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Steve Conner

Tue Oct 09 2007, 09:07AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

You probably ought to read up on capacitor discharge ignition systems. These work by charging a capacitor to a high voltage and then slam-dunking it into the primary of the ignition coil, using a SCR. To get more voltage, you just use a higher voltage capacitor and a higher voltage rated SCR.

Using this method you can easily get enough voltage to destroy any transformer or ignition coil you can make. The hobbyist ignition coil driver using a lamp dimmer and capacitor is an example of it, so you can try this for your experiments.

You don't need to connect the output of one transformer to the input of another, which doesn't work anyway for the reasons that other posters have explained. To avoid magnetic saturation, the secondary of the last transformer in the chain needs just as many turns as you'd have had to wrap to build a single transformer with the same output voltage.

There is a connection called a "transformer cascade" that you should study too, though. Commercial HV labs sometimes use two large transformers in cascade to make AC voltages over 1MV.

thrival

Tue Oct 09 2007, 05:22PM

Registered Member #1019 Joined: Sat Sept 22 2007, 02:39AM
Location:
Posts: 29

OK, two more terribly naive questions;

If a person drives an ignition coil to resonance at its nominally rated input voltage
(12V), using a flyback circuit,

1. Will it overheat if run continuously, or in other words, does running a coil at continuous resonance, necessarily destroy the coil? (speaking of a potted e-core, no oil bath)...and

2. Will the secondary winding experience a higher V than when the coil is normally operated,
single-fire, outside of resonance?

Knowing this would be a useful tether to reality, thanks.

...

Tue Oct 09 2007, 10:22PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

If you adjust your driver to never give more than 12v into the primary winding, you will have a very hard time to kill the transformer. You definitely won't do it by overheating it. Of course, most resonant circuits put out more voltage than you put in...

I also doubt that you will be able to get more voltage than when operating it 'normally, because the whole point of an ignition coil is to store energy in the core (by running it at 12v), and then disconnecting the 12v supply (that is what the points in a car do), which creates a large spike in the input of the coil, and that is what creates the high voltage pulse. So if you are limiting yourself to never having >12v going into the coil you will have a hard time getting more voltage out. More power, yes, more voltage, probably not.

Sulaiman

Tue Oct 09 2007, 11:14PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Depends how you look at it;
with 12 volts dc and a mosfet switching at the resonant frequency (e.g. 555)
the output will be enormous!
So large that it will be difficult to insulate the secondary.

I did this once, from memory about 5 kHz was the resonant frequency for the coil I was using.
The can got hot, presumably due to core losses at 5 kHz heating the core which heats the oil.
I could see no benefit in operating at the resonant frequency
I think I used a diode between the mosfet drain and the coil primary, and a low duty-cycle.

I ruined the coil;
the hv at (relatively) high frequency punched/burned through the plastic top-cap of the coil
preventing use at hv after that.

Now I just use 'normal' flyback mode for my ignition coil hv supply.
(33 Vdc supply, c900 Hz switching frequency, variable duty)

Dr. Slack

Wed Oct 10 2007, 07:25AM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

Electrical engineering is like hill walking. Well, not exactly like hill walking, but a little bit like it. You can stick to the well-beaten paths, or you can head off yourself into the wilderness. If you stick to the paths, then there will be lots of people able to give you directions that work - use this transformer like it's intended, look up capacitor discharge ignition systems, that sort of thing. You might even be given good direction to take short detours from the path - double the rated voltage here if you keep it clean, dry, under oil, and are prepared for it to fail early, triple the rated current there for a short while before it gets too hot. If you head off into the wilderness, then you'd better have a compass, oscilloscope, GPS receiver, high voltage divider, and be able to use them. If you insist in tramping off towards the top of the waterfall of cascading two identical step up transformers, then that's your right, just don't say we didn't warn you.

I'm not surprised your ears pricked up when I mentioned driving an iggy coil at resonance. The word has a kind of je ne sais quoi , which seems to disproportionately attract certain people.

Using a coil this way is on the path, but it's quite a steep and narrow path. If I were to tell you that as a transformer, an ignition coil is about 100:1 step up, and that when being driven conventionally from 12v, the primary flies up to 300v or so to deliver the 30kV on the secondary, does it mean anything to you? I doubt it, because if it did, you wouldn't have asked the question. I was using a 40v sine wave, from an audio amplifier, to drive my coil, and it gave a 6x increase in output above the 100:1 at the 8kHz resonance. I would strongly suggest that you borrow or buy an oscillioscope, and play with an ignition coil for a while, and see what it does. Then you'll have made a start on knowing how to use the navigation tools to work off the beaten track. Using 12v disruptively at resonance is perhaps a bit vicious, as Sulaiman found out.

