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Basic filtering circuit maybe?

  1. Sep 8, 2007 #1
    i wanna build one of these

    http://funditor.110mb.com/LaserListener.html [Broken]

    but he alludes to some kind of circuit at the end that could filter out the noise using analog components and i'm thinking it's some kind of low pass filter. am i right? i really only have a little electronics knowledge? i guess i need something called a preamp too? note i'm not malicious or anything i just think it would be a fun little project.

    basically i want it to be portable cause i don't have a laptop
    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. Sep 9, 2007 #2


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    Don't bother. I can't believe the author has actually built that. A CDS cell (cadmium sulfide) does not have a fast enough response time to actually be useful with audio.
  4. Sep 9, 2007 #3
    :( really ? that's exactly the kind of photocell i bought, what kind can i use?
  5. Sep 10, 2007 #4


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    A cheap CDS cell has a response time of the order of 0.1sec so you are not going to get much audio out of it.

    You could use a high speed photodiode, but you would have to redesign the rest of the circuit, and the whole idea looks a bit far fetched to me.

    You use a proper laser doppler vibrometer (LDV) - that would work, but not in your price range!
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