magnet

124 Articles

Fail Of The Week: How Not To Die Of Boredom During Isolation

April 1, 2020 by 26 Comments

They say you can’t actually die from boredom, but put a billion or so people into self-isolation, and someone is bound to say, “Hold my beer and watch this.” [Daniel Reardon]’s brush with failure, in the form of getting magnets stuck up his nose while trying to invent a facial touch reminder, probably wasn’t directly life-threatening, but it does underscore the need to be especially careful these days.

The story begins with good intentions and a small stack of neodymium magnets. [Daniel]’s idea for a sensor to warn one of impending face touches was solid: a necklace with magnetic sensors and wristbands studded with magnets. Sounds reasonable enough; one can easily see a compact system that sounds an alarm when a hand subconsciously crosses into the Danger Zone while going in for a scratch. Lacking any experience in circuits, though, [Daniel] was unable to get the thing working, so he started playing with the magnets instead. One thing led to another, and magnets were soon adorning his earlobes, and then his nostrils. Unfortunately, two magnets became locked on either side of his septum, as did two others meant to neutralize the pull of the first pair. So off [Daniel] went to the emergency department for a magnetectomy.

Of course it’s easy to laugh at someone’s misfortune, especially when self-inflicted. And the now-degaussed [Daniel] seems to be a good sport about the whole thing. But the important thing here is that we all do dumb things, and hackers need to be especially careful these days. We often work with sharp, pointy, sparky, toxic, or flammable things, and if we don’t keep our wits about us, we could easily end up in an ER somewhere. Not only does that risk unnecessary exposure to COVID-19, but it also takes medical resources away from people who need it more than you do.

By all means, we should be hacking away these idle hours. Even if it’s not in support of COVID-19 solutions, continuing to do what we do is key to our mental health and well-being. But we also need to be careful, to not stretch dangerously beyond our abilities, and to remember that the safety net that’s normally there to catch us is full of holes now.

Thanks to [gir.st] for the tip — you actually were the only one to send this in.

Inverse Kinematics Robot Arm Magna-Doodles The Time For You

March 24, 2020 by 8 Comments

Following a surge of creativity fueled by the current lockdown, [Diglo] writes in with his tabletop clock driven by a robotic arm drawing on a Magna Doodle tablet. And if you have one of those still lying around with some old toys and don’t mind cannibalizing it for the project, you too can follow along the source files to build your own.

The clock works by exploiting the principle that Magna Doodle tablets work by being drawn on with a magnetic stylus. That way, to draw on one of them you don’t need to add a point of articulation to bring the pen up and down, [Diglo] simply attached a controllable electromagnet to the end of a two-dimensional SCARA arm. In total, the whole build uses three stepper motors, two to control the movement of the arm, and one on the back of the tablet to sweep a magnetic bar which “erases” it.

This clock is similar to another we’ve featured a few years ago, which also used a Magna Doodle, but greatly improves on the idea. If a Magna Doodle seems too childish to build a magnetic clock however, there’s always ferrofluidic displays to try to dip your fingers into, but we really think you should watch this one in action after the break first.

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A Tin Can Phone, But With Magnets

February 29, 2020 by 17 Comments

The tin can phone is a staple of longitudinal wave demonstrations wherein a human voice vibrates the bottom of a soup can, and compression waves travel along a string to reproduce the speaker in another can at the other end. All the parts in this electrical demonstration are different, but the concept is the same.

Speakers are sound transducers that turn electrical impulses into air vibrations, but they generate electricity when their coil vibrates. Copper wires carry those impulses from one cup to another. We haven’t heard of anyone making a tin can phone amplifier, but the strictly passive route wasn’t working, so an op-amp does some messy boosting. The link and video demonstrate the parts and purposes inside these sound transducers in an approachable way. Each component is constructed in sequence so you can understand what is happening and make sense of the results.

Can someone make a tin can amplifier transformer? We’d like to see that. In another twist of dual-purpose electronics, did you know that LEDs can sense light?

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Sequence Your Beats With The Magic Of Magnets

February 15, 2020 by 10 Comments

Typically, when we think of a music sequencer, we envisage LEDs and boards covered in buttons. Of course, there are naturally other ways to build such a device. MesoTune takes a different tack entirely, relying on magnets and rotating mechanisms to get the job done.

MesoTune acts as a MIDI controller, and is designed to be hooked up to a computer or other MIDI synthesizer device. The heart of MesoTune is a set of eight magnet wheels, rotating together on a common shaft. The rotational speed of the shaft, dictated by the requested tempo in beats per minute, is controlled by an Arduino. Each magnet wheel has 16 slots into which the user can place a spherical magnet. Every time a magnet on the wheel passes a hall sensor, it sends a MIDI message to the attached computer which is then responsible for using this to synthesize the relevant sound.

There are other useful features, too. Each of the eight magnet wheels, or channels, gets its own fader, which can be used to control volume or other parameters. There’s also a handy tempo display, and a 16-button touchpad for triggering other events. These additions make it more practical to use in a compositional context, where it’s nice to have extra controls to make changes on the fly.

