Handle Sheet Metal With The Power Of Microwave Oven Electromagnets

For those of us who don’t do it every day, handling sheet metal can be a nerve-wracking affair. Sheet metal is thin, heavy, and sharp, and one wrong move while handling it can have much the same result as other such objects, like guillotine blades. If only there was a way to lessen the danger.

Perhaps something like this electromagnetic sheet metal handler by [Lucas] over at “Cranktown City” would be useful in keeping one’s fingers and toes attached. Like many interesting builds, this one starts with the dismemberment of a couple of old microwave ovens, to liberate their transformers. Further dissection resulted in open-frame electromagnets, which when energized with a battery from a Ryobi cordless tool do a fine job sticking to stuff.

[Lucas] then harvested the battery connector from the cheapest possible Ryobi tool — an electric fan — and built a prototype, which worked well enough to proceed to a more polished version two. This one had the same guts in a nicely designed case, 3D-printed from lime green filament for that OEM look. The video below shows the design and build, as well as field testing. We have to say this gave us a bit of pause, especially when the battery popped out of one of the handlers and sent the sheet on a near-miss of [Lucas]’ toes. Close call there.

If you’re thinking that you’ve seen MOTs repurposed as electromagnets before, you’re right. Whether climbing like [Spider-Man], lifting heavy steel beams, or walking upside down, microwave oven transformers are the key.

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Levitating Banana Is An Excellent Conversation Starter

“I really like your floating banana.” If that’s something you’ve always wanted your guests to say when visiting your living room, this levitating banana project from [ElectroBing] is for you.

The design is simple. It relies on a electromagnet to lift the banana into the air. As bananas aren’t usually ferromagnetic, a simple bar magnet is fitted to the banana to allow it to be attracted to the electromagnet. One could insert the magnets more stealthily inside the banana, though this would come with the risk that someone may accidentally consume them, which can be deadly.

Of course, typically, the magnet would either be too weak to lift the banana, or so strong that it simply attracted the banana until it made contact. To get the non-contact levitating effect, some circuitry is required. A hall effect sensor is installed directly under the electromagnet. As the banana’s magnet gets closer to the electromagnet, the hall effect sensor’s output voltage goes down. Once it drops below a certain threshold, a control circuit cuts power to the electromagnet. As the banana falls away, power is restored, pulling the banana back up. By carefully controlling the power to the electromagnet on a continuous basis, the banana can be made to float a short distance away in mid-air.

It’s a fun build, and one that teaches many useful lessons in both physics and electronics. Other levitation techniques exist, too, such as through the use of ultrasound. Video after the break.

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A row of electromagnetic coils fastened to a metal track

Propel Paper Planes, Bisect Sausages With Electromagnets

Are you still launching paper airplanes using your hands? That’s like a baby’s toy! [Tom Stanton] and his homebrew electromagnetic rail launcher are sure to bring your paper airplane game into the 21st century.

To be fair, these kinds of linear motors can be used for more than just launching paper airplanes, and can already be found in niche industrial applications, mass transportation systems and roller coasters. And, yes, the potential to leverage electromagnetism in the theater of war is also being vigorously explored by many of the world’s superpowers in the form of Gauss rifles and railguns. In the meantime, the video (after the break) proves that it’s entirely possible to build a rudimentary yet effective linear motor in your makerspace, using relatively basic components and fundamental physics.

In short, these launch systems use electromagnetism and well timed electronics to propel a mass of magnetic material down a straight (or sometimes curved) track. Multiple pairs of coils are placed along the track, with each pair subsequently energized by high current as the payload approaches. By using many coils in succession, the mass and its payload can be accelerated to high speed.

While a homemade rail launcher is unlikely to turn the tides of war, [Tom Stanton] explores their lethal potential with an experiment involving high-speed video and supermarket sausages, with gruesome results.

If you’re looking for more, why not check out our our previous coverage on electromagnetic weaponry?

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Is This 12-layer PCB Coil The Next Step In Ferrofluid Displays?

[Applied Procrastination] is in the business of vertical ferrofluid displays, but struggles somewhat with the electromagnets available off the shelf and the proliferation of wiring that results. [Carl Bugeja] is in the business of making PCB coils, both with rigid and flex PCB substrates, so when the opportunity for a collaboration arose, [AP] jumped at the opportunity.

As [Simen from AP] mentions in the video after the break, they had considered using a large PCB with embedded coils for Fetch their ferrofluid display unit, but the possible magnetic field was just too weak, and attempting to crank up the amps, just overheats them. Some improvements were made, first sticking the coil PCB to a small disk of ferrous metal, which doubled up as a handy heatsink. Next, he tried adding a permanent magnet, which added a bit of bias field. Alone this was not enough to hold the ferrofluid in place, but with the coil powered, it was starting to look encouraging.

Much more progress was made when [Carl] sent over a new design of his, a 12-layer PCB coil. This obviously had a much larger field, but still not enough without the extra boost from permanent magnet.

