

www.kitsrus.com

Figure 31-1

Tele-alert main board

Listen¯in Module

R1

2.2 K ohm 1⁄ W

4

resistor

R2, R7

10 K ohm 1⁄ W

4

Programming

resistor

PC

Telephone

R3, R5

100 K ohm 1⁄ W

line

4

Power

resistor

Tele alert

R4

5.6 K ohm 1⁄ W

4

resistor

R6

5 megohm 1⁄ W

IN 1

IN 2

IN 3

IN 4

4

Siren

resistor

C1

2.2 μF 35 V

electrolytic capacitor

( )

C2

.1 μF 35 V disc

capacitor

C3, C4

10 μF 35 V

electrolytic capacitor

Figure 31-2

Tele-alert block diagram

329

sensors as shown in Figure 31-2, and report the

PIC 16C57 is a very capable and versatile little

particular channel which was activated.

microprocessor which can perform many tasks.

The Tele-Alert can be configured to monitor voltage

In order to turn the BS2 “look alike” into a Tele-Alert levels, temperature changes, movement, contact

project, a few more parts must be added to the basic

closures, windows, doors, safes, and perimeters, as well configuration. First, you need to configure pins

as computer equipment. The Tele-Alert can be utilized 10 through 17 as inputs for a total of 8 inputs which can to protect your home, office, shop, or vacation home.

be used to sense events or alarm conditions. The first The Tele-Alert is used with your existing telephone

four input pins are brought out to the terminal block for line, so no additional charges are added to your monthly easy access. These first four inputs IN1 through IN4 are phone bill. The Tele-Alert can be programmed to call

used as inputs to the microprocessor. Pins 18 through you on your cell phone, or to call a friend, neighbor, 25 are configured as output pins. Pin 18 is used to

co-worker, or a relative if desired. The Tele-Alert

activate or enable the microphone in the Listen-in

project is flexible and the software programs can be

Module, if utilized. Pin 19 is used to drive the solid expandable for future applications. The Tele-Alert can state relay at U4. The microprocessor activates the

monitor four different input events or alarm conditions.

LED in U4, which in turn closes the relay contacts at The Tele-Alert is compact and easy to use; simply

pins 4 and 6 of the relay, which essentially shorts out, plug in a 9-V power supply, connect up your

blocking capacitor C11 and allows the phone to go “on telephone line and the input connections and you are

hook” and begins dialing your cell phone or pager.

ready to go. The optional Motion Module allows the

Pins 20 and 21 of U1 are audio output pins. Pin 20 of Tele-Alert to detect moving persons and will trigger the U1 outputs the touch-tone signals needed to dial a

Tele-Alert; in addition the Motion Module also contains phone when an alarm condition is sensed, while Pin 21

two normally open and two normally closed alarm loop

is used to output the tone sequences which are used to channels, so a number of alarm sensors/switches can be indicate via your cell phone which event/alarm channel used. The optional Temperature/Voltage Level module

has been activated. The capacitors at C9 and C10 are

allows your Tele-Alert to monitor up to four

used to couple the touch tones and the alarm sequence temperature or voltage level presets, and report the

tones to the coupling transformer network formed by T1

changes via your cell phone or pager. The optional

and the associated components. Capacitor C10 is placed Listen-in Module will allow you to listen in for up to across T1 while Zener diodes D2 and D3 are used as

two minutes to the area being protected.

voltage clamps diodes at the input of the transformer.

The Tele-Alert multi-channel alarm reporting system

Transformer T1 is used to couple the audio from the

begins with the Alternative BASIC STAMP 2 circuit

Tele-Alert to the phone line, once the unit has been

diagram shown in Figure 31-3.

triggered. Resistor R9 is used to couple one side of the The heart of the Tele-Alert is the PIC 16C57 chip

transformer to the phone line at J6, and also acts to hold which emulates the BASIC STAMP II computer. The

the phone line. The other secondary transformer lead is PIC 16C57 is preloaded with a BASIC interpreter

coupled to the phone line via C11. C11 is a blocking

much like the Parallax BASIC STAMP 2 (BS2). The

capacitor which keeps the phone off hook until an alarm PIC 16C57, however, is a much less expensive approach condition occurs. The solid state relay at U4 acts to to solving a problem, but requires a few more external short out C11 when an event or alarm condition occurs, parts than the BS2. The PIC 16C57 requires very little thus coupling the T1 to the phone line. Resistor R16 is a in the way of support chips to make it function. The

metal oxide varistor (MOV) and is used to protect the PIC 16C57 basically requires only two support chips,

circuit from high voltage spike. Pins 22 and 23 may be a 24LC16B EEPROM for storage and a MAX232 for

utilized as auxiliary outputs to drive local alarm sirens communication. Only a few extra components are

or outdoor lamps if desired, while pin 24 is left for needed to form a functional microprocessor with

further expansion. Pin 25 of U1 is used as a status

serial input/outputs. A 20 MHz ceramic resonator and

indicator, when the microprocessor is configured as a a few resistors and a diode are all that are needed to Page-Alert. The 20 MHz ceramic resonator is connected Chapter Thirty-One: Tele-Alert Project use the processor in its most simple form. The 28 pin between pins 26 and 27 to establish the clock reference 330

S1

+5

N/O

R12

C7

8

1

U2

2

7

3

6

XTL

1

28

4

5

U1

2

27

R2

3

26

R13

D4

+5 V

4

25

R3

5

J4-3

24

OT3

6

Basic

J4-2

23

OT2

C8

7

stamp 2

J4-1

22

OT1

C12

U4

8

(ALT)

21

1

6

9

+

20

5 V

C6

10

19

C9

R14 2

4

11

+

18

12

17

13

16

16

1

14

15

R15

+

U3

15

C5

2

14

R4

R9

J5

3

J6

C11

+

13

4

R5

R10

C4

D2

12

1

RX

D1

5

R6

R11

C10

J5-1

11

+

6

D3

10

R7

2

R17

TX

R1

C3

7

9

Phone

J5-2

8

R8

T1

line

ATN

R16

J5-3

IN 5

IN 6

IN 7

IN 8

GND

J5-4

+9 V

J3

In

Out

U5

le

n i

+5

io

+

+

IN 1

IN 2

IN 3

IN 4

d

Input

C1

C2

Enab

Au

J1-1

J1-10

J2-1

J2-10

Figure 31-3

Tele-alert main circuit diagram

331

for the BASIC interpreter chip at U1. Pin 28 is utilized soldering iron, a length of 60/40 tin–lead solder, and a to reset the micro-processor, via S1 if the system

small canister of Tip Tinner, available at your local

“locks up”. The serial 16 K EEPROM memory is

RadioShack store; Tip Tinner is used to condition the coupled to the microprocessor via pins 6 and 7.

soldering tip between solder joints. You drive the

The microprocessor communicates via U3, a

soldering tip into the compound and it cleans and

MAX232 serial communication chip. The MAX232 is

prepares the soldering tip. Next grab a few small hand coupled to the microprocessor through pins 8 and 9,

tools; try to locate small flat blade and Phillips

very simply an input and output pin respectively.

screwdrivers. A pair of needle-nose pliers, a pair of Four capacitors are all that are required to animate

tweezers along with a magnifying glass, and a pair of the MAX232, serial communication chip. These

end-cutters and we will begin constructing the project.

capacitors are required as a charge pump to create

Now locate your schematic diagram and parts layout

a minus voltage for the serial chip. The MAX232

diagram along with all of the components needed to

is coupled to a 9-pin serial connector for serial

build the project.

communication with a laptop or personal computer

The Home Phone Intercom controller is built on

for programming purposes.

double-sided PC board. The main Tele-Alert circuit

The Tele-Alert circuit is powered via the regulator at board measures 4 × 2 1⁄2′′ and can be housed in a

U5 which provides 5 V to U1, U2, and U3. A nine volt

suitable plastic enclosure. Note, the basic Tele-Alert is DC “wall wart” or wall cube power supply is used to

only about 1⁄2′′ high, but if you intend to add optional provide power to the Tele-Alert circuit. The 9 volt

modules at a later time you should consider an

source is also used to provide power to optional

enclosure which has more height to accommodate the

enhancement modules.

optional circuit boards. Once all the components are in front of you, you can check them off against the project parts list to make sure you are ready to start building the Circuit assembly

project. Now, locate Tables 31-1 and 31-2, and place

them in front of you. Table 31-1 illustrates the resistor Before we begin constructing the Tele-Alert, you will code chart and how to read resistors, while Table 31-2

need to locate a clean, well-lit worktable or workbench.

illustrates the capacitor code chart, which will aid you Next we will gather a small 25–30-W pencil tipped

in constructing the project.

Table 31-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

Chapter Thirty-One: Tele-Alert Project

No color

20%

332

Chapter Thirty-One: Tele-Alert Project

Table 31-2

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

1.0

1R0

3,900

3.9

.0039

392

1.2

1R2

4,700

4.7

.0047

472

1.5

1R5

5,600

5.6

.0056

562

1.8

1R8

6,800

6.8

.0068

682

2.2

2R2

8,200

8.2

.0082

822

2.7

2R7

10,000

10

.01

103

3.3

3R3

12,000

12

.012

123

3.9

3R9

15,000

15

.015

153

4.7

4R7

18,000

18

.018

183

5.6

5R6

22,000

22

.022

223

6.8

6R8

27,000

27

.027

273

8.2

8R2

33,000

33

.033

333

10

100

39,000

39

.039

393

12

120

47,000

47

.047

473

15

150

56,000

56

.056

563

18

180

68,000

68

.068

683

22

220

82,000

82

.082

823

27

270

100,000

100

.1

104

33

330

120,000

120

.12

124

39

390

150,000

150

.15

154

47

470

180,000

180

.18

184

56

560

220,000

220

.22

224

68

680

270,000

270

.27

274

82

820

330,000

330

.33

334

100

.0001

101

390,000

390

.39

394

120

.00012

121

470,000

470

.47

474

150

.00015

151

560,000

560

.56

564

180

.00018

181

680,000

680

.68

684

220

.00022

221

820,000

820

.82

824

270

.00027

271

1,000

1

105

330

.00033

331

1,500

1.5

155

390

.00039

391

2,200

2.2

225

470

.00047

471

2,700

2.7

275

560

.00056

561

3,300

3.3

335

680

.00068

681

4,700

4.7

475

820

.00082

821

6.8

685

1,000

1.0

.001

102

10

106

1,200

1.2

.0012

122

22

226

1,500

1.5

.0015

152

33

336

1,800

1.8

.0018

182

47

476

333

Table 31-2—cont’d

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

2,200

2.2

.0022

222

68

686

2,700

2.7

.0027

272

100

107

3,300

3.3

.0033

332

157

157

Code = 2 significant digits of the capacitor value + number of zeros to follow 10 pF = 100

For values below 10 pF, use “R” in place of decimal e.g. 8.2 pF = 8R2

100 pF = 101

1,000 pF = 102

22,000 pF = 223

330,000 pF = 334

1 μF = 105

Refer now to the resistor color code chart in

and then with a pair of end-cutters trim the excess

Table 31-1, which will help you identify the resistor component leads flush to the edge of the circuit board.

values before installing them on the PC board. Note that Next locate the remaining resistors and install them in each resistor will have either three or four color bands, their respective locations on the main controller

which begin at one end of the resistor’s body. The first PC board. Solder the resistors to the PC board, and

colored band represents the resistor’s first digit, while remember to cut the extra component leads with your

the second color represents the second digit of the

end-cutters.

resistor’s value. The third colored band represents the Note that capacitors generally come from two major

resistor’s multiplier value, and the fourth color band groups or types. Non-polar types, such as the ones in represents the resistor’s tolerance value. If there

this project, have no polarity and can be placed in either is no fourth colored band then the resistor has a

direction on the circuit board. The other type of

20% tolerance value. If the resistor’s fourth band is capacitors are called polarized types, these capacitors silver then the resistor has a 10% tolerance value

have polarity and have to be inserted on the board with and if the fourth band is gold then the resistor’s

respect to their polarity marking in order for the circuit tolerance value will be 5%.

to operate correctly. On these types of capacitors, you We are ready to begin assembling the project, so let’s will observe that the components actually have a plus or get started. The prototype project was constructed on minus marking or a black or white band with a plus or a single-sided printed circuit board or PCB. With your minus marking on the body of the capacitors.

PC board in front of you, we can now begin populating Capacitors must be installed properly with respect to the circuit board. We are going to place and solder the polarity in order for the circuit to work properly. Failure lowest height components first, the resistors and diodes.

to install electrolytic capacitors correctly could cause First, locate our first resistor R1. Resistor R1 has a damage to the capacitors as well as to other components value of 4,700 ohms and is a 5% tolerance type. Now

in the circuit when power is first applied.

take a look for a resistor whose first color band is

Many capacitors are quite small in physical size, so

yellow, violet, red, and gold. From the chart you will manufacturers have devised a three-digit code which

notice that yellow is represented by the digit (4), the can be placed on the capacitor instead of the actual

second color band is violet, which is represented by (7).

value. The code occupies a much smaller space on the

Notice that the third color is red and the multiplier is capacitor and can usually fit nicely on the capacitor (100), so (4) (7) × 100 = 4,700 or 4.7 K ohms.

body, but without the chart the builder would have a

Go ahead and locate where resistor R1 goes on the

difficult time determining the capacitor’s value. Now Chapter Thirty-One: Tele-Alert Project PC and install it, next solder it in place on the PC board, look for the capacitors from the component stack and

334

Chapter Thirty-One: Tele-Alert Project

locate capacitors C2, C7, C8, and C9; they are small

doubt you ability to correctly orient the ICs, then

capacitors labeled (104). Refer to Table 31-2 to find seek the help of a knowledgeable electronics

code (104) and you will see that it represents a capacitor enthusiast. IC U4 is an opto-isolator and has

value of .1 μF. Go ahead and place these capacitors on six pins but the procedure for installation is the

the circuit board and solder them in place. Now take

same as for the other ICs.

your end-cutters and cut the excess component leads

The Tele-Alert controller circuit utilizes a single

flush to the edge of the circuit board. Once you have LED at D4, which also must be oriented correctly if the installed these components, you can move on to

circuit is to function properly. An LED has two leads, installing the remaining capacitors. Save the larger

a cathode and an anode lead. The anode lead will

electrolytic capacitors for mounting last. The

usually be the longer of the two leads and the cathode electrolytic capacitors will have a plus or minus

lead will usually be the shorter lead, just under the flat sign or a black or white color band. Be sure to

side edge of the LED; this should help orient the LED

orient the electrolytic capacitors correctly when

on the PC board. You may want to leave about 1⁄2 lead placing them on the PC board.

length on the LED, in order to have the LED protrude

The Tele-Alert project contains three silicon diodes.

through the enclosure box. Solder the LED to the

Diodes, as you will remember, will always have some

PC board and then trim the excess leads.

type of polarity markings, which must be observed

Now, locate the crystal (XTL) and install it in its

if the circuit is going to work correctly. You will notice proper location between pins 26 and 27 of U1 and

that each diode will have a black or white colored band ground as shown on the schematic. Next locate the

at one edge of the diode’s body. The colored band

MOV protection device which is placed across the

represents the diode’s cathode lead. Check your

telephone line at R17. This device has no polarity so schematic and parts layout diagrams when installing

it can be installed in either direction. Solder it in these diodes on the circuit board. Place all the diodes on place and then trim the excess leads.

the circuit board in their respective locations and solder Next, install the coupling transformer at T1. The

them in place on the PC board. Diode bridge BR1

transformer is used to isolate the telephone line from the on the right side of the schematic can be installed now.