Made out of 3D printed parts and readily available off the shelf components, it’s a fun alternative sequencer design that we’re sure many makers could whip up in just a weekend. We’d love to see other remixes of the design – if you’ve got one, hit us up at the tipline. We’ve seen other great sequencer builds before, too. Video after the break.

A Nifty Tool For Separating Magnets

February 15, 2020 by 3 Comments

Neodymium magnets are fun to play with, largely thanks to their incredibly strong magnetic field. This also gives them plenty of applications where other magnets won’t cut the mustard. This very strength is also a drawback, making them difficult to work with and posing a danger to squishy human bodies. To help ease the task, [RandomCitizen4] developed a handy magnet separator tool.

The tool is similar in design to a pair of scissors, with two blades that are slid together when the handles are squeezed. The design is subtly different, however, with plastic blades that slide in between the gaps of a pair of magnets stuck together, pushing them apart. With just three parts to be 3D printed, a handful of fasteners and a rubber band, the tool is easy to build, too.

As someone who has spent significant time sliding magnets apart on the edge of a desk, wearing away the skin on my hands in the process, this tool would certainly come in handy. It might also be useful if you find yourself experimenting with magswitches or similar. Video after the break.

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Emergency Torch Runs Without Batteries

February 14, 2020 by 29 Comments

It’s always good to have a torch on hand for emergencies. Unfortunately, sometimes these torches can be forgotten, and wind up with dead batteries when you need them most. For those cases, this build from [techrallyofficial] is just the ticket.

Instead of a battery, the torch relies on a 1.5 farad supercapacitor to store energy. The body of the torch is constructed out of PVC pipe and fittings, and packs strong neodymium magnets inside. A coil of wire wrapped is formed around an old solder spool, which, when shaken past the magnets, generates a current. This is rectified with a series of diodes and charges the supercapacitor, powering the light.

It’s a classic design that is available commercially, but it’s one easily replicated in the home shop, too. It would make a great educational project, particularly as students would be left with a useful device to take home at the end of the lesson. We’ve seen others resurrect commercial builds with upgrades, too. Video after the break.

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Hackaday Links: January 5, 2020

January 5, 2020 by 30 Comments

It looks like the third decade of the 21st century is off to a bit of a weird start, at least in the middle of the United States. There, for the past several weeks, mysterious squads of multicopters have taken to the night sky for reasons unknown. Witnesses on the ground report seeing both solo aircraft and packs of them, mostly just hovering in the night sky. In mid-December when the nightly airshow started, the drones seemed to be moving in a grid-search pattern, but that seems to have changed since then. These are not racing drones, nor are they DJI Mavics; witnesses report them to be 6′ (2 meters) in diameter and capable of staying aloft for 90 minutes. These are serious professional machines, not kiddies on a lark. So far, none of the usual government entities have taken responsibility for the flights, so speculation is all anyone has as to their nature. We’d like to imagine someone from our community will get out there with radio direction finding gear to locate the operators and get some answers.

We all know that water and electricity don’t mix terribly well, but thanks to the seminal work of White, Pinkman et al (2009), we also know that magnets and hard drives are a bad combination. But that didn’t stop Luigo Rizzo from using a magnet to recover data from a hard drive. He reports that the SATA drive had been in continuous use for more than 11 years when it failed to recover after a power outage. The spindle would turn but the heads wouldn’t move, despite several rounds of percussive maintenance. Reasoning that the moving coil head mechanism might need a magnetic jump-start, he probed the hard drive case with a magnetic parts holder until the head started moving again. He was then able to recover the data and retire the drive. Seems like a great tip to file away for a bad day.

It seems like we’re getting closer to a Star Trek future every day. No, we probably won’t get warp drives or transporters anytime soon, and if we’re lucky velour tunics and Spandex unitards won’t be making a fashion statement either. But we may get something like Dr. McCoy’s medical scanner thanks to work out of MIT using lasers to conduct a non-contact medical ultrasound study. Ultrasound exams usually require a transducer to send sound waves into the body and pick up the echoes from different structures, with the sound coupled to the body through an impedance-matching gel. The non-contact method uses pulsed IR lasers to penetrate the skin and interact with blood vessels. The pulses rapidly heat and expand the blood vessels, effectively turning them into ultrasonic transducers. The sound waves bounce off of other structures and head back to the surface, where they cause vibrations that can be detected by a second laser that’s essentially a sophisticated motion sensor. There’s still plenty of work to do to refine the technique, but it’s an exciting development in medical imaging.

And finally, it may actually be that the future is less Star Trek more WALL-E in the unlikely event that Segway’s new S-Pod personal vehicle becomes popular. The two-wheel self-balancing personal mobility device is somewhat like a sitting Segway, except that instead of leaning to steer it, the operator uses a joystick. Said to be inspired by the decidedly not Tyrannosaurus rex-proof “Gyrosphere” from Jurassic World, the vehicle tops out at 24 miles per hour (39 km/h). We’re not sure what potential market for these things would need performance like that – it seems a bit fast for the getting around the supermarket and a bit slow for keeping up with city traffic. So it’s a little puzzling, although it’s clearly easier to fully automate than a stand-up Segway.