High voltage experiments (tinfoil hat owners only)

[vlad01]

here is a simple flyback driver to make AC



and better circuit here.



Both have the flyback transformer from a CRT in mind where there are multiple primaries or wind you own on the ferite core that loops around them.

Ignition coil has no such extra primaries. The other thing in mind is these circuits are self resonant, be nice to drive them with an IC to be able to control such things as frequency, pulse width and amplitude etc..

[j_ds_au]

I see virtually everyone who builds these normally use a coil and drive it in flyback setup, but I don't know how their multipliers seem to work well from what I understand would only be a single polarity HV at the coil. Perhaps others aren't getting full potential from their multipliers because of this?

Yes, that's correct.

Note that the two schematics you've posted are push-pull forward mode, not flyback mode. The output voltage then is determined simply by the input voltage and the turns ratio, so you won't get such extreme voltages as with an ignition coil in flyback mode (unless you have an extreme turns ratio).

Joe.

[vlad01]

I ran an old TV transformer years ago which was from an old black and white TV and it did not have a built in tripper, So the arc was nice and was AC, But I cooked it pretty quick. Got 1" sparks from it.

I have one still operational with built in tripper, gets about 70mm sparks. But its DC so I can't use it to power the multiplier.

As for the turn ratio, yes if you use the forward mode cicuits like above, similar to the one I have already the turn ratio is stupidly high. I only have something like 6 turns and the HT side would have up and around a couple 1000 or so.

[vlad01]

found this circuit. looks like a good solution, though 240ac in might over drive the coil? well only one way to find out lol other thing is 50Hz is pretty crap for what i have in mind.

[Circlotron]

vlad01, that circuit is a death trap! Don't try it without an isolation transformer!!!

Have a look at this CDI circuit on page 36 -> http://www.siliconchip.com.au/Issue/2014/December
It will drive the coil primary both directions. Technically, it would be a pretty rough setup though because the CDI is a *voltage* source, not a current source, and so the current going into the voltage multiplier caps would be somewhat high-ish until the thing got up to a steady voltage. You would be relying entirely on the ignition coil leakage inductance to soften things. I suppose you could put a bit of extra inductance in series with the primary or perhaps the secondary. Maybe also crank up the switching frequency from IIRC 2KHz to whatever the coil will stand.

[vlad01]

Its only a deathtrap if you dont look at what you are doing. Yeah isolation transformer is always a good idea, was thinking a ballast as well for current limiting but the limitation here is the very low frequency.

So anyway I read up on the types of flyback transformers used in TVs, and what what I want the old vintage stuff is good, ones that are disk shaped dont have a rectifier and noramlly have a higher turn raio and exposed cores, perfect for winding your own primaries.

Added a few on ebay to my list. Found a real cool vintage one here.

Ultimately a transformer like that will make the circuit a KISS one.

http://www.ebay.com.au/itm/131556316432 ... EBIDX%3AIT

http://www.ebay.com.au/itm/291120775844 ... EBIDX%3AIT

[vlad01]

lol time for some fun. The seller chucked in a freebie baby cap for nothing.

[vlad01]

played with the smaller can, awesome and these one of the bigger ones.

[youtube]https://www.youtube.com/watch?v=s7r9ROLouRc[/youtube]

Tried to rectify it with an LED, didn't go so good lol.

1st spark, exploded the LED instantly.

[vlad01]

So I ended up buying 100 1N5408 1000V 3A diodes and made to strings of 50 submerged in oil.

Knowing they have a slow recovery time I didn't expect my TV flyback transformer running on a self resonant circuit to work well as its up in the 20-30Khz range. Well it didn't


So I decided to get my long time in storage NST and control box out. (neon sign transformer) which is something I made back when I was 14 or 15 for a Tesla coil power suply but never finished the project as enamel wire is something very hard to obtain in 300+ m lengths back then.

So to my surprise it worked extremely well. The NST in full sine wave gives out 10Kv ac and in short conditions 25mA, you never get both as the the transformer had a huge ballast built in to limit current for shorted 24/7 operation, effectively what a gas tube is for high voltage.

I had the control box with 3 "speed control knob, ones used for ceiling fans. It does some weird things in med to low power, Im guessing because of the choppy wave the NST starts to work in a flyback mode and the peak voltages go up dramatically.

I had a single stage multiplier setup with the 2 strings of diodes. I managed to get big fat sparks up to 120mm long and most where around 80mm -100mm long.

So many days of experimenting and today my mate came over for a look at its progress, We fried a string of diodes. I suspect from over voltage and the thing when into a cascade failure, ie one diode dies as a short, the others take up more voltage before long, in a blink of an eye the whole string is just a short lol

Worked very reliably for hours of use but I know the diodes were being pushed to the limits. So my mate having an altronics trade account, I am thinking of making up PCBs which will house 100 diodes each for an effective 100Kv and 3A capability, about double the expected peak voltage. Designing it to be potted in a tube with some sort of resin. So I need to buy 2000 diodes at least lol but the price will be cheap from the trade account. About 140 bucks for the 2000 I estimate.

Given what I got from a single stage, 10 stage could see somewhere from 800Kv to a potential 1Mv.

[Holden202T]

geez your having a go

I just have one question, where is the video ??