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.

Crookes Tube - early cathode ray device

Way back when I was still at school, I took a trip to Europe. Whilst browsing Portobello Road in London, I came across a bloke selling old Geissler and Crookes tubes. I was amazed by these antique electrical devices.

A Geissler tube is something like an old neon sign tube, but uses higher voltage and gives much more interesting colours. They glow depending on the materials within.

Tidy those alligator leads!

Like any true electronics geek, I tend to have a decent pile of alligator clip leads (or "Croc clips" as they're known in .au) lying around the bench. They are incredibly useful for quickly hooking up connections without having to warm up the iron. Unfortunately they tend to end up in a pile, and tangle-free but accessible storage is always a challenge.

A few head scratchings didn't give me any real ideas for how to solve the problem. Bags and boxes end up tangled, hanging them off the shelves obscures access, and anything else was just too far to reach - I'm a firm believer that all frequently used bits should be in easy reach.

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.

Main screen turn on

One corner of the bench...

I've done it.

After much procrastination, ideas, thinking and planning, the Buxtronics blog is up. It's finally good to have it up, and all these ideas for articles that I've been going over in my head can finally get down on paper...er keyboard.

As a tinkerer and builder of various electronic gadgets, and brewer of beer, it was a shame to not be able to share my creations with others online. I decided I needed to document these various projects, even if just for my own benefit.

Some of my projects are already online, but they are in raw html and take a fair bit of work to put up. So I've gone with a traditional blog format for future projects. Some of those existing projects may get a revisit here though, particularly as they have been improved and changed somewhat.

Some existing projects that will get a mention here soon include:

• Marx Generators
• Brewing stir plate
• Tesla coil
• Various milled gadgets
• Various destructive high voltage fun
• Microcontroller based projects

So stick around, subscribe and stay tuned for an insight into my crazy hobbies!