can ir be discriminated based on frequency

Discussion in 'General Electronics Chat' started by scottm1306, Apr 15, 2009.

  1. scottm1306

    Thread Starter New Member

    Apr 13, 2009
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    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
     
  2. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    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.
     
  3. beenthere

    Retired Moderator

    Apr 20, 2004
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    If each transmitter sends an identifier or address word along with the data, that might clear up your source of confusion.
     
  4. scottm1306

    Thread Starter New Member

    Apr 13, 2009
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    would that mean i have to use a encoder and decoder?
     
  5. beenthere

    Retired Moderator

    Apr 20, 2004
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    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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