LASER TORCH-BASED VOICE TRANSMITTER AND RECEIVER GROUP MEMBERS JISHNU SEBASTIAN CTAIEAE014 JITHIN CHERIYAN.V CTAIEAE015 JIYO JOSE CTAIEAE016 JOSEPH K ROY CTAIEAE017

INTRODUCTION LASER COMMUNICATION a)Less problem of interference b)High deal of secrecy c)Viable alternative to RF communication d)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 a) CONDENSER MIC

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 nm

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 I

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 TRANSMITTER SECTION

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 speake r

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 1.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.