In high voltage applications involving tens of thousands of volts, too often people think about the high voltage needed but don’t consider the current. This is especially so when part of the circuit that the charge travels through is an air gap, and the charge is in the form of ions. That’s a far cry from electrons flowing in copper wire or moving through resistors.
Consider the lifter. The lifter is a fun, lightweight flying machine. It consists of a thin wire and an aluminum foil skirt separated by an air gap. Apply 25kV volts across that air gap and it lifts into the air.
Lifter flying with high voltage power supply
So you’d think that the small handheld Van de Graaff generator pictured below, that’s capable of 80kV, could power the lifter. However, like many high voltage applications, the lifter works by ionizing air, in this case ionizing air surrounding the thin wire resulting in a bluish corona. That sets off a chain of events that produces a downward flowing jet of air, commonly called ion wind, lifting the lifter upward.
Having hacked away with high voltage for many years I’ve ended up using a large number of very different high voltage sources. I say sources and not power supplies because I’ve even powered a corona motor by rubbing a PVC pipe with a cotton cloth, making use of the triboelectric effect. But while the voltage from that is high, the current is too low for producing the necessary ion wind to make a lifter fly up off a tabletop. For that I use a flyback transformer and Cockcroft-Walton voltage multiplier power supply that’s plugged into a wall socket.
So yes, I have an unorthodox skillset when it comes to sourcing high voltage. It’s time I sat down and listed most of the power sources I’ve used over the years, including a bit about how they work, what their output is like and what they can be used for, as well as some idea of cost or ease of making. The order is from least powerful to most powerful so keep reading for the ones that really bite.
You’ve no doubt encountered this effect. It’s how your body is charged when you rub your feet on carpet and then get a shock from touching a door knob. When you rub two specific materials together there’s a transfer of electrons from one to the other. Not just any two materials will work. To find out which materials are good to use, have a look at a triboelectric series table.
Materials that are on the positive end of the table will become positively charged when rubbed against materials on the negative end of the table. Those materials will become negatively charged. The further apart they are in the table, the stronger the charging.
[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.
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.
[Skyy] sent us a video of him cooking s’mores with an electric arc. He’s using a flyback transformer with a zero voltage switching (ZVS) driver. This produces about 50 kV, which is more than enough to toast the marshmallow.
ZVS is a technique that triggers the semiconductor switches when they have zero voltage across them. This ensures that there’s minimal heat created by the switches, since they are not interrupting any current at the time they are toggled. ZVS is also used in lighting dimmers to switch off power without creating interference.
If you’re interested in the details, there’s a great tutorial on building the driver. If you’re interested in learning how it works, check out this simulation video.
[Skyy] admits that his setup isn’t terribly safe since it uses a breadboard, which isn’t rated for the high voltages and currents. Keep in mind that these circuits could kill you. After the break, watch a marshmallow fry in a 50 kV arc.
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.
[Grenadier] Had some spare wire, electrical tape, and a giant ferrite core laying about and decided to create a massive and pretty snappy looking disk shaped flyback transformer. Dubbed the Fryback, he claims that it will “revitalise your health and bring wondrous wealth and prosperity to your family”.
He chose a disk shaped transformer because they look cooler, fair enough.. (oh and they reduced inter-winding capacitance and the voltage difference between layers). The construction is fairly simple, but time consuming. Grenadier goes through the important steps on his website, but be prepared for 25 hours of winding wire if you decide to make your own.
Running at 48V the Fryback can output 8kV at a very high current, producing some nice thick 30cm long sparks. Check out the video after the break to see the Fryback in action.