Harvesting Electricity From High-Voltage Transmission Lines Using Fences

January 27, 2024 by Maya Posch 372 Comments

When you have a bunch of 230 kV transmission lines running over your property, why not use them for some scientific experiments? This is where the [Double M Innovations] YouTube channel comes into play, including a recent video where the idea of harvesting electricity from HV transmission lines using regular fences is put to an initial test.

The nearly final measurement by [Double M Innovations]. — The nearly final voltage measurement by [Double M Innovations].

A rather hefty 88 µF, 1200 V capacitor, a full bridge rectifier, and 73 meters (240 feet) of coax cable to a spot underneath the aforementioned HV transmission lines. The cable was then put up at a height consistent with that of fencing at about 1.2 m (4 ft), making sure that no contact with the ground occurred anywhere. One end of the copper shield of the coax was connected to the full bridge rectifier, with the opposite AC side connected to a metal stake driven into the ground. From this the capacitor was being charged.

As for the results, they were rather concerning and flashy, with the 1000 VAC-rated multimeter going out of range on the AC side of the bridge rectifier, and the capacitor slowly charging up to 1000 V before the experiment was stopped.

Based on the capacity of the capacitor and the final measured voltage of 907 VDC, roughly 36.2 Joule would have been collected, giving some idea of the power one could collect from a few kilometers of fencing wire underneath such HV lines, and why you probably want to ground them if energy collecting is not your focus.

As for whether storing the power inductively coupled on fence wire can be legally used is probably something best discussed with your local energy company.

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An Adjustable High-Voltage Power Supply Built With Safety In Mind

January 6, 2024 by Dan Maloney 11 Comments

It’s not entirely clear why [Advanced Tinkering] needs a 50,000-volt power supply, but given the amount of work he put into this one, we’re going to guess it will be something interesting.

The stated specs for this power supply are pretty simple: a power supply that can be adjusted between 20kV and 50kV. The unstated spec is just as important: don’t kill yourself or anyone else in the process. To that end, [Advanced] put much effort into making things as safe as possible. The basic architecture of the supply is pretty straightforward, with a ZVS driver and an AC flyback transformer. Powered by a 24-volt DC supply and an adjustable DC-DC converter, that setup alone yields something around 20kV — not too shabby, but still far short of the spec. The final push to the final voltage is thanks to a three-stage Cockcroft-Walton multiplier made with satisfyingly chunky capacitors and diodes. To ensure everything stays safe in the high-voltage stage, he took the precaution of potting everything in epoxy. Good thing, too; tests before potting showed arcing in the CW multiplier despite large isolation slots in the PCB.

Aside from the potting, some really interesting details went into this build, especially on the high-voltage side. The 3D-printed and epoxy-filled HV connector is pretty cool, as is the special wire needed to keep arcs at bay. The whole build is nicely detailed, too, with care taken to bond each panel of the rack-mount case to a common ground point.

It’s a nice build, and we can’t wait to see what [Advanced Tinkering] does with it. In the meantime, if you want to get up to speed on handling high voltage safely, check out our HV primer.

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Powering A Cavity Magnetron, From A Battery

December 4, 2023 by Jenny List 47 Comments

While vacuum electronic devices have largely been superseded over much of consumer electronics, there’s one place where they can still be found for now. The cavity magnetron is a power RF oscillator device in which electrons are induced to move in a circular path through a tuned cavity, inducing a high-power RF field, and it lies at the heart of a domestic microwave oven. They usually need a high-voltage mains transformer and a rectifier to work, but [Hyperspace Pirate] has managed to make a solid-state power supply to power one from a 12 volt battery. Better still, he’s put the resulting combo in a Care Bears lunchbox. Take a look at the video below the break.

The video starts with a potted history of the magnetron before looking at the circuit of a typical oven, which uses a single diode and a capacitor in a simple voltage multiplier. The capacitor value is adjusted to lower the power output, and a pretty thorough job is done of characterising the circuit.

The low-voltage supply starts with an XVS inverter to make the high voltage via another multiplier, but the interesting part comes with the magnetron’s heater. It’s designed for 50 or 60Hz household electricity, but there it’s receiving 40 kHz and has an appreciable impedance. The addition of a capacitor soon restores it to a reasonable performance.

In case you noticed that the ZVS converter might be improved upon, take a look at a flyback converter. Meanwhile, we should probably echo the safety message in the video that playing with magnetrons and their associated transformers can be a nasty way to die. Please take care out there!

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Tattoo-Removal Laser Brought Out Of Retirement For A Megawatt Of Fun

October 11, 2023 by Dan Maloney 13 Comments

We’ve got to say that [Les Wright] has the most fun on the internet, at least in terms of megawatts per dollar. Just look at his new video where he turns a $30 eBay tattoo-removal laser into a benchtop beast.

