ElectriPop Turns Cut Mylar Into Custom 3D Structures

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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Simple Tip Helps With Powder Coating Perfection On Difficult Parts

To say that that the commercially available garden path lights commonly available at dollar stores are cheap is a vast overstatement of their true worthlessness. These solar-powered lights are so cheaply built that there’s almost no point in buying them, a fact that led [Mark Presling] down a fabrication rabbit hole that ends with some great tips on powder coating parts with difficult geometries.

Powder coating might seem a bit overkill for something as mundane as garden lights, but [Mark] has a point — if you buy something and it fails after a few weeks in the sun, you might as well build it right yourself. And a proper finish is a big part of not only getting the right look, but to making these totally un-Tardis-like light fixtures last in the weather. The video series below covers the entire design and build process, which ended up having an aluminum grille with some deep grooves. Such features prove hard to reach with powder coating, where the tiny particles of the coating are attracted to the workpiece thanks to a high potential difference between them. After coating, the part is heated to melt the particles and form a tough, beautiful finish.

But for grooves and other high-aspect-ratio features, the particles tend to avoid collecting in the nooks and crannies, leading to an uneven finish. [Mark]’s solution was to turn to “hot flocking”, where the part is heated before applying uncharged coating to the deep features. This gets the corners and grooves well coated before the rest of the coating is applied in the standard way, leading to a much better finish.

We love [Presser]’s attention to detail on this build, as well as the excellent fabrication tips and tricks sprinkled throughout the series. You might want to check out some of his other builds, like this professional-looking spot welder.

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Hackaday Links: November 22, 2020

Remember DSRC? If the initialism doesn’t ring a bell, don’t worry — Dedicated Short-Range Communications, a radio service intended to let cars in traffic talk to each other, never really caught on. Back in 1999, when the Federal Communications Commission set aside 75 MHz of spectrum in the 5.9-GHz band, it probably seemed like a good idea — after all, the flying cars of the future would surely need a way to communicate with each other. Only about 15,000 vehicles in the US have DSRC, and so the FCC decided to snatch back the whole 75-MHz slice and reallocate it. The lower 45 MHz will be tacked onto the existing unlicensed 5.8-GHz band where WiFi now lives, providing interesting opportunities in wireless networking. Fans of chatty cars need not fret, though — the upper 30 MHz block is being reallocated to a different Intelligent Transportation System Service called C-V2X, for Cellular Vehicle to Everything, which by its name alone is far cooler and therefore more likely to succeed.

NASA keeps dropping cool teasers of the Mars 2020 mission as the package containing the Perseverance rover hurtles across space on its way to a February rendezvous with the Red Planet. The latest: you can listen to the faint sounds the rover is making as it gets ready for its date with destiny. While we’ve heard sounds from Mars before — the InSight lander used its seismometer to record the Martian windPerseverance is the first Mars rover equipped with actual microphones. It’s pretty neat to hear the faint whirring of the rover’s thermal management system pump doing its thing in interplanetary space, and even cooler to think that we’ll soon hear what it sounds like to land on Mars.

Speaking of space, back at the beginning of 2020 — you know, a couple of million years ago — we kicked off the Hack Chat series by talking with Alberto Caballero about his “Habitable Exoplanets” project, a crowd-sourced search for “Earth 2.0”. We found it fascinating that amateur astronomers using off-the-shelf gear could detect the subtle signs of planets orbiting stars half a galaxy away. We’ve kept in touch with Alberto since then, and he recently tipped us off to his new SETI Project. Following the citizen-science model of the Habitable Exoplanets project, Alberto is looking to recruit amateur radio astronomers willing to turn their antennas in the direction of stars similar to the Sun, where it just might be possible for intelligent life to have formed. Check out the PDF summary of the project which includes the modest technical requirements for getting in on the SETI action.

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Whirling Shutters On This Field Mill Measure Electrostatic Charges At Distance

Hardly a person hasn’t experienced the sudden, sharp discharge of static electricity, especially on a crisp winter’s day. It usually requires a touch, though, the classic example being a spark from finger to doorknob after scuffing across the carpet. But how would one measure the electrostatic charge of an object without touching it? Something like this field mill, which is capable of measuring electrostatic charge over a range of several meters, will do the trick.

We confess to not having heard of field mills before, and found [Leo Fernekes]’ video documenting his build to be very instructive. Field mills have applications in meteorology, being used to measure the electrostatic state of the atmosphere from the ground. They’ve also played a role in many a scrubbing of rocket launches, to prevent the missile from getting zapped during launch.

