I was looking at the 25Kv DC generator at the bottom of <a href="http://www.powerlabs.org/igncoildrivers.htm" target="_blank">this</a> page and thinking that it would be a rather useful thing to own (being portable and reasonably small).

I was wondering if anyone has any ideas on how to improve on this design (more/bigger batteries, better transformer, different pulse circuit), and also if someone could tell me how he used that damn relay to pulse the power as I have thought of several different ways to connect a relay so that it switched on and off rapidly but none of them seem to work.

The other thing I considered was an entirely different circuit to pulse the power and I would like a circuit diagram for an SCR based one (I am reasonably new to this kind of electronics).

Now I can't see the transformer you are referring to so this is out of the blue : Your key components could be an electronic ignition system from a car and a coil from a car aswell. The electronic switching is more reliable than mechanical switches in a relay. My experience is that such mechanical contacts get worn quite fast.

You could perhaps use two coils with common ground and then with different polarisation to get double voltage.

Now I don't know how stable you want your 25kV and how much current you would want available at that voltage...

This circuit has nothing to do with car coils OK? It is just on the powerlabs coil driver page because it didn't fit anywhere else. The transformer I will be using is a 240v/12v step down which I will run in reverse.

Why make a 25KV generator? It is nothing special. You can buy 20,000 volt ion kits at almost any electronic store or online kit store. They are also found in many high power ozone generators. Why not build a 100kv or 200kv generator? You could start off with a small 9KV 30mA or less (12V 5A operation) automotive neon transformer to save yourself the trouble of building an oscillating circuit. Or INFORMATION UNLIMITED, I am sure you have already heard of it, has some 2KV-7KV 10mA battery operated transformers that you could use as a power source (very compact and lightwieght). I got a 4KV one to power my voltage multiplier. Kits and plans (online) has some 30mA 12KV diodes 10 for $30 that you could use if you could not find a low enough current transformer or current limiting resistor or if you wanted it to charge faster. Information unlimited also sells diodes and capacitors for voltage multipliers. What is your 20,000 volt generator for?

Information unlimited is a piece of shit (and I'm sure most people here agree)

If I make a 200,000 volt generator instead of a 20,000 volt one then the current will be a lot lower, I want to be able to run it on a few 9 volt batteries. (25Kv is all I need anyway, It will jump through clothing)

I will probably use it for charging capacitors or as a shocker.

If you want 20-30 KV then just buy a stun gun, they are around that range although they claim to be much higher.

Quote "This circuit has nothing to do with car coils OK?"
Actually, its everything like the old car coil circuits. Specifically its identical in method to the model T ford circuit which is a copy of the victorian induction coil. The relay is made to oscillate in exactly the same way, you wire the normally closed contacts in series to the relay coil.

Mechanical contacts dont just wear out quickly, they are too slow to produce the high frequency you need for compact power transfer. Tesla coils use very high frequency, generated with a tank circuit, crude but effective, with very highly refined resonant transfer (both matched frequency and standing wave) to achive extremely high voltages and high power transfer through an air coil. This is exceptionally good engineering for the time, but is basically a reflection on the state of transformer cores at the end of 19th century. Anyone wanting to work with high voltages would do well to understand how a good tesla design works fully, rather than the lazy drop-available-componants-and-get-sparking designs that seem to permiate the internet.

Today you can get a lot of power through a small coil with a high quality ferrite core at high frequency (eg 100khz), and this is definatly the way to go for small EHT power applications. But for use as a weapon 20odd kv DC is useless. Its a bad way of generating the power, its a bad way of storing the power, its a bad way of switching the power and its a very uncontrollable (and therefore unreliable) way of delivering the power.

Modern stun guns work like a camera flash triggers (usually around 3-6kv, but the same engineering applies) and defribulators. The battery is stepped up to a few hundred volts over a large electrolytic (and therefore high energy / mass and size) capacitor over a period of time and when the pulse is needed its dumped through a power transistor or more easily with a thyratron into the primary of the main output EHT coil. In Idoru gibson mentions people making stun guns out of disposable cameras, which is a possitivly godlike idea and quite feasable. You only require a self built EHT coil, and a beefy replacement transistor to make it work (They burn out very easily as sold), at least in theory. A camera flash is essentially light produced by a shorted thyratron.

When you have the electrolytic method working, you can read up about human health effects based on energy rather than voltage, which is a better indicator and this will give you a rough indication how much power will hurt a lot, and how much will cause perminant damage, two very important limits for determing how far you want to go. EHT is fun to experiment with, and as safe (or as unsafe) as you are willing to make it, but this almost goes without saying that development as a weapon at some point would have to involve lining up a number of people willing to die in the process, police squad style, and electricuting them one after another. Remind me never to visit western australia.

Cockroft walton ladders, and similar passive devices are extremely cunning, and very useful for building stable low power EHT supplies, but are rather a dissapointment when it comes to rate of energy transfer. A modification of the ladder, which uses a series of coils on a common core, is much better for high power (up to about 1MW in short bursts or small devices overheat) applications even over 1MV but its difficult to insulate and couple the the transformer windings.

As an end note, 9v batteries are pretty crappy in terms of internal impedence, and therefore maximum available power, try NiCd cells in series to the same voltage.

Use Ni metal Hydride 9V batteries. They pack more juice than any other commonly available battery (about 15 C.D) and are rechargeable. Also Lithium ion .... but I don't think they can be charged.

Thats true, but what concerns projects like this more is power rather than stored energy. Power is the rate at which you can get the energy into the electronics to do something useful with.

You can get rechargeable Li batteries, and NiMH do last a lot longer than NiCd, I'm not sure what the impedence is for NiMH, but for sheer melt-the-wires power, you cant do a lot better than NiCd or Lead-Acid.

I'll second that. The new 3Ah Sanyo Nicd cells are good for about 90A continuous!

OK, so it does have something to do with car coils but I don't intend to use one for this circuit as it would be too large and bulky.

I can't buy a stun gun because I am in Australia and you can't get anything like that here.

Can someone post a diagram for a good pulse circuit as I can't find one anywhere.