microwave oven transformer

19 Articles

Don’t Try This At Home, Transcranial Magnetic Stimulation Edition

October 7, 2026 by 21 Comments

Transcranial magnetic stimulation is one of those things that seems too wacky to be true. Depression not responding to treatment? Let’s smack you upside the head with strong magnetic fields! As odd as it sounds, it’s actually very well studied and works often enough that it has been approved by regulatory agencies as real evidence based medicine.

It’s also now open source, thanks to the OpenTMS project by [Zach McGinty]. Though since its not approved by the FDA or your local authority, be very aware of [Zach]’s disclaimer that this is not a medical device and if you do build something based on the extensive data on his GitHub, you do so at your own risk.

He’s got plans for the coils that go next to your head — made of hollow copper pipe to carry coolant, just like the pros do it — and the power supply to pulse them with mind-altering amounts of electricity. That might be literal in this case, but it’s also a hefty power supply: a pair of microwave oven transformers, switched through IGBTs in a flyback configuration. We’re talking kiloamps here, so make sure you know what you’re about before you try putting that kind of power right next to your skull.

[Zach] did, and he’s still here. Though to be fair, we’re not sure if he’s a very good engineer or just very lucky. Given he’s isolated the IGBT gate controls with fiber optics, and seems to follow other best practices, we’re going to guess the former, but it might still be both.

Either way, this one is going firmly into the “don’t try this at home” bucket. Even so we’re happy to see more medicine go open source, be it assistive sip-and-puff pointing devices, or ESP32 electroencephalograms. If nothing else, it keeps the big boys on their toes, and that’s what hacking is all about.

Handle Sheet Metal With The Power Of Microwave Oven Electromagnets

May 23, 2023 by 17 Comments

For those of us who don’t do it every day, handling sheet metal can be a nerve-wracking affair. Sheet metal is thin, heavy, and sharp, and one wrong move while handling it can have much the same result as other such objects, like guillotine blades. If only there was a way to lessen the danger.

Perhaps something like this electromagnetic sheet metal handler by [Lucas] over at “Cranktown City” would be useful in keeping one’s fingers and toes attached. Like many interesting builds, this one starts with the dismemberment of a couple of old microwave ovens, to liberate their transformers. Further dissection resulted in open-frame electromagnets, which when energized with a battery from a Ryobi cordless tool do a fine job sticking to stuff.

[Lucas] then harvested the battery connector from the cheapest possible Ryobi tool — an electric fan — and built a prototype, which worked well enough to proceed to a more polished version two. This one had the same guts in a nicely designed case, 3D-printed from lime green filament for that OEM look. The video below shows the design and build, as well as field testing. We have to say this gave us a bit of pause, especially when the battery popped out of one of the handlers and sent the sheet on a near-miss of [Lucas]’ toes. Close call there.

If you’re thinking that you’ve seen MOTs repurposed as electromagnets before, you’re right. Whether climbing like [Spider-Man], lifting heavy steel beams, or walking upside down, microwave oven transformers are the key.

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The Deadliest Project On The Internet?

May 2, 2022 by 96 Comments

Before deciding whether the headline of this article is clickbait, please take a moment to watch the excellent video by [BigClive] below the break. And then, go to your local search engine and search the phrase “fractal burning death”. We’ll wait.

With that out of the way, we have to admit that when we saw the subject “The most deadly project on the Internet” on [bigclivedotcom]’s YouTube channel, we were a bit skeptical. It’s a big claim. But then we watched the video and did some googling. Sadly, there are over 30 documented cases of this project killing people, and more cases of permanent grievous injury.

The results of Fractal Wood Burning with High Voltage

Fractal Burning is a hobby where wood is burned by slathering wood in a conductive slurry and then applying high voltage to either side of the wood, usually using something not rated for high voltage, such as jumper cables. The High Voltage is supplied by an unmodified Microwave Oven Transformer. Other projects using MOT’s typically rip out the high voltage secondary windings and re-wind them as low voltage, high amperage transformers, and are using in Spot Welders and even arc welders.

As laid out by [BigClive], the voltages coming from an unmodified MOT, ranging from 2-3 KV (That’s between two and three thousand Volts) at a very low impedance are right up there in the “Don’t go near it!” territory.

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Ambitious Spot Welder Really Pushes The Amps

April 16, 2021 by 18 Comments

On the face of it, a spot welder is a simple device. If you dump enough current through two pieces of metal very quickly, they’ll heat up enough to melt and fuse together. But as with many things, the devil is in the details, and building a proper spot welder can be as much about addressing those details as seeing to the basics.

We haven’t featured anything from our friends over at [Make It Extreme], where they’re as much about building tools as they are about using them to build other things, if not more so. We expect, though, that this sturdy-looking spot welder will show up in a future video, because it really looks the business, and seems to work really well. The electronics are deceptively simple — just rewound microwave oven transformers and a simple timer switch to control the current pulse. What’s neat is that they used a pair of transformers to boost the current considerably — they reckon the current at 1,000 A, making the machine capable of welding stock up to 4 mm thick.

