[sdiy] optical theremin, 555 cool stuff (it's all in the duty-cycle)

[anthony]

Here is a good optical theremin circuit: (Hey did I find this link here?)
http://www.baragon.8m.com/555.jpg

And then check this out:
http://www.schematica.com/555_Timer_design/555.htm

This little program is so cool!

You can find the best parts for changing the duty-cycle by adding a
couple of diodes.

Why change the duty-cycle? I read somewhere that at a 33% duty-cycle,
2nd order harmonics are way up and third order harmonics are almost nil.
At 25% you have the most of the 2nd order, but there's some 3rd order.

Variations along the range sound better than a plain old 50% duty-cycle 
square wave.