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IR detector — Parallax Forums

IR detector

LuNaTeeQLuNaTeeQ Posts: 1
edited 2007-12-10 14:41 in Robotics
Heey all,

I was doing some test with the LED infrared transmitters and receivers and i stumbled upon something funny:·when you put the frequency of·FREQOUT up a notch towards 64000 for example, the detector doesn't detect a piece of (black) rubber, but does detect a tiny piece of metal. Does anyone know the exact explanation for this situation. I think it has got someting to do with or the color black or the bandpass filter of the IR detector. If any has a proper explanation·would·I be truly grateful, i can't figure it out. There aren't any proper specs about the detector.

Much thanks

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2007-12-10 14:41
    The number used with FREQOUT is only valid to 32767. It effectively wraps around at 32768, so 65535 produces a frequency of 32767Hz. What you're seeing is probably a combination of the bandpass filter of the IR detector and the different reflectivities of the two materials at IR wavelengths. I would expect the metal to be highly reflective as it is in visible light. The rubber is probably absorbent as it is in visible light, but that's not always true of materials.
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