17-03-2011, 11:25 AM
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OBJECTIVES:-
To Design a circuit of an electronic infrared communication system.
Develop new ideas to implement this circuit purposely.
To study the circuitry and different types of components & DTMF generator, DTMF decoder, op-amp and infrared-LED in the circuit.
INTRODUCTION
For years, infrared LED has been merely a system for piping light around corners and into the inaccessible places to allow the hidden to be lighted. But now, infrared LED has evolved into a system of significantly greater importance and use. Throughout the world, it is now being used to transmit voice, television and data signals as light waves. Its advantages as compared with conventional coaxial cable or twisted wire pairs are manifold. As a result, millions of dollars are being spent to put these light wave communication systems into operation.
One of the most interesting developments in recent years in the field of telecommunication is the use of laser light to carry information over large distances. It has been proved in the past decade that light wave transmission through laser light is superior to that achieved through wires and microwave links. Typically, infrared LED has a much lower transmission loss per unit length (0.15-5db/km) and is not susceptible to electromagnetic interference. Economically also, it serves our purpose. The ever increasing cost and the lack of space available in the congested metropolitan cities asks for advent of a less costly system.
The conventional telephonic systems use copper wires, which easily get oxidized and as such require high maintenance cost. The laser light being made of glass are non-reactive and hence economical. Also, the noise pick up by the copper wire or in electrical signals is quite substantial whereas in laser light, the noise pick up is negligible.
Basic elements of a infrared LED system
Applications
(i) Applications for video transmission include high quality video Trunked from studio Transferee, Broadcast CATV video, Video Trunking within city or between cities, Baseband Video for closed.
CONSTRUCTION AND WORKING
MIKE: Its converts sound signals into electrical signals.
AMPLIFIER (A): Signals from mike are amplified so that it can drive to infrared-LED.
INFRARED-LED: It carries signals.
PHOTO TRANSISTOR: The electrical signals are regained from the optical signals.
AMPLIFIER (B): Energy of signals is amplified to drive the speaker.
SPEAKER: Electrical signals which are amplified are reconverted into sound signals at the speaker.
DTMF CODER: It is generates the DTMF signal corresponding to the number entered from the keyboard.
DTMF DECODER : It is fed to DTMF decoder which gives the binary output corresponding to the signal received from the transmitter.
DECODER DRIVER : To drive the 7 segment display.