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27929RES: [SeattleRobotics] Re: Sensing Lasers..

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  • Pedro Drummond
    Jun 2, 2006
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      >The application actually requires sensing the laser from about 1 m and that
      >is the reason behind using a laser instead of ir led.

      I'm not sure I understand this, but do you mean 1m is too much for IR? I
      have seen homemade IR links (lens-less) up to 10m, and up to 20m using
      lenses. Our TV remote has a better range than 1m.

      --- In SeattleRobotics@yahoogroups.com, Alan King <alan@...> wrote:
      > 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
      > 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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