Generating HT

Get LTSpice fom Linear Technology webpages, learn to use it, and create your circuit on it.

Youbetcha. Tap the coil way down and drive the tap. Or go to a junk yard and buy a spark coil off an old car.

What kind of coil?

If it's an auto ignition coil, charge a cap, a couple of uF of film cap, to around 400 volts, and dump it into the coil primary through an SCR. No snubber. A diode across the SCR, to allow reverse conduction, may make a fatter spark.

The old junkyard metal-case oil-filled coils are fabulous. A 2" arc is possible.

I used to dump oil caps into a coil through a thyratron tube. I had to add an oil-filled extension tube to the neck of the coil to stop the arc from climbing over the top and down into the the primary terminals. It would blow right through electrical tape.

Ever build a Marx generator? The ones made of big high voltage resistors and old Soviet "doorknob" capacitors that boost the supply up to hundreds of thousands of volts can make some pretty sick foot long arcs...

k?

most ignition coil now are just driven with an IGBT, quite a few have them build in, dwell time a few millisecond for 5-10A primary current

primary voltage limited in case of a misfire by the IGBT clamping at ~400V

-Lasse

A steel-cored solenoid from a relay in this case. Some old ex-military job about 4" long by 3/4" thick. But I've tried others, including air- cored coils with lower parasitic capacitance and still no joy/pain. :)

That won't make serious HV. With a snubber diode, it won't make any HV.

You need a step-up transformer to make serious zaps. A car ignition coil is one way to go. To make single bangs, charge a few uF of film cap to a few hundred volts and then manually connect it to the coil primary... through a couple of feet of test lead.

A voltage multiplier can make serious kilovolts of DC

given some moderately high AC voltage, preferably high frequency.

You can also make a poor-mans Marx generator: charge a bunch of capacitors and mechanically connect them in series. Hey, imagine charging a pile of doorknob caps and then dropping them down into a plastic tube, so they stack up in series.

Be careful.

Isn't that the methodology employed in Taser design? Like so IIRC: HF exciter ---> current amp/buffer ----> step-up tranformer ---> CW multiplier (I think that's how it goes anyway).

ITYF the multiplier comes before the transformer. But I could be wrong...

Can't be can it! Think about it.

It's a DC transformer, don't you know 8-) ...Jim Thompson

There isn't such a thing is there, Jim?

If your dc is just a short pulse a transformer can indeed transform it.

NT

When the fet turns off, coil current flows through the diode, hence no voltage increase. Put the diode on the output side & a zener & it'll deliver something, but not EHT.

Set your relay vibrating & drive a small Tesla coil. They're not hard to make.

NT

The question was put to the engineer, not the oil rag.

Many people assume current has to be AC for a transformer to be able to step it up or down, but that's a "red herring" as you say I believe. What really matters is *change* in current. That is what generates a magnetic field and it matters not if that current flows only in one direction - provided it *changes* in amplitude (and for your purposes, the faster the better).

Seems like sort of splitting hairs...that just sounds like an AC current with a DC offset.

Transformers that are designed to carry a large DC current need to have large core structures with air gaps (to increase the reluctance of the magnetic circuit), or be made of something like powdered iron where the "gap" is intrinsic to the material, to avoid saturation of the magnetizing inductance.

.... Phil

I guess the engineer that worked with one today won't help you then. Weird bloke.

NT