High-voltage experimenters have been using automotive ignition coils to generate impressive sparks in the home lab for decades, and why not? They’re cheap, easily obtainable, and at the end of the day, producing sparks is literally what they’re designed to do. But that doesn’t mean there isn’t room for improvement.
In his latest Plasma Channel video [Jay Bowles] revisits this classic experiment, bringing to bear the considerable high-voltage experience he’s gained over the last several years. Building on an earlier setup that used a single Honda ignition coil, this new dual-coil version can produce up to 60,000 volts and is driven by a cleaner and more reliable circuit based on the iconic 555 timer. A pair of potentiometers on the front of the driver can adjust its square wave output from 1 to 10 kilohertz manually, while a commercial Bluetooth audio receiver tied into the 555 circuit allows the output to be modulated by simply playing audio from a paired device.
It probably won’t come as much surprise to find that a blast of hot plasma can be used to sterilize a surface. Unfortunately, said surface is likely going to look a bit worse for wear afterwards, which limits the usefulness of this particular technique. But as it turns out, it’s possible to generate a so-called “cold” plasma that offers the same cleansing properties in a much friendlier form.
Cold plasma stopped bacterial growth in the circled area.
[Jay] takes viewers through a few of the different approaches he tried before finally settling on the winning combination of a glass pipette with a copper wire run down the center. When connected to a party store helium tank and the compact Slayer Exciter coil he built last year, the setup produced a focused jet of plasma that was cool enough to touch.
It’s beautiful to look at, but is a pretty light show all you get for your helium? To see if his device was capable of sterilizing surfaces, he inoculated a set of growth plates with bacteria collected from his hands and exposed them to the cold plasma stream. Compared to the untreated control group the reduction in bacterial growth certainly looks compelling, although the narrow jet does have a very localized effect.
If you’re just looking to keep your hands clean, some soap and warm water are probably a safer bet. But this technology does appear to have some fascinating medical applications, and as [Jay] points out, the European Space Agency has been researching the concept for some time now. Who knows? In the not so distant future, you may see a similar looking gadget at your doctor’s office. It certainly wouldn’t be the first time space-tested tech came down to us Earthlings.
Finding high voltage capacitors can be tricky. Sure, you can buy these capacitors, but they are often expensive and hard to find exactly what you want. [RachelAnne] needed some low-value variable capacitors that would work at 100 kV. So she made some.
Instead of fabricating the plates directly, these capacitors use laminations from a scrap power transformer. These usually have two types of plates, one of which looks like a letter “E” and the other just like a straight bar. For dielectric, the capacitors use common transparency film.
The average Hackaday user could probably piece together a rough model of a simple DC motor with what they’ve got kicking around the parts bin. We imagine some of you could even get a brushless one up and running without too much trouble. But what about an electrostatic corona motor? If your knowledge of turning high voltage into rotational energy is a bit rusty, let [Jay Bowles] show you the ropes in his latest Plasma Channel video.
Like many of his projects, this corona motor relies on a few sheets of acrylic, a handful of fasteners, and a healthy dose of physics. The actual construction and wiring of the motor is, if you’ll excuse the pun, shockingly simple. Of course part of that is due to the fact that the motor is only half the equation, you still need a high voltage source to get it running.
An earlier version of the motor ended up being too heavy.
In this case, [Jay] is revisiting his earlier experiments with atmospheric electricity to provide the necessary jolt. One side of the motor is connected to a metallic mesh electrode that’s carried 100 m into the air by a DJI Mini2 drone, while the other side is hooked up to several large nails driven into the ground.
The potential between the two gets the motor spinning, and makes for an impressive demonstration, but it’s not exactly the most practical way to experiment with your new corona motor. If you’d rather get it running on the workbench, he also shows that a more traditional high voltage source like a Van de Graaff generator will do the job nicely. As an added bonus, it can even power the device wirelessly from a few feet away.