[Simen] currently doesn’t think the PCB approach is quite there yet, and is looking for help to source PCB-mounted electromagnets of the wired variety. We would imaging prototyping with such a large 12-layer PCB would be rather prohibitively expensive anyway.

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DIY Machine Enables PEMF Therapy On A Budget

We’re certainly not qualified to say whether or not pulsed electromagnetic field (PEMF) therapy will actually reduce your stress or improve your circulation, but there seems to be enough legitimate research going on out there that it might be worth a shot. After all, unless you’ve got a pacemaker or other medical implant, it seems pretty unlikely a magnetic field is going to make anything worse. Unfortunately commercial PEMF machines can cost thousands of dollars, making it a fairly expensive gamble.

But what if you could build one for as little as $10 USD? That’s the idea behind the simple DIY PEMF machine [mircemk] has been working on, and judging by its ability to launch bits of metal in the video below, we’re pretty confident it’s indeed producing a fairly powerful electromagnetic field. Even if it doesn’t cure what ails you, it should make an interesting conversation piece around the hackerspace.

While the outside of the machine might look a bit imposing, the internals really are exceptionally straightforward. There’s an old laptop power supply providing 19 VDC, a dual-MOSFET board, a potentiometer, and a simple signal generator. The pulses from the signal generator trip the MOSFET, which in turn dumps the output of the laptop power supply into a user-wound coil. [mircemk] has a 17 cm (6.7 inch) open air version wrapped with 200 turns of copper wire used for treating wide areas, and an 8 cm (3 inch) diameter version with 300 windings for when you need more targeted energy.

Some skepticism is always in order with these sort of medicinal claims, but commercial PEMF machines do get prescribed to users to help promote bone growth and healing, so the concept itself is perhaps not as outlandish as it might seem.

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Fetch ferrofluid display

Ferrofluid Display Gets New, Better Driver Circuitry

In 2019 [Simen] and [Amud], two students from the University of Oslo, set out to design a unique open-source display. The result was Fetch, a display that uses electromagnets to suspend ferrofluid on 252 “pixels” across the screen. After some delays due to COVID, they have recently unveiled version 2.0 of the display on their project’s page.

While the duo managed to overcome the mechanical challenges associated with using ferrofluids fairly easily, they were quickly bottlenecked by their electronics. The use of electromagnets holding up a liquid presented a unique challenge; the magnets could not be switched off, even for a millisecond, or else the “pixel” would fall down to the bottom of the screen. That immediately ruled out any sort of multiplexing and meant everything would have to be driven in parallel. As if that wasn’t already difficult enough to work around, the effect of having multiple electromagnets activated next to each other would change how the ferrofluid flows. This meant that the strength of each electromagnet would have to be adjusted based on what is currently being displayed, rather than just being on or off.

The mess of connections were not helped with the layout of the old driver boards shown here. The new design puts the connections closer to each individual electromagnet.

All of this, paired with other overhead like generating pulse-width modulation for the inputs, was just too much for a single microcontroller to handle. So, the pair set out to design a better version of their electronics that would offload a lot of the hard work. At the same time, they decided a bit of mechanical optimization was in order; they redesigned the boards to be longer and thinner, allowing them to fit cleanly behind the row of electromagnets they controlled.

The new boards feature a PCA9685 IC, which allows for the control of up to 16 channels of 12-bit PWM over i2C, perfect for the size of the display. Since this IC can’t source enough current to drive the electromagnets, it was paired with a ULN2803 Darlington Transistor Array, capable of delivering up to 500mA to each electromagnet.

With prototypes in hand (and a few bodge wires here and there), [Simen] and [Amud] had the new driver boards running beautifully, displaying text in a mesmerizing way that no ordinary display could match. Watch the video after the break for a demonstration of the new controllers in action, as well as a deeper dive into the process of developing them.

Want to learn more? Check out our previous article about Fetch! Or if you’re looking for another cool way to use ferrofluids, how about making it dance in a custom speaker!

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A 3D Printer With An Electromagnetic Tool Changer

The versatility of 3D printers is simply amazing. Capable of producing a wide variety of prototypes, miscellaneous parts, artwork, and even other 3D printers, it’s an excellent addition to any shop or makerspace. The smaller, more inexpensive printers might do one type of printing well with a single tool, but if you really want to take a 3D printer’s versatility up to the next level you may want to try one with an automatic tool changing system like this one which uses magnets.

This 3D printer from [Will Hardy] uses an electromagnet to attach the tool to the printer. The arm is able to move to the tool storage area and quickly deposit and attach various tools as it runs through the prints. A failsafe mechanism keeps the tool from falling off of the head of the printer in case of a power outage, and several other design features were included to allow others to tweak this design to their own particular needs, such as enclosing the printer and increasing or decreasing the working area of the Core-XY printer as needed.

While the project looks like it works exceptionally well, [Will] notes that it is still in the prototyping phase and needs work on the software in order to refine its operation and make it suitable for more general-purpose uses. It’s an excellent design though and shows promise. It also reminds us of this other tool-changing system we featured a few months ago, albeit with a less electromagnetic twist.

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