electromagnet

67 Articles

Interactive Project Teaches Lessons About Electromagnets And Waves

October 4, 2024 by 3 Comments

Whether you’re a kid or a nerdy adult, you’ll probably agree that the interactive exhibitions at the museum are the best. If you happened to get down to the Oregon Science Festival in the last couple of years, you might have enjoyed “Catch The Wave!”—a public education project to teach people about electromagnets and waves. Even better, [Justin Miller] has written up how he built this exciting project.

Catch The Wave! consists of four small tabletop cabinets. Each has physical controls and a screen, and each plays its role in teaching a lesson about electromagnets and sound waves, with a context of audio recording and playback.

The first station allows the user to power up an electromagnet and interact with it using paper clips. They can also see the effect it has on a nearby compass. The second illustrates how reversing current through an electromagnet can reverse its polarity, and demonstrates this by using it to swing a pendulum. The third station then ties this to the action of a speaker, which is effectively a fancy electromagnet—and demonstrates how it creates sound waves in this way. Finally, the fourth station demonstrates the use of a microphone to record a voice, and throws in some wacky effects for good fun.

If you’ve ever tried to explain how sound is recorded and reproduced, you’d probably have loved to had tools like these to do so. We love a good educational project around these parts, too.

Drive For Show, Putt For Dough

October 2, 2024 by 2 Comments

Any golfer will attest that the most impressive looking part of the game—long drives—isn’t where the game is won. To really lower one’s handicap the most important skills to develop are in the short game, especially putting. Even a two-inch putt to close out a hole counts the same as the longest drive, so these skills are not only difficult to master but incredibly valuable. To shortcut some of the skill development, though, [Sparks and Code] broke most rules around the design of golf clubs to construct this robotic putter.

The putter’s goal is to help the golfer with some of the finesse required to master the short game. It can vary its striking force by using an electromagnet to lift the club face a certain amount, depending on the distance needed to sink a putt. Two servos lift the electromagnet and club, then when the appropriate height is reached the electromagnet turns off and the club swings down to strike the ball. The two servos can also oppose each other’s direction to help aim the ball as well, allowing the club to strike at an angle rather than straight on. The club also has built-in rangefinding and a computer vision system so it can identify the hole automatically and determine exactly how it should hit the ball. The only thing the user needs to do is press a button on the shaft of the club.

Even the most famous golfers will have problems putting from time to time so, if you’re willing to skirt the rules a bit, the club might be useful to have around. If not, it’s at least a fun project to show off on the golf course to build one’s credibility around other robotics enthusiasts who also happen to be golfers. If you’re looking for something to be more of a coach or aide rather than an outright cheat, though, this golf club helps analyze and perfect your swing instead of doing everything for you.

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Electromagnetic Actuator Mimics Muscle

July 26, 2024 by 11 Comments

Most electromagnetic actuators are rotating motors, or some variation on the theme, like servos. However, it’s possible to do linear actuation with electomagnetics, too. [Adrian Perez] demonstrates this with Linette, his design of a linear actuator that he was inspired to build by the structure of our own muscles.

The design uses a coil of copper wire in a 3D-printed plastic housing, surrounded by a claw full of strong magnets. When the coil is activated, the magnets are pulled towards the coil. When the coil is not energized, the magnets fall away. [Adrian] demonstrates the actuator under the control of an Arduino, which switches power to the coil to move it up and down.

He also notes that the design is similar solenoids and voice coil style actuators, though unlike most his uses discrete magnets rather than a single monolithic magnet. It’s possible to get more capacity out of the Linette design through stacking. You can parallelize the actuators to get more pulling force, with neighboring coils sharing the same magnets. Alternatively, you can stack them in series to get longer stroke lengths.

[Adrian] hasn’t put the design to a practical application yet, but we could see multiple uses for robotics or small machines. We’ve seen some other neat DIY magnetic actuators before, too. Video after the break.

