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How to detect coloured strips digitall?

  1. Sep 17, 2011 #1
    how to detect coloured strips digitall???

    hi, how can i detect colored(red) strip of tape. This is required so that I can digitally count the no of rotations of a flywheell.

    the thing is, the flywheel attached to the wall has a small red strip on its wheel. i need a sensor to detect that red strip as the flywheel rotates so that it can input data to the digital counter which counts those rotations.

    so how can i use to detect red colored strip ..
    plz thanx
    Last edited: Sep 17, 2011
  2. jcsd
  3. Sep 18, 2011 #2


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    Re: how to detect coloured strips digitall???

    Welcome to PhysicsForums!

    If there's a little red dot somewhere near the outside edge of this flywheel, you might be able to detect it using a sensor placed on the same circumference which utilizes some of the ideas here at the Society of Robotics:

    Now, if you can replace that red piece of tape with a piece of shiny aluminum foil (and assuming the room's dark) you can use a laser pointer (or laser diode) and photodiode to detect the reflected light (once per revolution). If the whole flywheel happens to be quite reflective, placing some dark fabric tape (or some matte black paint, or something similar) would allow you to detect the absence of reflected laser light whenever the patch crosses the sensor and absorbs the laser light.
  4. Sep 18, 2011 #3
    Re: how to detect coloured strips digitall???

    Thanks :d
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