[Leo]’s mill works much like the commercial units: a grounded shutter rotates in front of two disc-shaped electrodes, modulating the capacitance of the system relative to the outside world. The two electrodes are fed into a series of transimpedance amplifiers, which boost the AC signal coming from them. A Hall sensor on the shutter allows sampling of the signal to be synchronized to the rotation of the shutter; this not only generates the interrupts needed to sample the sine wave output of the amplifier at its peaks and troughs, but it also measures whether the electrostatic field is positive or negative.┬áCheck out the video below for a great explanation and a good looking build with a junk-bin vibe to it.

Meteorological uses aside, we’d love to see this turned toward any of the dozens of Tesla coil builds we’ve seen. From the tiny to the absurd, this field mill should be able to easily measure any Tesla coil’s output with ease.

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Gravity-Defying Cosmetics Explained By Science!

There probably comes a point in every female technical journalist’s career at which she covers her first make-up story and wonders aloud whether this is what her life has come to. But this make-up story involves some physics, and follows a series of viral videos in the TikTok community in which specialist cosmetics vloggers were surprised to see lip gloss apparently levitating — defying gravity — from the ends of its applicators. This caught the attention of [Steve Mould], who followed up on his hunch that static electricity might be responsible. What follows in the video below the break are a variety of attempts to recreate and characterise the phenomenon.

The tried-and-trusted approach of rubbing feet on the carpet failing to cause any movement in the damp atmosphere of a British January, he’s off to try a Van de Graaff generator Even the hefty electrostatic charge from that failed to produce more than a tiny blip, but did at least give a suggestion that the effect might be electrostatic.

Finally he was able to replicate the beauty vloggers’ results using the FunFlyStick electrostatic toy, with satisfying threads of lip gloss heading off into the air. The FunFlyStick is an interesting device in its own right, being a Van de Graaff generator in toy form and capable of generating significant quantities of charge. The flying lip gloss is an interesting phenomenon, but speaks further about just how much electrostatic charge can accumulate on mundane objects in a dry climate. Those of in damper climes would do well to take note before we travel.

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DIY Ionizer Clears The Air On A Budget

Have you ever had a good, deep breath of the air near a waterfall, or perhaps after a thunderstorm? That unmistakably fresh smell is due to ionized air, specifically negative ions, and many are the claims concerning their health benefits. A minor industry has sprung up to capitalize on the interest in ionized air, and while [Amaldev] wanted to clean up the Mumbai air coming into his home, he didn’t want to pay a lot for a commercial unit. So he built his own air ionizer for only about $10.

When [Amaldev] dropped this in the Hackaday tip line, he indicated that he’d been taking some heat for the design from Instagram followers. We imagine a fair number of the complaints stem from the cluster of sewing needles that bristle from one end of the PCB and are raised to 6,000 volts by a fifteen-stage Cockcroft-Walton multiplier. That’s sure to raise eyebrows, or possible the hair on one’s head if you happen to brush by the emitters. Or perhaps [Amaldev]’s critics are dubious about the benefits of ionized air; indeed, some commenters on the video below seem to think that the smoke in the closed jar was not precipitated by the ion stream as [Amaldev] claims, but rather somehow was settled by heat or some other trickery.

Neither of those bothers us as much as the direct 230-volt mains connection, though. We’d have preferred to see at least an isolation transformer in there, or perhaps a battery-powered flyback circuit to supply the input to that multiplier. Still, the lesson on cascade multipliers was welcome, and we found the smoke-clearing power of ionized air pretty amazing.

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Look Ma, No Glue! Electrostatic Adhesion As If By Magic

One of the projects at the recent Hacker Hotel hacker camp in the Netherlands appeared to have achieved the impossible. A vertical PCB surface was holding pieces of paper as though they were pinned to it as on a notice board, yet there was no adhesive or fixings in sight. Was Harry Potter among the attendees, ready with a crafty bit of magic at a waggle of a wizard’s wand, or was a clever hack at work?

Of course, it was the latter, as [Jana Marie Hemsing], had created an electrostatic adhesion plate because she was curious about the phenomenon. A PCB with extra insulation has an array of conductors on one side that carry a very high voltage. High enough for electrostatic attraction to secure a piece of paper to the PCB.

The voltage is generated from an AC source by a Cockroft-Walton multiplier on the back of the PCB, and the front is coated with Plasti-Dip for insulation. It seems that soldermask is not a reliable insulator at such high voltages.

Using the board, [Jana] was able to attach a piece of paper to it with a shearing force of 5 mN at 3 kV applied voltage, which may not sound like much but appeared to be just enough to carefully pick the contraption up by the piece of paper. The boards are designed for tessellation, so larger arrays could easily be assembled.

We’ve never had a project quite like this one, but we have brought you an electrostatic ping-pong ball accelerator.