BS2. The transformer is a 600 to 600 ohm matching

After soldering in the diodes and the diode bridge,

transformer so it can be mounted in either direction, remember to cut the excess component leads with your

since both windings are the same. Use the two

end-cutters, flush to the edge of the circuit board.

transformer tabs to secure the transformer to the

PC board. Solder the transformer in place now.

The main Tele-Alert controller circuit also

contains five ICs. ICs are often static sensitive,

Go ahead and install the normally open RESET

so they must be handled with care. Use a grounded

switch at S1. This PC board push-button switch mounts anti-static wrist strap and stay seated in one location directly to the circuit board. Locate and install the when handling the ICs. Take out a cheap insurance

10-position header jack J1–J10 and install it at the

policy by installing IC sockets for each of the ICs.

bottom edge of the circuit board. Finally, mount the

In the event of a possible circuit failure, it is much three position header jack OT1–OT3 on pins 22, 23,

easier to simply unplug a defective IC than trying

and 24 of U1, these are the relay output jacks.

to unsolder 14 or 16 pins from a PC board without

Once the main Tele-Alert circuit board has been

damaging the board. ICs have to be installed correctly completed, take a short break and then we will inspect if the circuit is going to work properly. IC packages the PC board for possible “cold” solder joints and

will have some sort of markings which will help you

“short” circuits. Pick up the PC board with the foil side orient them on the PC board. An IC will have either

facing upwards toward you. Carefully inspect the solder a small indented circle, a cutout, or notch at the top joints, these should look smooth, clean, and bright.

end of the IC package. Pin 1 of the IC will be just

If any of the solder joints look dull, dark, or blobby, to the left of the notch, or cutout. Refer to the

then you should remove the solder with a solder sucker manufacturer’s pin-out diagram, as well as the

or a solder wick and then resolder the joint all over schematic, when installing these parts. If you

again. Now we will inspect the PC board for possible

335

short circuits. Short circuits can be caused from small Remember a digit 10 is programmed by a zero. If you

solder blobs bridging the circuit traces or from cut

want to dial a long distance number just add the full component leads which can often stick to the circuit

sequence of numbers. If you wish to dial out from a

board once they have been cut. A sticky residue from

PBX telephone system, you will need to first put in the solder will often trap component leads across the circuit access number such as an 8 or 9 followed by a comma

traces. Look carefully for any bridging wires across

then the actual phone number.

circuit traces.

Once the Tele-alert board is powered-up and the

The main Tele-Alert circuit is powered via the

programming cable attached, then you can go to the tool regulator at U5. Power to the regulator is from a 9 V

bar in the STAMP 2 editor program and run the

DC “wall wart” power supply. Notice that the 9 V

talert.bs2 program.

are brought out to pin 9 on the header to power the

Next, press ALT-R to load the program into the

add-on modules, if used. Five volts from the regulator Tele-Alert circuit. Your Tele-Alert is now programmed output are brought out on pin1 of the header, while the and ready to operate. At last, you can connect your

ground is on pin 2 of the header.

event or alarm inputs to the set of solder pads at the Operation of the Tele-Alert is simple. First, connect far edge of the circuit board, just below the phone

up a 9 V wall wart power supply to the circuit via the line connection. Remember, you must use normally

two power input pins at the top of the board. Next you open circuit switches for the alarm inputs unless

will need to make up a serial communication or

you are using the optional Switch/Sensor-module.

programming cable which connects the Tele-Alert

The Switch/Sensor provides both normally open

header J5 to the serial port of your programming

and normally closed inputs. Connect your phone

computer; see Figure 31-4. Now you will need to

line via the phone jack and your Tele-Alert is

“fire-up” your PC and load the supplied disk into

now ready to serve you.

your computer.

Now you are ready to simulate an alarm condition to

Make a directory called Tele-Alert and dump the see if your Tele-Alert functions. You can test the circuit contents of the disk into that directory. Download a

in one of two ways. A simulated approach is to connect copy of the BASIC STAMP Windows Editor, PBASIC

a crystal headphone across the secondary of T1 at J6, 2.5 or above from www.parallax.com and place it on

with the Tele-Alert disconnected from the phone line.

your PC. Bring up the Windows STAMP 2 editor

Apply power to the circuit, and connect a normally

program and type in or load the talert.bs2 program and open switch across input IN1. Activate the switch at

save it. Attach the programming cable from your PC or IN1 and you should begin hearing activity at the

laptop to the BS2 microcontroller and then connect up crystal headphone. First you should hear the touch-tone the power source to the Tele-Alert board. Scroll down sequences followed by the alarm tone sequence. If this the displayed program, and look for the simulated phone checks-out then you can move on to a “real” test by

number and replace it with your own phone number.

connecting the Tele-Alert to the phone line, and repeat the same test over again.

J5-1

The main Tele-Alert circuit board has two ten

J5-2

position female header jacks, i.e. J1 and J2, near the J5-3

input terminal solder pads. These two10 pin headers

allow you to add the optional enhancement modules,

J5-4

such as the Switch/Sensor Module, and the TVM

1

2

3

4

5

Modules which are described in chapter 30. The Motion Module and the Listen-in Module are described below.

6

7

8

9

The Tele-Alert board provides two headers, the

J1 and J2 headers. These headers are provided to plug DSR

RTS

in the various modules. Table 31-3 illustrates the header Chapter Thirty-One: Tele-Alert Project Figure 31-4 STAMP 2 Programming cable terminal pin-outs for the Tele-main Tele-Alert board.

336

Chapter Thirty-One: Tele-Alert Project

Table 31-3

Input/output terminal connections

Alarm Input Terminals and Header Block – J1

J1-1

J2-1

+5 volt DC input

J1-2

J2-2

Ground

J1-3

J2-3

N/C

J1-4

J2-4

IN1 input channel #1

J1-5

J2-5

IN2 input channel #2

Tele-alert input pins

J1-6

J2-6

IN3 input channel #3

J1-7

J2-7

IN4 input channel #4

J1-8

J2-8

Microphone enable

J1-9

J2-9

+9 volts DC output

J1-10

J2-10

Audio input mic

Auxiliary Inputs – Not implemented J3-1

IN5

Future Expansion

J3-2

IN6

J3-3

IN7

J3-4

IN8

Auxiliary Outputs

J4-1

OT1

Aux output channel #1

For external siren

J4-2

OT2

Aux output channel #2

For external lamp

J4-3

OT3

Aux output channel #3

Future use

Serial Communication

J5-1

RX

Pin 2

RS232

DB-9S

J5-2

TX

Pin 3

RS232

DB-9S

J5-3

ATN

Pin 4

RS232

DB-9S

J5-4

GND

Pin 5

RS232

DB-9S

J6-1

L1

Phone line connection

J6-2

L2

Phone line connection

The Tele-Alert system is very flexible and can be

multi-zoned alarm systems to simple multi-event

used in a number of different alarm configurations.

annunciators with a little imagination. The Tele-Alert The Tele-Alert could be used to monitor safes,

can also drive a siren or flashing outdoor lights to

doors, windows, floor mats, computers, movement,

create a local “noisy” alarm if desired. The diagram in temperature and voltage changes, as well as smoke and Figure 31-5 illustrates optional local alarm connections.

fire sensors. The Tele-Alert can even monitor existing Relay 1 can be used to drive small loads such as an

local alarms by using the Tele-Alert as a multi-channel electronic Sonalert, or with the addition of Relay 2 you dialer. With the Tele-Alert and the Motion Module you can drive larger loads, such as motor sirens or flashing can easily protect an entire vacation house or cabin, outdoor lamps. You can drive two external loads

using the existing phone line. You can even monitor an from OT-1 and OT-2. Output OT-3 is left for future

overheating computer or UPS failure. The Tele-Alert

expansion. The Tele-Alert can be used day or night

can be utilized in almost any alarm configuration from with your existing phone line; no additional phone lines 337

+9 V

Siren

Con 12

6–9 volt coil

Tele

Con 9

N/O

110 V AC

MIC

Con 8

IN4001

N/C

recall_delay

Con 120

N/C

Relay1

C

Con 2000

OT1–OT3

2N2222

N/O

D

Con 1000

AUX

300 Ω

E

Con 500

Relay2

110 V coil

G

Con 350

R

Con 0

Siren

init:

Figure 31-5

AUX-output relay driver

DIRL = %00000000

DIRH = %11111111

or phone bills are incurred. Now with the Tele-Alert

new_io_state = %00000000

you can be notified of an alarm condition when you are old_io_state = %00000000

shopping, boating, driving, golfing, traveling, or working outdoors. The Tele-Alert can dial multiple phone numbers for flash = 1 to 3

or repeatedly dial the same number, as desired. The

high LedPin

Tele-Alert can be used to call a friend, a neighbor,

pause 1500

a relative, or a co-worker in the event of an alarm

low LedPin

condition. If a second party is notified, the condition can pause 2500

be verified and then the police could be called, depending next

upon the severity of the alarm condition.

The Tele-Alert is very flexible and can be tailored to main:

many applications with a little imagination. Once you high LedPin

build the Tele-Alert you can experiment with different new_io_state = INL

sounds and sound patterns which are sent to the remote pause 100

phone. The Tele-Alert is always there to serve you, to low LedPin

free you, and to give you piece of mind! Why not build pause 100

one for yourself!

if new_io_state < > %00000000 then

dial_cell

after_io1:

Tele-Alert program

old_io_state = new_io_state

goto main

‘Tele-Alert Program

‘identify variables

delay_and_scan

flash

Var byte

old_io_state = new_io_state

new_io_state

Var byte

for timer = 1 to recall_delay

old_io_state

Var byte

high LEDPin

call_state

Var byte

new_io_state = INL

io

Var byte

pause 500

timer

Var byte

low LedPin

i

Var byte

pause 500

f

Var word

if new_io_state < > old_io_state

then dial_cell

TXpin

Con 10

old_io_state = new_io_state

LedPin

Con 15

next

Chapter Thirty-One: Tele-Alert Project

Lamp

Con 13

goto after_io1

338

Chapter Thirty-One: Tele-Alert Project

dial_cell:

low Tele

if new_io_state = %00000000 then main

low LedPin

high LedPin

low Siren

high Tele

low Lamp

high Lamp

low MIC

high Siren

pause 100

pause 500

return

dtmfout TXPin, 600, 600, [8]

end

dtmfout TXPin, 500, 100, [7,9,9,4,

9,9,0]

gosub_chan_3:

sleep 10

for i= 0 to 25

gosub send_msg

lookup i,[G,E,D,C,G,E,D,C,G,E,D,

C,G,E,D,C,G,E,D,C,G,E,D,C,G],f

goto delay_and_scan

freqout 11,350,f,(f-1) max 32768

send_msg:

next

io = new_io_state

‘high MIC

‘pause 10000

if io.bit0 = 1 then gosub_chan_1

low Tele

if io.bit1 = 1 then gosub_chan_2

low LedPin

if io.bit2 = 1 then gosub_chan_3

low Siren

if io.bit3 = 1 then gosub_chan_4

low Lamp

pause 100

low MIC

gosub_chan_1:

pause 100

for i = 1 to 15

return

lookup i,[E,D,E,D,E,D,E,D,E,D,E,D,

end

E,D,E],f

gosub_chan_4:

freqout 11,750,f,(f−1) max 32768

next

for i = 0 to 30

high MIC

lookup i,[C,D,E,G,C,D,E,G,C,D,E,G,C,D,E,

pause 10000

G,C,D,E,G,C,D,E,C,D,E,G,C,D,E],f

low Tele

freqout 11,200,f,(f-1) max 32768

low LEdPin

next

low Siren

‘high MIC

low LAMP

‘pause 10000

low MIC

low Tele

pause 100

low LEDPin

return

low Siren

end

low Lamp

low MIC

gosub_chan_2:

pause 100

for i = 1 to 20

return

lookup i,[E,D,C,E,D,C,E,D,C,E,D,C,E,

end

D,C,E,D,C,E,D],f

freqout 11,500,f,(f−1) max 32768

Motion module

next

‘high MIC

The Pyro-electric Motion Module is a great addition

‘pause 10000

to the Tele-Alert or Page-Alert microprocessor

339

voltage regulator. Table 31-4 lists the pinouts of the 20

pin PIR controller chip.

The Motion Module circuit is illustrated in the

system diagram in Figure 31-8. The circuit begins

with the sensitive PIR detector. The pyro-electric

infra-red sensor or PIR is a sensitive three-lead

high impedance sensor, which is shown with

a 47 K ohm output resistor at R1. A “sensitivity”

or “range” control for the PIR sensors is shown at R2.