Electromagnets Make Vertical CNC Cutter A Little Stickier

April 12, 2024 by 12 Comments

Workholding is generally not a problem on a big CNC plasma cutter.; gravity does a pretty good job of keeping heavy sheet steel in place on the bed. But what if your CNC table isn’t a table? The answer: magnets — lots of magnets.

The backstory on this is a bit involved, but the condensed version is that [Lucas] needed a CNC plasma cutter big enough to cut full-sized sheets of steel, but lacked the floor space in his shop for such a beast. His solution was to build a custom CNC machine that stands more or less vertically, allowing him to cut full sheets in a mere fraction of the floor space. It’s a fantastic idea, one that he put a lot of effort into, but it’s not without its problems. Chief among them is the tendency for the sheet metal to buckle and bulge during cutting since gravity isn’t working for him, along with the pesky problem of offcuts slipping away.

To help hold things in place, [Lucas] decided to magnetize the bed of his cutter. That required winding a bunch of magnets, which is covered in the video below. Mass production of magnets turns out not to be as easy as you’d think. Also unexpected was the need to turn off magnets when the cutting torch is nearby, lest the magnetic field bork the cutting plasma. [Lucas] grabbed some code from the LinuxCNC forum that streams the gantry coordinates over serial and used an Arduino to parse those messages. When the torch is getting close to one of the magnets, a relay board cuts power to just that magnet. You can see it in action in the video below; at around the 18:15 mark, you can see the sheet bulging up a bit when the torch comes by, and sucking back down when it moves on.

The amount of work [Lucas] put into this project is impressive, and the results are fantastic. This isn’t the first time he’s relied on the power of magnets to deal with sheet steel, and it probably won’t be the last.

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Vibratory Rock Tumbler Bounces On Printed Spring

April 4, 2024 by 26 Comments

If you’re reading Hackaday, there’s a good chance you had a rock tumbler in your younger days. Hell, we’d put odds on a few of you having one rumbling away in the background as you read this. They’re relatively simple contraptions, and a common enough DIY project. But even still, this largely 3D printed rock tumbler from [Fraens] is unique enough to stand out.

To make a basic rock tumbler, all you really need to do is rotate a cylindrical chamber and let physics do its thing. Such contraptions are known as, unsurprisingly, rotary rock tumblers. But what [Fraens] has put together here is a vibratory tumbler, which…well, it vibrates. If this was Rockaday we might go farther down this particular rabbit hole and explain the pros and cons of each machine, but the short version is that vibratory tumblers are more mechanically complex and are generally better suited to fine finish work than rotary tumblers which take a brute force approach that tends to round off the rocks.

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Sort Of Electromagnet Attracts Copper, Aluminum

March 27, 2024 by 10 Comments

It is a common grade school experiment to wind some wire around a screw, power it up, and watch it pick up paper clips or other ferrous materials. It is also grade school science to show that neither an electromagnet nor a permanent magnet will pick up nonferrous items like copper or aluminum. While technically not an electromagnet, it is possible to build a similar device that will weakly pull on copper and aluminum, and [Cylo] shows us how it works in a recent video you can see below.

The device sure looks like an electromagnet made with magnet wire and a steel core. But when he shows the ends of the core, you’ll see that the side that attracts aluminum has a copper ring embedded in it. The coil is fed with AC.

The magnetic field from the coil induces an opposite field in the copper ring that is out of phase with the exciting field. The two fields combine to produce a force on the metal it interacts with. This is often referred to as a shaded pole, and the same technique can help AC motors self-start as well as hold in relays driven by AC. If you want to see much more about aluminum floating on a magnetic field, check out the 1975 video from [Professor Laithwaite] in the second video below.

You probably have a shaded pole AC motor in your microwave oven. Or, maybe,your old 8-track player.

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Handle Sheet Metal With The Power Of Microwave Oven Electromagnets

May 23, 2023 by 17 Comments

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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