I find Falstad-ing things like this to be a helpful sanity check: https://tinyurl.com/23w7rxts

Left is a bipolar center-tapped full wave, right is a bipolar halfwave. The disadvantage of a center-tapped full wave is that it requires double the supply voltage. You can also use a center-tap grounded transformer in the halfwave bipolar CW (I think... the high inductance between the multiplier and ground could be an issue (e.g. secondary flashover) during low-impedance sparking), so you really do need a supply with double the voltage capability. On the other hand, you'll notice that under a 4MΩ load the output voltage of the center-tapped full wave is around 2.75 times that of the halfwave.

I believe using higher voltages per stage is advantageous in regards to voltage sag (even accounting for the accompanying reduction in capacitance) due to the reduced stage count, so the higher required supply voltage would become a larger issue if you push stage voltages higher. Another bonus of lower stage counts is that the first capacitor only sees pk supply voltage, not 2x pk supply voltage, so you need fewer capacitors total.

I HAD a complete THT UD2.7 (and then later UD2.9) BOM at arrow. We were planning on group-buying 10 boards, which would have been ~$17 per board in component price. Something went wrong with the BOM Tool, however, and all members with access to the BOMs have lost access to all of their BOMs and the ability to create new BOMs, seemingly permanently on those accounts. Made a new account and started putting some of the items in and it failed again. Third account did not fail, even with the same items as the second, so I decided that it was too inconsistent to be worth redoing there.

Alas, I never saved any of the BOMs of locally, so I have them no longer.

My question is, is it possible to join two of these dual coil setups, for a lot more voltage or maybe current?  I've tried several wiring combinations with no luck.

You could put more ignition coils in series on either side center-tapped formation that you have right now, but you'd need to have floating drivers for the high-side ignition coils (since primary and case are tied to one of the outputs, which would need to be floating at the output voltage of that side's first ignition coil).

You could put as many as you want in parallel: match the primary directions on the coils you are paralleling.

You won't see any output increase if you keep the capacitor the same, however, since it's doing most of the current limiting. Increasing the capacitor size will increase output and putting more coils in parallel will decrease the coils' heating.

If they aren't getting particularly hot you could just increase the capacitor size, though you might risk damaging them.

Increasing the capacitor size may also increase voltage output (more power on the primary).

Hello,

I am releasing the DRSSTC PCB pack.  This includes the UD2.9 skip pulse gerbers, as well as PCBs for interrupters and bridge boards.  These boards are all less than 10 by 10 cm and so can be made for $5 from many PCB houses (not including shipping).  If you get many boards made at once, you can spread the cost of the shipping over these boards.

Boards included:

1)   UD2.9 skip pulse
2)   UD2.7 conventional board (without skip pulse)
3)   UD3.1 that uses the PSoC5 CYC8KIT
4)   Half Bridge with 2 transistors and a place for a capacitive divider for the other side of the bridge, and a place for RC snubbers on each transistor
5)   Half Bridge with 8 transistors (4 on each LO/HI side)
6)   Full bridge with 4 transistors and a place for RC snubbers on each transistor
7)   Full Bridge with 8 transistors (2 on each LO/HI side, two half bridges)
   Burst interrupter with external triggering
9)   AC line interrupter, includes a spot for the ATTINY85 to implement the OneTesla tiny USB interrupter.

These are all made with kicad, so you can modify them as you need to (kicad is open source software).

Dan

LATEST VERSIONS!: https://highvoltageforum.net/index.php?topic=353.msg2401#msg2401

Hi,

The UD2.9 BOM seems to be missing parts? I don't see the TL3116 on it, for instance? Is this intentional, or...?

Nice work. Amazing arc length.

A while back I was haunting Ebay looking for vintage AC flybacks for a plasma project.
I found that late model (maybe late 60's early seventies) TV flybacks for color TVs had the best
performance. The secondaries appeared to be potted in silicon rubber, not wax like a typical
vintage unit.

I am curious about where you are getting yours and what the parts are.

Cheers.

Thanks! I scrapped this one from a very old crt.

Specifically because the old ones are made with paper insulation, I think they are better suited for over voltage since paper’s rating increases a lot with oil! I’ll post some pictures of the flyback I’m using, the other one I have that I want to see if the mazilli also locks to secondary resonance on, and some pictures from the 25 cm run.
I also want to add staccato. Before that I want to be able see peak collector current (yes I use igbts in my ZVS, and this is so I don’t kill them lol), tank voltage (I am able to now, just shittily), and gate voltage at the same time, which will require several different steps.

Using a single vintage AC flyback potted in oil (and vacuumed), I managed to get 18cm strike distance.
This seems to be near dual resonance. It's driven by a single-choke mazilli that for some reason is latching to the secondary resonant frequency, ~20kHz. The tank is at a similar frequency, but certainly not very tuned. My choke is 1mH, so I'm not benefitting from the large spikes that very small inductance (10s of µH) chokes provide (I can't recommend doing this, it's a great way to slaughter transistors). I wasn't paying too much attention, but I believe this video was probably around 70v RMS at ignition. I do not smooth the input at all because it makes the streamers nicer and decreases power draw when an arc strikes. It might also increase jump length.

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I think I can push it farther but don't want to risk killing it. Perhaps I should kill it and buy another! I do also have a second, but it has an E core and very crumbly wire...

I also managed to get 15cm with a single DC tv flyback under oil with no vacuuming. It died on the second try, however.
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I saw someone on youtube get 5 inches with a single DC flyback in air, although have not been able to find the video since.

If any of you have high voltage HF AC transformers that you'd be willing to try using to jump similar or larger gaps, please record it doing so! Ideally with some sort of ramping, even if it's just from mains, so we can see the streamers!
You should be able to jump a much larger gap than 1kv/mm, particularly with ramping.

In the mean time, I'm off to try half-wave rectifier input and try to getting 25cm (and more importantly, the streamers that coincide with larger distances)!

Hi,

My friend is trying to pick an IGBT brick but it's his first time and he doesn't really know how. He's figured out how to pick out a good bit of the stuff but needs help with the remaining bits. Do any of you have experience picking IGBT bricks?

Hi Phoenix,

I recently saw that jmartis2 ran a DRSSTC on uninterrupted half-wave rectified AC, and thought I'd share it in case it hasn't yet been seen by you all.

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Your coil is really impressive, by the way, and I'm looking forward to seeing more of it. Do you know what the peak tank current is now? I saw that you said it was 60A peak earlier, which seems fairly low for a DRSSTC with such high on times at these powers.