The PIR sensor is coupled to a specially designed

Figure 31-6

Tele-Alert infra-red sensor board

PIR controller chip which is optimized for PIR

alarm sensors.

alarm controller. The Pyro-electric Motion Module

The PIR sensor requires a Fresnel beam focusing

centers around a pyro-electric or “body heat”

lens. The Fresnel lens is placed ahead of the PIR sensor infra-red sensor and the controller chip, and is

to give the sensor a specific pattern of coverage. PIR

shown in Figure 31-6.

Fresnel lenses come in two basic types. The most

The PIR controller chip block diagram is depicted

common beam pattern is the wide angle lens which

in Figure 31-7. The PIR controller is a complex

looks out to about twelve feet with a 30–50 degree

chip, which provides amplification, filtering,

pattern; the second Fresnel lens is a narrow angle

clock, comparators, a daylight detector, and a

type which looks out to about fifty feet with

VCC

KC 788B

U2

Sensitivity adj

Offset filter

PYRO (D)

PIR front-end

Switched

PYRO (S)

amplifiers

capacitor

Gain select

and noise

bandpass

cancellation

Anti alias

filter

circuits

DC cap

LED

Threshold

Free

Oscillator &

comparators

R

synchronization

and timing

circuitry

circuitry

C

Out

Daylight sense

Daylight detector

Voltage

VREG

amplifiers

regulator

Daylight adjust

comparator

GND

Chapter Thirty-One: Tele-Alert Project Figure 31-7 PIR controller chip 340

Chapter Thirty-One: Tele-Alert Project

Table 31-4

Resistors R3 and R4 are utilized as a frequency

KC778B PIR controller pinouts

reference between pin #20 and Vcc. The PIR sensor is

placed across pins #2, #7, and #8 of the controller chip.

Pin

Name

Description

The actual alarm output pin of the controller is located 1

Vcc

at pin #16, which is coupled to the output driver

+5 volt supply

transistor at Q1. The R/C time constant for the output 2

sensitivity adj

PIR sensitivity input

“on time” of the controller is between pins #18 and #19, 3

offset filter

PIR offset filter

and is controlled by R5, R6, and C8. A “movement”

4

anti alias

PIR anti alias filter

indicator LED is located between pin #17 and pins #9

5

DC capacitor

PIR gain stabilization filter

and #10, the analog and digital ground pins. The chip 6

V reg

voltage regulator output

employs a daylight detector which is not implemented

7

pyro (D)

pyro drain reference

in our application. Power to the controller chip is

8

pyro (S)

pyro source input

brought to pin 1 of U1 via a 78l05 regulator. The input 9

ground (A)

analog ground

to the regulator is a 9 V DC power supply which is

10

ground (D)

digital ground

used to power the Tele-Alert controller.

11

daylight adj

daylight adj and and CDS

12

daylight sense

silicon photo dioed input

13

gain select

PIR gain select

Circuit assembly

14

on/auto/off

mode selecttri-state input

Before we begin constructing the PIR Motion Module

15

toggle

mode select toggle input

board, you will need to locate a clean, well-lit worktable 16

out

output

or workbench. Next we will gather a small 25–30-W

17

LED

indicator LED

pencil tipped soldering iron, a length of 60/40 tin–lead 18

C

off timer OSC

solder, and a small canister of Tip Tinner, available at 19

R

off timer OSC

your local RadioShack store; Tip Tinner is used to

20

Fref

frequency reference OSC

condition the soldering tip between solder joints. You drive the soldering tip into the compound and it cleans a narrow beam pattern. The PIR Motion Module kit

and prepares the soldering tip. Next grab a few small comes with both types of Fresnel lens.

hand tools; try to locate small flat blade and Phillips Capacitors C5, C6, and C7 are offset filters,

screwdrivers. A pair of needle-nose pliers, a pair of anti-aliasing filters and a DC capacitor respectively.

tweezers along with a magnifying glass, and a pair of C7

R3

R4

+5 V

+5 V

P1-1

+5 V

1

20

U1

R5

R6

19

C6

C5

+

3

18

+5 V

C4

C8

4

16

5

Q1

+

Output

C3

7

17

2

+5 V

R7

PIR

C1

R2

P1-10

8

12

D1

sensor

9

G

D

10

S

R1

C2

Figure 31-8

PIR infra-red motion module

341

end-cutters and we will begin constructing the project.

in their respective locations on the main controller

Now locate your schematic diagram and parts layout

PC board. Solder the resistors to the PC board, and

diagram along with all of the components needed to

remember to cut the extra component leads with your

build the project.

end-cutters.

Once all the components are in front of you,

Note that capacitors generally come from two major

you can check them off against the project parts list to groups or types. Non-polar types, such as the ones in make sure you are ready to start building the project.

this project, have no polarity and can be placed in either Now, locate Tables 31-1 and 31-2, and place them in

direction on the circuit board. The other type of

front of you.

capacitors are called polarized types, these capacitors have polarity and have to be inserted on the board with Table 31-1 illustrates the resistor code chart and

respect to their polarity marking in order for the circuit how to read resistors, while Table 31-2 illustrates the to operate correctly. On these types of capacitors,

capacitor code chart which will aid you in constructing you will observe that the components actually have

the project. Refer now to the resistor color code

a plus or minus marking or a black or white band with chart shown in Table 31-1, which will assist you in

a plus or minus marking on the body of the capacitors.

identifying the resistor values used in the project.

Capacitors must be installed properly with respect to Note that each resistor will have either three or four polarity in order for the circuit to work properly. Failure color bands, which begin at one end of the resistor’s to install electrolytic capacitors correctly could cause body. The first colored band represents the resistor’s damage to the capacitors as well as to other components first digit, while the second color represents the second in the circuit when power is first applied.

digit of the resistor’s value. The third colored band Many capacitors are quite small in physical size,

represents the resistor’s multiplier value, and the fourth therefore manufacturers have devised a three-digit

color band represents the resistor’s tolerance value.

code which can be placed on the capacitor instead

If there is no fourth colored band then the resistor has of the actual value. The code occupies a much

a 20% tolerance value. If the resistor’s fourth band is smaller space on the capacitor and can usually

silver then the resistor has a 10% tolerance value and fit nicely on the capacitor body, but without the

if the fourth band is gold then the resistor’s tolerance chart the builder would have a difficult time

value will be 5%.

determining the capacitor’s value.

Finally, we are ready to begin assembling the project, Now look for the capacitors from the component

so let’s get started. The Motion Module is fabricated on stack and locate capacitors C1, C4, and C7. These

a single sided 13⁄4 by 21⁄2 inches circuit board. With your are all small capacitors labeled (104). Refer to the

PC board in front of you, we can now begin populating Table 31-2 to find code (104) and you will see that it the circuit board. We are going to place and solder the represents a capacitor value of 100 nF. Go ahead and

lowest height components first, the resistors and diodes.

place these capacitors on the circuit board and solder First, locate our first resistor R1. Resistor R1 has a them in place. Now take your end-cutters and cut the

value of 47,000 ohms and is a 5% tolerance type.

excess component leads flush to the edge of the circuit Now take a look for a resistor whose first color band is board. Once you have installed these components, you

yellow, violet, orange, and gold. From the chart you

can move on to installing the remaining low profile

will notice that yellow is represented by the digit (4), the capacitors. Save the larger electrolytic capacitors for second color band is violet, which is represented by (7).

mounting last. The electrolytic capacitors will have

Notice that the third color is orange and the multiplier is a plus or minus sign or a black or white color band.

(1,000), so (4) (7) × 1,000 = 47,000 or 47 K ohms.

Be sure to orient the electrolytic capacitors correctly Go ahead and locate where resistor R1 goes on the

when placing them on the PC board. Locate capacitors

PC and install it, next solder it in place on the PC board, C3 and C5, which are low leakage 10 μF electrolytic

and then with a pair of end-cutters trim the excess

capacitors; go ahead and install on the PC board and

component leads flush to the edge of the circuit board.

solder them in place. Do not forget to trim the excess Chapter Thirty-One: Tele-Alert Project Next locate the remaining resistors and install them leads with your end-cutters.

342

Chapter Thirty-One: Tele-Alert Project

The PIR Motion Module utilizes a single

the LED protrude through the enclosure box. Solder the conventional transistor. Transistors are generally three LED to the PC board and then trim the excess leads.

lead devices, which must be installed correctly if the The Motion Module uses two printed circuit

circuit is to work properly. Careful handling and proper potentiometers, a 200 K ohm at R2 and a 1 megohm

orientation in the circuit is critical. A transistor will potentiometer at R6. Mount the two potentiometers on

usually have a Base lead, a Collector lead, and an

the PC board and solder them in place, trimming leads Emitter lead. The base lead is generally a vertical line as necessary.

inside a transistor circle symbol. The collector lead is Finally, locate and carefully pickup the PIR motion

usually a slanted line facing towards the base lead and sensor using your grounded anti-static wrist band and the emitter lead is also a slanted line facing the base install it on the PC board. Note that the Gate lead

lead but it will have an arrow pointing towards or away connects to ground, while the Source lead connects to from the base lead. Now, identify the two transistors, the junction of R1/C2 and the Drain lead is connected to referring to the manufacturer’s specification sheets as capacitor C1. The components, especially the controller well as the schematic and parts layout diagrams when

chip and PIR sensor, can be damaged if they are placed installing the two transistors. If you have trouble

incorrectly. Note that the PIR sensor is placed on the installing the transistors, get the help of an electronics foil side of the circuit board.

enthusiast with some experience. Install the transistors At one edge of the PC board, you will find the 10 pin in their respective locations and then solder them in solder tabs which are used to secure the 10 pin male

place. Remember to trim the excess component leads

header pins that couple the Motion Module to the

with your end-cutters.

Tele-Alert. The top pin #1 is reserved for the 9 volt The Motion Module circuit contains a special purpose

power input power pin. Pin #2 is used as the system

IC. ICs are often static sensitive, so they must be handled ground, while pin #3 is the output pin from the Motion with care. Use a grounded anti-static wrist strap and Module to the Tele-Alert main board. The rest of the

stay seated in one location when handling the ICs. Take header pins are not used. The 10 pin header is placed out a cheap insurance policy by installing IC sockets for on the component side of the PC board and soldered

each of the ICs. In the event of a possible circuit failure, on the foil side of the Motion Module PC board.

it is much easier to simply unplug a defective IC, than Once the Motion Module circuit board has been

trying to unsolder 14 or 16 pins from a PC board without completed, take a short break and then we will inspect damaging the board. ICs have to be installed correctly if the PC board for possible “cold” solder joints and

the circuit is going to work properly. IC packages will

“short” circuits. Pick up the PC board with the foil side have some sort of markings which will help you orient facing upwards toward you. Carefully inspect the solder them on the PC board. An IC will have either a small

joints, these should look smooth, clean, and bright. If indented circle, a cutout, or notch at the top end of the any of the solder joints look dull, dark, or blobby, then IC package. Pin 1 of the IC will be just to the left of the you should remove the solder with a solder sucker or

notch, or cutout. Refer to the manufacturer’s pin-out a solder wick and then resolder the joint all over again.

diagram, as well as the schematic, when installing these Now we will inspect the PC board for possible short

parts. If you doubt your ability to correctly orient the ICs, circuits. Short circuits can be caused from small solder then seek the help of a knowledgeable electronics

blobs bridging the circuit traces or from cut component enthusiast to help you.

leads which can often stick to the circuit board once they The Motion Module circuit utilizes a single LED at

have been cut. A sticky residue from solder will often D1, which also must be oriented correctly to function trap component leads across the circuit traces. Look

properly. An LED has two leads, a cathode and an anode carefully for any bridging wires across circuit traces.

lead. The anode lead will usually be the longer of the two leads and the cathode lead will usually be the shorter Circuit testing

lead just under the flat side edge of the LED, this should help orient the LED on the PC board. You may want to

Once the Motion Module has been completed, you can

leave about 1⁄2 lead length on the LED, in order to have easily test the board, by applying a 9 volt transistor 343

battery to pins #1 and #2 of the header. Connect a

voltmeter or oscilloscope to the output pin #4 and the ground pin #2 and you are ready to test the Motion

Module board. Once power is applied, wait about five

seconds, then wave your hand in front of the PIR

sensor. The Fresnel lens does not have to be in front of the PIR for this test. The indicator LED should

light once your hand is waved in front of the PIR

sensor. At this point in time, you should also see the Figure 31-9

Tele-Alert listen-in board

output pin #3 jump from zero volts to 5 volts on

your meter or scope. You may have to adjust the PIR

sensitivity control at R2 or the “time on” control at The sensitive electret microphone is first biased via R1, R6 for optimum, once the Fresnel lens is in place and which is enabled via the microprocessor. The sound

the enclosure is shut and you become familiar with

output from the electret microphone is coupled through the detector’s operation. This completes the testing of C1 and R2 to the dual op-amp at U1(A) which acts as

your new Motion Module.

an audio pre-amplifier. The LM358 op-amp at U1 is a

Next, you will need to connect the Motion Module to

single supply device eliminating the need for the usual the Tele-Alert controller. The Motion Module should be two power supplies used with most op-amps. The gain

plugged into the 10 pin female header on the main

of U1 is essentially controlled by resistors R3 and R6.

Tele-Alert board labeled J1. On the Tele-Alert board, The output of the first pre-amp stage is next coupled to the first header next to the screw terminals is the 10 pin the second amplifier stage at U1(B) via C2 and R5.

header which is used for the Listen-in board, while the The output of the second audio amplifier stage at

second header (J2) is a 10 pin one which is used for the U1(B) is coupled directly to the telephone coupling

TVM or Motion Module board. Once the two boards

transformer T1 via C3. The listen-in board kit is

are fastened together, you will need to place a hole in powered by the 9 volt system power source through

the Tele-Alert enclosure to allow the PIR to “see” the the main Tele-Alert board.

room. You will at this point have to place the Fresnel lens ahead of the PIR sensor before securing the top

Circuit assembly

of the Tele-Alert enclosure.

