eddy current

7 Articles

Hoverboard Rides On Eddy Currents

May 22, 2023 by 32 Comments

The famous hoverboards of Back to the Future haven’t quite gotten here yet, but that hasn’t stopped anyone with a unique personal vehicle from using the name any time they need some quick marketing. The self-balancing scooter trend of the mid-2010s was the best example of this in recent memory, but there are also water-propelled platforms that use the popular name as well as a myriad of other more skateboard-like devices that never got off the ground at all. This project from [Damien Dolata], on the other hand, might be the most authentic prototype we’ve seen compared against the fictional version presented in the movie.

The hoverboard uses a set of rotating magnets, referred to in this build as magneto-rotational repulsors, which spin up to an extremely high rotational speed underneath the board. When above a metal surface, the spinning magnets generate eddy currents in the metal beneath them which create the strong magnetic field needed to levitate the board. Unlike the Lexus hoverboard system which used supercooling magnets, this is a much more affordable way of producing magnetic fields but is a little bit more complicated due to the extra moving parts.

As this is still in the prototyping stages, it has only been able to lift around 30 kg and hasn’t been tested in motion yet, but there are two small turbines built into the hoverboard to generate thrust whenever [Damien] gets to that point. It would require a larger metal surface to move across as well, which might be the main reason why it hasn’t been tested this way yet. For any native French speakers taking a look at this project, be sure to fill in any of our gaps in the comments below, and for other ways that eddy currents have been used in transportation take a look at this bicycle that uses them in its drivetrain.

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Jet Engine Tachometer Turned Into Unique CPU Utilization Meter

May 4, 2023 by 16 Comments

When you’ve got a piece of interesting old aviation hardware on your desk, what do you do with it? If you’re not willing to relegate it to paperweight status, your only real choice is to tear it down to see what makes it tick. And if you’re lucky, you’ll be able to put it to work based on what you learned.

That’s what happened when [Glen Akins] came across a tachometer for a jet airplane, which he promptly turned into a unique CPU utilization gauge for his computer. Much of the write-up is concerned with probing the instrument’s innards to learn its secrets, although it was clear from the outset that his tachometer, from Kollsman Instruments, was electrically driven. [Glen]’s investigation revealed a 3-phase synchronous motor inside the tach. The motor drives a permanent magnet, which spins inside a copper cup attached to the needle on the tach’s face. Eddy currents induced in the cup by the spinning magnet create a torque that turns the needle against the force of a hairspring. Pretty simple — but how to put the instrument to work?

[Glen]’s solution was to build what amounts to a variable frequency drive (VFD). His power supply is based on techniques he used to explore aircraft synchros, which we covered a while back. The drive uses a trio of MCP4802 8-bit DACs to generate three phase-shifted sine waves via direct digital synthesis with an RP2040. The 3-phase signal drives the motor and spins the dial, with 84-Hz corresponding to full-scale deflection.

The video below shows the resulting CPU utilization gauge — which just queries for the current load level and sends it to the RP2040 over serial — in action. It’s not exactly responsive to rapid changes, but that’s to be expected from a mechanical system. And compared to exploring such a nice instrument, it really doesn’t matter.

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Visualizing Eddy Currents

February 19, 2019 by 18 Comments

If [Electroboom] gives up making videos and decides to become a lounge lizard in the Poconos, we hope he adopts the stage name Eddy Currents. However, he is talking about eddy currents in his recent video post that you can see below.

We know he doesn’t really think he can get the magnet to slow down with one sheet of aluminum foil and that he stages at least most of his little electric accidents, but we still enjoy watching it. Meanwhile, he also has a good explanation of why a copper pipe will slow down a magnet and how eddy current affects transformer efficiency.

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Inventing The Induction Motor

September 21, 2017 by 36 Comments

When you think of who invented the induction motor, Nikola Tesla and Galileo Ferraris should come to mind. Though that could be a case of the squeaky wheel being the one that gets the grease. Those two were the ones who fought it out just when the infrastructure for these motors was being developed. Then again, Tesla played a huge part in inventing much of the technology behind that infrastructure.

Although they claimed to have invented it independently, nothing’s ever invented in a vacuum, and there was an interesting progression of both little guys and giants that came before them; Charles Babbage was surprisingly one of those giants. So let’s start at the beginning, and work our way to Tesla and Ferraris.

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A Simple Induction Heater

October 27, 2011 by 23 Comments

For those of you not familiar, an induction heater is a device capable of heating something up very rapidly using a changing magnetic field. [RMC Cybernetics] decided to build one and was nice enough to write up the project for the Internet’s learning and amusement. A full explanation as well as a schematic and build instructions are provided on their website.

This heater works using a principle involved in most transformers. When there is a change in the magnetic field near a conductive object, a current will be induced in it and it will generate heat. Interestingly enough, while transformers are designed to minimize this heat, an induction heater instead aims to maximize this heat in whatever object is placed within the coils.

[RMC] Has provided a video of how to build the heater as well as it in action after the break! Skip to to 1:42 to see the heating in action. Or watch the whole thing to see how it’s built.

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Hand-cranked Magnet Machine Is Endless Fun

May 25, 2011 by 41 Comments

magnet_machine

We can’t think of a single person who doesn’t enjoy playing with a handful of rare earth magnets now and again. We know that [Dave Johnson] certainly does. As a gift to his father in law, he constructed a magnificent machine that does little more than manipulate spherical rare earth magnets with hypnotizing grace.

The machine is constructed almost entirely from wood, save for a few fasteners and rods. Even the gears have been carefully cut from wood, with special attention paid to ensure smooth operation. When cranked, the machine slices off a single magnet from one end of a long chain, passing it along to a lift arm. The lift arm deposits the magnet into a metal tube, and with the help of eddy currents, it drifts slowly down before being redeposited at the end of the magnet chain.

Be sure to check out a video demonstration of the machine after the break, it really is fun to watch.

[via LaughingSquid]

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Induction Furnace

June 22, 2009 by 19 Comments

induction furnace

[Tim Williams] made his own induction furnace. A copper tubing coil forms the primary winding, as the material to be heated becomes the short circuited secondary. The load material is subject to high power magnetic fields operating at radio frequency. The rapidly changing field induces current flow within the material, creating a great deal of heat. The brute power required a cooling system to match. In the video below, the induction furnace can be seen melting common table salt.

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