The junk laser in question is a neodymium:YAG pulse laser that clearly has seen better days, both externally and internally. The original pistol-grip enclosure was essentially falling apart, but was superfluous to [Les]’ plans for the laser. Things were better inside the business end of the gun, at least in terms of having all the pieces in place, but the teardown still revealed issues. Chief among these was the gunk and grunge that had accumulated on the laser rod and the flash tube — [Les] blamed this on the previous owner’s use of tap water for cooling rather than deionized water. It was nothing a little elbow grease couldn’t take care of, though. Especially since the rest of the laser bits seemed in good shape, including the chromium:YAG Q-switch, which allows the lasing medium to build up a huge pulse of photons before releasing them in one gigantic pulse.

Cleaned up and with a few special modifications of his own, including a custom high-voltage power supply, [Les]’ laser was ready for tests. The results are impressive; peak optical power is just over a megawatt, which is enough power to have some real fun. We’ll be keen to see what he does with this laser — maybe blasting apart a CCD camera?

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DIY Repair Brings An X-Ray Microscope Back Into Focus

September 22, 2023 by Dan Maloney 6 Comments

Aside from idle curiosity, very few of us need to see inside chips and components to diagnose a circuit. But reverse engineering is another story; being able to see what lies beneath the inscrutable epoxy blobs that protect the silicon within is a vital capability, one that might justify the expense involved in procuring an X-ray imager. But what’s to be done when such an exotic and expensive — not to mention potentially deadly — machine breaks down? Obviously, you fix it yourself!

To be fair, [Shahriar]’s Faxitron MX-20 digital X-ray microscope was only a little wonky. It still generally worked, but just took a while to snap into the kind of sharp focus that he needs to really delve into the guts of a chip. This one problem was more than enough to justify tearing into the machine, but not without first reviewing the essentials of X-ray production — a subject that we’ve given a detailed look, too — to better understand the potential hazards of a DIY repair.

With that out of the way and with the machine completely powered down, [Shahriar] got down to the repair. The engineering of the instrument is pretty impressive, as it should be for something dealing with high voltage, heavy thermal loads, and ionizing radiation. The power supply board was an obvious place to start, since electrostatically focusing an X-ray beam depends on controlling the high voltage on the cathode cup. After confirming the high-voltage module was still working, [Shahriar] homed in on a potential culprit — a DIP reed relay.

Replacing that did the trick, enough so that he was able to image the bad component with the X-ray imager. The images are amazing; you can clearly see the dual magnetic reed switches, and the focus is so sharp you can make out the wire of the coil. There are a couple of other X-ray treats, so make sure you check them out in the video below.

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Electro-Optical Control Of Lasers With A Licorice Twist

September 5, 2023 by Dan Maloney 8 Comments

You’ve got to hand it to [Les Wright]; he really knows how to dig into optical arcana and present topics in an interesting way. Case in point: an electro-optical control cell that’s powered by ouzo.

OK, the bit about the Greek aperitif may be stretching things a bit, but the Kerr Cell that [Les] builds in the video below does depend on anethole, the essential component of aniseed extract, which lends its aromatic flavor to everything from licorice to Galliano and ouzo. As [Les] explains, the Kerr effect uses a high-voltage field to rapidly switch light passing through a medium on and off. The most common medium in Kerr cells is nitrobenzene, a “distressingly powerful organic solvent” with such fun side effects as toxicity, flammability, and carcinogenicity.

Luckily, [Les] found a suitable substitute in the form of anethole — a purified sample, not just an ouzo nip. The solution went into a plain glass cuvette equipped with a pair of aluminum electrodes, which got connected to one of the high-voltage supplies we’ve seen him build before for his nitrogen laser. A pair of polarizing filters go on either end of the cuvette, and are adjusted to blank out the light passing through it. Applying 45 kilovolts across the cell instantly turns the light back on. Watch it in action in the video below.

There’s a lot of room left for experimentation on this one, including purification of the anethole for potentially better results. We’d also be curious if plain ouzo would show some degree of Kerr effect. For science, of course.

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Little Ionic Thruster Blows Out Candles With Ease

August 22, 2023 by Donald Papp 24 Comments

Want to generate some thrust by way of an exposed high voltage discharge that looks great when you turn down the lights? [Integza] has a video showing how to do exactly that with some simple components. His little thruster manages to blow out candles at surprising distances before being pressed into service propelling a model boat.

Here’s how it works: ionic wind is generated when a strong enough electric field causes nearby air to ionize, for example from sharp tips of a conductor carrying a high enough voltage. This discharge creates ionized air molecules with an electrical charge matching the polarity of the nearby conductor. Because matching polarities repel one another, the small cloud of ionized air molecules are repelled from both the nearby conductor, as well as from each other.

The result is a wind-like force from a device with no moving parts, and if the parts are structured right, it’ll blow out a candle with ease. [Integza] attached a cheap DC high-voltage transformer to a nickel strip cut into sharp points and rolled into a circlet. The other half of the thruster — in contrast to the thin crown of sharp points — is a smooth ring shaped a little like a thruster nozzle. 3D models of the parts are available online should you wish to try it yourself without all the trial and error of trying to optimize.

In an effort to minimize mass, [Integza] electroplates a 3D-printed version of the large ring with great results, spraying it with graphite first to make it conductive. Cheap and safe copper electroplating is entirely within the reach of hobbyists, and the resulting unit does a pretty nice job. You can watch it in action in the video, embedded below.

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