So what can you do with a corona motor? While [Jay] is quick to explain that these sort of devices aren’t exactly known for their torque, he does show that his motor is able to lift a 45 gram weight suspended from a string. That’s frankly more power than we expected, and makes us wonder if there is some quasi-practical application for this contraption. If there is we suspect it’ll be featured in a future Plasma Channel video, so stay tuned.
When we use an electronic component, we have some idea of what goes on inside it. We know that inside a transistor there’s a little piece of semiconductor with a junction made from differently doped regions etched into it, and in a capacitor, there will be metalized plates on the surface of some kind of dielectric. Reverse engineering has given us extensive die photography of integrated circuits, but there remain a few component mysteries to be uncovered. One is laid bare by [WizardTim], as he cross-sections a 20KV high-voltage diode.
A conventional low-voltage silicon diode has a forward voltage drop of about 0.7V and a relatively low maximum reverse voltage, for example with the 1N4001 rectifier it’s 50V. For the higher-spec 1N4007, the reverse voltage rating is 700V. This diode has a 25KV reverse voltage, and a clue to its construction comes in its quoted 45V forward voltage. Sure enough, when mounted in resin and carefully sanded and polished flat it reveals its interior as a stack of diodes in series to increase the reverse voltage at the expense of forward voltage.
Revealing the inner workings of an unusual component is fascinating, and the lapping technique used is definitely worth a look. It’s something we’ve seen before, for example in reducing CPU thickness for increased performance.
While we typically encourage hackers to make their own tools or machines when practical, x-ray machines don’t usually make that list. Despite the risk of radiation, [William Osman] has done just that and built a homemade x-ray machine. After receiving an eye-watering medical bill, [William] resolves to make his own x-ray machine in the hopes of avoiding future bills. Thanks to his insurance, the total owed was smaller but still ridiculous to those who live in single-payer health care countries, but it got William thinking. What if he could make an x-ray machine to do cheap x-rays?
Armed with a cheap high voltage DC power supply he acquired from an online auction house, he started to power up his x-ray vacuum tube. A smaller power supply energizes the cathode and forms an electron beam. Then the high voltage (30-150kv) is applied as a tube voltage, accelerating the electrons into x-rays. Safety measures are taken somewhat haphazardly with Geiger counters and lead sheets. With a finger bone cast in ballistic shell [William] made his first x-ray with a long exposure on a DSLR. The next items to go in the x-ray “chamber” were a phone and a hand. The results were actually pretty decent and you can clearly see the bones.
We’ve seen homemade X-Ray machines here at Hackaday before, but not one that is constructed perhaps so haphazardly — his approach makes this obvious: don’t try this at home. Video after the break.
It’s easy to think that devices which generate thousands of volts of electricity must involve relatively modern technology, but the fact is, machines capable of firing sparks through open air predate Edison’s light bulb. Which means that recreating them with modern tools, construction techniques, and part availability, is probably a lot easier than most people realize. The fascinating machine [Jay Bowles] put together for his latest Plasma Channel video is a perfect example, as it’s capable of developing 6,000 volts without any electronic components.
Now as clever as [Jay] might be, he can’t take credit for the idea on this one. That honor goes to Lord Kelvin, who came up with this particular style of electrostatic generator back in 1867. Alternately called “Kelvin water dropper” or “Lord Kelvin’s Thunderstorm”, the machine is able to produce a high voltage charge from falling water without using any moving parts.
Diverging streams means a charge is building up.
Our very own [Steven Dufresne] wrote an in-depth look at how these devices operate, but the short version is that a negative and positive charge is built up in two sets of metallic inductor rings and buckets, with the stream of water itself acting as a sort of wire to carry the charge up to the overhead water reservoir. As [Jay] demonstrates the video, you’ll know things are working when the streams of water become attracted to the inductors they are passing through.
Rather than connecting a separate spark gap up to the water “receivers” on the bottom of his water dropper, [Jay] found the handles on the metal mugs he’s using worked just as well. By moving the mugs closer and farther away he can adjust the gap, and a second adjustment lets him move the vertical position of the inductors. It sounds like it takes some fiddling to get everything in position, but once it’s working, the whole thing is very impressive.
