A Quickly-Hacked-Together Avalanche Pulse Generator

There are times when you make the effort to do a superlative job in the construction of an electronic project. You select the components carefully, design the perfect printed circuit board, and wait for all the pieces to come together as they come in the mail one by one. You then build it with tender care and attention, printing solder paste and placing components by hand with a fastidious attention to detail. There follows an anxious wait by the reflow oven as mysterious clouds of smoke waft towards the smoke detector, before you remove your batch of perfect boards and wait for them to cool.

Alternatively, there are other times when you want the device but you’re too impatient to wait, and anyway you’ve only got half of the components and a pile of junk. So you hack something a bit nasty together on the copper groundplane of a surplus prototype PCB in an evening with ‘scope and soldering iron. It’s not in any way pretty but it works, so you use it and get on with your life.

Our avalanche pulse generator schematic. The pulse generator itself is the single 2N3904 on the right.
Our avalanche pulse generator schematic. The pulse generator itself is the single 2N3904 on the right.

When you are a Hackaday writer with some oscilloscope bandwidths to measure, you need a picosecond avalanche pulse generator, and you need one fast. Fortunately they’re a very simple circuit with only one 2N3904 transistor, but the snag is they need a high voltage power supply well over 100 V. So the challenge isn’t making the pulse generator, but making its power supply.

For our pulse generator we lacked the handy Linear Technologies switcher used by the avalanche pulse generator project we were copying. It was time for a bit of back-to-basics flyback supply creation, robbing a surplus ATX PSU for its base drive transformer, high voltage diode and capacitor, and driving it through a CRT line output transistor fed by a two-transistor astable multivibrator. Astoundingly it worked, and with the output voltage adjusted to just over 150V the pulse generator started oscillating as it should.

We’ve looked at avalanche pulse generators once before here at Hackaday, and very recently we featured one used to measure the speed of light. We’ll be using this one tomorrow for a ‘scope comparison.

Play Music on a High Voltage Keyboard

[Matt] works at a neon sign power supply company. When a vendor error left him with quite a few defective high voltage transformers, he couldn’t bring himself to toss them in the bin. [Matt] was able to fix the transformers well enough to work, and the idea for a high voltage keyboard began to brew. Unfortunately, the original transformers were not up to the task of creating a musical arc. At that point the project had taken on a life of its own. Matt grabbed some higher power transformers and started building.

The keyboard has 25  keys, each connected to an individual high voltage circuit with its own spark gap. The HV circuit is based upon a IR2153D self-oscillating half-bridge driver. (PDF link). The 2153D is modulated by a good old-fashioned 555 timer chip. No micros in this design, folks! The output of the IR2153D switches a pair of N-channel MOSFETS which drive the flyback transformers.

[Matt] created 25 copies of his circuit and built them up on individual PCBs. He assembled everything on a wooden board shaped roughly like a grand piano. The final project looks great – though [Matt] admittedly has no musical ability, so we can’t hear AC/DC flying out of those spark gaps just yet.

If you do want to hear sparks playing music, check out the OneTesla project we saw at MakerFaire NY 2013.

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An Easy Way To Power Flyback Transformers


Let’s be honest. Playing with high voltage is awesome. Dangerous, but awesome — well, as long as you handle it properly. Flyback transformers are a great way to make a nice big electrical arc, but powering them isn’t that easy — or is it?

First off, for those that may not know, a flyback transformer is the type of transformer most commonly found in old TVs and CRT monitors. They typically can put out anywhere from 10kV to 50kV — the problem is, they aren’t that easy to power. Common methods include using a transistor style driver, or zero voltage switching (ZVS) — which is how [Skyy] cooked some s’mores at 50,000V.

As it turns out there’s another much easier and straight forward method. All you need is a fluorescent light ballast. Use the output on the ballast as the input on the primary winding of the flyback transformer — which can be found using a multimeter, just find the highest resistance between pins to identify it. Now because you’re working with such high voltages, you may want to insulate the flyback transformer by submerging it in mineral oil as to not short it out. That’s it.

Now it’s time to make some sparks.

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Homebuilt 30kV High Voltage Power Supply

If you have need for 30,000 volts to launch your ionocraft (lifter) or power other DIY projects then shuttle over to RimstarOrg’s YouTube channel and checkout [Steven Dufresne’s] homebuilt 30kV power supply. The construction details that [Steven] includes in his videos are always amazing, especially for visual learners. If you prefer text over video he was kind enough to share a schematic and full write up at rimstar.org.

The power supply can be configured for 1.2kV – 4.6kV or 4kV – 30kV at the output while requiring 0-24V DC at the input. In the video [Steven] tries two power supplies. His homemade DC bench power supply at 8V and 2.5A and also a laptop power supply rated at 20V 1.8A DC. A couple of common 2N3055 power transistors, proper wattage resistors, a flyback transformer and a high voltage tripler is about all you’ll need to scrounge up. The flyback transformer can be found in old CRT type televisions, and he does go into details on rewinding the primary for this build. The high voltage tripler [Steven] references might be a bit harder to source. He lists a few alternates for the tripler but even those are scarce: NTE 521, Siemens 76-1 N094, 1895-641-045. There are lots of voltage multiplier details in the wild, but keep in mind this tripler needs to operate up to 30kV.

Join us after the break to watch the video and for a little advice from Mr. Safety.

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High Voltage: Controlling a flyback transformer with an Arduino

If you’d like to build a Jacob’s ladder, an ignition system for a flamethrower, or for some ungodly reason you need 15 kilovolts for a prop replica or cosplay build, this one is for you. It’s an easy to build high voltage power supply that interfaces with an Arduino.

After harvesting a flyback from the power board of a CRT, [Andrew Moser] added a new primary coil to the transformer. This boosts 12 volts that can be easily controlled by an Arduino to something that will arc an inch and a half. The next step building the flyback driver. [Andrew] used a MOSFET and MOSFET driver for this circuit (although he says this guy works without the driver). After that, all that’s left to do is write some software and test it out.

Of course this comes with the boilerplate warning, “If you don’t know what you’re doing, you might die.” That being said, if you ever wanted to test out an Arduino’s resistance to EMP, this is the project for you. Check out the flyback powering a Jacob’s ladder after the break.

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More high voltage experimentation with a flyback inverter

[Electorials] actually makes working with a flyback inverter sound rather easy. This comes hot on the heals of the huge high voltage collection we saw the other day, but slows way down in the presentation of information. This makes the project very approachable for the newbie, especially considering that the majority of the testing is done with low voltages.

He’s using a flyback transform for this project, which can be pulled from an old CRT monitor. Once you have one in hand, all that’s required to figure out how to use it is a voltometer, a 9V battery, a MOSFET (also salvaged in this case), and miscellaneous components. Once he establishes what each external connection does electronically, [Electorials] builds his circuit on a breadboard, then uses it to create plasma in the bulb above as well as to light up a CCFL.

Ionocraft aka Lifters

It’s hard to believe that in five years we haven’t covered lifters before. This realization was sparked when [Tyler] tipped us off about a lifter project demonstrated at the Kansas City hackerspace called CCCKC.

Lifters, the casual name for ionocraft, fly without combustion or moving parts. We’re not going to tackle the particulars of what makes flight possible, but high voltage is required to feed the phenomenon that provides the lift. One of the first comments when we asked what to do with old CRT monitors was to use them for lifters. The flyback transformer puts out plenty of voltage if you can tap into it without killing yourself (no, seriously, that’s an issue).

This is the method that the CCCKC folks used. Take a peek at the video after the break. If you’re thirsting for more fun with lifters, stop by the Lifter Project.

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