At 01:07 AM 5/11/2004 +1200, Russell McMahon wrote:

>> I am asking if anyone can help me in understanding how to create a circuit
>that will vary the voltage to the A/C converter on a Pic chip based on
>varying capacitance due to a hand or body part near a piece of metal.
>
>My idea is to create a Theremin or some sort of proximity detector.
>
>My problem is that I cannot seem to _get_ the fundamentals of this sort of
>circuit.  I've searched through this Piclist archives as well as the
>internet, and of course I've come across lots of circuits that probably
>provided me with the answer I'm looking for, but unfortunately I cannot
>comprehend the basics of how they work.

A Theremin is simply two oscillators, both operating in the range of about 1 MHz.
Your hand varies the pitch of one of them, by changing the capacitance of an antenna.  When the two oscillators are mixed, the result is an audio tone.
The second antenna picks up the signal through your body, and that directly affects amplitude.

http://www.thereminworld.com/

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