high voltage

236 Articles

Liquid Metal Ion Thrusters Aren’t Easy

December 7, 2024 by 10 Comments

What do scanning electron microscopes and satellites have in common? On the face of things, not much, but after seeing [Zachary Tong]’s latest video on liquid metal ion thrusters, we see that they seem to have a lot more in common than we’d initially thought.

As you’d expect with such a project, there were a lot of false starts and dead ends. [Zach] started with a porous-emitter array design, which uses a sintered glass plate with an array of tiny cones machined into it. The cones are coated in a liquid metal — [Zach] used Galinstan, an alloy of gallium, indium, and tin — and an high voltage is applied between the liquid metal and an extraction electrode. Ideally, the intense electric field causes the metal to ionize at the ultra-sharp tips of the cones and fling off toward the extraction electrode and into the vacuum beyond, generating thrust.

Getting that working was very difficult, enough so that [Zach] gave up and switched to a slot thruster design. This was easier to machine, but alas, no easier to make work. The main problem was taming the high-voltage end of things, which seemed to find more ways to produce unwanted arcs than the desired thrust. This prompted a switch to a capillary emitter design, which uses a fine glass capillary tube to contain the liquid metal. This showed far more promise and allowed [Zach] to infer a thrust by measuring the tiny current created by the ejected ions. At 11.8 μN, it’s not much, but it’s something, and that’s the thing with ion thrusters — over time, they’re very efficient.

To be sure, [Zach]’s efforts here didn’t result in a practical ion thruster, but that wasn’t the point. We suspect the idea here was to explore the real-world applications for his interests in topics like electron beam lithography and microfabrication, and in that, we think he did a bang-up job with this project.

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An exploded view of an electrostatic motor from manufacturer C-Motive. There is a silvery cylinder on the left, two half silver and half golden disks on either side and two thinner gold disks in the center. A square mountin plate is on the right hand side next to one of the silver/gold disks.

Electrostatic Motors Are Making A Comeback

October 29, 2024 by 21 Comments

Electrostatic motors are now common in MEMS applications, but researchers at the University of Wisconsin and spinoff C-Motive Technologies have brought macroscale electrostatic motors back. [via MSN/WSJ]

While the first real application of an electric motor was Ben Franklin’s electrostatically-driven turkey rotisserie, electromagnetic type motors largely supplanted the technology due to the types of materials available to engineers of the time. Newer dielectric fluids and power electronics now allow electrostatic motors to be better at some applications than their electromagnetic peers.

The main advantage of electrostatic motors is their reduced critical materials use. In particular, electrostatic motors don’t require copper windings or any rare earth magnets which are getting more expensive as demand grows for electrically-powered machines. C-Motive is initially targeting direct drive industrial applications, and the “voltage driven nature of an electrostatic machine” means they require less cooling than an electromagnetic motor. They also don’t use much if any power when stalled.

Would you like a refresher on how to make static electricity or a deeper dive on how these motors work?

A Field Guide To The North American Substation

August 22, 2024 by 15 Comments

Drive along nearly any major road in the United States and it won’t be long before you see evidence of the electrical grid. Whether it’s wooden poles strung along the right of way or a line of transmission towers marching across the countryside in the distance, signs of the grid are never far from view but often go ignored, blending into the infrastructure background and becoming one with the noise of our built environment.

But there’s one part of the electrical grid that, despite being more widely distributed and often relegated to locations off the beaten path, is hard to ignore. It’s the electrical substation, more than 55,000 of which dot the landscape of the US alone. They’re part of a continent-spanning machine that operates as one to move electricity from where it’s produced to where it’s consumed, all within the same instant of time. These monuments of galvanized steel are filled with strange, humming equipment of inscrutable purpose, seemingly operating without direct human intervention. But if you look carefully, there’s a lot of fascinating engineering going on behind those chain-link fences with the forbidding signage, and the arrangement of equipment within them tells an interesting story about how the electrical grid works, and what the consequences are when it doesn’t.

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Retrotechtacular: Powerline Sagging And Stringing In The 1950s

August 17, 2024 by 13 Comments

While high-voltage transmission lines are probably the most visible components of the electrical grid, they’re certainly among the least appreciated. They go largely unnoticed by the general public — quick, name the power line closest to you right now — at least until a new one is proposed, causing the NIMBYs and BANANAs to come out in force. To add insult to injury, those who do notice the megastructures that make modern life possible rarely take a moment to appreciate the engineering that goes into stringing up hundreds of miles of cable and making sure it stays up.

Not so the Bonneville Power Administration, the New Deal-era federal agency formed to exploit the hydroelectric abundance of the Pacific Northwest of the United States, which produced this 1950 gem detailing the stringing and sagging of power lines. Unsurprisingly, the many projects needed to wire together the often remote dams to the widely distributed population centers in an area that was only just starting to see growth began in the BPA’s offices, where teams of engineers hunched over desks worked out the best routes. Paper, pencil, and slide rules were the tools of the trade, along with an interesting gadget called a conductor sag template, a hardware implementation of the catenary equation that allowed the “sagger” to determine the height of each tower. The conductors, either steel-cored aluminum or pure copper, were also meticulously selected based on tensile strength, expected wind and ice loading, and the electrical load the line was expected to carry.

