Elenco Fiber Optics Voice and Data Kit User Manual

FIBER OPTICS KIT

MODEL FO-30K

Assembly and Instruction Manual

Copyright © 2012, 1994 by ELENCO®All rights reserved. Revised 2012 REV-U 753259

No part of this book shall be reproduced by any means; electronic, photocopying, or otherwise without written permission from the publisher.

ELENCO

®

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

-1-

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

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.

TRANSMITTER RECEIVERFIBER OPTIC CABLE

DRIVER

SOURCE

DETECTOR

OUTPUT
CIRCUIT

IDENTIFYING RESISTOR VALUES

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

IDENTIFYING CAPACITOR VALUES

Capacitors will be identified by their capacitance value in pF
(picofarads), nF (nanofarads), or μF (microfarads). Most capacitors
will have their actual value printed on them. Some capacitors may
have their value printed in the following manner.

For the No.01234589

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

Multiplier

1 2 Multiplier

Tolerance

BANDS

Second Digit

First Digit

Multiplier

Tolerance

103K

100V

Maximum
Working Voltage

The value is 10 x 1,000 = 10,000pF or
.01μF, ±10%, 100V

The letter M indicates a tolerance of +20%
The letter K indicates a tolerance of +10%
The letter J indicates a tolerance of +

5%

Note:

The letter “R” may be used at times

to signify a decimal point; as in 3R3 = 3.3

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

Electrolytic capacitors have a
positive and a negative electrode.
The negative lead is indicated on
the packaging by a stripe with
minus signs and possibly
arrowheads.

Warning:

If the capacitor is
connected with
incorrect polarity, it
may heat up and
either leak, or
cause the capacitor
to explode.

Polarity
Marking

(+)

(–)

Qty. Description Part #

r 1 PC Board 519015A
r 2 Switch 541103
r 1 Microphone 568000
r 1 Battery Holder 590096
r 2 Screw 2-56 x 1/4” 641230
r 2 Nut 2-56 644201

Qty. Description Part #

r 1 Lug 661106
r 1 IC Socket 8-Pin 664008
r 2 Test Pins 665008
r 1 Polishing Paper #400 735005
r 3’ Fiber Optic Cable 810020
r 1 Lead-free Solder Tube 9LF99

TRANSMITTER SECTION

PARTS LIST

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

®

(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 #

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

CAPACITORS

Qty. Symbol Value Description Part #

r 1 C3 100pF (101) Discap 221017
r 1C2 .01μF (103) Discap 241031
r 1 C4 .022μF (223) Mylar 242217
r 1C1 1μF Electrolytic 261047

SEMICONDUCTORS

Qty. Symbol Value Description Part #

r 1 Q1 2N3904 Transistor NPN 323904
r 1 U1 LM741 Integrated Circuit 331741
r 1 D1 LED Red 350002
r 1 D2 LED Transmitter Clear 350005

MISCELLANEOUS

-2-

PARTS IDENTIFICATION

Resistor Capacitors

Electrolytic

Discap

Transistor

Red

Integrated Circuit IC Socket Switch

Lug

LEDs

Microphone

Mylar

Transmitter

Battery Holder Test Pin

-3-

SCHEMATIC DIAGRAM

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 op-amp, 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.

Figure 1A

-4-

CONSTRUCTION

Solder

Soldering Iron

Foil

Solder

Soldering Iron

Foil

Component Lead

Soldering Iron

Circuit Board

Foil

Rosin

Soldering iron positioned
incorrectly.

Solder

Gap

Component Lead

Solder

Soldering Iron

Drag

Foil

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.

1. Insufficient heat - the solder will
not flow onto the lead as shown.

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

4.

Here is what a good solder
connection looks like.

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 terminals.

4. Solder bridges - occur when
solder runs between circuit paths
and creates a short circuit. This is
usually caused by using too much
solder.
To correct this, simply drag your
soldering iron across the solder
bridge as shown.

What Good Soldering Looks Like

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

Types of Poor Soldering Connections

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 watts is
recommended. The tip of the iron must be kept clean at all times and

well tinned.

