There’s something rather futuristic about talking ‘over’ a laser beam, which is what this inexpensive project allows. It will easily give a communication distance of several hundred metres, and with a parabolic light reflector, up to several kilometres. It transmits high quality audio and the link is virtually impossible for anyone else to tap into.
So clearly, this project is ideal for setting up a speech channel between two areas, say adjacent houses, or offices on opposite sides of the street. Or you could use it as a link between the work shop and the house. For duplex (two way) communication, you’ll obviously need two laser ‘channels’.
An important feature of transmission by laser beam is privacy. Because a laser beam is intentionally narrow, it’s virtually impossible for someone to tap into the link without you knowing. If someone intercepts the beam, the link is broken, signalling the interception. Fibre-optic cables also have high security, as it’s very difficult to splice into the cable without breaking the link. However it’s theoretically possible; so for the highest security, you probably can’t beat a line-of-sight laser beam.
You can also use an infrared laser. While this gives even better security, as you can’t see the laser beam without special IR sensitive equipment, it also makes alignment more difficult.
Main component of this project is laser diode. A laser diode needs a certain value of current, called the threshold current, before it emits laser light. A further increase in this current produces a greater light output. The relationship between output power and current in a laser diode is very linear, once the current is above the threshold, giving a low distortion when the beam is amplitude modulated. For example, the 65Onm 5mW laser diode used in this project has a typical threshold current of 3OmA and produces its full output when the current is raised by approximately 1OmA above the threshold to 4OmA. Further increasing the current will greatly reduce the life of the laser diode, and exceeding the absolute maximum of 8OmA will destroy it instantly. Laser diodes are very fragile and will not survive electrostatic discharges and momentary surges!
In this project we transmit two type of data from the circuit. One is analogue data and second is dtmf data . In the analogue data we transfer the data from the mike and this sound is transmit through the laser and then receive on the speaker at the other side.
In dtmf mode we use one 12 key as a input keyboard in the circuit and when we press any number then this data is available on the other end and display on the seven segment display.
In addition of these two signal we also applied a signal from the mobile phone and we follow the same process of transfer the data in the from of sound and numeric data from the keypad of the mobile phone.
Transformer 9v 500mA
LASER he-Ne 5mm
IC74154
IC4049
IC7447
Seven segment display
Ic 741
IC 7805
Diode
IC 91214
Ic8870
Optical fiber
Resistances- 10k,1k,4.7k,220k
Capacitors- 0.1microfarad,00.1 microfarad,1000µf,470µf
Cupper clad board
Software Required:-
Window os
OrCAD
MS word
Applications:-
Ø Networking between Computers.
Ø Data downloading from PC to Mobile & vice versa
Ø Communication between Buildings
Ø For Security purposes- To protect house or lockers
Ø For Military equipments- To find the target
Ø For Medical machines- treatment of stone problem
Ø For lightening purpose in sky
Ø For Cutting of Glass or hard sheets
Ø For controlling devices – Switch on/off
Ø For Remote purpose
