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RE: Terry's DRSSTC

Original poster: Terry Fritz <teslalist@xxxxxxxxxxxxxxxxxxxxxxx>

Hi Steve,

At 03:04 AM 1/12/2005, you wrote:
>Like hitting the primary
>every tenth cycle after breakout or something to maintain say 100 amps in
>the primary.  All kinds of wild possibilities! but they require passing
>high speed digital to the coil back to computers and such.


Coincidentally I've been working on a similar idea. My plan is to chop out
cycles of gate drive as needed to keep the current below a user defined
limit. ut I shied away from putting an embedded controller in the thing.
It's not so much that I think it's a bad idea (although there would be some
serious "issues" if it crashed mid-burst) but more that embedded controllers
and DSP are my day job. It's a relief to escape to some 1970s style analog
electronics where the chips have 14 large pins that you can actually see ;)

I just got two new pairs of reading glasses and a low power scope 8-)) Most of the basic control functions can be done with the AND, OR, NOT gates and todays "simple" logic parts are super nice!! +-20mA, schottky, 4nS... ;-))

But I think we need a "new" H-bridge design... More on that latter since I just thought of it while waiting in line at the fast food place ;-) But we might be able to use the same ones too... Have to think more on that...

I originally tried to use nothing except 555 timers in my SSTCs, but I have
got more adventurous now, with a whole alphabet soup of 4046s, 4011s, 4013s,
LM339s, TL074s, TC4429s, etc.

Simple logic can do most of the immediate fast stuff while higher logic can manipulate it. The circuits should try to "self protect" themselves if the computer side goes haywire. Neat about your PLL stuff!!

I'll publish my current measuring and control circuitry once I've actually
tested it all on a coil and seen that it works.

I've updated my website at http://scopeboy.com/tesla/ with the DRSSTC and
induction heating work.

Cool!! I'll get the link added to drsstc.com asap!! Nice blown IGBT pics!! I think the little ones have an advantage of not having as much bulk material to spray around when they go. Nothing there but "pure energy"! But they sound like a 30-06!!! We used to have arrays of ten big TO-247 FETs across 600V buss caps that would all blow one by one in the space of about 1/10th sec. The noise would almost knock you over!! Sounded like a close lightning hit!! After they went for about the 100th time I got so I would hardly flinch... I could hear the gate drives squeal about 1/2 sec before it blew so I learned to not let it scare me ;-)) The little FETs were easy to replace for the next blast while the big bricks made a gooey mess and ripped PC boards and near by stuff apart... The small parts also blow themselves away very quickly helping to prevent secondary damage (like a fuse ;-)) So I am going for the "little IGBT" approach. Just have to try extra hard to keep them cool.

Looking forward to seeing how your stuff progresses too!!



Steve C.