[Homework] Resonance and capacitor values.

[Bill Bowden]

  You have back ground IR to worry about, sun light contributes to ~50%
of IR out side. Being inside you have other sources that can saturate
the detector.

   If you put a detector in operation in a linear state, you can see a
lot of this noise on the scope. If you have a scope with FFT on it you
can also locate or should be able to, signals from a remote.

   I suppose one could make a regenerative oscillator with the IR
detector element as part of the circuit in the gain loop.

Jamie

Yes, noise is a problem and generates false responses. But I've
noticed most all IR remotes use error correction where part or all of
the transmission is repeated. The Phillips RC5 format for example
sends the entire message twice separated by 100 milliseconds. So, if
you compare the first message to the second, most all errors are
eliminated. But I've often wondered how the automatic doors that
detect IR work to eliminate false responses? They must use some sort
of error correction.

-Bill