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Re: [TCML] SISG First Light

Hi John,

Yes, prices generally go with usage. If little are used, high prices are the result.

I'll take some photo's of sparks and coil at some point, full specs and schematic, but I'm still in the first day of light and simply enjoying a successful coil at the moment. All I have documented at the moment is in the link below. The gif schematic is not what I'm doing at this time, so ignore that. The wiring internally has changed also to accommodate the cap in series with the primary and SISG in parallel with the transformer. If it performs well enough over some runs, I'll likely pull out the RSG from the cabinet to make it strictly an SISG coil. But due to the caps used now, I'll keep the cabinet height.

Interesting to me, when I use my ears to detect a well running coil and hold power to that level, it's almost self limiting. There is a difference with spark gap coils as I can push the power up to whatever and get the spark length desired, but with the SISG, it let's me know it's "happy power point". I did run it into a chaotic pps by pushing up the power. Sparks length of course increased, but I wasn't comfortable with it so I backed off (probably babying the IGBT's as I wasn't ready for destructive testing yet). A large Cp is certainly the way to go with this particular scheme. I can get longer spark lengths with a conventional rotary for the Cp size, but this is a limitation to switching in the SISG circuit. If I increase Cp, then I can put the sparks to the test (and the IGBT's). I guess others have already been down this path since they all seem to use large tank capacitance.


futuret@xxxxxxx wrote:
Hi Bart,

Maybe the prices went up due to commodity prices which may still have been soaring a year ago. But still the price increase seems extreme, but then again I have no idea how they determine prices on these things. I remember seeing some postings about the die size and all recently, I guess those were yours. Well I'll be looking forward to your ongoing results. I guess you'll be posting pictures and full specs eventually (or maybe I missed them). Maybe eventually as these type of IGBT's are used in more commercial products maybe it will be possible to find them in
scrapyards and flea markets, etc, inside certain equipment.

I'm working on a very small simple VTTC at the moment which is actually some progress for me since I haven't been doing much TC work lately. Your JavaTC
is coming in handy for the VTTC.


-----Original Message-----
From: bartb <bartb@xxxxxxxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Sun, 19 Oct 2008 8:46 pm
Subject: Re: [TCML] SISG First Light

Hi John, Originally, I think they were in the $8 range. But 1 year later, they were over $20 each and hard to come by and as time progressed, they were closer to $30ea. When I bought Marks boards, I decided to pick up the components myself. I waited for a time to see if prices would drop down (it didn't). I think Mark picked up a batch later on for a decent bulk price and was able to sell them at a very low cost ($10 each or something like that) and had offered to sell me some at that price. I declined the offer only because I couldn't afford the expense at the time (without my wife killing me). So I waited. Then I got tired of waiting and started looking for an alternative. That's when I came across the Fairchild IGBT's. The specs were close enough to be a drop in replacement and it was only the power dissipation which I worried about. When Terry picked the IGBT for his SISG, he went with the best out there at the time and the price back then was doable. The main difference is the die size which dictates thermal dissipation. My IGBT's have a smaller die size and will run warmer, but if they have ample heat sinking and air, then it's manageable. After the run, I put my hand down by the air exit hole in the cabinet (with the fan still blowing) and the air was only a slight temp difference, but barely noticeable. Of course, I'm just starting out. If I double up on the current, maybe then I'll see an issue or at least a noticeable change in temp. I think I'll bring home a temp probe and attach it to one of the IGBT's and measure how hot it actually gets. This was a long continuous run, so the IGBT's had plenty of time to heat up to the maximum allowable temp under the conditions and stabilized (which I think was relatively cool). Take care, Bart futuret@xxxxxxx wrote:
Hi Bart, That all sounds wonderful, definitely so. It is truly a marvelous >
invention by Terry.
What is the main differences with this new IGBT as compared to the >
type, the type that Mark Dunn was selling for a time?. I guess the >
peak current
rating is a little lower, but the price is much lower? Is that about the extent of it? I seem to remember the other IGBT's were about $10 each? John -----Original Message----- From: bartb <bartb@xxxxxxxxxxxxxxxx> To: Tesla Coil Mailing List <tesla@xxxxxxxxxx> Sent: Sun, 19 Oct 2008 6:19 pm Subject: Re: [TCML] SISG First Light Hi John, > > I just finished installing the 6th SISG board and
running the system. > I have k low at 0.112 (meas.). I'm running low Cp at a measured 65nF. > I just came in from a 10 minute duration run with the coil. It ran > flawlessly throwing out 5 foot free air streamers at 200V/11A input. > It looks like (in my case anyway), your spark length equation holds > well for my SISG coil. During the run, I ran at higher and lower > voltages and compensated with current. In both cases, it didn't make > much of a difference (I20could do about the same with both extremes). > One thing I noticed is when I increase power, pps would increase and > there is a spot where your just on the edge of the coil running a nice > 120 bps (as well as my ears could detect), but when I threw more power > at it, the coil began to sound odd. I could tell the sisg was not > firing smoothly. Kind of a DRSSTC sound to the sparks. So I kept it at > that edge of running smoothly and just let it run. > > I did have a fan blowing inside the chamber. I'm using a Fairchild > IGBT on the boards (HGTG18N120B). Mouser has them for $5.30ea in > quantities of 1. Mouser has 283 in stock and nearly 10,000 showing up > in a few days, so these IGBT's are probably the way to go with the > SISG boards (IMHO). They probably run a little hotter, but with air > cooling, that's no big deal. Here's the data sheet. > http://www.fairchildsemi.com/ds/HG/HGTG18N120BND.pdf > > Anyway, a great continuous 10 minute run and no problems at all. I > think I see why large Cp would be best for an SISG. Had I double the > tank C, I could have doubled the current at the pps where the IGBT was > happy. But as far as running ability with a low Cp, there are no > problems that I can detect. So an SISG can be a direct replacement for > a conventional spark gap. > > I'm happy with my SISG coil. I designed it for no primary tuning
(ribbon), so I'm using the full turns. All I
did was raise the toroid > 2 inches. I measured within 1kHz of the calculated value, so it all > worked out as planned. > > I should note I am still using a breakout point. It did breakout of > the 9" x 30" toroid with the 6th board, but it=2
0was not consistent. > > Another very important point to note. After
my 10 minute run, I went > and asked my wife about static on the TV. There was "NONE" she said! > What an improvement! Might make the "perfect" spark gap replacement > for those who live in apartments. > > So kudo's to Terry Fritz for inventing the SISG and to Mark Dunn and > others who took the SISG to new levels. > > Cheers, > Bart > > futuret@xxxxxxx wrote: >> Bart, >> >> Congratulations on your initial results. I have the SISG boards and > > IGBT's >> but have not done anything further yet. >> >> John > _______________________________________________ > Tesla mailing list > Tesla@xxxxxxxxxxxxxx > http://www.pupman.com/mailman/listinfo/tesla >
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