CMOS Theremin

[droffset]

SURELY this must be in the Lunetta spirit? I'm so building one.
http://home.att.net/~theremin1/101/101.html

[hexagon5un]

Even more in the CMOS/Lunetta style:

I made an more minimal version of Art's design with a 74HCU04 for the oscillators fed straight into a 74HC86 XOR for the "ring modulation".

Copy his two oscillators (U1A and U1B, U2A and U2B) onto a single chip. The U in 74HCU04 is important -- I had trouble with oscillators syncing with each other when I used 74HC04's. Then just run the outs of those two oscillators straight into the XOR chip.

And because I'm really minimal, for output I just put a 100uF cap on the XOR out, to a speaker, and to ground.

For an antenna, I just use an alligator clip and a foot-square piece of aluminum foil, because then the whole shebang fits in your pocket.

I run it on a rechargeable 3.6v cell phone battery most of the time and I find it helps the range a lot to couple myself to the circuit's ground wire because the battery is not earth-grounded. So I pulled out the ground line to a patch of aluminum foil that I can contact with my fingers. Since this radically changes the frequency of the variable oscillator, you can use it as a simple playable gate for the sound.

I've attached my notes. I'm actually running a small workshop building these tonight at my local hackerspace. (www.hacdc.org).

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[droffset]

Great idea, would make a fun evening project, cheers!

[hexagon5un]

Made this sketch for the class. You'll also need power and ground lines, and possibly a decoupling cap (10u?) across them. I located mine physically between the chips.

Enjoy.

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