Your Tele-Alert is now a complete motion detector

Before we begin constructing the Listen-in module,

alarm controller/dialer which can be used to protect a you will need to locate a clean, well-lit worktable or house, cottage, or work-shop area. If you are clever in workbench. Next we will gather a small 25–30-W pencil the placement of the PIR sensor, you can easily protect tipped soldering iron, a length of 60/40 tin–lead solder, large areas using a single PIR Motion sensor.

and a small canister of Tip Tinner, available at your local RadioShack store; Tip Tinner is used to condition the soldering tip between solder joints. You drive the Listen-in module

soldering tip into the compound and it cleans and

prepares the soldering tip. Next grab a few small hand The Tele-Alert Listen-in Module allows you to listen-in tools; try to locate small flat blade and Phillips

to the room or area being monitored by the Tele-Alert screwdrivers. A pair of needle-nose pliers, a pair of alarm controller. With the Listen-in board you can

tweezers along with a magnifying glass, and a pair of listen-in for up to two minutes after you have been

end-cutters and we will begin constructing the project.

called by the Tele-Alert unit. The Listen-in board is Now locate your schematic diagram and parts layout

shown in Figure 31-9.

diagram along with all of the components needed to

The Listen-in board begins at the sensitive electret

build the project.

microphone at MIC, shown in the schematic diagram at

Once all the components are in front of you, you can

Chapter Thirty-One: Tele-Alert Project Figure 31-10.

check them off against the project parts list to make sure 344

Chapter Thirty-One: Tele-Alert Project

Enable

+9 V

R1

R3

P1-1

R6

M1

R2

+

2 _

C2

1

6 _ 8

U1:A

C3

C1

3

7

+

R5

U1:B

+

5

Audio out

+

4

Enable

R4

+9 V

+9 V

+

J1-10

R7

Figure 31-10

Listen-in module

you are ready to start building the project. Now, locate components first, the resistors and diodes. First, locate Tables 31-1 and 31-2, and place them in front of you.

our first resistor R1. Resistor R1 has a value of 2,200

Table 31-1 illustrates the resistor code chart and

ohms and is a 5% tolerance type. Now take a look for a how to read resistors, while Table 31-2 illustrates the resistor whose first color band is red, red, red, and gold.

capacitor code chart which will aid you in constructing From the chart you will notice that blue is represented the project.

by the digit (2), the second color band is black, which is represented by (2). Notice that the third color is red and Refer now to the resistor color code chart shown in

the multiplier is (100), so (2) (2) × 100 = 2,200 or

Table 31-1, which will help you identify the resistor 2.2 K ohms.

values for the project. Each resistor will have either three or four color bands, which begin at one end of the Go ahead and locate where resistor R1 goes on the

resistor’s body. The first colored band represents the PC and install it, next solder it in place on the PC board, resistor’s first digit, while the second color represents and then with a pair of end-cutters trim the excess

the second digit of the resistor’s value. The third colored component leads flush to the edge of the circuit board.

band represents the resistor’s multiplier value, and the Next locate the remaining resistors and install them in fourth color band represents the resistor’s tolerance their respective locations on the main controller

value. If there is no fourth colored band then the resistor PC board. Solder the resistors to the board, and

has a 20% tolerance value. If the resistor’s fourth band remember to cut the extra lead with your end-cutters.

is silver then the resistor has a 10% tolerance value and Note that capacitors generally come from two major

if the fourth band is gold then the resistor’s tolerance groups or types. Non-polar types, such as the ones in value will be 5%.

this project, have no polarity and can be placed in either So finally we are ready to begin assembling

direction on the circuit board. The other type of

the project. The Listen-in board kit measures

capacitors are called polarized types, these capacitors 2 by 11⁄4 inches, and was designed to plug-in easily to have polarity and have to be inserted on the board with the main Tele-Alert board. The Listen-in board is simple respect to their polarity marking in order for the circuit to construct, and can be completed in about a half hour to operate correctly. On these types of capacitors, you or so. So let’s get started. With your PC board in front will observe that the components actually have a plus or of you, we can now begin populating the circuit board.

minus marking or a black or white band with a plus or We are going to place and solder the lowest height

minus marking on the body of the capacitors.

345

Capacitors must be installed properly with respect to Next we will install the electret microphone. The

polarity in order for the circuit to work properly. Failure electret microphone has two leads which first must be to install electrolytic capacitors correctly could cause identified before placing it on the circuit board. One damage to the capacitors as well as to other components lead is fastened to the case or body of the microphone in the circuit when power is first applied.

and this is the ground lead. The other microphone lead Many capacitors are quite small in physical size, so

is the “hot” or active lead that is powered by the enable manufacturers have devised a three-digit code which

pin through resistor R1 which is connected to the

can be placed on the capacitor instead of the actual

header pins at the edge of the PC board.

value. The code occupies a much smaller space on the

The Listen-in module contains a single in-line row of capacitor and can usually fit nicely on the capacitor 10 male header pins at one edge of the circuit board

body, but without the chart the builder would have a

which allows the board to connect to the main Tele-Alert difficult time determining the capacitor’s value.

board. The first of the ten header pins at P1-1 is the Now look for the capacitors from the component

5-V supply, followed by the system ground connection

stack and locate capacitor C2, which is a small

at pin P1-2. Many of the solder pads are not used except capacitor labeled (104). Refer to Table 31-2 to find

for the power pins, the audio output pin at P1-10, and code (104) and you will see that it represents a capacitor audio enable connection at pin P1-8. The ten pin male value of .1 μF. Go ahead and place C2 on the circuit

header is inserted and soldered on the foil side of the board and solder it in place. Now take your end-cutters circuit board, once the board has been completed. Both and cut the excess component leads flush to the edge

circuit boards should have the components facing

of the circuit board. Now you can move on to installing upwards when connected together and finished.

the remaining capacitors. Next, we will install the

Once the main Listen-in module board has been

remaining capacitors, which are all electrolytic types.

completed, take a short break and then we will

Remember electrolytic capacitors have polarity and

inspect the PC board for possible “cold” solder joints must be installed correctly if the circuit is to function and “short” circuits. Pick up the PC board with the foil properly. Go ahead and install these capacitors paying side facing upwards toward you. Carefully inspect the close attention to the polarity markings. Remember to solder joints, these should look smooth, clean, and

trim the excess component leads from the PC with

bright. If any of the solder joints look dull, dark, or your end-cutters.

blobby, then you should remove the solder with a

solder sucker or a solder wick and then resolder the

The Listen-in module circuit contains a single dual

joint all over again. Now we will inspect the PC board stage IC. ICs are often static sensitive, so they must be for possible short circuits. Short circuits can be caused handled with care. Use a grounded anti-static wrist strap from small solder blobs bridging the circuit traces or and stay seated in one location when handling the ICs.

from cut component leads which can often stick to the Take out a cheap insurance policy by installing an IC

circuit board once they have been cut. A sticky residue socket for the IC. In the event of a possible circuit from solder will often trap component leads across

failure, it is much easier to simply unplug a defective the circuit traces. Look carefully for any bridging

IC than trying to unsolder 14 or 16 pins from a PC

wires across circuit traces.

board without damaging the board. ICs have to be

Once completed the Listen-in board can be tested

installed correctly if the circuit is going to work

by applying a 9-V source to the two power pins,

properly. IC packages will have some sort of markings system ground at P1-2, and 9 volts at P1-9 (see pinouts which will help you orient them on the PC board. An

in Table 31-5).

IC will have either a small indented circle, a cutout, or notch at the top end of the IC package. Pin 1 of the IC

You can then connect a headphone to the output pin

will be just to the left of the notch, or cutout. Refer to P1-10 and ground; you must also apply 5 V to the

the manufacturer’s pin-out diagram, as well as the

enable pin at P1-8, in order to activate the electret schematic when installing these parts. If you doubt your microphone. You should now be able to hear room

ability to correctly orient the ICs, then seek the help of sounds in the headphone, and the Listen-in board is

Chapter Thirty-One: Tele-Alert Project a knowledgeable electronics enthusiast to help you.

complete and ready to use.

346

Chapter Thirty-One: Tele-Alert Project

Table 31-5

connections at the outside edge of the board, followed Listen-in module pinouts

by two rows of header sockets. The first row of female 10 pin header sockets at the outside edge are used to Pin

Name

Description

hold the Listen-in board while the second set of inside 1

N/C

system ground

header pins are used to power the TVM board and the

Motion module board. The TVM or Motion module

2

Gnd

microphone enable

“daughter” boards can be utilized at the same time as 3

N/C

audio ouput pin from module

the Listen in board if desired. Grasp the Tele-Alert

4

N/C

9 volt system power for module

board in one hand and now plug the Listen-in module to 5

N/C

the first or outside 10 pin female header.

6

N/C

Now you are now ready to utilize the Listen-in board

7

N/C

with your main Tele-Alert system board. Connect a 9 V

8

enable

“wall wart” power supply, phone line, and alarm switch 9

Audio

or sensor contacts to the Tele-Alert main board and

10

+9 V

you are ready to go! The Listen-in board can be used

in conjunction with the Motion module to detect

You are now ready to attach the Listen-in board to the movement, then let you listen-in to room sounds once

main Tele-Alert board. Take a look at the Tele-Alert

motion is detected, so your Tele-Alert can be used as a board; at one edge you will notice the input terminal complete self contained alarm.

347

Chapter 32

Remote Temperature Monitor

U4

LM2940 regulator

Parts list

(National)

S1

momentary pushbutton

Remote Temperature

(Reset)

Monitor

J1

RJ¯11 telephone jack

R1, R6, R8

330 ohm,

1

⁄ W, 5% resistor

J2

DB¯9F - RS¯232

4

female - serial port

R2, R3, R4

10 K ohm,

connector

1

⁄ W, 5% resistor

4

Misc

PC board, wire,

R5, R7, R9

10 K ohm,

IC sockets, hardware,

1

⁄ W, 5% resistor

4

enclosure, etc.

R10, R11

100 ohm, 1⁄ W,

4

The Remote Temperature Monitor is a useful and fun

5% resistor

microprocessor controlled remote reading temperature

R12

1 K ohm, 1⁄ W,

4

project. You can remotely read the high, low, and current 5% resistor

temperature of your home, your office, or your cabin

R14, R15

330 ohm, 1⁄ W,

in the woods. You connect the Remote Temperature

4

5% resistor

Monitor circuit to a standard telephone line in you

remote location and then simply use your computer to

C1, C2

47 μF, 35 V

call and remotely read the temperature using the Remote electrolytic capacitor

Temperature Monitor’s modem (see Figure 32-1).

C3, C4

0.1 μF, 35 V

ceramic capacitor

Q1, Q2

2N3906 PNP

transistor

M1

250 volt, metal

oxide varistor (MOV)

D1, D2, D3, D5

Red LEDs

D4

Yellow LED

U1

BASIC STAMP 2 -

microcontroller

(Parallax, Inc)

U2

CH1786 MODEM -

(Parallax, Inc)

U3

DS1620 - Temperature

Sensor (Dallas

Figure 32-1

Remote temperature monitor. Courtesy of

Semiconductor)

Parallax, Inc

348

Copyright © 2009 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Chapter Thirty-Two: Remote Temperature Monitor

The Remote Temperature Monitor centers around the

for sensing and control. The STAMP 2 is easily

BASIC STAMP 2 microprocessor which is illustrated in

programmed in a small modified form of BASIC

the block diagram shown in Figure 32-2.

called PBASIC, and was originated by Parallax, Inc.

The STAMP 2 is a powerful microprocessor with

The Remote Temperature Monitor schematic is

15 general purpose input/output pins which can be used shown in Figure 32-3.

PND

4.7 K

Dull NPN

4.2 V Brow-out

transistor pack

resistor pack

transistor pack

regulator

SOUT

1

24 VIN +9–12 V

SIN

2

23 VSS

G

V

OUT

ATN

3

22 RES

IN

WC

GND

GND

VSS

4

WP

VDD

SCL

SD4

21 VDD +5 V

OR

EEPR

OUT

GND

GND

NC

Lm2636-5 V

NC

NC

NC

VSS

24LC16B/Sw

P0

5

20 P15

P1

6

19 P14

+

15 μF

20 MHZ RES

P2

7

18 P13

10 K

P3

8

17 P12

1

28

VSS

RES

2

27

VSS

X1

P4

9

3

26

VDD

16 P11

X0

4

25

VDD

P15

5

24

SDF

P14

6

23

SCL

P13

7

22

P5

10

RX

P12

15 P10

8

21

TX

P11

9

20

P0

P10

10

19

P1

P9

11

18

P2

P6

11

P6

12

P Basic 2/52

P1C16 C 57C – 20/55

17

14 P9

P3

P7

13

16

P4

P6

14

15

VSS

P5

P7

12

13 P8

Figure 32-2

BASIC STAMP 2 – (Original). Courtesy of Parallax Inc 349

Programming

cable

DB-9F

7 6 5 4 3 2

+

+7–15 V DC

J2

5 V

Out

In

U4

+

+

R1

C3

C2

C1

J1 { 4 Pin header

D1

P1

Stamp2

1

24

TX

VCC

2

23

RX

U1

GND

Reset

3

22

S1

ATX

RST

+5 V

4

21

GND

+5

5

20

PD

P15

6 P1

P14 19

7

R2

18

+5 V

P2

P13

8 P3

P12 17

+5 V

9

16

CH1786

+5 V

P4

P11

10 P5

P10 15

Modem

R4

R3

11

14

+5 V

P6

P9

12

1

P7

P8 13

R5

2

U2

17

Q1

U3

3

15

8

1

4

12

.1 μF

VDD DQ 2

CLK

R12

R6

C4

3

RST

20

4

GND

R9

DS1620

+5 V

D2

temp

M1

R7

sensor

Q2

R11

Phone

R8

jack

R10

D3

J3

Figure 32-3

Remote temperature monitor

The Remote Temperature Monitor consists of four

pin on the modem is tied to ground via a 10 K ohm

major building blocks which center around the BASIC

resistor. The modem is connected to the BS2

STAMP 2 microprocessor, a CH1786 modem, a digital

microprocessor through four pins. The TX and RX pins

DS1620 temperature sensor, a power supply, and a

are the communication lines which allow the modem

few transistors and status LEDs. The heart of the

and STAMP to serially talk to each other. The DCD and circuit revolves around the BASIC STAMP 2 (BS2)

RI lines on pins 17 and 15 of the modem connect to

microprocessor which animates the temperature sensor, P13 and P12 of the BS2 microprocessor.

