My 40kV Uncle Fester impression

With my SIDAC driver and a light bulb, I thought I'd try my hand at doing an Uncle Fester impression. Remember him from the Addams Family?

I'm putting about 40kV out of the ignition coil, enough to spark around the globe. What might not be so obvious is the little ground wire hanging off the globe's base. I'm not actually conducting the electricity myself!

Needless to say, this was done with a full understanding of the dangers of HV and the particulars of this setup.

Plenty of ozone going around, I have to hold my breath for most of it. At some stage I'll actually get a better set of photos, but the vid will do for now. :)

Marx Generator + NST

My Marx Generator gives pretty juicy sparks, but at about 1 every 2-3 seconds from a Flyback
transformer, it's not the most intimidating. Not a lot of power can be gotten from a Flyback (except
perhaps in ZVS mode).

So I hooked it up to a beefier 15kV supply - a Neon Sign Transformer rated at almost a Kilowatt. A
couple of microwave oven diodes rectified the AC into the necessary DC.

Check out the results...

Big ignition coil sparks

An ignition coil typically runs from about 12 volts, and can generate sparks about 1cm max from this input voltage. 1cm sparks re boring though. Sparks several inches long can be created from an ignition coil (IC) by dumping a thousand volts into it.

To do this, a special component called a SIDAC is used. This is a silicon device that blocks conduction, until a specific threshold voltage is reached, at which point it suddenly conducts fully, until current flow stops. It's similar to how a spark gap works.

Marx 2 - A Bigger Bang

Last year whilst in America for work, I visited a flea market and came across a box of impressive capacitors. Inside the box were ten 8-inch long glass-encapsulated capacitors, each of them .01uF at 14kV. Considering the size of them, they were obviously rated for heavy discharge use. A quick look at the manufacturer website confirmed that they're indeed intended for pulse applications.

At $50 for the lot of 10, it was a bargain.

Big capacitor + metal shavings = ?

... a very fast (100th of a second) shower of metal sparks.

A while back I acquired a very beefy capacitor. It is 0.25uF, rated at 35,000v. That is a total energy storage of 150 Joules! A typical camera flash has but 10 Joules of energy. Charging it takes about 30 seconds with a Flyback supply, and I can only get to about 25kV (78 Joules), but I'm hoping to boost that with a neon sign transformer.

Self contained flyback

A 1 hour build. Finally put a flyback transformer and driver on a single PCB for easier moving
around. Up to now the transformer has been loose, not attached to a driver PCB.

Note, this is another supply, in addition to my portable supply.

Input: 5 to 15 volts.
Output: 25,000 volts (depending on input).

Bracket with banana socket serves as ground, screw terminals for supply voltage. Arcs are easily 2-3cm, as visible in the photo. Driver is standard 555 + MOSFET. Flyback has primary I wound myself (red wire in the photo).

A Marx Generator

When you want to generate large pulses of terrifyingly high voltages, the tool of choice among the potentially inclined is the Marx Generator. This deceptively simple device is built using nothing more than capacitors, resistors and spark gaps.

It  takes a relatively low voltage input, generally in the range of 5-20kV, and spits out a pulse that is multiplied in proportion to the number of capacitors in the device. So even with just 10 x 20kV capacitors, its possible to generate a juicy 200,000 volts that can jump close to a foot.

The picture on the masthead of this blog shows an actual Marx generated spark as wide as my face.

Portable high voltage supply

Playing with sparks requires generating high voltages.

There are a multitude of ways to generate such voltages. One of the easiest is to use a flyback transformer from an old TV or PC monitor. By driving one of these with a 555 timer and MOSFET, it's very easy to get 20-30kV with just 12V input.

This post describes one that I built.