With the electrical end worked out, the rest of the build concentrated on the housing. A key to good-quality spot welds is solid physical pressure between the electrodes, which is provided by a leverage-compounding linkage as well as the long, solid-copper electrodes. We’ve got to say that the sweep of the locking handle looks very ergonomic, and we like the way closing down the handle activates the current pulse. Extra points for the carbon-fiber look on the finished version. The video below shows the build and a demo of what it can do.

Most of the spot welders we see are further down the food chain than this one, specialized as they are for welding battery packs and the like. We do recall one other very professional-looking spot welder, though.

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Modified Tombstone Welder Contains A Host Of Hacks

September 12, 2019 by 30 Comments

State-of-the-art welding machines aren’t cheap, and for good reason: pushing around that much current in a controlled way and doing it over an entire workday takes some heavy-duty parts. There are bargains to be found, though, especially in the most basic of machines: AC stick welders. The familiar and aptly named “tombstone” welders can do the business, and they’re a great tool to learn how to lay a bead.

Tombstones are not without their drawbacks, though, and while others might buy a different welder when bumping up against those limits, [Greg Hildstrom] decided to hack his AC stick welder into an AC/DC welder with TIG. He details the panoply of mods he made to the welder, from a new 50 A cordset made from three extension cords where all three 12 gauge wires in each cord are connected together to make much larger effective conductors, to adding rectifiers and a choke made from the frame of a microwave oven transformer to produce DC output at the full 225 A rating. By the end of the project the tombstone was chock full of hacks, including a homemade foot pedal for voltage control, new industry-standard connectors for everything, and with the help of a vintage Lincoln “Hi-Freq” controller, support for TIG, or tungsten inert gas welding. His blog post shows some of the many test beads he’s put down with the machine, and the video playlist linked below shows highlights of the build.

This isn’t [Greg]’s first foray into the world of hot metal. A few years back we covered his electric arc furnace build, powered by another, more capable welder.

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Vacuum Sputtering With A Homemade Magnetron

July 23, 2019 by 8 Comments

“You can never be too rich or too thin,” the saying goes, and when it comes to coatings, it’s true that thinner is often better. The way to truly thin coatings, ones that are sometimes only a few atoms thick, is physical vapor deposition, or PVD, a technique where a substance is transformed into a vapor and condensed onto a substrate, sometimes using a magnetron to create a plasma.

It sounds complicated, but with a few reasonable tools and a healthy respect for high voltages, a DIY magnetron for plasma sputtering can get you started. To be fair, [Justin Atkin] worked on his setup for years, hampered initially by having to settle for found parts and general scrap for his builds. As with many things, access to a lathe and the skills to use it proved to be enabling, allowing him to make custom parts like the feedthrough for the vacuum chamber as well as a liquid-cooled base, which prevents heat from ruining the magnets that concentrate the plasma onto the target metal. Using a high-voltage DC supply made from old microwave parts, [Justin] has been able to sputter copper films onto glass slides, with limited success using other metals. He also accidentally created a couple of dichroic mirrors by sputtering with copper oxides rather than pure copper. The video below has some beautiful shots of the ghostly green and purple glow.

A rig such as this opens up a lot of possibilities, from optics to DIY semiconductors. It may not be quite as elaborate as some PVD setups we’ve seen, but we’re still pretty impressed.

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Fail Of The Week: The Spot Welder Upgrade That Wasn’t

April 22, 2018 by 28 Comments

Even when you build something really, really nice, there’s always room for improvement, right? As it turns out for this attempted upgrade to a DIY spot welder, not so much.

You’ll no doubt recall [Mark Presling]’s remarkably polished and professional spot welder build that we featured some time ago. It’s a beauty, with a lot of thought and effort put into not only the fit and finish but the function as well. Still, [Mark] was not satisfied; he felt that the welder was a little underpowered, and the rewound microwave oven transformer was too noisy. Taking inspiration from an old industrial spot welder, he decided to rebuild the transformer by swapping the double loop of battery cable typically used as a secondary with a single loop of thick copper stock. Lacking the proper sized bar, though, he laminated multiple thin copper sheets together before forming the loop. On paper, the new secondary’s higher cross-sectional area should carry more current, but in practice, he saw no difference in the weld current or his results. It wasn’t all bad news, though — the welder is nearly silent now, and the replaced secondary windings were probably a safety issue anyway, since the cable insulation had started to melt.

Given [Mark]’s obvious attention to detail, we have no doubt he’ll be tackling this again, and that he’ll eventually solve the problem. What suggestions would you make? Where did the upgrade go wrong? Was it the use of a laminated secondary rather than solid bar stock? Or perhaps this is the best this MOT can do? Sound off in the comments section.

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