To continue with the hill walking metaphor. There is talk in these parts of a Shangrila. It lies far, far over there, beyond that cloud-enshrouded mountain, unreachable from the beaten track, it is necessary to strike out across the bogs and quicksands to reach it. It is a land running in free energy. We, the experienced hill walkers, enjoy crashing off into the undergrowth from time to time with compass in hand, and the beaten track is really good if you want to get somewhere fast and reliably. But we know that Shangrila is just a fairy story. And frankly we get p*$$ed at the idiots trying to reach it who don't appreciate the wisdom of the track, or the excitement of navigating the undergrowth. Not so much for what they are doing, but because they keep asking us the way, and then refusing to learn from the answers, perhaps because they realise the answers deny the existence of Shangrila.

ragnar

Wed Oct 10 2007, 08:50AM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425

A good post with many great points, Neil.

Thrival, I really think you should completely drop the idea of cascaded transformers.

Just TRY some higher-energy ignition coil drivers. TRY driving two coils in 'antiparallel', TRY a voltage multiplier! Then you can speak from your experiences on what needs improvement.

Steve Conner

Wed Oct 10 2007, 10:15AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

NeilThomas, you are this week's Master Of The Metaphor!

I must remember to pack an oscilloscope next time I go hiking.

Seriously, Neil's post made my head hurt because it sums up the conflict I have been feeling myself lately. I started off as an electronic hobbyist, wandering the hills at random just for pleasure. If you've ever read any of John Muir's

essays, well, that's how I felt about electronics.

I'm now a professional EE, and it feels more like the mental equivalent of carrying slabs of beer up to Everest base camp on my head every day for the tourists. In flip-flops.

So what does any of this have to do with this thread? I think it is relevant, so please forgive my digression. I remember thrival mentioning that he wanted to design transformers without hand-holding. Well, you need to go and take a trekking holiday in the Smokey Transformer Mountains! Get some practical experience for yourself of what the things will and won't do. I destroyed, and made, a bunch of transformers before I "grokked" the right way to make and use them.

What you're doing right now is like calling a professional mountain guide on the phone and asking him to talk you through the Smokey Transformer Mountains so you can experience them without getting off your couch. For free.

If you just want a HV source as support for some free energy experiments (which we'll not discuss here please!) I'd suggest just buying a high powered car ignition unit. You can always sell it again later.

Or if you want to live really dangerously, borrow the power supply from my old colleagues' Plasma Channel Drilling machine. It drives a spark-plug like electrode with enough pulsed power to drill through rock. I believe it works with a bunch of Maxwell capacitors and spark gaps: there are no pulse transformers involved.

thrival

Wed Oct 10 2007, 02:02PM

Registered Member #1019 Joined: Sat Sept 22 2007, 02:39AM
Location:
Posts: 29

Neil (& everyone)

Most the facts you mentioned about ignition coils I had gleaned from my readings
of other webpages a while back-- mega-squirts, Snock, Jochen's, Barros, but thanks
for underestimating me, I get that a lot, and there's a particular freedom it allows.
Admittedly transformer design is a weakness I'm working to overcome. On the other
hand I've long since gotten past the quicksand and found Shangri-la, not asking
any of you to believe or show me the way, which is NOT the topic anyway. But it might
amaze most of you how a person can know something profound without having every
basic covered. Well, the truth is stranger, as they say. It's kinda' like doctors
who just assume a cure for any disease MUST come from their own ranks, when some-
times it comes from a witch-doctor/shaman who practices herbs, communes with devas
and shakes feather rattles. Oh yes, it pisses the doctors off when that happens, and
they do everything to suppress the guy and his info, plus (or because) the fact that
doctors are more interested in managing disease than curing it, but I'm not
accusing any of you of being in that category. The problem is that society hands and
forces a person to use a faulty yardstick, such that errors get passed on for generations,
and hugely important facts get buried.

But something else life has taught me: competition with other human beings is stoopid.
The real competitive challenge is with one's lower nature, overcoming one's own
personal weaknesses, which lie in the ego. Pumping iron, ground-&-pounding one's
enemies, won't do it. Once you get that little imp under control, you'll understand 90% of
where the world's problems originate. Learning, and things you never thought, become
possible again.

Anyway I recognize that I will always be a pariah to this board, (birds of a feather)
and grateful enough when my technical questions are answered.

Bjørn

Wed Oct 10 2007, 03:03PM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

We are not surpressing you or your information. We are telling you that you suffer from serious delusions. That worries us because they are destructive.

If you don't bother us with your delusions we don't bother you about them. If your delusions are so powerful that you can't accept or understand that we will protect ourself by removing you and your problems from this forum. You are still free to bother someone else.

The next post by anyone must be strictly on topic and scientifically sound or it will be deleted and the thread locked.

Dr. Slack

Wed Oct 10 2007, 03:39PM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

Looking back at the first post, I'd say that all the on-topic points have been answered, so it might as well be locked

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