Tesla coil tuning

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Breneman, Chris" <brenemanc@xxxxxxxxxxxxxx>

Hello,

I'm thinking about trying to make a digital Tesla coil tuner based on 
(probably) an Atmel microcontroller, and was trying to think of 
various ways to determine the resonant frequency digitally.
My first idea was to make something similar to Terry's TCT, but 
digital.  ie. sweep a frequency range when connected to the 
primary/secondary circuits and see which frequency passes the 
highest/lowest current.  The problems with this are that it's not 
trivial to accurately do this digitally because of the harmonics 
inherent in any digital square wave and the difficulty in accurately 
measuring RMS voltage/current on a waveform that's not perfectly 
sinusoidal without carefully calibrated equipment.  This method would 
also be relatively slow.
Then I had another idea ... but I'm not sure if it would work.  Would 
it be possible to calculate the DC resistance, inductance, and 
capacitance of the primary and secondary (and from that, the resonant 
frequency) by applying three sine wave (generated by external 
oscillators) of different frequencies, measuring the current for 
each, and solving a systems of equations?  This method would be much 
faster and would solve many of the problems above.  Any feedback?
Also, if anyone else has any other ideas for methods, they are very 
welcome.  If I get it finished, I'll post the schematic, parts list, 
microcontroller code, and hex dump of the code.  It should be a 
pretty cheap way of easily and accurately measuring resonant 
frequency (if it works).  Atmel microcontrollers are all <$10 a piece 
(usually around $5 or less from retailers), and the other components 
(like cheap LCD display, resistors, caps, etc.) would be pretty cheap as well.

Anyway, thanks for any feedback,
Chris