What Goes Into A High Voltage Diode?

October 3, 2021 by Jenny List 12 Comments

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.

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a very slapdash x-ray machine on a table

Building An X-Ray Machine

September 9, 2021 by Matthew Carlson 56 Comments

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.

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Lord Kelvin’s Contraption Turns Drips Into Sparks

July 22, 2021 by Tom Nardi 21 Comments

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.

Of course if you’re looking to get serious with high voltage experiments, you’ll want to upgrade to some less whimsical equipment pretty quickly. Luckily, [Jay] has shown that putting together a reliable HV supply doesn’t need to be expensive or complicated.

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Overdriving Vacuum Tubes And Releasing The Magic Light Within

July 15, 2021 by Dan Maloney 53 Comments

We’ve all seen electronic components that have been coaxed into releasing their small amount of Magic Smoke, which of course is what makes the thing work in the first place. But back in the old times, parts were made of glass and metal and were much tougher — you could do almost anything to them and they wouldn’t release the Magic Smoke. It was very boring.

Unless you knew the secret of “red plating”, of course, which [David Lovett] explores in the video below. We’ve been following [David]’s work with vacuum tubes, the aforementioned essentially smokeless components that he’s putting to use to build a simple one-bit microprocessor. His circuits tend to drive tubes rather gently, but in a fun twist, he let his destructive side out for a bit and really pushed a few tubes to see what happens. And what happens is pretty dramatic — when enough electrons stream from the cathode to the anode, their collective kinetic energy heats the plate up to a cherry-red, hence the term “red plating”.

[David] selected a number of victims for his torture chamber, not all of which cooperated despite the roughly 195 volts applied to the plate. Some of the tubes, though, cooperated in spades, quickly taking on a very unhealthy glow. One tube, a 6BZ7 dual triode, really put on a show, with something getting so hot inside the tube as to warp and short together, leading to some impressive pyrotechnics. Think of it as releasing the Magic Light instead of the Magic Smoke.

Having seen how X-ray tubes work, we can’t help but wonder if [David] was getting a little bit more than he bargained for when he made this snuff film. Probably not — the energies involved with medical X-ray tubes are much higher than this — but still, it might be interesting to see what kinds of unintended emissions red-plating generates.

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Is That An EMP Generator In Your Pocket Or Is My Calculator Just Broken?

June 17, 2021 by Dan Maloney 39 Comments

Ah, what fond memories we have of our misspent youth, walking around with a 9,000-volt electromagnetic pulse generator in our Levi’s 501s and zapping all the electronic devices nobody yet carried with them everywhere they went. Crazy days indeed.

We’re sure that’s not at all what [Rostislav Persion] had in mind when designing his portable EMP generator; given the different topologies and the careful measurement of results, we suspect his interest is strictly academic. There are three different designs presented, all centering around a battery-powered high-voltage power module, the Amazon listing of which optimistically lists as capable of a 400,000- to 700,000-volt output. Sadly, [Rostislav]’s unit was capable of a mere 9,000 volts, which luckily was enough to get some results.

Coupled to a spark gap, one of seven different coils — from one to 40 turns — and plus or minus some high-voltage capacitors in series or parallel, he tested each configuration’s ability to interfere with a simple pocket calculator. The best range for a reset and scramble of the calculator was only about 3″ (7.6 cm), although an LED hooked to a second coil could detect the EMP up to 16″ (41 cm) away. [Rostislav]’s finished EMP generators were housed in a number of different enclosures, one of which totally doesn’t resemble a pipe bomb and whose “RF Hazard” labels are sure not to arouse suspicions when brandished in public.

We suppose these experiments lay to rest the Hollywood hype about EMP generators, but then again, their range is pretty limited. You might want to rethink your bank heist plans if they center around one of these designs.

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Flat Transformer Gives This PCB Tesla Coil Some Kick

June 9, 2021 by Dan Maloney 16 Comments

Arguably, the most tedious part of any Tesla coil build is winding the transformer. Getting that fine wire wound onto a suitable form, making everything neat, and making sure it’s electrically and mechanically sound can be tricky, and it’s a make-or-break proposition, both in terms of the function and the aesthetics of the final product. So this high-output printed circuit Tesla should take away some of that tedium and uncertainty.

Now, PCB coils are nothing new — we’ve seen plenty of examples used for everything from motors to speakers. We’ve even seen a few PCB Tesla coils, but as [Ray Ring] points out, these have mostly been lower-output coils that fail to bring the heat, as it were. His printed coil generates some pretty serious streamers — a foot long (30 cm) in some cases. The secondary of the coil has 6-mil traces spaced 6 mils apart, for a total of 240 turns. The primary is a single 240-mil trace on the other side of the board, and the whole thing is potted in a clear, two-part epoxy resin to prevent arcing. Driven by the non-resonant half-bridge driver living on the PCB below it, the coil can really pack a punch. A complete schematic and build info can be found in the link above, while the video below shows off just what it can do.

Honestly, for the amount of work the PCB coil saves, we’re tempted to give this a try. It might not have the classic good looks of a hand-wound coil, but it certainly gets the job done. Continue reading “Flat Transformer Gives This PCB Tesla Coil Some Kick” →

High Voltage Gives Metal Balls A Mind Of Their Own

May 25, 2021 by Tom Nardi 19 Comments

Have you ever seen something that’s so fascinating you’re sure there has to be some kind of practical application for it, but you just can’t figure out what? That’s how we feel when watching tiny ball bearings assemble themselves into alien-like structures under the influence of high voltage in the latest Plasma Channel video from [Jay Bowles].

Now to be clear, [Jay] isn’t trying to take credit for the idea. He explains that researchers at Stanford University first documented the phenomenon back in 2015, and that his goal was to recreate their initial results as a baseline and go from there. The process is pretty simple: put small metal ball bearings into a tray of oil, apply high voltage, and watch them self-assemble into “wires” that branch out in search of the ground terminal like a plant’s roots looking for water. With the encouragement of his 500,000 volt Van de Graaff generator, the ball bearings leaped into action and created structures just like in the Stanford study.

With the basic pieces now in place, [Jay] starts to push the envelope. He experiments with various oils to see how their viscosity impacts the ball’s ability to assemble, finding that olive oil seems to be the ideal candidate (at least of those he’s tried so far). He also switches up the size and shape of the tray, to try and find how far the balls can realistically stretch out on their own.

In the end we’re no closer to finding a practical application for this wild effect than the good folks at Stanford were back in 2015, but at least we got to watch the little fellows do their thing in glorious 4K and with the exceptional production value we’ve come to expect from Plasma Channel. That said, [Jay] does hint at his ongoing efforts to turn the structures into works of art by “freezing” them with clear resin, so keep your eyes out for that.

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