my first arduino project! i've been fiddling around trying to make a theremin, but my electronics knowledge is sooo bad... perhaps i could use arduino instead?
anyhoo, before i go and short circuit the thing in a fit of blissful electronic ignorance, i thought i'd best get a few opinions.
what if we use one of the analog outputs to charge up a capacitor - then, when it's charged, switch off the output and let the cap discharge through an analog input. when the cap has fully discharged and the input goes low, measure how many microseconds have elapsed since the program started, feed that number into a tone generator function, then repeat.
my preliminary schematic:
[or goto http://www.jonandaviva.googlepages.com/theremin_schematic.jpg
a change in antenna capacitance will alter the cycle time marginally, and this difference can be amplified before the result goes to the tone generator.
do you think i need the diodes? did i even show them pointing the right way?? what about a resistor - some kind of load to work against?? hmmm. what's stopping all the charge from just going from A0 (out) to A1 (in) rather than charging the cap? maybe put a resistor at A1 instead of a diode?
here's the programming concept:
1. set A0 high for x microseconds (long enough to charge the cap).
2. once A0 is low, wait for A1 to go low (while the cap discharges through it)
3. once A1 is low, measure the elapsed time in u-secs (MILLIS command? ideas?) from the beginning of step 1.
4. process the u-secs value mathematically to detemine pitch (larger value = hand closer to antenna = higher pitch)
5. execute a module to play resulting pitch through another analog output with speaker attached.
6. while the pitch generator module is in operation, loop back to step 1.
sorry for posting such a sketchy concept, but i need all the help i can get. hope to hear your ideas!