Once the engineers had their say, the hard work of physically stringing the wires began out in the field. One suspects that the work today is much the same as it was almost eighty years ago, save for much more stringent health and safety regulations. The prowess needed to transfer the wires from lifting sheaves to the insulators is something to behold, and the courage required to work from ladders hanging from wires at certain death heights is something to behold. But to our mind, the real heroes were the logistics fellows, who determined how much wire was needed for each span and exactly where to stage the reels. It’s worth sparing a moment’s thought for the daring photographer who captured all this action, likely with little more than a leather belt and hemp rope for safety.

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Who’s Afraid Of A CRT?

April 13, 2024 by 25 Comments

Older consumer electronic devices follow a desirability curve in which after they fall from favour they can’t be given away. But as they become rarer, they reach a point at which everyone wants them. Then, they can’t be had for love nor money. CRT TVs are now in the first stage, they’re bulky and lower-definition than modern sets, and thus thrift stores and dumpsters still have them in reasonable numbers. To retrogamers and other enthusiasts, this can be a bonanza, and when he saw a high-end late-model JVC on the sidewalk [Chris Person] wasted no time in snapping it up. It worked, but there were a few picture issues, so he set about fixing it.

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Electrospinning Artificial Heart Valves

March 29, 2024 by 10 Comments

When you think about additive manufacturing, thoughts naturally turn to that hot-glue squirting CNC machine sitting on your bench and squeezing whatever plastic doodad you need. But 3D printing isn’t the only way to build polymer structures, as [Riley] shows us with this fascinating attempt to create electrospun heart valves.

Now, you may never have heard of electrospinning, but we’ll venture a guess that as soon as you see what it entails, you’ll have a “Why didn’t I think of that?” moment. As [Riley] explains, electrospinning uses an electric field to build structures from fine threads of liquid polymer solution — he uses polycaprolactone (PCL), a biodegradable polyester we’ve seen used in other medical applications, which he dissolves in acetone. He loads it into a syringe, attaches the positive terminal of a high-voltage power supply to the hypodermic needle, and the negative terminal to a sheet of aluminum foil. The charge turns the PCL droplets into fine threads that accumulate on the foil; once the solvent flashes off, what’s left is a gossamer layer of non-woven plastic fabric.

To explore the uses of this material, [Riley] chose to make an artificial heart valve. This required a 3D-printed framework with three prongs, painted with conductive paint. He tried a few variations on the design before settling on a two-piece armature affixed to a rotating shaft. The PCL accumulates on the form, creating a one-piece structure that can be gingerly slipped off thanks to a little silicon grease used as a release agent.

The results are pretty impressive. The structure bears a strong resemblance to an artificial tricuspid heart valve, with three delicate leaves suspended between the upright prongs. It’s just a proof of concept, of course, but it’s a great demonstration of the potential of electrospinning, as well as an eye-opening look at what else additive manufacturing has to offer.

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High-Voltage Fun With An Inexpensive Power Supply

March 14, 2024 by 25 Comments

It used to be that nearly every home had at least one decent high-voltage power supply. Of course, it was dedicated to accelerating electrons and slamming them into phosphors so we could bathe ourselves in X-rays (not really) while watching Howdy Doody. These days the trusty tube has been replaced with LEDs and liquid crystals, which is a shame because there’s so much fun to be had with tens of thousands of volts at your disposal.

That’s the impetus behind this inexpensive high-voltage power supply by [Sebastian] over at Baltic Labs. The heavy lifting for this build is done by a commercially available power supply for a 50-watt CO2 laser tube, manufactured — or at least branded — by VEVOR, a company that seems intent on becoming the “Harbor Freight of everything.” It’s a bold choice given the brand’s somewhat questionable reputation for quality, but the build quality on the supply seems decent, at least from the outside. [Sebastian] mounted the supply inside a rack-mount case, as one does, and provided some basic controls, including the obligatory scary-looking toggle switch with safety cover. A pair of ammeters show current and voltage, the latter with the help of a high-voltage resistor rated at 1 gigaohm (!). The high-voltage feedthrough on the front panel is a little dodgy — a simple rubber grommet — but along with the insulation on the high-voltage output lead, it seems to be enough.

The power supply’s 30 kV output is plenty for [Sebastian]’s current needs, which from the video below appear to mainly include spark gap experiments. He does mention that 50 kV commercial supplies are available too, but it would be tough to do that for the $150 or so he spent on this one. There are other ways to go, of course — [Niklas] over at Advanced Tinkering recently shared his design for a more scratch-built high-voltage supply that’s pretty cool too. Whatever you do, though, be careful; we’ve been bitten by a 50 kV flyback supply before and it’s no joke.

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