the modem, and the status lamps. The incoming phone

The Dallas Semiconductor DS1620 digital

line is connected via the RJ11 telephone jack. The two temperature sensor is a small 8-pin DIP style package, telephone line wires are connected to the circuit via two which communicates with the microprocessor through

100-ohm resistors across the phone line. A 250 volt

three pins (see the block diagram in Figure 32-4).

metal oxide varistor (MOV) is used to protect the

modem from ringing voltage and voltage spikes. The

The chart in Table 32-1 describes the pin-out

ring and tip phone wires enter the mini-modem at pins functions of the chip. The DS1620 is a digital

1 and 2 as shown. The data carrier detect (DCD) output thermometer and thermostat which provides a 9–bit

pin on the modem goes low after the modem, goes

temperature reading which is used indicate the

“off-hook”, or answers the call. The output of this pin ambient room temperature in our project. The DQ

drives a transistor at Q1 which lights LED D2. The

or input/output lead conveys the temperature

ring indicator (RI) pin on the modem is used to drive signal data to BS2 through a 1 K ohm resistor.

transistor Q2 which in turn lights the LED at D3 when The clock pin (CLK) is used by the microprocessor

Chapter Thirty-Two: Remote Temperature Monitor the phone is ringing. The data terminal ready (DTR) to clock the temperature chip in order to send the

350

Chapter Thirty–Two: Remote Temperature Monitor

4

GND

Status register &

control logic

8

VDD

2

CLK

Temperature sensor

Address

&

1

DQ

Reset

High temp trigger (TH)

3

RST

THIGH

Low temp trigger (TL)

7

TLow

6

Digital

comparator logic

TCom

5

Figure 32-4

DS1620 Digital temperature sensor. Courtesy of Dallas Semiconductor data readings to the microprocessor. The Reset pin

The mini-modem is a Cermetek CH1786 full function

(RST)on the temperature sensor is controlled by

2,400 bps modem. The modem measures a slight

the microprocessor. The data line or DQ line on

1.01 × 1.27 × 0.52′′and occupies a small footprint

pin 1 of the DS1620 is coupled to pin 8 of BS2, while on the PC board; see Figure 32-5.

the CLK line at pin 2 is fed to the P7 I/O data line

The block diagram of the mini-modem is shown

on the microprocessor. The RST line from the

in Figure 32-6. The CH1786 only requires two

temperature sensor on pin 3 is sent to the P6 I/O line external interfaces, a serial interface that can be

on the BS2 processor. A .1 μF capacitor is tied across routed directly to a microprocessor, and a tip and

the power or Vdd pin to ground.

The second major building block of the

Remote Temperature Monitor is the mini-modem.

Table 32-1

DS 1620 Digital temperature sensor pinouts

Pin

Symbol

Description

1

DQ

Input/output pin for 3-wire communication

2

CLK/Conv

Clock input pin for 3-wire communication

3

RST

Reset input pin for 3-wire communication

4

GND

Ground pin

5

TCOM

High/low combination trigger – goes high

with temp exceeds TH

6

TLOW

Low temp trigger – goes high when temp

falls below TL

7

THIGH

High temp trigger – goes high when temp

exceeds TH

Figure 32-5

Modem board layout. Courtesy of

8

Vdd

+5 volt power supply pin

Parallax, Inc

351

CH1786 Modem

Modem

NV/RAM

controller

Serial

interface

Telephone

Modulation

Tip

line

Telephone

demodulation

interface

line

Ring

Speaker

interface

+5 V

GND

Figure 32-6

CH1786 Modem block diagram. Courtesy of Parallax, Inc ring telephone line interface which goes directly to

supports asynchronous operation at 2,400 bps,

an RJ-11 jack for the PSTN line connection.

1,200 bps, and 300 bps The CH1786 modem

The CH1786 modem can be controlled with

operates from a 5-V supply. A pinout chart for

industry standard AT commands. The CH1786 modem

the mini-modem is shown in Table 32-2.

Table 32-2

CERMETEK CH1786 mini-modem pinouts

Pin

Name

TypeE

Function

1

RING

I/O

RING – connects to telephone line through RJ11 jack

2

TIP

I/O

TIP – connects to telephone line through RJ11 jack

3

RXA

O

analog voice injected – receive signal – let float if not used 4

TXA

I

analog voice injected – transmit signal – let float if not used 5

SPK

O

audio output for speaker if used

6

NC

—

no connection

7

NC

—

no connection

8

SLEEP

O

a low – indicates idle mode, used to control other devices 9

NC

—

no connection

10

TXD

I

serial transmit data input, marking or binary 1-is xmited when high 11

RXD

O

serial receive data output – rcvd marking or binary 1-indicated by high 12

V/D

O

voice data-used to switch between phone and modem use 13

DTR

I

data terminal ready – active low

14

DSR

O

data set ready – Low indicates handshaking with remote modem 15

RI

O

ring indication – follow frequency of ringing

16

CTS

O

clear to send – no connect if not using FAX option

17

DCD

O

data carrier detect – low indicates data carrier from a remote modem 18

HS

O

speed indication – low indicates 2,400 bps

19

VCC

—

power supply pin 5 V

20

GND

—

ground connection

21

RST

I

reset – active high – must be high for 10 ms to reset Chapter Thirty-Two: Remote Temperature Monitor 22

NC

—

no connection

352

Chapter Thirty-Two: Remote Temperature Monitor

Basic stamp 2

a pair of tweezers along with a magnifying glass, and a 1

SOUT

pair of end-cutters and we will begin constructing the Serial port

2

SIN

3

project. Now locate your schematic diagram and parts

ATN

DSR

1

6

2

4

GND

layout diagram along with all of the components needed RTS

7

3

.1

8

μF

to build the project.

4

.1

9

μF

5

Once all the components are in front of you,

DB-9

you can check them off against the project parts list to make sure you are ready to start building the project.

Now, locate Tables 32-4 and 32-5, and place them in

Figure 32-7

Computer to STAMP programming cable

front of you.

Table 32-4 illustrates the resistor code chart and

The STAMP can be programmed via pins 1 through

how to read resistors, while Table 32-5 illustrates the 4 connected to a DB-9F connector, as seen in

capacitor code chart which will aid you in constructing Figure 32-7.

the project.

The chart shown in Table 32-3 depicts the BASIC

Refer now to the resistor color code chart shown in

STAMP 2 microprocessor pinout and functions.

Table 32-4, which will assist you in identifying the

resistor values for the project. Note that each resistor Circuit assembly

will have either three or four color bands, which begin at one end of the resistor’s body. The first colored band Before we begin constructing the Remote Temperature

represents the resistor’s first digit, while the second Monitor, you will need to locate a clean, well-lit

color represents the second digit of the resistor’s value.

worktable or workbench. Next we will gather a small

The third colored band represents the resistor’s

25–30-W pencil tipped soldering iron, a length of

multiplier value, and the fourth color band represents 60/40 tin–lead solder, and a small canister of Tip Tinner, the resistor’s tolerance value. If there is no fourth available at your local RadioShack store; Tip Tinner is colored band then the resistor has a 20% tolerance

used to condition the soldering tip between solder

value. If the resistor’s fourth band is silver then the joints. You drive the soldering tip into the compound resistor has a 10% tolerance value and if the fourth band and it cleans and prepares the soldering tip. Next grab is gold then the resistor’s tolerance value will be 5%.

a few small hand tools; try to locate small flat blade Finally, we are ready to begin assembling the project, and Phillips screwdrivers. A pair of needle-nose pliers, so let’s get started. The prototype was constructed on a Table 32-3

Basic STAMP 2 – pinouts

Pin

Name

Description

1

Sout

Serial out, connects to PC serial port (DB-9, pin-2)

2

Sin

Serial in, connects to PC serial port (DB-9, pin-3)

3

ATN

Attention, connects to PC serial port -DTR pin (DB-9, pin-4) 4

VSS

System ground, connects to PC serial port (DB-9, pin-5) 5-20

P0-P15

General purpose input/output lines, source/sink 30 mA, (21-36)

X0-X15

BS2P40-only – auxiliary bank of input/outputs source/sink 100 mA max 21(37)

VDD

5-volt DC input – from external regulator - recommended with loads 22(38)

RES

Reset pin, goes ow when power supply less than 4.2 V

23(39)

VSS

System ground same as pin-4, connects to power supply ground 24(40)

Vin

Unregulated power input accepts 5.5–12 V DC, 7.5 recommended 353

Table 32-4

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

No color

20%

Table 32-5

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

1.0

1R0

3,900

3.9

.0039

392

1.2

1R2

4,700

4.7

.0047

472

1.5

1R5

5,600

5.6

.0056

562

1.8

1R8

6,800

6.8

.0068

682

2.2

2R2

8,200

8.2

.0082

822

2.7

2R7

10,000

10

.01

103

3.3

3R3

12,000

12

.012

123

3.9

3R9

15,000

15

.015

153

4.7

4R7

18,000

18

.018

183

5.6

5R6

22,000

22

.022

223

6.8

6R8

27,000

27

.027

273

8.2

8R2

33,000

33

.033

333

10

100

39,000

39

.039

393

12

120

47,000

47

.047

473

15

150

56,000

56

.056

563

18

180

68,000

68

.068

683

22

220

82,000

82

.082

823

27

270

100,000

100

.1

104

33

330

120,000

120

.12

124

39

390

150,000

150

.15

154

47

470

180,000

180

.18

184

Chapter Thirty-Two: Remote Temperature Monitor 56

560

220,000

220

.22

224

354

Chapter Thirty-Two: Remote Temperature Monitor

Table 32-5—cont’d

Three-digit capacitor codes

pF

nF

m F

Code

pF

nF

m F

Code

68

680

270,000

270

.27

274

82

820

330,000

330

.33

334

100

.0001

101

390,000

390

.39

394

120

.00012

121

470,000

470

.47

474

150

.00015

151

560,000

560

.56

564

180

.00018

181

680,000

680

.68

684

220

.00022

221

820,000

820

.82

824

270

.00027

271

1,000

1

105

330

.00033

331

1,500

1.5

155

390

.00039

391

2,200

2.2

225

470

.00047

471

2,700

2.7

275

560

.00056

561

3,300

3.3

335

680

.00068

681

4,700

4.7

475

820

.00082

821

6.8

685

1,000

1.0

.001

102

10

106

1,200

1.2

.0012

122

22

226

1,500

1.5

.0015

152

33

336

1,800

1.8

.0018

182

47

476

2,200

2.2

.0022

222

68

686

2,700

2.7

.0027

272

100

107

3,300

3.3

.0033

332

157

157

Code = 2 significant digits of the capacitor value + number of zeros to follow 10 pF = 100

For values below 10 pF, use “R” in place of decimal e.g. 8.2 pF = 8R2

100 pF = 101

1,000 pF = 102

22,000 pF = 223

330,000 pF = 334

1 μF = 105

single-sided printed circuit board or PCB. With your

Go ahead and locate where resistor R1 goes on the

PC board in front of you, we can now begin populating PC and install it, next solder it in place on the PC board, the circuit board. We are going to place and solder the and then with a pair of end-cutters trim the excess

lowest height components first, the resistors and diodes.

component leads flush to the edge of the circuit board.

First, locate our first resistor R1. Resistor R1 has a Next locate the remaining resistors and install them in value of 330 ohms and is a 5% tolerance type. Now take their respective locations on the main controller

a look for a resistor whose first color band is brown, PC board. Solder the resistors to the board, and

black, orange, and gold. From the chart you will notice remember to cut the extra lead with your end-cutters.

that orange is represented by the digit (3), the second Note that capacitors generally come from two major

color band is orange, which is represented by (3).

groups or types. Non-polar types, such as the ones in Notice that the third color is brown, so the multiplier is this project, have no polarity and can be placed in either (10), then (3) (3) × 10 = 330 ohms.

direction on the circuit board. The other type of

355

capacitors are called polarized types, these capacitors the emitter lead is also a slanted line facing the base have polarity and have to be inserted on the board

lead but it will have an arrow pointing towards or away with respect to their polarity marking in order for the from the base lead. Now, identify the two transistors, circuit to operate correctly. On these types of capacitors, referring to the manufacturer’s specification sheets as you will observe that the components actually have a

well as the schematic and parts layout diagrams when

plus or minus marking or a black or white band with

installing the two transistors. If you have trouble

a plus or minus marking on the body of the capacitors.

installing the transistors, get the help of an electronics Capacitors must be installed properly with respect to enthusiast with some experience. Install the transistors polarity in order for the circuit to work properly. Failure in their respective locations and then solder them in to install electrolytic capacitors correctly could cause place. Remember to trim the excess component leads

damage to the capacitors as well as to other components with your end-cutters.

in the circuit when power is first applied.

The Remote Temperature Monitor circuit contains

Many capacitors are quite small in physical size, so

four ICs. ICs are often static sensitive, so they must manufacturers have devised a three-digit code which

be handled with care. Use a grounded anti-static wrist can be placed on the capacitor instead of the actual

strap and stay seated in one location when handling

value. The code occupies a much smaller space on the

the ICs. Take out a cheap insurance policy by installing capacitor and can usually fit nicely on the capacitor IC sockets for each of the ICs. In the event of a

body, but without the chart the builder would have a

possible circuit failure, it is much easier to simply difficult time determining the capacitor’s value.

unplug a defective IC than trying to unsolder 14 or

16 pins from a PC board without damaging the board.

Now look for the lowest profile capacitors from the

ICs have to be installed correctly if the circuit is going component stack and locate capacitors C3 and C4,

to work properly. IC packages will have some sort of

labeled .1 μF or (104). Note that there are a number of markings which will help you orient them on the PC

small capacitors in the circuit that may not be labeled board. An IC will have either a small indented circle, with their actual value, so you will have to check

a cutout, or notch at the top end of the IC package.

