Elenco Electronics FO-30K Assembly And Instruction Manual

FIBER OPTICS KIT

MODEL FO-30K

Assembly and Instruction Manual

Elenco®Electronics, Inc.

ight © 2005, 1994 b

yr

Cop

t of this book shall be reproduced b

No par

y Elenco

®

Electronics

y means;

y an

, Inc.

electronic

ights reser

All r

, photocopying, or otherwise without written permission from the publisher.

ved. Revised 2005 REV-P 753259

INTRODUCTION

The FO-30 kit, an optical voice link, will introduce you to the wonderful world of fiber optics. By building this kit,
you will learn how fiber optics works and how it could be applied to the field of communication.

GENERAL OVERVIEW

Fiber optics is a medium linking two electronic
circuits. As shown in the block diagram below, this
FO-30 kit consists of three basic elements; they are
transmitter, fiber optic cable and receiver.
The Transmitter converts an electrical signal into a
light signal. The source, either a light-emitting-diode
(LED) or laser diode, does the actual conversion.
The drive circuit changes the electrical signal fed to
the transmitter into a form required by the source.

1

Fiber-optic cable is the medium for carrying the
light. The cable includes the fiber and its protective
covering.

2

TRANSMITTER

DRIVER

SOURCE

The Receiver accepts the light and converts it back
into an electrical signal. The two basic parts of the
receiver are the detector, which converts it back into
an electrical signal, and the output circuit, which
amplifies and, if necessary, reshapes the electrical
signal.

3

The other parts which are not included in the
diagram consists of connectors which are used to
connect the fibers to the source and detector.

RECEIVERFIBER OPTIC CABLE

DETECTOR

OUTPUT
CIRCUIT

1, 2, 3 The above paragraphs are reproduced by permission TECHNICIAN’S GUIDE TO FIBER OPTICS 2E (PAGE 2)

By Donald J Sterling, Jr. - DELMAR PUBLISHERS, INC., Albany, New York, Copyright 1993

IDENTIFYING RESISTOR VALUES

Use the following information as a guide in properly identifying the
value of resistors.

ANDS

B

1 2 Multiplier

Tolerance

IDENTIFYING CAPACITOR VALUES

Capacitors will be identified b
(picofarads), nF (nanofarads), or
will have their actual value printed on them. Some capacitors may

e their value printed in the following manner.

v

ha

The letter M indicates a toler
The letter K indicates a tolerance of +
The letter J indicates a tolerance of +

Note: The letter
to signify a decimal point; as in 3R3 = 3.3

“R” may be used at times

ance of

For the No.01234589

Multiplier

Multiply By 1 10 100 1k 10k 100k .01 0.1

-1-

y their capacitance value in pF

µF (microfarads). Most capacitors

First Digit

+

10%
5%

20%

103K

Second Digit
Multiplier

Tolerance

100V

Maxim
Working Voltage

alue is 10 x 1,000 = 10,000pF or

The v
.01µF 100V

um

PARTS LIST

TRANSMITTER SECTION

If you are a student, and any parts are missing or damaged, please see instructor or bookstore.
If you purchased this fiber optics kit from a distributor, catalog, etc., please contact Elenco

®

Electronics

(address/phone/e-mail is at the back of this manual) for additional assistance, if needed. DO NOT contact your
place of purchase as they will not be able to help you.

RESISTORS

Qty. Symbol Value Color Code Part #

1 R8 220Ω 5% 1/4W red-red-brown-gold 132200
1 R7 1kΩ 5% 1/4W brown-black-red-gold 141000
2 R1, R3 2.2kΩ 5% 1/4W red-red-red-gold 142200
3 R2, R4, R5 10kΩ 5% 1/4W brown-black-orange-gold 151000
1 R6 100kΩ 5% 1/4W brown-black-yellow-gold 161000

CAPACITORS

Qty. Symbol Value Description Part #

1 C3
1 C2 .01µF (103) Discap 241031
1 C4 .022µF (223) Mylar 242217
1 C1 1

100pF (101) Discap 221017

µF Electrolytic 261047

SEMICONDUCTORS

Qty. Symbol Value Description Part #

1 Q1
1 U1 LM741 Integrated Circuit 331741
1 D1 LED Red 350002
1 D2

2N3904 Transistor NPN 323904

Transmitter Clear

LED

350005

MISCELLANEOUS

Qty. Description Part #

1 PC Board 519015A
2 Switch 541103

Microphone 568000

1
1 Battery Holder 590096
1 Polishing Paper 600000
2 Screw 2-56 x 1/4” 641230
2 Nut 2-56 644201

