Optical Fiber Voice Link Kit
Student self assembly instruction and
Bill of materials
This manual is available for download at
http://www.labtech.com.hk/index_topic.php?did=162489&didpath=/152483/162489
Optical Fiber Voice Link Kit
The Kit consists of two modules, the transmission Module and the Receiver Module.
It allows you to either to send your voice, or signal from a given FM radio, through an
industrial optical fiber optic cable from the transmission module to the receiver
module.
One Meter of Optical Fiber is included, and good reception of voice can be made for
fiber over 200 meters long.
FM radio is optional and sold separately
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Circuit Description:
The circuits for the Transmission Module and the Receiver Module are depicted as in
diagram one
Diagram 1. Circuit for the Optical Fibre Transmission and Receiver Module
In the transmission circuit, the microphone picks up your voice and send it to one
of the operational amplifiers in LM358 for amplification, the signal is further
amplified by the other half of the LM358 and finally the signal is used to drive a super
bright LED with Transistor BC547 . The Intensity of the LED is modulated by the
voice signal and is sent through the optical fiber to the receiver module.
When an electrical voice signal from an FM radio (sold separately) is fed to the
transmission module, the phone socket have its switch off for the microphone signal
and gives way to the electrical signal, normally, the voice signal from an commercial
radio would be too strong so that they are attenuated by an factor of about 20 before
they are again amplifier as before.
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The receiver module aims to convert the intensity modulated light signal which
carries the sound to the corresponding sound signal in electrical form.
The work is done by the photo transistor and the sound signal is amplified by
preamplifier made by 1/2 of LM358 and further driven for power using audio IC
LM386n. Volume Control is by means of trim pot VR1.
Tools and Assembly Instruction.
To assemble the kit, you will need a soldering iron of about 40W, a nice wire
cutter to cut away extruded components leads , a pliers for fixing the the 4mm socket
and a small screw driver with a cross head.
Study package List for the Transmission and receiver Module and see if there is
any missing item.
Start off with soldering the resistor first, check with the component list for the
colour coding of the resistor.
You can then start with the rest of the components in whatever order you like.
Finally, Fix the Optical Fibre Connector with a small screwdriver with cross heads
using the supplied M2 screws and tape the rubber feet on to the corners of the circuit
board. At last, insert the IC into the respective sockets, make sure you observe
polarity or orientation for the components as follows:
1) Tantalum or electrolytic capacitor
2) Transistor, microphones.
The components which do not need specific orientation are mono capacitor (103
and 104), resistors.
Then solder the IC into the circuit board. It would be advantageous to solder
one pin first, and try to alight the socket to the base of the circuit board, then solder
the remaining pins of the IC socket.
Make sure the direction of the IC is correct !!!!!!!!
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Circuit Testing
Once the two circuit boards are completed, you will need to prepare a
loudspeaker for trying the circuit. A big loudspeaker as found in most school
laboratory would be an ideal for very much better sound quality. However, you can
solder the UL wires to the given 1W loudspeaker with the connections made to the
given two 4mm plugs.
Insert the optical fibers on the fiber connectors and insert battery, speak to the
microphone and you will hear voice coming out from the receiver module.
If the circuit does not work, check for poor soldering. This is the most common
mistake, and also check for component values for the layout.
Additional Instruction Sheet can be downloaded at
URL://http:www.labtech.com.hk
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Optical Fibre Communication Kit
Package List for transmitter Module
Resistors
5% 1/4 W:
R1
R2
22 K
100 K
Red Red Orange
Brown Black Yellow
R5
R6
100 Ohm
100 Ohm
R3
R4
10 K
680 K
Brown Black Orange
Blue Grey Yellow
R7
R8
R9
1K
1 Ohm
15 Ohm
Brown Black Brown
Brown Black Brown
Brown Black Red
Brown Black
Brown Green Black
Capacitor :
C1
C2
0.1 uF Mono Cap
0.01 uF Mono Cap
(104)
(103)
C3
0.01 uF Mono Cap
(103)
Semi-conductors :
IC1 :
LM358
x1
Transistor :
x1
BC547
Miscellaneous Items :
Super Bright LED
9V battery Holder
3.5mm Mono Socket
Fiber Optics Connector
M2 screw nuts
x 1 PCS
x 1 PCS
x 1 PCS
x 1 PCS
x 3 PCS
Optical Fiber
x 1 meter
Condenser Microphone
3M Rubber Feet
x 1 PCS
x 4 PCS
M2x 6 screw
Circuit Board
x 5 PCS
x 1 PCS
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Optical Fiber Communication ,Receiver Module
Package List
Resistors 1/4W , 5%
R11
R12
220K
100K
red red yellow
brown black yellow
R14
R15
100K
1M
brown black yellow
Brown black green
R13
10 K
brown black orange
R16
100K
brown black yellow
POT
100K trim pot for volume control x 1 PCS
Capacitors
C11
10 uF electrolytic Capacitor
C16
0.1uF Mono cap (104)
C12
C13
C14
C15
0.1uF Mono cap (104)
0.1uF Mono cap (104)
0.1uF Mono Cap(104)
10uF electrolytic Capacitor
C17
C18
C19
C20
100 uF Electrolytic cap
0.01uF Mono cap (103)
0.1uF Mono Cap (104)
0.1uF Mono Cap (104)
ICs & Semiconductors :
Photo Transistor CL138-2
U11
LM78L05
x1
x1
U12
U13
x1
x1
LM358
LM386
Miscellaneous Items
9V Battery Holder
x1
Aluminum Fiber Optic Connector
x 1 PCS
M2x6 screw
M2 screw nuts
x 5 PCS
x 3 PCS
3M Rubber Feet
Loudspeaker
Length of Wire
Printed Circuit Board
x 4 PCS
x 1 PCS
x 2 lengths
x 1 PCS
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