Table 32-5 to learn how to use the three-digit capacitor Pin 1 of the IC will be just to the left of the notch, codes. Go ahead and place C3 and C4 on the circuit

or cutout. Refer to the manufacturer’s pinout diagram, board and solder them in place. Now take your

as well as the schematic when installing these parts.

end-cutters and cut the excess component leads flush to If you doubt you ability to correctly orient the ICs, the edge of the circuit board. Next, locate the remaining then seek the help of a knowledgeable electronics

low profile capacitors and install them on the printed enthusiast.

circuit board, then solder them in place. Remember to trim the extra component leads. There are a number of The intercom controller circuit employs three indicator electrolytic capacitors in the circuit and placing them in or status LEDs at D1, D2, and D3 which also must be

the circuit with respect to their proper polarity is

oriented correctly if the circuit is to function properly.

essential for proper operation of the circuit. Once you An LED has two leads, a cathode and an anode lead. The have located the larger electrolytic capacitors install anode lead will usually be the longer of the two leads and them in their respective locations and solder them in the cathode lead will usually be the shorter lead, just place. Finally trim the excess component leads.

under the flat side edge of the LED; this should help orient the LED on the PC board. You may want to leave The Remote Temperature Monitor utilizes two

about 1⁄

conventional transistors. Transistors are generally three 2 lead length on the LED, in order to have the LED

protrude through the enclosure box. Solder the LEDs to lead devices, which must be installed correctly if the the PC board and then trim the excess leads.

circuit is to work properly. Careful handling and proper orientation in the circuit is critical. A transistor will The Remote Temperature Monitor uses a single

usually have a Base lead, a Collector lead, and an

250 V MOV at the input to the mini-modem to protect

Emitter lead. The base lead is generally a vertical line it from telephone ringing and surge voltages; this device inside a transistor circle symbol. The collector lead is has no polarity so it can be mounted in either direction Chapter Thirty-Two: Remote Temperature Monitor usually a slanted line facing towards the base lead and in the circuit.

356

Chapter Thirty-Two: Remote Temperature Monitor

Next, go ahead and install the mini push-button

With power applied to the Remote Temperature Monitor

switch at S1, which functions as a reset switch for the circuit, download the rtemp.bs2 program into the BS2

microprocessor. The reset switch is used in the event of microcontroller via the programming cable and you are a microprocessor lockup.

ready to begin remote monitoring. Your Remote

Once the Remote Temperature Monitor circuit board

Temperature Monitor can now be placed where you wish

has been completed, take a short break and then we will to monitor the remote location or cabin.

inspect the PC board for possible “cold” solder joints and Now, when you return to your home or workshop you

“short” circuits. Pick up the PC board with the foil side are ready to remotely interrogate the temperature sensor facing upwards toward you. Carefully inspect the solder from your home or office location.

joints, these should look smooth, clean, and bright. If any of the solder joints look dull, dark, or blobby, then you Operation

should remove the solder with a solder sucker or a solder wick and then resolder the joint all over again. Now we When you return to your home, turn on your computer

will inspect the PC board for possible short circuits. Short and bring up the Windows Hyper-terminal modem

circuits can be caused from small solder blobs bridging Window or any other window modem program and

the circuit traces or from cut component leads which can configure it for 2,400 bps with settings of 8-N-1 data often stick to the circuit board once they have been cut.

bits. From the Hyper-terminal Window dial the

A sticky residue from solder will often trap component telephone number of your remote location, i.e. the

leads across the circuit traces. Look carefully for any Remote Temperature Monitor. The modems will begin

bridging wires across circuit traces.

communicating with each other and soon you will

Once this inspection is complete, we can move

begin seeing the temperature readings appear in the

on to installing the circuit board into a suitable plastic Hyper-terminal window, as shown in Figure 32-8.

enclosure. Locate a suitable enclosure to house the circuit When you are finished reading the high, low and

board. Arrange the circuit board and the transformer on current temperature readings, you can ask the Hyper-the bottom of the chassis box. Now, locate four 1⁄4 ′′

terminal program to hang up; this will reset the modems standoffs, and mount the PC board between the standoffs for the next time you wish to call up the remote location and the bottom of the chassis box.

and read the remote temperature.

Finally, install a four pin header/jack connector at J1/P1

to allow connecting up the serial programming connector at J2. Next, go ahead and install the modular phone jack at J3 and a coaxial power jack for the power supply input.

Solder these components to the circuit board.

You can power the Remote Temperature Monitor

using a 12 V DC power cube or “wall-wart” type power

supply which can be readily purchased from your local RadioShack or electronic supply house. These power

supplies generally have coaxial plugs on them, which can mate to the coaxial power jack on the chassis of your Remote Temperature Monitor. Next, you will have to load the Rtemp.bs2 program into the Remote Temperature Monitor circuit. Refer to the programming cable diagram, and connect the programming cable between the Remote

Temperature Monitor and a personal computer or laptop.

Call up the BASIC STAMP editor program that you

downloaded from www.parallax.com. Copy the

rtemp.bs2 program into your laptop. Now call up the BS2 editor program and look for the rtemp.bs2 program.

Figure 32-8

Temperature readout screen

357

‘Remote temperature monitor – Bs2 program

‘Temperature (CH1786Temperature.BS2) Parallax

‘ This program monitors a Dallas Seminconductor DS1620 digital thermometer

‘ while waiting for an incoming call. When a call is received, the STAMP

‘ causes the modem to answer the call then displays temperature data on

‘ the remote terminal.

‘ -----[I/O Definitions]----------------------------------------------------

‘

‘ modem pins

‘

TX1 CON 15 ‘ CH1786 “Tx” pin

RX1 CON 14 ‘ CH1786 “Rx” pin

RI_ VAR In12 ‘ ring indicator

DCD_ VAR In13 ‘ carrier detect

‘ DS1620 pins

‘

Rst CON 6 ‘ DS1620.3

Clk CON 7 ‘ DS1620.2

DQ CON 8 ‘ DS1620.1

‘ -----[Constants]----------------------------------------------------------

‘

True CON 1

False CON 0

No CON 1

Yes CON 0

T2400 CON 396 ‘ 2400 baud for modem

LF CON 10 ‘ line feed character

FF CON 12 ‘ form feed (clear remote screen)

‘ DS1620 commands

‘

RTmp CON $AA ‘ read temperature

WTHi CON $01 ‘ write TH (high temp register)

WTLo CON $02 ‘ write TL (low temp register)

RTHi CON $A1 ‘ read TH

RTLo CON $A2 ‘ read TL

Strt CON $EE ‘ start conversion

StpC CON $22 ‘ stop conversion

WCfg CON $0C ‘ write configuration register

RCfg CON $AC ‘ read configuration register

NTasks CON 3 ‘ total number of tasks

‘ -----[Variables]----------------------------------------------------------

‘

tmpIn VAR Word ‘ 9¯bit temp input from DS1620

nFlag VAR tmpIn.Bit8 ‘ negative flag

hlfBit VAR tmpIn.Bit0 ‘ half degree C bit

Chapter Thirty-Two: Remote Temperature Monitor

358

Chapter Thirty-Two: Remote Temperature Monitor

tempF VAR Word ‘ converted fahrenheit value

tempC VAR Byte ‘ converted celcius value

tmpNow VAR Word ‘ current temperature

tmpLo VAR Word ‘ low temp

tmpHi VAR Word ‘ high temp

sign VAR Byte ‘ - for negative temps

sLo VAR Byte

sHi VAR Byte

inByte VAR Byte ‘ input from user terminal

cmd VAR Byte ‘ command pointer

answer VAR Byte ‘ user response to prompt

task VAR Byte ‘ task control variable

riFltr VAR Byte ‘ for ring indicator filter

‘ -----[EEPROM Data]--------------------------------------------------------

‘

‘ -----[Initialization]-----------------------------------------------------

‘

Init:

tmpLo = $FFFF ‘ start with opposite extremes

tmpHi = 0

I_Modm:

PAUSE 250 ‘ allow modem to power up

‘ train modem for speed

‘

SEROUT TX1, T2400, 10, [“AT”, CR]

SERIN RX1, T2400, 2500, Error, [WAIT (“OK”)]

PAUSE 250

‘ auto answer on second ring (S0 = 2)

‘ set max time for carrier detect to 30 secs (S7 = 30)

‘

SEROUT TX1, T2400, 10, [“ATS0 = 2 S7 = 30”, CR]

SERIN RX1, T2400, 2500, Error, [WAIT (“OK”)]

I_1620:

HIGH Rst ‘ alert the DS1620

SHIFTOUT DQ,Clk,LSBFIRST,[WCfg] ‘ write configuration

‘ use with CPU; free run mode

SHIFTOUT DQ,Clk,LSBFIRST,[%00000010]

LOW Rst

PAUSE 10 ‘ pause for DS1620 EE write cycle

HIGH Rst

SHIFTOUT DQ,Clk,LSBFIRST,[Strt] ‘ start temp conversions LOW Rst

debug “Initializing DS1620”,cr

NoDCD: IF DCD_ = Yes THEN NoDCD ‘ make sure DCD is clear

‘ -----[Main Code]----------------------------------------------------------

‘

Main: GOSUB ScanT ‘ get current temperature

IF DCD_ = Yes THEN GetMdm ‘ call received

359

BRANCH task, [Task0, Task1, Task2]

GOTO Main

Task0: ‘ task code here

‘

task = 1 ‘ select a specific task

GOTO NextT ‘ go do it

Task1: ‘ task code here

‘

task = 2

GOTO NextT

Task2: ‘ task code here

‘

task = 0

GOTO NextT

NextT: ‘ task = task + 1 // NTasks

‘ round¯robin to next task

GOTO Main

END

‘ -----[Subroutines]--------------------------------------------------------

‘

‘ = = = = = = = = = = =

‘ Modem Routines

‘ = = = = = = = = = = =

‘ error with modem

‘ - structured as separate routine to allow user indications/enhancements

‘

Error: ‘ additional code here

PAUSE 1000

GOTO I_Modm ‘ try to initialize again

GetMdm: PAUSE 5000 ‘ let other end get ready

Modm1: GOSUB DoMenu ‘ show readings and menu

Get1: SERIN RX1, T2400, [inByte] ‘ wait for input

‘ process user input

cmd = 99

‘ convert letter to digit (0..5)

LOOKDOWN inByte, [“tTrRdD”], cmd

cmd = cmd/2 ‘ fix for BRANCH

‘ branch to handler

BRANCH cmd, [Cmd0, Cmd1, Cmd2]

GOTO Modm1

Cmd0: GOSUB ScanT ‘ get current temp

GOTO Modm1

Cmd1: GOSUB RstT ‘ reset high and low

GOTO Modm1

Cmd2: GOSUB Discon ‘ disconnect from user

IF answer = No THEN Modm1 ‘ stay with user

GOTO NoDCD ‘ back to the beginning

Chapter Thirty-Two: Remote Temperature Monitor

‘ clear remote terminal and display menu

‘

360

Chapter Thirty-Two: Remote Temperature Monitor

DoMenu:

debug “DoMenu”,cr

SEROUT TX1, T2400, [FF]

SEROUT TX1, T2400, [“= = = = = = = = = = = = = = = = = = =”, CR, LF]

SEROUT TX1, T2400, [“Remote STAMP - Station 001”, CR, LF]

SEROUT TX1, T2400, [“= = = = = = = = = = = = = = = = = = =”, CR, LF]

SEROUT TX1, T2400, [LF]

SEROUT TX1, T2400, [“Temp (Now).... “, sign, DEC tmpNow, CR, LF]

SEROUT TX1, T2400, [“Temp (Low).... “, sLo, DEC tmpLo, CR, LF]

SEROUT TX1, T2400, [“Temp (High)... “, sHi, DEC tmpHi, CR, LF]

SEROUT TX1, T2400, [LF]

SEROUT TX1, T2400, [“[T] Re¯display current readings”, CR, LF]

SEROUT TX1, T2400, [“[R] Reset high and low temps”, CR, LF]

SEROUT TX1, T2400, [“[D] Disconnect”, CR, LF]

SEROUT TX1, T2400, [LF, “− −> ”]

RETURN

‘ reset high and low temperatures

‘

RstT: SEROUT TX1, T2400, [CR, LF, LF, “Reset? ”]

GOSUB YesNo

IF answer = No THEN RstX

GOSUB ScanT

tmpLo = tmpNow

sLo = sign

tmpHi = tmpNow

sHi = sign

RstX: RETURN

‘ disconnect

‘

Discon: SEROUT TX1, T2400, [CR, LF, LF, “Disconnect? ”]

GOSUB YesNo

IF answer = No THEN DiscX

SEROUT TX1, T2400, [CR, LF, LF, “Disconnecting.”, CR, LF]

‘ return modem to command state

‘ and hang up

‘

PAUSE 2000

SEROUT TX1, T2400, [“+ + +”]

PAUSE 2000

SEROUT TX1, T2400, 10, [“ATH0”, CR]

DiscX: RETURN

‘ confirm for [Y]es or [N]o

‘ and get user input (default = No)

‘

YesNo: SEROUT TX1, T2400, [“Are you sure? (Y/N): ”]

answer = No

‘ get answer

‘ - but only wait for 5 seconds

361

‘

SERIN RX1, T2400, 5000, YesNoX, [inByte]

IF inByte = “y” THEN IsYes

IF inByte = “Y” THEN IsYes

GOTO YesNoX

IsYes: answer = Yes

YesNoX: RETURN

‘ process ring indicator

‘ - filters pulsing ring indicator

‘ - waits for about 0.25 second of no RI pulsing before returning

‘

DoRing:

‘ your code here

‘ (i.e., count number of rings)

‘

RIWait: riFltr = 0 ‘ clear the “no pulses” counter

RIchk: IF RI_ = Yes THEN RIWait ‘ still pulsing

riFltr = riFltr + 1 ‘ not pulsing, increment count

IF riFltr > 50 THEN RIx ‘ RI clear now

PAUSE 5 ‘ 5 ms between RI scans

GOTO RIchk ‘ check again

RIx: RETURN ‘ done - outta here

‘ = = = = = = = = = = =

‘ DS1620 Routines

‘ = = = = = = = = = = =

‘ get current temperature

‘ — update high and low readings

‘

ScanT: HIGH Rst ‘ alert the DS1620

SHIFTOUT DQ,Clk,LSBFIRST,[RTmp] ‘ read temperature

SHIFTIN DQ,Clk,LSBPRE,[tmpIn\9] ‘ get the temperature LOW Rst

GOSUB GetF ‘ convert to Farhenheit

tmpNow = tempF

IF (tmpLo < tmpNow) THEN THigh

tmpLo = tmpNow ‘ set new low

sLo = sign

debug “Scan T”,cr

THigh: IF (tmpHi > tmpNow) THEN TDone

tmpHi = tmpNow ‘ set new high

sHi = sign

TDone: RETURN

‘ convert reading from 1⁄ degrees input (rounds up)

2

‘

GetC: IF nFlag = 0 THEN CPos ‘ check negative bit (8) sign = “−” ‘ set sign

Chapter Thirty-Two: Remote Temperature Monitor

tempC = −tmpIn/2 + hlfBit ‘ if neg, take 2’s compliment 362

Chapter Thirty-Two: Remote Temperature Monitor

GOTO CDone

CPos: sign = “ ”

tempC = tmpIn/2 + hlfBit

CDone: RETURN

‘ convert (1⁄ degrees C) to Fahenheit with rounding

2

‘ — general equation (for whole degrees): F = C ∗ 9/5 + 32

‘

GetF: sign = “ ”

IF nFlag = 0 THEN FPos1

tmpIn = -tmpIn & $FF ‘ convert from negative

IF tmpIn < 36 THEN FPos0

FNeg: sign = “−”

tempF = tmpIn * 9/10 + hlfBit − 32

GOTO FDone

FPos0: tempF = 32 − (tmpIn * 9/10 + hlfBit)

GOTO FDone

FPos1: tempF = tmpIn * 9/10 + 32 + hlfBit

FDone: RETURN

363

Appendix

Electronic Parts Suppliers

We have listed some electronic parts suppliers.

