Re: OL-DRSSTC 9 - Better trigger!!

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Original poster: "D.C. Cox" <resonance@xxxxxxxxxx>


Terry --- any photos yet of the spark output?

Dr. Resonance


> Hi All,
> The OL-DRSSTC coil now triggers at any input voltage so the power 
> can be "fully" controlled by a variac!  I went to a "fully resonant 
> tuned" trigger pulse and it will now fire "anything"!!
> http://hot-streamer.com/temp/OL-DRSSTC-2005-10-11-001.gif
> The trigger pulse is a big 35 amp 96kHz decrement sinewave now that 
> lasts for about 8 cycles!  It will start up any lazy ol-DRSSTC 
> :o))  It could probably even power a little Tesla coil all by 
> itself, but it is only 5.3mJ/bang or 0.32 watts.  Almost 1 inch by 
> the Freau equation...  Might be useful for "enyweeny" coils:
> http://www.roffesoft.co.uk/tesla/enyweeny/enyweeny.htm
> The drive circuit is here in the upper right:
> http://hot-streamer.com/temp/OL-DRSSTC-08.gif
> I took out the 2.7ohm resistor and added a reverse diode across the 
> SIDAC.  I added a loop of "primary" wire to the trigger loop so I 
> could tune it right to the Fo frequency of the primary coil.  So it 
> runs much like the original OLTC did.  There is not much to it (it 
> really only needs "one" cap...):
> http://hot-streamer.com/temp/OL-DRSSTC-2005-10-11-005.jpg
> One could probably fiddle with the part values as you please.  The 
> SIDAC "could" probably push 80 amps!!  Peak current is controlled by 
> the firing voltage and primary loop impedance.  The voltage ringup 
> is able to keep the circuit in conduction until the cap energy is 
> used up.  Really cool!! ;-))
>
> With a test load, the circuit fires right up!  Yellow is primary 
> current and blue is the trigger circuit loop current.
> http://hot-streamer.com/temp/OL-DRSSTC-2005-10-11-002.gif
> At 60BPS, this heated the IGBTs to about 40C with the fan in place 
> (could use a "better" instead of the "cheapest" fan...).
> I hooked it to the full coil and tuned it for some nasty primary 
> currents and it started and ran fine:
> http://hot-streamer.com/temp/OL-DRSSTC-2005-10-11-003.gif
> The firing pulse train looks like this:
> http://hot-streamer.com/temp/OL-DRSSTC-2005-10-11-004.gif
> So that is where I am...  Things to do...
> A simple inrush current limiter could replace the big blocking 
> inductor for less power but a far smaller size...
> The fan needs to be "better"...  Maybe a big CPU fan, but I don't 
> have the low voltage to run it...
> I need to put back in the 150nF primary cap and 16uH primary to 
> optimize it all much better.
> I need to get a few more parts from DigiKey....
> BTW - I think DK#  P12241-ND  2.4uF 400V poly caps could directly 
> replace the 2.5uF caps from Richardson...
>
> Cheers,
> Terry