Put Plasma to Work with this Basic Toolkit

Fair warning: [Justin Atkin]’s video on how to make plasma, fusors, and magnetrons is a bit long. But it’s worth watching because he’s laying a foundation for a series of experiments with plasma, which looks like it will be a lot of fun.

After a nice primer on the physics of plasma, [Justin] goes into some detail about the basic tools of the trade: high voltage and high vacuum. A couple of scrap microwave oven transformers, a bridge rectifier, and a capacitor provide the 2000 volts DC output needed. It’s a workable setup, but we’ll take issue with the incredibly dangerous “scariac” autotransformer, popularized by [The King of Random]. It seems foolish to risk a painful death mixing water and line current when a 20-amp variac can be had for $100.

A decent vacuum pump will be needed too, of course; perhaps the money you can save by building your own Sprengel vacuum pump can be put toward the electrical budget. Vacuum chambers are cheap too — Mason jars with ground rims and holes drilled for accessories like spark plugs. Magnets mounted below one chamber formed a rudimentary magnetron, thankfully without the resonating cavities needed for producing microwaves. Another experiment attempted vapor deposition of titanium nitride.

It’s all pretty cool stuff, and we’re looking forward to more details and results. While we wait, feel free to check out the tons of plasma projects we’ve featured, from tiny plasma speakers to giant plasma tubes.

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Trio of Magnetrons Power a Microwave Rifle

Can you build a working EM weapon from three microwave ovens? Apparently, yes. Should you do so? Maybe not when the best safety gear you can muster is a metallized Mylar film fetish suit and a Hershey’s Kiss hat.

Proving that language need not be a barrier to perfect understanding of bad ideas, the video below tells you all you need to know, even without subtitles in the non-Russian language of your choice. [KREOSAN]’s build is obnoxiously obvious — three magnetrons mounted on a tin can “resonator” with a foil-covered waveguide at the business end. The magnetrons are tickled by a stun-gun that’s powered by a pack of 18650 batteries. The video shows some “experiments”, like lighting up unpowered CFL bulbs from about 15 meters away and releasing the Blue Smoke from the electrical system of a running motor scooter. Assuming they weren’t added in post, the artifacts in the video belie the gun’s lack of shielding for the operator. We doubt any of the ad hoc safety gear would provide any protection from the resulting microwaves, but we also doubt that it matters much when things have gotten this far.

We’re not too sure about this one — some of the zapping stunts look a little too conveniently explosive. It’s hard to tell the details without a translation, so maybe one of our Russian-speaking readers can pitch in on the comments. Although this isn’t [KRESOAN]’s first microwave rodeo, having melted a few lightbulbs with magnetrons before. Even seeing this we still consider EMP Weapons a figment of Hollywood’s imagination.

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Microwaving Things Outside of the Microwave!


Ever wonder what would happen if you took a magnetron out of a microwave, strapped it to a stick, and pointed it at random everyday objects? Well, lucky for you a couple young Russians recorded their research before they presumably hurt themselves and were hospitalized, or maybe just became infertile — or caused cataracts — point is don’t do it.

They’ve taken a magnetron out of a microwave, and tied a soup can to the side of it to focus the microwaves. After discovering this, they did the next logical step — point it at various things and see what happens.

In this specific video (they have lots…) you can see them create plasma inside light bulbs, melt light bulbs, light up vacuum tubes, fluorescent bulbs, liquefy metal, and even catch a glimpse of radio waves.

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Ask Hackaday: The Many Uses of Microwaves

When most think of a microwave, they think of that little magic box that you can heat food in really fast. An entire industry of frozen foods has sprung up from the invention of the household microwave oven, and it would be difficult to find a household without one. You might be surprised that microwave ovens, or reactors to be more accurate, can also be found in chemistry labs and industrial complexes throughout the world. They are used in organic synthesis – many equipped with devices to monitor the pressure and temperature while heating. Most people probably don’t know that most food production facilities use microwave-based moisture solids analyzers. And there’s even an industry that uses microwaves with acids to dissolve or digest samples quickly. In this article, we’re going to look beyond the typical magnetron / HV power supply / electronics and instead focus on some other peculiarities of microwave reactors than you might not know.

Single vs Multimode

The typical microwave oven in the millions of households across the world is known as multimode type. In these, the microwaves will take on typical wavelike behavior like we learned about in physics 101. They will develop constructive and destructive interference patterns, causing ‘hot spots’ in the cavity. A reader tipped us off to this example, where [Lenore] uses a popular Indian snack food to observe radiation distribution in a multimode microwave cavity. Because of this, you need some type of turntable to move the food around the cavity to help even out the cooking. You can avoid the use of a turn table with what is known as a mode stirrer. This is basically a metal ‘fan’ that helps to spread the microwaves throughout the cavity. They can often be found in industrial microwaves. Next time you’re in the 7-11, take a look in the top of the cavity, and you will likely see one.

