Re: Tesla coil tuning

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Teslacoil Workshop" <workshop@xxxxxxxxxxxxx>

Chris,

I like ATMEL chips too!

How about incorporating a VCO (voltage controlled oscillator) that drives
the test circuit (coils) but is controlled by the microcontroller? Basically
a digitally controlled sine wave generator...

Jeff


----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Tuesday, April 17, 2007 3:58 PM
Subject: Tesla coil tuning


> 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
>
>
>