Solder

For many years leaded solder was the most common type of solder
used by the electronics industry, but it is now being replaced by lead­free solder for health reasons. This kit contains lead-free solder, which
contains 99.3% tin, 0.7% copper, and has a rosin-flux core.

Lead-free solder is different from lead solder: It has a higher melting
point than lead solder, so you need higher temperature for the solder to
flow properly. Recommended tip temperature is approximately 700

O

F;
higher temperatures improve solder flow but accelerate tip decay. An
increase in soldering time may be required to achieve good results.
Soldering iron tips wear out faster since lead-free solders are more
corrosive and the higher soldering temperatures accelerate corrosion,
so proper tip care is important. The solder joint finish will look slightly
duller with lead-free solders.

Use these procedures to increase the life of your soldering iron tip when
using lead-free solder:

• Keep the iron tinned at all times.

• Use the correct tip size for best heat transfer. The conical tip is the
most commonly used.

• Turn off iron when not in use or reduce temperature setting when
using a soldering station.

•

Tips should be cleaned frequently to remove oxidation before it becomes
impossible to remove. Use Dry Tip Cleaner (Elenco

®

#SH-1025) or Tip
Cleaner (Elenco®#TTC1). If you use a sponge to clean your tip, then use
distilled water (tap water has impurities that accelerate corrosion).

Safety Procedures

• Always wear safety glasses or safety goggles to
protect your eyes when working with tools or
soldering iron, and during all phases of testing.

• Be sure there is adequate ventilation when soldering.

•

Locate soldering iron in an area where you do not have to go around
it or reach over it. Keep it in a safe area away from the reach of
children.

• Do not hold solder in your mouth. Solder is a toxic substance.
Wash hands thoroughly after handling solder.

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.

DO NOT USE ACID CORE SOLDER!

'

Figure D

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

Warning: If the capacitor is
connected with incorrect polarity,
it may heat up and either leak or
cause the capacitor to explode.

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.

ASSEMBLY INSTRUCTIONS FOR TRANSMITTER

-5-

Figure A

Mount the lug as shown.

Figure B

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

Figure C

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

Figure F

Mount the transistor in the
correct direction as marked on
the top legend.

Figure G

Insert the IC socket
into the PC board
with the notch in the
direction shown on
the top legend.
Solder the IC socket
into place. Insert
the IC into the
socket with the
notch in the same
direction as the
notch on the socket.

A

B

C

D

Mount flush

with PC board

Flat

Lug

PC Board

Flat

Flat

(–) (+)

Polarity

Mark

IC

IC

Socket

PC Board

Notch

Notch

Marking

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)

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)

-6-

TESTING PROCEDURE

QUIZ 1

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

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

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.

3. If you have a voltmeter, measure the DC voltage
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

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 (toward 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.

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 receiver.

4. The receiver accepts a _____________ signal
and converts it back to an _____________
signal.

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 voltage divider.

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.

9V Battery Holder

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

To point marked
TP on PC board

GND & TP - Test Point

To point marked
GND on PC board

FIBER OPTICS

FIBER OPTICS AND ITS ADVANTAGES

SECTION A

-7-

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
are probably the most important features.

Bandwidth is an effective indication of the rate at
which information can be sent. Potential
information-carrying capacity increases with the
bandwidth of the transmission medium. From the
earliest days of radio, useful transmission
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 1012Hz).
The information-carrying possibilities of fiber optics
have only begun to be exploited, whereas the same
potentials of copper cable are pushing their limits. To
give perspective to the incredible capacity that fibers
are moving toward, a 10GHz (10 x 10

9

) signal has

ability to transmit any of the following per 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 interference
(EMI) that disrupts other equipment. Among
reported problems resulting from EMI are the
following:

• 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 by the Federal
Communications Commission (FCC) in 1979
emitted enough radiation to disrupt television
reception several hundred feet away.

Since fibers do not radiate or receive
electromagnetic energy, 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 transmission.

4

4

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

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