Electrostatic Puck: Making An Electret

December 1, 2024 by Danie Conradie 24 Comments

You might have heard of electrets being used in microphones, but do you know what they are? Electrets produce a semi-permanent static electric field, similar to how a magnet produces a magnetic field. The ones in microphones are very small, but in the video after the break [Jay Bowles] from Plasma Channel makes a big electret and demonstrates it’s effects.

Electrets have been around since the 1800s, and are usually produced by melting an insulating material and letting it solidify between two high-voltage electrodes. The original recipe used a mix of Carnauba wax, beeswax, and rosin, which is what [Jay] tried first. He built a simple electric field detector, which is just a battery, LED and FET, with an open-ended resistor on the FET’s gate.

[Jay] 3D printed a simple cylindrical mold and stuck aluminum foil to the outer surfaces to act as the electrodes. He used his custom 6000:1 voltage transformer to hold the electrodes at ~40 kV. The first attempt did not produce a working electret because the electrodes were not in contact with the wax, and kept arcing across, which causes the electric charge to drop off. Moving the aluminum electrodes the inner surfaces of the mold eventually produced an electret detectable out to 10 inches.

This was with the original wax recipe, but there are now much better materials available, like polyethylene. [Jay] heated a a block of it in the oven until it turned into a clear blob, and compressed it in a new mold with improved insulation. This produced significantly better results, with an electric field detectable out to 24 inches.

[Jay] also built an array of detectors in a 5×5 grid, which he used to help him visualize the size and shape of the field. He once pulled off a similar trick using a grid of neon bulbs.

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Static Electricity And The Machines That Make It

September 30, 2024 by Lewin Day 20 Comments

Static electricity often just seems like an everyday annoyance when a wool sweater crackles as you pull it off, or when a doorknob delivers an unexpected zap. Regardless, the phenomenon is much more fascinating and complex than these simple examples suggest. In fact, static electricity is direct observable evidence of the actions of subatomic particles and the charges they carry.

While zaps from a fuzzy carpet or playground slide are funny, humanity has learned how to harness this naturally occurring force in far more deliberate and intriguing ways. In this article, we’ll dive into some of the most iconic machines that generate static electricity and explore how they work.

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Probably The Simplest Radiation Detector You Already Own

September 26, 2022 by Jenny List 78 Comments

Over the years we’ve featured quite a few radiatioactivity detectors, which usually include a Geiger-Muller tube, or perhaps a large-area photodiode. But in the event of radiation exposure from a nuclear attack, how does the man in the street gauge the exposure without owning a dedicated instrument? This was a question of note at the height of the Cold War, and it’s one that [Dr. Marshall Brucer] answered in a 1962 paper entitled “When Do You Leave A Fallout Shelter“. The full paper is behind a paywall but the part we’re interested in is on the freely available first page.

Dr. Brucer‘s detector is simplicity itself, and it relies on the erosion of a static electric charge by radiation. Should you rub a plastic comb in your hair it will accumulate enough charge to pick up a small piece of paper, and under normal background radiation the charge will ebb away such that it will drop the piece of paper after about 15 seconds. His calculation is that once the field reaches around 10 roentgens per hour it will be enough to erase the charge and drop the paper immediately. There’s a comtemporary newspaper report (Page 7, just to the left of the large advertisment) which tells the reader that since the exposure limit is 100 roentgens (one sievert), this test failing indicates that they have nine hours to create a better shelter. For obvious reasons we can’t test this at the Hackaday bench, but those of us who remember the days when such topics were a real concern will be searching for a handy comb anyway.

Thanks [Victor Matthew] for the tip.

ElectriPop Turns Cut Mylar Into Custom 3D Structures

May 6, 2022 by Tom Nardi 14 Comments

Mylar has a lot of useful properties, and as such as see it pop up pretty often, not just in DIY projects but in our day-to-day lives. But until today, we’ve never seen a piece of Mylar jump up and try to get our attention. But that’s precisely the promise offered by ElectriPop, a fascinating project from Carnegie Mellon University’s Future Interfaces Group.

The core principle at work here is fairly simple. When electrostatically charged, a strip of Mylar can be made to lift up vertically into the air. Cut that strip down the center, and the two sides will repel each other and produce a “Y” shape. By expanding on that concept with enough carefully placed cuts, it’s possible to create surprisingly complex three dimensional shapes that pop up once a charge is applied. A certain degree of motion can even be introduced by adjusting the input power. The video after the break offers several examples of this principle in action: such as a 3D flower that either stands up tall or wilts in relation to an external source of data, or an avatar that flails its arms wildly to get the user’s attention.

