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photo diode spectral acceptance

I couldn't find this info anywhere.  What nanometer range of IR light will the photo diode register pulse rates?  I have a 904nm IR source that I want to decode.  Will this photo diode accept light in that spectral range?

 

Re: photo diode spectral acceptance

Reply #1
[quote author="pulsereader"]I couldn't find this info anywhere.  What nanometer range of IR light will the photo diode register pulse rates?  I have a 904nm IR source that I want to decode.  Will this photo diode accept light in that spectral range?[/quote]

The datasheet for the QSE159 detector is available here:

http://www.fairchildsemi.com/ds/QS/QSE159.pdf

There you can see that they spec this device for use at 880nm wavelength.  Fortunately, 904nm is very close and since it would be difficult indeed to design a sensor that picks up 880nm but rejects 904nm, we can assume that it will be sensitive to 904nm.  I doubt there will even be any drop in sensitivity compared to 880nm wavelength.  Keep in mind that there is currently no method implemented to get the actual raw output of the sensor out of the IRToy.  The QSE159 is used mostly to determine the modulation frequency and the demodulated envelope timing comes from the other sensor.  If you're planning to use this device for something other than record-playback of consumer infrared remote control signals, you're going to be very disappointed, as the IRToy is very much purpose-built for that one function and it can't do much of anything else.  You can get a little closer to raw by flashing the widget FW, as that will do actual raw pulse counting/timing vs the simple demod timing of the standard FW, but even then, it makes many assumptions about the signal that limit its usefulness to consumer IR remote control signals.

The demod sensor Vishay TSOP34838 peak sensitivity is at 950nm as you can see from the datasheet:

http://www.vishay.com/docs/82489/tsop322.pdf

It still maintains more than 80% sensitivity at 904nm.