21-07-2011, 10:59 AM
Presented by:
JISHNU SEBASTIAN
JITHIN CHERIYAN.V
JIYO JOSE
JOSEPH K ROY
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LASER TORCH-BASED VOICE TRANSMITTER AND RECEIVER
INTRODUCTION
LASER COMMUNICATION
Less problem of interference
High deal of secrecy
Viable alternative to RF communication
High data rate ,small antenna size , narrow beam divergence
Laser act as carrier for voice signal
Wireless, open channel system
Light up to a distance of 300mtr
Photo transmitter accurately oriented
BLOCK DIAGRAM
BLOCK DIAGRAM EXPLANATION
Capacitor or electrostatics microphone
Store energy in the form of electric field
More sensitive ,responsive and well suited to subtle nuances in sound
Change the distance between plate when diaphragm vibrates
Charge current due to increase in capacitance & trigger transmitting section
b) TRANSMITTING SECTION
Consist of pre amplifier , op-amp ,VR, heat sink and laser diode
Increasing the voltage at VR1 reduces laser current
Laser diode need a threshold current
Laser beam is amplitude modulated
Out put power VS current is linear
VR1 determines quiescent brightness and over all sensitivity
c) LASER TORCH
Laser medium for transmission
Transfer of data high rate
Similar to fiber optic cable system
Operate near infrared region of the spectrum
Wave length of between 780-920nm
d) RECEIVING SECTION
Consist of photo detector , common emitter amplifier, audio power amplifier and loud speaker
Photo detector pick up transmitter signal
Amplification with gain 20
Basic power amplifier with gain of 20 drives the speaker
e) LOUD SPEAKER
Transducer ,convert electrical signal into sound .
Paper cone moves in accordance with electrical signal
TRANSMITTER
RECEIVER
WORKING
Condenser microphone covert sound signal into electrical signal
Transistor BC 548 amplify the electrical signal
IC 741 act as a volume control
VR1 determines the current intensity
Heat sink absorb noise in the signal
Laser –amplitude modulated
RECEIVER SECTION
Phototransistor detect laser light
Amplification by CE amplifier
VR2 connect the output to LM386
Power amplifier has a gain of 20
Power amplifier drives the speaker
ADVANTAGES
Less costly
Circuit can be easily constructed
High data rate
No communication licenses required.
The laser transmission is very secure because it has a narrow beam.
There are no recurring line costs.
Compatibility with copper or fiber interfaces and no bridge or router requirements.
Lasers can also transmit through glass, however the physical properties of the
glass have to be considered.
Narrow beam divergence
Laser transmitter and receiver units ensure easy, straightforward
systems alignment and long-term stable, service free operation,
especially in inaccessible environments, optical wireless systems
offer ideal, economical alternative to expensive leased lines for
buildings.
DISADVANTAGES
To avoid 50Hz hum noise in the speaker, keep the phototransistor away from AC light sources such as bulbs. The reflected sunlight, however, does not cause any problem. But the sensor should not directly face the sun.
APPLICATIONS
Using this circuit we can communicate with our neighbors wirelessly
It can be used in inaccessible areas.
In future it can be commissioned in satellites for communication.
It can be used in conference halls.
FUTURE EXPANSION
Instead of the short range laser, high range lasers can be used which range a few hundred meters.
Provisions have to be made for cases when there is no heavy traffic.
CONCLUSION
After the successful working of the project , it can be concluded that this project is suitable for easily communication .
There can be further up gradations in the project which could lead to a much better system for communication.
Instead of the short range laser, high range lasers can be used which range a few hundred meters.
Provisions have to be made for cases when there is no heavy traffic.
