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Optical Theremin - Photocell Question

  1. Sep 3, 2009 #1
    I was endeavouring to build the (almost, at least) Theremin on this page:

    However, I was wondering what kind of resistance the photocells should have. I suppose I could work up a better abstract understanding of the circuit and make an educated guess - which would be my ultimate goal - however, I would like the build it first.

    Oh, and thanks for any response!
  2. jcsd
  3. Sep 3, 2009 #2


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    Pretty much any CdS cell will work. These range from the high-kOhm to the low MOhm range in total darkness to a few ohms in bright light.
  4. Sep 4, 2009 #3


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    They are often sold now as "light dependent resistors" too. Same thing, new name.

    They are not the same as phototransistors or photodiodes though. These may work but will not have the range of resistance levels that a CdS cell will have.
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