Multimode microwaves also require an isolator to protect the magnetron from reflected energy. These work like a diode, and do not let any microwaves bounce back and hit the magnetron. It absorbs the reflected energy and turns it into heat. It’s important to note that all microwave energy must be absorbed in a multimode cavity. What is not absorbed by the food will be absorbed by the isolator. Eventually, all isolators will fail from the heat stress. Think about that next time you’re nuking a small amount of food with a thousand watts!

Single Mode microwaves are what you will find in chemistry and research labs. In these, the cavity is tuned to the frequency of the magnetron – 2.45GHz. This allows for a uniform microwave field. There is no interference, and therefore no hot or cold spots. The microwave field is completely homogenous. Because of this, there is no reflected energy, and no need for an isolator. These traits allow single mode microwaves to be much smaller than multimode, and usually of a much lower power as there is a 100% transfer of energy into the sample.  While most multimode microwaves are 1000+ watts, the typical single mode will be around 300 watts.

single vs multimode cavity

Power Measurement

Most microwave ovens only produce one power level. Power is measured and delivered by the amount of time the magnetron stays on. So if you were running something at 50% power for 1 minute, the magnetron would be on for a total of 30 seconds. You can measure the output power of any microwave by heating 1 liter of water at 100% power for 2 minutes. Multiply the difference in temperature by 35, and that is your power in watts.

There are other types of microwaves that control power by adjusting the current through the magnetron. This type of control is often utilized by moisture solids analyzers, where are more precise control is needed to keep samples from burning.

Have you used a microwave and an arduino for something other than cooking food? Let us know in the comments!

Thanks to [konnigito] for the tip!

Hackaday Links: February 22, 2015

We met up with Freescale guy [Witek] at our party in Munich last year, and he wrote in to tell us about the Freescale booth at Embedded World this week in Nuremberg. They’re going to have a bunch of Freedom boards to play around with and an extremely powerful RIoTboard with a 1GHz iMX6 Solo processor, 1GB of RAM, and 4GB of EMMC Flash. It’s not a Raspi or BeagleBone killer, but if you need a small Linux board with a lot of horsepower, there ‘ya go.

SmarterEveryDay is finally getting around to doing a series of videos about space. This guy knows his stuff, and with the access he can get, it should make for interesting viewing.

Here’s something for your Sunday listening: [Vint Cerf] at Carnegie Mellon talking about the Olive Project and the Interplanetary Internet. The Olive project is an archive for executables, and solves the problem of having to preserve hardware along with software. Cool stuff.

10 GHz pulse magnetron destroys electronics. That’s the only information you’re going to get with this one. There’s a fine line between ‘don’t try this at home’ and ‘this project needs replication’.

Most of the northern half of the United States is covered in a billion tons of snow. [Jamie]’s electric snowmobile/Power Wheels is the perfect vehicle for this occasion. It’s 36V with two 500W motors. Figure out how to replace the wheels with small treads, and there’s really something interesting here.

Hackaday Links: August 3, 2014


A ton of people sent in this video of crazy Russians who have taken a microwave, removed the magnetron, taped it to a broom, and turned it on. Don’t try this at home. Or near us.

You know the Google Cardboard kit that’s a real VR headset made of cardboard (and a smart phone)? Google may have gotten their inspiration from Oculus, because every Oculus Rift DK2 ships with a Samsung Galaxy Note 3 inside.

paul allen

Ever design a PCB and be disappointed by the quality of the silkscreen? [Paul Allen] has been defining the edges of his PCB labels with the copper layer, and the examples are dramatic. Etching copper is what you actually pay for when you fab a board, so it should come as no surprise that the quality is a little higher.

Dunk tanks are fun, but how about competitive dunk tanks? [Chad] built a dunk tank (really more of a ‘dunk shower’) out of a 2×4 tripod, a garbage can, and a few parts from a the toilet aisle of Home Depot’s plumbing department. Then he built a second. Set up both dunk showers across from each other, give two people a few balls, and see who gets soaked last. Looks fun.

Want a MAME cabinet, but don’t want it taking up room in your house? Build a MAME coffee table! Here’s the reddit thread. Maybe we’re old-fashioned, but we’d rather have a giant NES controller coffee table.

Last week we saw a 16-bobbin rope braiding machine, but odd braiding machines like this aren’t limited to fibers. Here’s a wire twisting machine for making RS422 cables. It only produces a single twisted pair, but that’s really all you need to create a cable. Somebody get some paracord and make some Cat5.