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27924Re: [SeattleRobotics] Sensing Lasers..

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  • Alan King
    Jun 1, 2006
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      Mustafa wrote:

      >Hi everyone..
      >
      >I am making a circuit for sensing laser modulated at a frequency of
      >10kHz. I tried using phototransistors and photodiodes to sense the
      >laser, but both are unable to give sufficient response for laser. the
      >photodiode circuit works fine with ired, but does not show any change
      >in output with laser.. Does anyone know what can be used to solve the
      >problem? The laser used is a small ordinary one available from
      >road-side vendors.
      >
      >
      >


      Look at the beam angle and sensitivity. Lasers put out very little
      light except down the beam, unless your spot is right on the detector
      you won't see much of anything. Get one that has changable lenses and
      spread it out, or if you need long distances get the spot on the
      detector. If you've already got the spot on the detector, you may be
      just swamping out the detector, with so much light coming in it may just
      not be turning off at all. If it's working with the relatively low
      amount from an IR LED it may be way too sensitive for a direct laser
      beam.. Also, working with IR LED? Cheap red laser pointer? If it has
      a dark IR filter you may not be getting much of anything to the sensor
      at all if you're using the same sensor. Of course if you've tried
      several then most likely at least one or two were clear enough.

      Alan
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