can ir be discriminated based on frequency

Thread Starter

scottm1306

Joined Apr 13, 2009
2
i want to buid and ir transmiter and receiver. Because of size and cost of building 100's I dont know if i want to use an encoder/decoder chip.
Can a circuit for RECIEIVER be built that would discriminate frequency? in other words if its say 38kHz receiver says ok I Like you. if its Higher, say 39kHz receiver ignores signal. I found a receiver circuit that displays frequency on a meter in amps. any ideas if its possible? I want to make about 8 dif. transmiters (1 freq each)
Thanks,
Scott
 

thatoneguy

Joined Feb 19, 2009
6,359
Yes, a few "cable boxes" use a 120kHz carrier instead of a 38kHz.

The only issue is aliasing/intermodulation, e.g. a 1/4th of code at 120kHz matches a 38kHz code in use. Similar to the Nyquist Limit in DAC sampling.
 

beenthere

Joined Apr 20, 2004
15,819
If each transmitter sends an identifier or address word along with the data, that might clear up your source of confusion.
 

beenthere

Joined Apr 20, 2004
15,819
Say you place an eight section DIP switch in with each transmitter. That can allow you to set a code of 00000000 up to 11111111 that can be appended as the first data sent.

That won't need an encoder, but the receiver will have to have some smarts to read the addresses. You were probably going to use a microcontroller, so that should be no problem.

That way, everybody can use the same frequency - if you can keep the transmitters from stepping on each other's data.
 
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