Digi-Key Electronics — electronics parts

We cannot guarantee any particular level of service

701 Brooks Avenue South, Thief River Falls,

from these companies and supply this list only as a

MN 56701

convenience to our readers.

Tel: 800 344 4539 or 218 681 6674

Fax: 218 681 3380

Alltronics — Electronic parts, over runs, tec

http://www.digikey.com/

Box 730, Morgan Hill, CA 95038

Tel: 408 847 0033

DIY Electronics (HK) Ltd. — Electronics kit

Fax: 408 847 0133

manufacturer

http://www.alltronics.com

Peter Crowcroft & Ladda, PO Box 88458,

Sham Shui Po, Hong Kong

Carls Electronics — ElectroInc.s kits

Tel: 852 2304 2250

484 Lakepark Ave, Suite 59, Oakland, CA 94610

Fax: 852 2729 1400

Tel: 866 664 0627 (toll-free USA) or 510 451 4320

Fax: 510 903 9712

Elenco Electronics Inc. — Electronic kits,

http://www.electronickits.com/

educational products

150 Carpenter Ave., Wheeling, IL 60090

Cermetek Microelectronics, Inc. — Mini modems

Tel: 847 541 3800

1390 Borregas Avenue, Sunnyvale, CA 94089

Fax 847 520 0085

Tel: 408 752 5000

http://www.elenco.com/

Fx: 408 752 5004

www.cermetek.com

Freescale Semiconductor, Inc. — Semiconductors sales@cermetek.com

(formerly Motorola Semiconductor)

Tel: 800 521 6274

Circuit Specialists Inc. — Electronic parts, test http://www.freescale.com/

equipment

Paul Thorpe PO Box 3047, Scottsdale, AZ 85271-3047

Glolab — Electronic kits

Tel: 800 528 1417

307 Pine Ridge Drive, Wappingers Falls,

Fax: 602 464 5824

New York (NY), 12590

http://www.circuitspecialists.com/

Tel: 845 297 9772

Fax: 845 297 9772

Clare, Inc. – Teltone Products — Touch tone decoders http://www.glolab.com

78 Cherry Hill Drive, Beverly, MA 01915,

Tel: 978 524 6700

Fax: 978 524 4700

http://www.clare.com/

364

Copyright © 2009 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Appendix: Electronic Parts Suppliers

Hobby Engineering — Electronics parts, kits, etc.

Ocean State Electronics — Electronic parts

1405 Huntington Avenue, Suite 150, South

PO Box 1458, 6 Industrial Drive, Westerly RI 02891

San Francisco, CA 94080

Tel: 401 596 3080

Tel: 866 Robot 50 (866 762 6850) or 650 875 7987

Fax: 401 596 3590

Fax: 650 952 7629

http://www.oselectronics.com/

http://www.hobbyengineering.com/

Parallax, Inc. — BASIC STAMP, microcontrollers, Intersil corp — Semiconductor

accessories

1001 Murphy Ranch Road, Milpitas, CA 95035

599 Menlo Drive, Rocklin, CA 95765

Tel: 408 432 8888 or 888 INTERSIL (888 468 3774)

Tel: 888 512 1024 (toll-free sales)

Fax: 408 434 5351

Tel: 888 997 8267 (toll-free tech support)

http://www.intersil.com/cda/home/

http://www.parallax.com

Marlin P. Jones & Associates C — Electronic parts, Phillips Semiconductor NXP B — Semiconductors

over runs, power supplies, etc.

NXP Semiconductors

PO Box 12685, Lake Park FL 33403-0685

Tel: 800 447 1500

Tel: 407 848 8236

http://www.nxp.com/#[0]

Fax: 407 844 8764

http://www.mpja.com/

Ramsey Electronics — Large kit manufacturer

590 Fishers Station Dr., Victor, NY 14564

Maxim Integrated Products — Semiconductors

Tel: 800 446 2295 or 585 924 4560

(formerly Dallas Semiconductor)

Fax: 585 924 4886

120 San Gabriel Drive, Sunnyvale, CA 94086

http://www.ramseyelectronics.com/

Tel: 408 737 7600

Fax: 408 737 7194

Samsung Electronics C —Semiconductors

http://www.maxim-ic.com/

3655 North First Street, San Jose, CA 95134

Tel: 1 408 954 7000

Mouser Electronics, Inc. B — Large electronics http://www.samsungsemi.com

parts house

1000 North Main Street, Mansfield, TX 76063

Solder-it — Soldering accessories

Tel: 800 346 6873 or 817 804 3888

P.O. Box 360, Chagrin Falls, OH 44022

Fax: 817 804 3899

Tel: 800 897 8989 or 440 247 6322

http://www.mouser.com/

Fax: 440 247 4630

http://www.solder-it.com/

National Semiconductor B — Semiconductors

2900 Semiconductor Dr., P.O. Box 58090, Santa Clara,

Talking Electronics B — Electronics kits, extensive CA 95052-8090

web page projects

Tel: 408 721 5000

P.O. Box, Cheltenham, 3192 Victoria, Australia

http://www.national.com/

Tel: 0417329788

http://www.talkingelectronics.com/

Newark Electronics — Extensive electronic parts 4801 N. Ravenswood, Chicago, IL 60640-4496

Texas Instruments, Inc. — Semiconductors

Tel: 773 784 5100

13532 N. Central Expressway, M/S 3807, Dallas,

Fax: 888 551 4801

TX 75243-1108

http://www.newark.com/

http://www.ti.com/

365

Vellemen Inc. (USA) — Large electronic manufacturer Winbond Electronics Corporation America —

7354 Tower Street, Fort Worth, TX 76118

Memory storage devices

Tel: 817 284 7785

Information Storage Devices (ISD), 2727 North First

Fax: 817 284 7712

Street, San Jose, CA 95134

http://www.vellemanusa.com/us/

Tel: 408 943 6666

Fax: 408 544 178

Appendix: Electronic Parts Suppliers

366

Index

Figures and Tables in BOLD

Projects in BOLD ITALIC

Cut Phone Line Detector (Continued)

A

parts, 121–22

power supply, 121–22, 129, 129

amateur radio and telephone. See Radio Phone Patch

American Telephone and Telegraph (AT&T), 3–4

amplifier

D

differential Op-Amp, 21, 21

inverting input Op-Amp, 21, 21

De Forest, Dr. Lee, 3

non-inverting input Op-Amp, 21, 21

diodes, 14, 17

Op-Amp, 20–23, 21, 22, 24, 25

installation of, 28, 29

transistor audio, 23, 23, 24

light-emitting (LED), 15, 18

See also operational amplifier; Telephone Amplifier, Direct

DTMF. See Dual Tone Multiple Frequency

Connect; Telephone Amplifier, Magnetic Pickup; DTMF Telephone Controller. See Telephone Controller

Telephone FM Transmitter

DTMF Touch-Tone Decoder, 283, 283, 285

Answering Machine Protector, 42–43, 42

circuit, 283–90, 286

circuit, 43, 43–45

operation, 290

operation, 45

parts, 282–83

parts, 42

program, 291–93

Audion, 3

DTMF Touch-Tone Generator, 283, 284

circuit, 283–90, 285

operation, 290

B

parts, 282

program, 291

BASIC STAMP microcontroller

Dual Tone Multiple Frequency (DTMF), 7, 262, 262, 283, STAMP 1, 276, 276

283. See also DTMF Touch-Tone Decoder; STAMP 2, 275–81, 276, 277, 278, 279, 280, 281 ( see also

DTMF Touch-Tone Generator; Telephone Controller

Caller-ID/Blocker, DTMF Touch-tone Decoder;

DTMF Touch-tone Generator; Page-alert) battery, 1

E

Bell, Alexander Graham, 2–3

electret microphone, 10, 16, 18, 174, 176

electrolytic capacitors, 14, 17

C

electromagnetism, 1

Electronic Switching System (ESS), 4, 5

Caller-ID/Blocker, 295, 295

circuit, 295–302, 296, 297

operation, 302

F

parts, 294

program, 303–10

Faraday, Michael, 1

capacitor(s)

feld effect transistor (FET), 15, 17

codes, 26, 26–27

flux, 29, 30

installation of, 28, 28

full duplex, 7

types of, 13, 14, 16, 25–26

CB radio. See Radio Phone Patch

cellular phone, 4, 5

G

mechanism of, 11–12

Gray, Elisha, 2, 3

ceramic capacitors, 14, 17

Gray, Stephen, 1

Citizens Band radio. See Radio Phone Patch

comparator, 22, 22

controller, remote. See Telephone Controller

H

Cut Phone Line Detector, 128

Hayes, Hammond V., 3

circuit, 128–31, 129

heat sink, 16, 18

operation, 131

Henry, Joseph, 1–2

367

Copyright © 2009 by The McGraw-Hill Companies, Inc. Click here for terms of use.

polyester capacitors, 14, 17

I

potentiometer (pot), 13, 14

printed circuit (PC) board, 34–35

inductance, 18

soldering on, 35–37, 35, 36

inductors, 16, 18

pulse dialing, 7, 174, 178, 179. See also telephone: integrated circuit (IC), 15, 17–18

rotary dial

digital, 22, 23

installation, 29

See also operational amplifier

intercom. See Speaker-Phone; Telephone Phone Intercom

R

Radio Phone Patch, 213–14

circuit, 214, 214–19

L

operation, 219–20

light dependent resistor (LDR), 13, 14

parts, 213

long-distance telephone service, 3. See also transatlantic recording, scrambled audio, 245. See also Telephone

telephone service

Scrambler

loudspeaker. See speakers

Remote Temperature Monitor, 348

circuit, 348, 349–57, 350

operation, 357, 357

M

parts, 348

metal-oxide varistor (MOV), 43

program, 358–63

microcontroller. See BASIC STAMP microcontroller See also Page-Alert; Tele-Alert

microphone, 18

relays, 16, 19

electret, 10, 16, 18, 174, 176

resistors

telephone, 9–10, 9

color codes for, 25, 25

microwave system, 4

installation of, 28, 28

MKT capacitors, 14, 17

types of, 13, 14

Modem/Fax Protector, 42–43, 42

circuit, 43, 43–45

operation, 45

S

parts, 42

schematic, definition of, 22

monitoring, remote. See Page-Alert; Remote Temperature

Smart Phone Light, 141

Monitor; Tele-Alert; Telephone Tattletale

circuit, 141, 141–45

Morse, Samuel, 2

operation, 145

parts, 123

power supply, 123, 144, 145

P

solder, 30

Oersted, Christian, 1

soldering, 29–36, 34, 38

Off-line Telephone Tester, 153

on printed circuit (PC) boards, 34–37, 35, 36

circuit, 153–56, 154

See also unsoldering

operation, 156–57

soldering gun, 31–32

parts, 150

soldering iron, 30–31, 32, 37–38

See also Telephone Line Tester

soldering station, 31, 32

Ohm’s law, 20

Speaker-Phone, 232

operational amplifier (Op-Amp), 20–22, 21, 22, 24, 25

circuit, 232, 232–39, 233, 234

oscillator, 22, 22

operation, 239–40

parts, 231–32

speakers, 16, 18–19

P

telephone, 10–11

Page-Alert, 312

See also Speaker-Phone

circuit, 312, 313, 313–19

Strowger, Almon B., 3

operation, 319–20

Strowger switch, 3

parts, 311

surge voltage protector (SVP), 43

program, 320–21

switch, 16, 19

Sensor Module, 311, 321–23, 321

switching system, 4, 5

Temperature/Voltage Level Module, 311–12, 323–26,

323, 324

pager. See Page-Alert

T

Parallax microcontroller. See BASIC STAMP microcontroller

Tele-Alert, 329–30, 337

PC board. See printed circuit (PC) board

circuit, 329, 330–38, 331, 338

Index pictorial diagram, definition of, 22

Listen-in Module, 329, 330, 344, 344–47, 345

368

Index

Tele-Alert (Continued)

Telephone Conferencer Unit, 61

Motion Module, 328–29, 330, 339–44, 340, 341

circuit, 61, 61–65, 62

operation, 336

operation, 65–66

parts, 328

parts, 61

program, 338–39

Telephone Controller, 262

telegraph, 2

circuit, 262, 262–73, 263, 265

telephone

operation, 273–74

amplifier ( see Telephone Amplifier, Direct Connect; parts, 261–62

Telephone Amplifier, Magnetic Pickup; Telephone

telephone exchange, 3

FM Transmitter)

electronic, 4 ( see also Electronic Switching System) call recording ( see Telephone FM Transmitter; Telephone

