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Pseudo theremin using optics

Discussion in 'Hobby Electronics' started by Geoff C, Feb 10, 2004.

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  1. Geoff C

    Geoff C Guest

    My cousin wants to make a theremin-like device after seeing
    one in use, for his bands studio. The original analog
    theremins are still available apparently but pricey. I
    remember seeing a design idea in an electronics magazine a
    long time ago which used a CdS cell and a car headlight and
    used the illumination of the players hand as it came near the
    light source to alter the note.

    The circuit details don't bother me but I would like to know
    if anyone has experience in playing with such a device. The
    transfer function of hand distance change to note change is
    important I guess but I don't have a good feel for this. Also,
    I'm not too sure if a theremin always outputs a note or if is
    nominally silent.
     
  2. Andy Wood

    Andy Wood Guest

    I have a few pages torn from "Radio-TV Experimentor" magazine showing
    the "Photo-Theremin". It was my first electronics construction
    project. I can't really comment on how well it worked since I knew
    less about music than I did about electronis at the time.

    Besides, it was (gulp)) 40 years ago and I don't really remember much
    now...
    The Photo-Theremin has two CDS cells, one to control pitch, and one
    for volume. I believe the original non-optical Theremins also had two
    such controls.

    Andy Wood
     
  3. Unbeliever

    Unbeliever Guest

    Geoff,
    You might also have a look at the motorola MC33794 efield sensor. It
    apparently generates a low level electric field and detects loading on that
    field by objects that approach. I'm sure you can get it interfaced.

    Cheers,
    Alf
     
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