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Transmitting voice over a light beam.

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New Member
I came accross this project which is supposed to enable transmission of voice over a light beam. The list of devices used:

Here is a list of the parts needed for this project

1-audio output transformer
1- 14k ohm resistor
1- 220k ohm resistor
2-1n914 diodes
2-2n3904 transistor
1-2n3906 transistor
1-8 ohm speaker
1-infrared led
1-photo transistor
1-1 Meg potentiometer
1-500k potentiometer
3-741 Op-amps
2-1 micro farad capacitors
1-10 micro farad capacitor
9-10k ohm resistors
2-470k ohm resistors

Anyway, what really baffled me was the circuit diagrams. There is one for the reciever and one for the transmitter.
- reciever circuit diag.
- transmitter circuit diag.

Judging from the components used and the circuit diagrams, is there anyway anyone could tell me some useful info such as the range of transmission, the average cost of the items to be used... and last but surely not least a small guide if possible on how to construct such a thing. (Would it work?> lol).
Please reply, I need this for a project for my school... any help gr8ly appreciated. Thanx!


Active Member
I think this circuit only for demo, range max. 1...2meter (maybe in dark),LM741 output to 8ohm transformer no lucky...


New Member
why dont u try some modulation for the light, because i think u would pick up much noise, ffrom about everything... :?
and for improoving the range, wich i think it wouldnt exeed a few meters, try to put more leds for the transmitter....


New Member
True what bogdanfirst said. Taking in the schematic you found again on the reciever, it doesn't seem to have and IF's. Thus, taking into consideration what Sebi said about using it in the dark. To reduce interference. You could improve that circuit by finding out the frequency coming into the reciever in the dark, and then try to use IFs to block any unwanted noise if you use it in the light.
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