PARTS IDENTIFICATION

Resistor Capacitors

Discap

Battery Holder Test Pin

Integrated Circuit IC Socket Switch

Mylar

Electrolytic

Qty. Description Part #

1 Lug 661106
1 IC Socket 8-Pin 664008

Test Pins 665008

2
1 Manual 753259
3’ Fiber Optic Cable 810020
1 Solder 9ST4

Transistor

ransmitter

T

Lug

LEDs

Red

Microphone

-2-

TRANSMITTER

There are 5 main components in the transmitter
(see Figure 1A). They are:

a) Power supply (9V battery)
b) Microphone (MIC)
c) Op-amp LM741, (the driver)
d) NPN transistor 2N3904, and
e) Transmitter LED

The microphone picks up your voice signal and
converts it into a voltage signal. The strength of this
voltage signal depends upon the pitch and loudness
of your voice. This signal is then ac-coupled through
C1 and R2 to the input pin 2 of the LM741 op-amp
for amplification.

The gain of the op-amp LM741 depends on the ratio
of R6 to R2, which is equal to 100k/10k = 10.
Hence, the voice signal coming from the
microphone will be amplified 10 times by this op­amp, and the amplified signal will appear at the
output of the op-amp.

At 0 Hz (DC) the impedance of C1 is infinite. The
amplifier then acts as a voltage follower. A voltage
follower is an op-amp in which the output voltage is
equal to the input voltage. In our case, the output
voltage at pin 6 is equal to the input voltage at pin 3

and pin 2 which is about 4.5V. This 4.5V at the input
pins is due to the effect of resistors R4 and R5
which act as a voltage divider. This constant DC
voltage helps keep the NPN transistor (2N3904) on
all the time.

The function of the NPN transistor (2N3904) is
similar to that of a valve, it controls the flow of the
current through the LED. The flow of this current will
depend on the base voltage of the transistor. This
base voltage in turn depends on the loudness and
pitch of your voice. Thus, the light intensity of this
LED will vary as you speak into the microphone.
This encoded light signal will then be transmitted to
the receiver through a fiber optic cable.

The LED (D1) acts as an ON/OFF indicator. It will
also indicate the state of the battery. If the LED
becomes dim, the battery is weak and should be
replaced. C2 filters out any noise that comes
through the voltage divider. C3 helps in stabilizing
the op-amp. It will also reduce any high frequency
noise generated in the transmitter. When S2 is
closed (toward the LED D2), C4 is placed into the
circuit and the op-amp will oscillate at about 1kHz.
As a result, you will hear a shrill noise from the
speaker in the receiver.

SCHEMATIC DIAGRAM

Figure 1A

-3-

CONSTRUCTION

Introduction

The most important factor in assembling your FO-30K Fiber Optics Kit is good soldering techniques. Using the
proper soldering iron is of prime importance. A small pencil type soldering iron of 25 - 40 watts is
recommended. The tip of the iron must be kept clean at all times and well tinned.

Safety Procedures

• Wear eye protection when soldering.

•

Locate soldering iron in an area where you do not have to go around it or reach over it.

• Do not hold solder in your mouth. Solder contains lead and is a toxic substance. Wash your hands

thoroughly after handling solder.

• Be sure that there is adequate ventilation present.

Assemble Components

In all of the following assembly steps, the components must be installed on the top side of the PC board unless
otherwise indicated. The top legend shows where each component goes. The leads pass through the
corresponding holes in the board and are soldered on the foil side.

Use only rosin core solder of 63/37 alloy.
DO NOT USE ACID CORE SOLDER!

What Good Soldering Looks Like

A good solder connection should be bright, shiny,
smooth, and uniformly flowed over all surfaces.

1. Solder all components from
the copper foil side only.
Push the soldering iron tip
against both the lead and
the circuit board foil.

2. Apply a small amount of
solder to the iron tip. This
allows the heat to leave the
iron and onto the foil.
Immediately apply solder to
the opposite side of the
connection, away from the
iron. Allow the heated
component and the circuit
foil to melt the solder.

