RE: Tesla coil tuning

["Tesla list" <tesla@xxxxxxxxxx>]

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

Jeff,

I was considering that, but you have to consider the necessary 
accuracy as well.  You'd have to have a pretty accurate digital to 
analog converter (I don't believe the Atmel chips have any build in), 
and it would take up a lot of pins on the microcontroller.  Do you 
have a more specific idea on a good way to do this?

Chris


-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: Wed 4/18/2007 9:29 PM
To: tesla@xxxxxxxxxx
Subject: Re: Tesla coil tuning

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
 >
 >
 >