When it comes to high-speed, high-voltage switching, there are a wealth of components to choose from — MOSFETS, thyristors, IGBTs, and even vacuum tubes like thyratrons. But who needs all that expensive silicon (or glass) when all you need to build a high-voltage switch is some plumbing fixtures and a lathe?
At least that’s the approach that budget-minded laser experimenter [Les Wright] took with his latest triggered spark gap build. We’ve been watching his work for a while now, especially his transversely excited atmospheric (TEA) lasers. These are conceptually simple lasers that seem easy to build, at least compared to other lasers. But they do require a rapid pulse of high voltage across their long parallel electrodes to lase, and controlling the pulse is where this triggered spark gap shines.
The spark gap is made from brass plumbing fittings on either end of a short PVC coupler. [Les] used his lathe to put a thread into one of the caps to accept a spark plug, the center electrode of which pokes through a small hole in the metal cathode. To trigger the spark gap, [Les] built a trigger generator that outputs about 15,000 volts, which arcs from the spark plug electrode to the spark gap cathode in the low-pressure nitrogen environment. Little spark leads to big spark, big spark discharges a capacitor across the laser electrodes, and you’ve got a controlled single-shot laser. Check it out in the video below.
Every hacker out there is familiar with the zaps and sizzles of the Tesla coil, or the crash and thunder of lighting strikes on our hallowed Earth. These phenomena all involve the physics of plasma, a subject near and dear to Jay Bowles’s heart. Thus, he graced Remoticon 2021 with a enlightening talk taking us on a Dip Into the Plasmaverse.
Most of our projects are, to some extent, an exercise in glitch-reduction. Whether they’re self-inflicted software or hardware mistakes, or even if the glitches in question come from sources beyond our control, the whole point of the thing is to get it running smoothly and predictably.
That’s not always the case, though. Sometimes inducing a glitch on purpose can be a useful tool, especially when reverse engineering something. That’s where this low-cost electromagnetic fault injection tool could come in handy. EMFI is a way to disrupt the normal flow of a program running on an embedded system; properly applied and with a fair amount of luck, it can be used to put the system into an exploitable state. The PicoEMP, as [Colin O’Flynn] dubs his EMFI tool, is a somewhat tamer version of his previous ChipSHOUTER tool. PicoEMP focuses on user safety, an important consideration given that its business end can put about 250 volts across its output. Safety features include isolation for the Raspberry Pi Pico that generates the PWM signals for the HV section, a safety enclosure over the HV components, and a switch to discharge the capacitors and prevent unpleasant surprises.
In use, the high-voltage pulse is applied across an injection tip, which is basically a ferrite-core antenna. The tip concentrates the magnetic flux in a small area, which hopefully will cause the intended glitch in the target system. The video below shows the PicoEMP being used to glitch a Bitcoin wallet, as well as some tests on the HV pulse.
If you’re interested in the PicoEMP and glitching in general, be sure to watch out for [Colin]’s 2021 Remoticon talk on the subject. Until that comes out, you might want to look into glitching attacks on a Nintendo DSi and a USB glitch on a Wacom tablet.
When he’s not busy with his day job as professor of computer and automotive engineering at Weber State University, [John Kelly] is a prolific producer of educational videos. We found his video tracing out the 22+ meters of high voltage cabling in a Tesla Model S (below the break) quite interesting. [John] does warn that his videos are highly detailed and may not be for everyone:
This is not the Disney Channel. If you are looking to be entertained, this is not the channel for you.
We ignored the warning and jumped right in. The “high” voltages in the case of an electric vehicle (EV) like the Model S is approximately 400 volts. Briefly, external input via the charge connector can be single or three phase, 120 or 250 VAC, depending on your region and charging station. This get boosted to a nominal 400 VDC bus that is distributed around the various vehicle systems, including the motors and the battery pack.
On-board charger module
Rear motor inverter
High voltage junction block
Cabin air heater
DC to DC converter
Battery coolant heater
Air conditioning compressor
Front motor inverter
He goes through each module, showing in detail the power routing and functionality, eventually assembling the whole system spanning two work benches. We liked his dive into the computer-controlled fuse that recently replaced the standard style one, and were impressed with his thorough use of labels.
If you’ve ever been curious about the high voltage distribution of a EV, grab some popcorn and check out this video. Glancing through his dozens of playlists, [John]’s channel would be a good place to visit if you’re interested any topic related to hybrids and electric vehicles, drive trains, and/or transmissions. We’ve written about some Tesla teardowns before, the Model 3 and the Model S battery packs. Have you worked on / hacked the high voltage system in your EV? Let us know in the comments below.
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.
[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.
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.