3. Allow the solder to flow
around the connection.
Then, remove the solder
and the iron and let the
connection cool.
solder should have flowed
smoothly and not lump
around the wire lead.

4.

Here is what a good solder
connection looks like.

The

Component Lead

Foil

Solder

Foil

Solder

Foil

Soldering Iron

Circuit Board

Soldering Iron

Soldering Iron

Types of Poor Soldering Connections

1. Insufficient heat - the

solder will not flow onto the
lead as shown.

2. Insufficient solder - let the

solder flow over the
connection until it is
covered. Use just enough
solder to cover the
connection.

3. Excessive solder - could

make connections that you
did not intend to between
adjacent foil areas or

.

minals

ter

4. Solder bridges - occur

een

ing

ag y

uns betw

our solder

when solder r
circuit paths and creates a
short circuit. This is usually
caused by using too much
solder. To correct this,
simply dr
iron across the solder
bridge as shown.

Rosin

Soldering iron positioned
incorrectly.

Solder

Component Lead

Solder

Soldering Iron

Foil

Dr

Gap

ag

-4-

ASSEMBLY INSTRUCTIONS FOR TRANSMITTER

Lug (see Figure A)

D2 - LED Transmitter Clear

(see Figure B)

S2 - Switch
R7 - 1kΩ 5% 1/4W Resistor

(brown-black-red-gold)

8-Pin IC Socket
U1 - 741CN

(see Figure G)

D1 - LED Red (see Figure C)

S1 - Switch
R2 - 10kΩ 5% 1/4W Resistor

(brown-black-orange-gold)

C1 - 1µF Electrolytic Capacitor

(see Figure D)

Figure A

Mount the lug as shown.

Lug

PC Board

Figure B

Bend the leads as shown. Mount the
LED transmitter with the flat side in the
direction shown below.

Figure D

Electrolytics have a polarity
marking indicating the (–)
lead. The PC board is
marked to show the lead
position.

Polarity

Mark

Q1 - 2N3904 NPN Transistor

(see Figure F)

C4 - .022µF (223) Capacitor
R5 - 10kΩ 5% 1/4W Resistor

brown-black-orange-gold)

(

C3 - 100pF (101) Capacitor
R6 - 100kΩ 5% 1/4W Resistor

(brown-black-yellow-gold)

R8 - 220Ω 5% 1/4W Resistor

(red-red-brown-gold)

R4 - 10kΩ 5% 1/4W Resistor

(brown-black-orange-gold)

C2 - .01µF (103) Capacitor

MIC - Microphone

(see Figure E)

R1 - 2.2kΩ 5% 1/4W Resistor
R3 - 2.2kΩ 5% 1/4W Resistor

(red-red-red-gold)

Figure E

You have received one of four different
types of microphones. If you have type A or
B, mount it with the leads in the correct
holes on the PC board. If you have type C
or D, then bend the leads as shown.

A

C

Flat

Figure C

Mount the LED with the flat side in the
same direction as marked on the top
legend.

Mount flush

with PC board

Flat

(–) (+)

Figure F

Mount the tr
in the correct direction
as mar

ked on the top

legend.

ansistor

Flat

-5-

B

Insert the IC socket
into the PC board
with the notch in the

.

wn on

k

Inser

direction sho
the top legend.
Solder the IC soc
into place
the IC into the

et with the

sock
notch in the same
direction as the
notch on the socket.

Figure G

Notch

et

t

Notch

Marking

D

IC

IC

Socket

PC Board

9V Battery Holder

Solder the 9V battery holder to pad
J1 and J2 in the correct position as
shown in the pictorial diagram.

Screws and Nuts

Mount the two screws in the position as shown in the
pictorial diagram. Place the nuts on the screws and
tighten them from the back side of the PC board.

To point marked
TP on PC board

TESTING PROCEDURE

1. Connect a 9 volt battery to the battery holder.

2. Switch S2 to the 1kHz position (toward LED D2)

and S1 on (toward LED D1). Observe that LED
D1 and D2 are on.

ou have a voltmeter, measure the DC voltage

3. If y

on pins 2, 3, and 6 of the IC. All of these voltages
should be 1/2 the battery voltage.

4. If you have an oscilloscope, connect it to test

point TP. Switch S2 in the 1kHz position (toward

QUIZ 1

1. The FO-30 Kit consists of three basic elements

that are found in every fiber optic link. They are
_____________, _____________, and
_____________.