Telephone FM Transmitter, 166–67

Recorder Switch)

calibration, 171

cellular (see cellular phone)

circuit, 166, 167, 167–71

components, 8–11

operation, 171

constructing a (see Telephone Project)

parts, 166

definition of, 1

Telephone Line-in-Use, 78, 124

functioning of (see telephone, mechanism of)

circuit, 78, 78–80, 124–28, 125

history of, 1–5, 2

operation, 80, 128

line monitoring ( see Cut Phone Line Detector; Telephone

parts, 75, 121

Line-in-Use; Telephone Line Vigilant; Telephone

relay controller ( see Telephone Line-in-Use Relay

Single Line Status Indicator; Telephone Two-Line

Controller)

Status Indicator)

Telephone Line-in-Use Relay Controller, 131

mobile wireless, 4

circuit, 132, 132–34

Model 500C, 8, 8

operation, 134

rotary dial, 3, 7, 9, 9, 175, 175–76, 176 ( see also pulse parts, 122

dialing)

power supply, 122, 133, 134

touch-tone, 5, 7, 262, 262, 283 ( see also Dual Tone

Telephone Line Simulator, 159, 160

Multiple Frequency)

circuit, 160–64, 161

telephone, mechanism of, 6–7

operation, 164–65

components, 8–11 ( see also Telephone Project) parts, 151

dialing ( see pulse dialing; tone dialing)

Telephone Line Vigilant, 145

ringing, 7, 11, 11 ( see also Telephone Project: ringer circuit, 145–48, 146

component)

operation, 146, 149

microphone, 9, 9–10 ( see also Telephone Project: audio parts, 144

component)

Telephone Line Tester, 151–52, 157

Model 500C, 8, 8

circuit, 151, 151–53, 157, 157–59

signaling, 7–8

operation, 153, 159

speaker, 10–11, 11 ( see also Telephone Project: audio parts, 150–51

component)

See also Off-Line Telephone Tester

See also cellular phone: mechanism of

Telephone On-Hold, 78

Telephone Amplifier, Direct Connect, 52

circuit, 78, 78–80

circuit, 52, 52–54

operation, 80

operation, 54

parts, 75

parts, 46–47

Telephone On-Hold, Automatic Music, 89–90

See also Telephone Amplifier, Magnetic Pickup; circuit, 90, 91, 90–97

Telephone FM Transmitter

operation, 97

Telephone Amplifier, Magnetic Pickup, 47

parts, 76–77

circuit, 47, 47–51, 52

power supply, 77, 94, 94

operation, 51

Telephone On-Hold, Manual Music, 80

parts, 46

circuit, 81, 81–84

See also Telephone Amplifier, Direct Connect; Telephone

operation, 84

FM Transmitter

parts, 75

Telephone Bug/Transmitter, 204–5

Telephone On-Hold, Universal, 84–85

circuit, 205, 205–12, 206, 211

circuit, 84, 85, 84–89, 89

operation, 204–5

operation, 89

parts, 204

parts, 75–76

Telephone Call Frustrator, 68

Telephone Phone Intercom, 222

circuit, 68, 68–74, 69

alert module circuit, 223–24, 225, 226, 230

operation, 68, 74

controller circuit, 223, 224, 224–30

parts, 67–68

operation, 222–23

telephone call screening. See Telephone Call Frustrator

parts, 221–22, 222

369

Telephone Privacy Guard, 39

Telephone Single Line Status Indicator, 134

circuit, 39, 40, 39–41

circuit, 135, 135–37

operation, 41

operation, 137

parts, 39

parts, 122

Telephone Project, 174, 174

Telephone Smart Light. See Smart Phone Light

audio component, 175–78, 176, 177, 183–84

telephone switchboard, 3

circuit, 180–85

Telephone Tattletale, 252

dialer component, 175, 178–79, 179, 184

circuit, 252, 252–60, 253

local loop circuit, 174–75, 175

operation, 252, 259–60

operation, 185–86

parts, 251–52

parts, 173–74

Telephone Tollsaver, 195–96

ringer component, 179–80, 180, 184

circuit, 196–203, 197

Telephone Recorder Switch, 55–56

operation, 203

circuit, 55, 56, 56–60

parts, 195

operation, 60

Telephone Two-Line Status Indicator, 137

parts, 55

circuit, 137–40, 138

Telephone Ring Detector, 108

operation, 141

circuit, 108, 108–10, 109

parts, 122–23

operation, 111

tone dialing, 7, 174, 178, 179. See also Dual Tone Multiple parts, 98–99

Frequency

Telephone Ringer, Remote, 105

touch-tone. See Dual Tone Multiple Frequency;

circuit, 105, 105–7, 106

tone dialing

operation, 107–8

transatlantic telephone service, 4. See also long-distance parts, 98

telephone service

Telephone Ringer, Silent Cellular, 100

transformer, 16, 18

circuit, 100–104, 101

transistors, 4

operation, 104–5

installation of, 29

parts, 98

types of, 15, 17

Telephone Ringer, Talking/Musical, 187–88, 188

Trimpot, 13, 14

circuit, 188, 188–93, 189

operation, 193, 193–94

parts, 187

U

Telephone Ringer, Wireless, 111

unsoldering, 37

circuit, 111, 111–16, 112

operation, 116–17

parts, 99–100

V

Telephone Ring Generator, 117

circuit, 117, 117–19

variable capacitors, 14, 17

operation, 120

Volta, Alessandro, 1

parts, 100

Telephone Scrambler, 241–42, 242

circuit, 242, 242–49, 244

W

operation, 249–50

Watson, Thomas, 2

parts, 241

Western Union Telegraph Company, 3–4

Index

370

Table of Contents

Chapter 9 illustrates an automatic phone

Chapter 23 presents a speaker-phone project

Chapter 1

Chapter One: Telephone History

Chapter One: Telephone History

Chapter 2

Chapter Two: How the Telephone Works

Chapter Two: How the Telephone Works

Chapter Two: How the Telephone Works

Chapter Two: How the Telephone Works

Chapter 3

Chapter Three: Identifying Electronic Components

Chapter Three: Identifying Electronic Components

Chapter Three: Identifying Electronic Components

Chapter 4

Chapter Four: Reading Schematics

Chapter Four: Reading Schematics

Chapter Four: Reading Schematics

Chapter Four: Reading Schematics

Chapter 5

Chapter Five: Installation and Soldering

Chapter Five: Installation and Soldering

Chapter Five: Installation and Soldering

Chapter 6

Chapter Six: Telephone Privacy Guard

Chapter 7

Chapter Seven: Modem Protector

Chapter 8

Chapter Eight: Telephone Amplifiers and Projects

Chapter Eight: Telephone Amplifiers and Projects

Chapter Eight: Telephone Amplifiers and Projects

Chapter Eight: Telephone Amplifiers and Projects

Chapter Eight: Telephone Amplifiers and Projects

Chapter 9

Chapter Nine: Phone Recorder Switch Project

Chapter Nine: Phone Recorder Switch Project

Chapter 10

Chapter Ten: Telephone Conferencer Unit

Chapter Ten: Telephone Conferencer Unit

Chapter Ten: Telephone Conferencer Unit

Chapter Ten: Telephone Conferencer Unit

Chapter 11

Chapter Eleven: The Frustrator

Chapter Eleven: The Frustrator

Chapter Eleven: The Frustrator

Chapter 12

Chapter Twelve: Hold Circuits and Projects

Chapter Twelve: Hold Circuits and Projects

Chapter Twelve: Hold Circuits and Projects

Chapter Twelve: Hold Circuits and Projects

Chapter Twelve: Hold Circuits and Projects

Chapter Twelve: Hold Circuits and Projects

Chapter Twelve: Hold Circuits and Projects

Chapter Twelve: Hold Circuits and Projects

Chapter 13

Chapter Thirteen: Telephone Ringer Projects

Chapter Thirteen: Telephone Ringer Projects

Chapter Thirteen: Telephone Ringer Projects

Chapter Thirteen: Telephone Ringer Projects

Chapter Thirteen: Telephone Ringer Projects

Chapter Thirteen: Telephone Ringer Projects

Chapter Thirteen: Telephone Ringer Projects

Chapter Thirteen: Telephone Ringer Projects

Chapter Thirteen: Telephone Ringer Projects

Chapter 14

Chapter Fourteen: Phone Line Status Circuits

Chapter Fourteen: Phone Line Status Circuits

Chapter Fourteen: Phone Line Status Circuits

Chapter Fourteen: Phone Line Status Circuits

Chapter Fourteen: Phone Line Status Circuits

Chapter Fourteen: Phone Line Status Circuits

Chapter Fourteen: Phone Line Status Circuits

Chapter Fourteen: Phone Line Status Circuits

Chapter Fourteen: Phone Line Status Circuits

Chapter Fourteen: Phone Line Status Circuits

Chapter Fourteen: Phone Line Status Circuits

Chapter Fourteen: Phone Line Status Circuits

Chapter Fourteen: Phone Line Status Circuits

Chapter 15

Chapter Fifteen: Telephone and

Chapter Fifteen: Telephone and

Chapter Fifteen: Telephone and

Chapter Fifteen: Telephone and

Chapter Fifteen: Telephone and

Chapter Fifteen: Telephone and

Chapter Fifteen: Telephone and

Chapter Fifteen: Telephone and

Chapter Fifteen: Telephone and

Chapter 16

Chapter Sixteen: FM Telephone Transmitter

Chapter Sixteen: FM Telephone Transmitter

Chapter Sixteen: FM Telephone Transmitter

Chapter Sixteen: FM Telephone Transmitter

Chapter Sixteen: FM Telephone Transmitter

Chapter 17

Chapter Seventeen: Telephone Project

Chapter Seventeen: Telephone Project

Chapter Seventeen: Telephone Project

Chapter Seventeen: Telephone Project

Chapter Seventeen: Telephone Project

Chapter 18

Chapter 19

Chapter Nineteen: Telephone Tollsaver

Chapter Nineteen: Telephone Tollsaver

Chapter Nineteen: Telephone Tollsaver

Chapter 20

Chapter 21

Chapter Twenty-One: Radio Phone Patch

Chapter Twenty-One: Radio Phone Patch

Chapter Twenty-One: Radio Phone Patch

Chapter Twenty-One: Radio Phone Patch

Chapter Twenty-One: Radio Phone Patch

Chapter Twenty-One: Radio Phone Patch

Chapter 22

Chapter Twenty-Two: Telephone Phone Intercom

Chapter Twenty-Two: Telephone Phone Intercom

Chapter Twenty-Two: Telephone Phone Intercom

Chapter Twenty-Two: Telephone Phone Intercom

Chapter Twenty-Two: Telephone Phone Intercom

Chapter 23

Chapter Twenty-Three: Speaker-Phone Project

Chapter Twenty-Three: Speaker-Phone Project

Chapter Twenty-Three: Speaker-Phone Project

Chapter Twenty-Three: Speaker-Phone Project

Chapter Twenty-Three: Speaker-Phone Project

Chapter 24

Chapter Twenty-Four: Telephone Scrambler

Chapter Twenty-Four: Telephone Scrambler

Chapter Twenty-Four: Telephone Scrambler

Chapter 25

Chapter Twenty-Five: Telephone Tattletale

Chapter Twenty-Five: Telephone Tattletale

Chapter Twenty-Five: Telephone Tattletale

Chapter Twenty-Five: Telephone Tattletale

Chapter Twenty-Five: Telephone Tattletale

Chapter Twenty-Five: Telephone Tattletale

Chapter 26

Chapter Twenty-Six: DTMF Telephone Controller

Chapter Twenty-Six: DTMF Telephone Controller

Chapter Twenty-Six: DTMF Telephone Controller

Chapter Twenty-Six: DTMF Telephone Controller

Chapter Twenty-Six: DTMF Telephone Controller

Chapter Twenty-Six: DTMF Telephone Controller

Chapter Twenty-Six: DTMF Telephone Controller

Chapter Twenty-Six: DTMF Telephone Controller

Chapter Twenty-Six: DTMF Telephone Controller

Chapter Twenty-Six: DTMF Telephone Controller

Chapter 27

Chapter Twenty-Seven: BASIC STAMP

Chapter Twenty-Seven: BASIC STAMP

Chapter Twenty-Seven: BASIC STAMP

Chapter Twenty-Seven: BASIC STAMP

Chapter 28

Chapter Twenty-Eight: DTMF Touch-Tone Generator

Chapter Twenty-Eight: DTMF Touch-Tone Generator

Chapter Twenty-Eight: DTMF Touch-Tone Generator

Chapter Twenty-Eight: DTMF Touch-Tone Generator

Chapter Twenty-Eight: DTMF Touch-Tone Generator

Chapter Twenty-Eight: DTMF Touch-Tone Generator

Chapter Twenty-Eight: DTMF Touch-Tone Generator

Chapter Twenty-Eight: DTMF Touch-Tone Generator

Chapter 29

Chapter 30

Chapter Thirty: Page-Alert

Chapter Thirty: Page-Alert

Chapter Thirty: Page-Alert

Chapter Thirty: Page-Alert

Chapter Thirty: Page-Alert

Chapter Thirty: Page-Alert

Chapter Thirty: Page-Alert

Chapter 31

Chapter Thirty-One: Tele-Alert Project

Chapter Thirty-One: Tele-Alert Project

Chapter Thirty-One: Tele-Alert Project

Chapter Thirty-One: Tele-Alert Project

Chapter Thirty-One: Tele-Alert Project

Chapter Thirty-One: Tele-Alert Project

Chapter Thirty-One: Tele-Alert Project

Chapter Thirty-One: Tele-Alert Project

Chapter Thirty-One: Tele-Alert Project

Chapter Thirty-One: Tele-Alert Project

Chapter Thirty-One: Tele-Alert Project

Chapter 32

Chapter Thirty-Two: Remote Temperature Monitor

Chapter Thirty-Two: Remote Temperature Monitor

Chapter Thirty-Two: Remote Temperature Monitor

Chapter Thirty-Two: Remote Temperature Monitor

Chapter Thirty-Two: Remote Temperature Monitor

Chapter Thirty-Two: Remote Temperature Monitor

Chapter Thirty-Two: Remote Temperature Monitor

Chapter Thirty-Two: Remote Temperature Monitor

Chapter Thirty-Two: Remote Temperature Monitor

Chapter Thirty-Two: Remote Temperature Monitor