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Maximum (cutoff) freq for a photoresistor

  1. Apr 27, 2015 #1

    I am working on a project where I want to use a photoresistor to measure displacement, by reflecting light off of a small component and measuring the light that is reflected. the goal is to measure vibration.

    I am having a hard time finding information on the cutoff frequencies of photoresistors, possibly because I do not fully understand their operation.

    Can anyone shed some insight on this?

  2. jcsd
  3. Apr 27, 2015 #2


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    Citing from http://en.wikipedia.org/wiki/Photoresistor : "Photoresistors also exhibit a certain degree of latency between exposure to light and the subsequent decrease in resistance, usually around 10 milliseconds. The lag time when going from lit to dark environments is even greater, often as long as one second. This property makes them unsuitable for sensing rapidly flashing lights, but is sometimes used to smooth the response of audio signal compression."
  4. Apr 27, 2015 #3
    Simply instead of a photo resistorplease use a phototransistor /photodiode.
  5. Apr 28, 2015 #4
    Thanks - Ill try that out.
  6. Apr 29, 2015 #5


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