2. The function of the transmitter is to convert an

_____________ signal into a _____________
signal.

3. The function of the fiber optic cable is to transmit

a _____________ signal from the transmitter to

.

the receiv
The receiv

4.

and con
signal.

er

er accepts a _____________ signal

ts it bac

er

v

k to an _____________

To point marked
GND on PC board

GND & TP - Test Point

LED D2) to place C4 in the circuit. You should
see a 6V peak-to-peak square wave of about
1kHz on the scope

5. Switch S2 to the mic position (to

.

ward the
battery), speak into the microphone and observe
your voice waveform on the scope.

If you experience any problems, see the
Troubleshooting Guide on page 20.

5. The microphone picks up a _____________
signal and converts it to an _____________
signal.

6. The gain of the LM-741 is equal to
_____________.

7. The DC output to the op-amp is _____________
volts.

8. The NPN transistor (3904) controls the
_____________ through the LED.

9. The LED (D1) indicated the state of the
_____________.

10. C2 filters out any _____________ that comes

through the v

oltage divider.

4. light, electrical; 5.voice, electrical; 6. IO; 7. 4.5; 8.current; 9. battery; 10.noise

Answers: 1. transmitter, fiber optic cable, receiver; 2. electrical, light; 3. light;

-6-

FIBER OPTICS

SECTION A

FIBER OPTICS AND ITS ADVANTAGES

The obvious questions concerning fiber optics are
these: Why go through all the trouble of converting
the signal to light and back? Why not just use wire?
The answers lie in the following advantages of fiber
optics.

a) Wide bandwidth
b) Low loss
c) Electromagnetic immunity
d) Light weight
e) Small size

f ) Safety

g) Security

Of all the above mentioned advantages, wide
bandwidth, low loss and electromagnetic immunity

eatures.

are probably the most impor

tant f

Bandwidth is an effective indication of the rate at
which inf

ormation can be sent.

Potential
information-carrying capacity increases with the
bandwidth of the transmission medium. From the

liest da

ear

ys of radio, useful tr

ansmission
frequencies have pushed upward five orders of
magnitude, from about 100kHz (100 x 10

3

Hz) to
about 10GHz (10 x 109Hz). Optical fibers have a
potential useful range to about 1THz (1 x 10
The infor
have only begun to be e

mation-carrying possibilities of fiber optics

xploited, whereas the same

12

Hz).

potentials of copper cable are pushing their limits.

o give perspective to the incredible capacity that

T
fibers are moving toward, a 10GHz (10 x 10
has ability to tr

ansmit any of the following per

9

) signal

second.

a) 1,000 books
b) 130,000 voice channels

Loss indicates how far the information can be sent.
As a signal travels along a transmission path, be it
copper or fiber, the signal loses strength. The loss
of strength is called attenuation. In a copper cable,
attenuation increases with frequency. The higher
the frequency of the information signal, the greater
the loss. In an optical fiber, attenuation is flat. Loss
is the same at any signaling frequency up until a
very high frequency. The combination of high
bandwidth and low loss has made the telephone
industry probably the heaviest user of fiber optics.

Unlike copper cables, optical fibers do not radiate or
pick-up electromagnetic radiation. Any copper
conductor acts like an antenna, either transmitting
or receiving energy. One piece of electronic
equipment can emit electromagnetic interf

erence
(EMI) that disrupts other equipment. Among
reported problems resulting from EMI are the

wing:

follo

• An electronic cash register interfered with

aeronautical transmissions at 113MHz.

• Coin-operated video games interfered with police

radio transmissions in the 42MHz band.

• Some personal computers tested b

y the Feder

al
Communications Commission (FCC) in 1979
emitted enough radiation to disrupt television
reception se

Since fibers do not r
electromagnetic energy

veral hundred feet away.

adiate or receive

, they make an ideal
transmission medium when EMI is a concern.
Furthermore, signals do not become distorted by
EMI in fiber. As a result, fiber offers very high
standards in error-free tr

ansmission.

4

4 The above paragraphs are reproduced by permission TECHNICIAN’S GUIDE TO FIBER OPTICS 2E (PAGES 24-29)

By Donald J Ster

ling, Jr

- DELMAR PUBLISHERS

.

-7-

., Albany, New York, Copyright 1993

, INC