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help me with this IR Transceiver

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burhanmz

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i am making a IR transmitter receiver for audio signal, for home use

in the transmitter part i removed the transformer and the voltage divider circuit and made the rest as such.. it works giving me 240mA for the IR LEDs from 12 volts regulated supply

in the receiver part, i used a BD139 instead of BEL187, and BC548 instead of BC549. the rest of the circuit is as such..

both the circuits work.. i tested them.. but the problem is the the range is no more than 6 cm.. and i getting a very low volume of sound at the receiving end...
whats wrong with it.. how can i increase the range as well as the amplification of the received signal?
 

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Nigel Goodwin

Super Moderator
Most Helpful Member
Sorry, but the entire thing is absolutely rubbish - it pops up here time and time again, and never works - for one thing the transmitter rectifies the incoming audio!.
 

burhanmz

Member
but if it were rectifying the signal... then i shouldn't get any audio on the receiver end .. but thats not so. i am getting a very low audio signal..
 

burhanmz

Member
in my first post, when said i had removed the voltage divider, i forgot to mention that i fixed biased it with 2.2kohms at Rb and connected parallel to Rc of 100ohms..

but my problem isn't the transmitter .. its the receiver...
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Then check it with a scope, but there's really not a great deal of gain in the receiver, and the transmitter doesn't provide very much output as it's continuous carrier, so you can't pulse the LED's at high current like remote controls do.
 

burhanmz

Member
thats exactly wht i am asking... how to increase the gain of the receiver... because when i tried to use a pre-amp audio amplifier with TDA2030, the signal stays as such,, but it works on other direct audio signals.
 

burhanmz

Member
how about if i use a 555 as a VCO at transmitting and receiving ... with carrier frequency.. so that the audio is frequency modulated.. i can then control the duty cycle,.... would it work then?
 

Nigel Goodwin

Super Moderator
Most Helpful Member
how about if i use a 555 as a VCO at transmitting and receiving ... with carrier frequency.. so that the audio is frequency modulated.. i can then control the duty cycle,.... would it work then?
A 555 is a pretty poor VCO anyway, and you're indroducing further complications.

If you want to go FM, then look at the 4046 PLL chip, a much better VCO in that.
 

burhanmz

Member
thanks for the suggestion.. i'll try it first then if the results are satisfying, i'll post the improved circuit diagram..
 
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