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Supersized Van De Graaff Generator Packs A Punch

April 27, 2021 by Tom Nardi 19 Comments

The Van de Graaff generator is a staple of science museums, to the point that even if the average person might not know its name, there’s an excellent chance they’ll be familiar with the “metal ball that makes your hair stand up” description. That’s partly because they’re a fairly safe way to show off high voltages, but also because they’re surprisingly cheap and easy to build.

In his latest Plasma Channel video [Jay Bowles] builds a large Van de Graaff generator that wouldn’t look out of place in a museum or university, which he estimates is producing up to 500,000 volts. It can easily throw impressive looking (and sounding) sparks 10 inches or more, and as you can see in the video below, is more than capable of pulling off those classic science museum tricks.

It’s really quite amazing to see just how little it takes to generate these kinds of voltages with a Van de Graaff. In fact there’s nothing inside that you’d immediately equate with high voltage, the only electronic component in the generator’s base beyond the battery pack is a motor speed controller. While everything else might look suspiciously like magic, our own [Steven Dufresne] wrote up a properly scientific explanation of how it all works.

In this particular case, the motor spins a nylon pulley in the base of the generator, which is connected to a Teflon pulley in the top by way of a neoprene rubber belt. Combs made from fine metal mesh placed close to the belt at the top and bottom allow the Van de Graaff to build up a static charge in the sphere. Incidentally, it sounds like sourcing the large metal sphere was the most difficult part of this whole build, as it took [Jay] several hours to modify the garden gazing ball to fit atop the acrylic tube that serves as the machine’s core.

In the past we’ve seen Van de Graaff generators built out of literal trash, and back in 2018, [Jay] himself put together a much smaller and more simplistic take on the concept. But this beauty certainly raises the bar beyond anything we’ve seen previously.

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One Anti-Static Ring To Delight Them All

March 12, 2020 by Kristina Panos 17 Comments

What’s the worst thing about winter? If you’re as indoorsy as we are, then static electricity is probably pretty high on the list. It can ruin your chips, true, but you always wear a wrist ground strap when you handle those, right? But away from the bench, every doorknob and light switch is lying in wait, ready to shock you. If you had an anti-static ring like [LaPuge], you could be watching a tiny neon bulb light up instead of the air between your poor finger and the discharge point.

The ring itself is printed in TPU 95A filament for comfort and flexibility. There isn’t a whole lot to the circuit, just a neon bulb, a 1MΩ resistor, and some copper tape, but this piece of functional jewelry has the potential to spark up plenty of charged conversations. Zap your way past the break to see it light up against a door handle.

If you want to light up neon bulbs all year long, build a field of them and wave them near your Tesla coil!

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Mini Van De Graaff Is A Shocking Desk Toy

December 10, 2018 by Tom Nardi 21 Comments

The Van De Graff generator is a device capable of generating potentially millions of volts of electricity which you can build in an afternoon, probably from parts you’ve got in the junk bin. This is not a fact that’s escaped the notice of hackers for decades, and accordingly we’ve seen several Van De Graaff builds over the years. So has high voltage hacker [Jay Bowles], but he still thought he could bring something new to the table.

The focus of his latest build was to not only produce one of the most polished and professional versions of this venerable piece of high voltage equipment, but also make it accessible for others by keeping the design simple and affordable. The final result is a 40,000 volt Van De Graaff generator that’s powered by two AA batteries and can fit in the palm of your hand.

Put simply, a Van De Graaff generator creates static electricity from the friction of two metal combs rubbing against a moving belt, which is known as the triboelectric effect. The belt is stretched between the two combs and passes through an insulated tube, which serves to “pump” electrons from one side to the other. The end result is that a massive charge builds up on the positive side of the Van De Graaff generator, which is all too willing to send a spark firing off towards whatever negatively charged object gets close enough.

The video after the break guides viewers through the process of turning this principle into a practical device, illustrating how remarkably simple it really is. A common hobby motor is used to get the belt going, in this case just a wide rubber band, and the rest of the components are easily sourced or fabricated. Even for what’s arguably the most intricate element of the build, the combs themselves, [Jay] uses nothing more exotic than aluminum foil tape and a piece of stranded wire splayed out.

Combined with the acrylic base and the purpose-made metal sphere (rather than using a soda can or other upcycled object), the final result not only generates healthy sparks but looks good doing it. Though if the final fit and finish isn’t important, you could always build one out of stuff you found in the trash.

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