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Thursday 15 December 2011

New Tesla parts

Found a new pair of neon sign transformers off Ebay the other day.

Advertised as a 7.5kv/30mA transformer, details in the auction revealed that there were two 7.5-0-7.5 30mA transformers, for a total of 15kV@60mA.
Manufactured only 6 years ago, and for $100 shipped, this was quite a find!

A doubling of my Tesla coil's power is imminent...

Monday 24 October 2011

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. :)

Tuesday 18 October 2011

Transformer heaven

Not far from where I live is a large metal scrapyard. They have a section where motors and transformers go to die, and a lot of what they get is from the local utility + military. Military and utility transformers are highly prized for Tesla coils and other HV experiments, so I really wanted in. My TC really could do with a decent upgrade!

A friendly chat to the workers eventually led me to the owner. This place has a reputation for allowing access to artists (sparks count as "art", surely), so it didn't take long. Access granted! All the blokes there were incredibly friendly and helpful during this.

Of course, my first visit to the place would not have been complete without taking some metal to recycle. So I took some aluminium cans for them, which they particularly appreciated as they'd first have to deal with the beer contained within.

It really is like a toyshop there, except the useful stuff is well hidden. This is what I faced when I went:

I could have spent hours there, but had to be elsewhere so only spent 15 minutes or so. Countless motors there, plus loads of transformers, such as those from microwave ovens, massive utility ones, and a few hefty 3-phase types. But no pole-pig or potential transformers yet (my real desires).

Despite this, I did come away with a beat up old Neon Sign Transformer, which is seen at the bottom of the left photo. And it works it seems! Stay tuned for a quick post on how I tested it "in-heap".

I suspect this will be a regular haunt of mine now, much to the detriment of the girlfriend..

Monday 10 October 2011

GPS feline tracker.

Say hello to Ash. Isn't that a nice collar on him?

Ash is my Russian Blue cat, and loves his neighbourhood adventures. Regularly off for hours on end, he could end up in who knows what garden, possibly halfway down the street. After endless such adventures, I figured it was time to find out where he really was going.

GPS is of course the way to go, so I looked around for a tracker I could attach to him. Turns out that all the ones commercially available are far too large. A common one available on ebay is about the size of a matchbox - too large for a cat. All other pet trackers are made for dogs, it seems.

So it was time to roll my own.

Wednesday 5 October 2011

Rotary encoders, done properly

Rotary encoders, in the most recognisable form, are mechanical devices that look a bit like potentiometers, and are often used in their place. Some audio gear uses them, and are recognisable as volume controls with regular bumps or clicks as they turn. They are also used in mechanical trackballs and mice, as well as lots of other applications that require accurate rotational sensing.

In hobbyist applications, they are handy for all sorts of things - potentiometer replacements, up/down switching, etc. Using them with AVRs, PICs and Arduinos is quite common and they are easily available.

Saturday 1 October 2011

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...

Thursday 29 September 2011

Open Bench Logic Sniffer "case"

The Open Bench Logic Analyser is a cheap ($50) open source logic analyser board, which talks a standard (ie open) protocol to a PC client. Very useful!

As it's just a bare board, lots of people have designed and build their own case for it. Many are built with 3d printers and related methods. I did one too, but instead of going the real high tech route, I just used a slab of 6mm Perspex, cut into 3 pieces and with slots milled for the PCB to slide into.

Check it out:

Sunday 25 September 2011

Brewing stir plate

As an avid homebrewer, I'm constantly trying ways to improve the quality of my brew. Unless you brew Westvleteren, there is always room for improvement. Tweaks to the recipes, better equipment and better technique are all ways I try to better my beer. And as a maker, I find joy out of building better brew gear.

Whilst reading Brew Like A Monk, I learned of the importance of yeast in beer, in particular how the Belgians don't just chuck in whatever yeast they get their hands on, but rather consider it one of the most important aspects to get right. Careful yeast propagation, concentrations and temperatures all affect beer quite dramatically.

So after been enlightened on the culture of yeast [bad pun, sorry], I decided that my brews were going to get a better yeasting.

Tuesday 13 September 2011

Old PCB pen holder

Old circuit boards can be found all over the place. Large boards loaded with logic chips are particularly interesting finds. Rather than let them go to waste, or trying to reuse the chips, why not turn them into a pen holder? That's what I did, and it suits my desk perfectly.

This board has 17 x 74LS chips, and 4 sram chips.. Does your pen holder have 16k of RAM?

All I did was cut the board into 4 equal sized pieces, then joined them at right angles.

For the bottom (not visible in these photos), I used a piece of mousemat which protects pen nibs.

Saturday 10 September 2011

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.

Monday 5 September 2011

High Voltage Capacitor vs CD

It's hard to beat an afternoon blowing crap up, and my toy of choice is my 0.25uF/35kV capacitor. This beast stores 150 joules of energy and can dump it all in a tiny fraction of a second.

It amounts to a peak energy of millions of watts of power! It's hard to pass up some fun with this baby.

Saturday 3 September 2011

A Nixie Tube clock

This is a repost from my old mothballed blog, this project still gets interest.

For the last couple of years I've been keen to build a nixie tube clock.

Nixie tubes are those early (1950's-70s) display tubes often used in industrial and commercial applications, before the advent of LEDs and LCDs. They novelty and attractiveness led me to finally wanting to build one, but it wasn't until after I'd moved back to Sydney from Holland that I was able to get around to it.

My clock is built entirely from scratch, and is based on 4000 series logic ICs for the actual clock counting, and 74141 chips for the tube drivers. It's self contained, requiring only a 12v AC/DC plug pack to run. It features 6 digits (HH.MM.SS), buttons for setting hours, minutes, and zero seconds, 1 minute per year accuracy, supercap power backup and an LDR to shut the display off after a predetermined period of darkness (switch overridable).

Wednesday 31 August 2011

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.

Monday 29 August 2011

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.

Wednesday 24 August 2011

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).

Sunday 21 August 2011

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.

Friday 19 August 2011

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.

Monday 15 August 2011

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.

Sunday 14 August 2011

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.

Wednesday 10 August 2011

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 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!