magnet

114 Articles

Turn A Ceiling Fan Into A Wind Turbine… Almost

June 30, 2019 by 9 Comments

It’s not uncommon to drive around the neighborhood on trash day and see one or two ceiling fans haphazardly strewn onto a pile of garbage bags, ready to be carted off to the town dump. It’s a shame to see something like this go to waste, and [Giesbert Nijhuis] decided he would see what he could do with one. After some painstaking work, he was able to turn a ceiling fan into a wind turbine (of sorts).

While it’s true that some generators and motors can be used interchangeably by reversing the flow of electricity (motors can be used as generators and vice-versa) this isn’t true of ceiling fans. These motors are a type called induction motors which, as a cost saving measure, have no permanent magnets and therefore can’t simply be used as a generator. If you make some modifications to them, though, like rewiring some of the windings and adding permanent magnets around them, you can get around this downside of induction motors.

[Giesbert] does note that this project isn’t a great way to build a generator. Even after making all of the changes needed to get it working, the motor just isn’t as efficient as one that was built with its own set of magnets. For all the work that went into it, it’s not that great of a time investment for a low-quality generator. However, it’s interesting to see the theory behind something like this work at all, even if the end result wasn’t a complete wind turbine. Perhaps if you have an old ceiling fan lying around, you can put it to better use.

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Magnetic Attraction Of Microduino MCookie Modules

June 27, 2019 by 8 Comments

We’ve seen countless different robot kits promoted for STEM education, every one of which can perform the robotic “Hello World” task of line following. Many were in attendance at Maker Faire Bay Area 2019 toiling in their endless loops. Walking past one such display by Microduino, Inc. our attention was caught by a demonstration of their mCookie modules in action: installing a peripheral module took less than a second with a “click” of magnets finding each other.

Many Arduino projects draw from an ecosystem of Arduino shields. Following that established path, Microduino had offered tiny Arduino-compatible boards and peripherals which connected with pins and headers just like their full-sized counterparts. Unfortunately their tiny size also meant their risk of pin misalignment and corresponding damage would be higher as well. mCookie addresses this challenge by using pogo pins for electrical contacts, and magnets to ensure proper alignment. Now even children with not-quite-there-yet dexterity can assemble these modules, opening up a market to a younger audience.

Spring loaded electric connections are a popular choice for programming jigs, and we’ve seen them combined with magnets for ideas like modular keyboards, and there are also LittleBits for building simple circuits. When packaged with bright colorful LEGO-compatible plastic mounts, we have the foundation of an interesting option for introductory electronics and programming. Microduino’s focus at Maker Faire was promoting their Itty Bitty Buggy, which at $60 USD is a significantly more affordable entry point to intelligent LEGO creations than LEGO’s own $300 USD Mindstorm EV3. It’ll be interesting to see if these nifty mCookie modules will help Microduino differentiate themselves from other LEGO compatible electronic kits following a similar playbook.

Rare Earth Metals Caught In Trade War

June 4, 2019 by 78 Comments

It seems these days that the news is never good. Speaking from experience, that’s really nothing new; there’s always been something to worry about, and world leaders have always been adept at playing the games that inevitably lead to disturbing news. Wars always result in the very worst news, of course, and putting any kind of modifier in front of the word, like “Cold” or “proxy”, does little to ameliorate the impact.

And so the headlines have been filled these last months with stories of trade wars, with the primary belligerents being the United States and China. We’ve covered a bit about how tariffs, which serve as the primary weapons in any trade war, have impacted the supply of electronic components and other materials of importance to hackers.

But now, as the trade war continues, a more serious front is opening up, one that could have serious consequences not just to the parties involved but also to the world at large. The trade war has escalated to include rare earth metals, and if the threats and rumors currently circulating come to fruition, the technologies and industries that make up the very core of modern society will be in danger of grinding to a halt, at least temporarily.

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Custom Rotary Switch Takes A Motor

April 10, 2019 by 9 Comments

There are certain challenges we all will have to face sooner or later. Changing a flat tire in the rain, trying to put on a shirt that doesn’t quite fit, or producing a 16 position rotary switch for a replica computer front panel. There was a time when something like this would be a major undertaking, but with the help of a 3D printer [Mike Gardi] was able to build good looking switches that were big enough to be motor driven.

Switches of course are old tech, and there are plenty of ways to make contacts. [Mike] settled on using 16 small magnets and reed switches. This works, but you probably wouldn’t want to use it where the switch might get close to an external magnet. It does however make for a neat assembly without a lot of mechanical work. It also resists wear compared to a brush type arrangement.

The switch is a little large, but it could probably be made smaller with proper contacts. However, you still need at least some magnets to provide the detents without making mechanical changes.

We couldn’t help but think of the homemade rotary switches from the do it yourself computer that used sewing thread spools, wires, and paper clips. It would be fun to revisit that computer with an eye to making things using a 3D printer. We liked the knob, but if you only need a reproduction knob, there are other ways to go.

Shop-Built Fixtures Reveal The Magic Of Switchable Permanent Magnets

April 7, 2019 by 22 Comments

Have you ever wondered how switchable magnets work? Not electromagnets, but those permanent magnet fixtures like the ones that hold dial indicators to machine tools, or the big, powerful chucks for surface grinders that can be mysteriously demagnetized at the flick of a lever. It seems like magic.

Thanks to [Andrew Klein] and this video on shop-built magnetic switches, the magic is gone. As it turns out, the ability to nullify the powerful magnetic field from a bunch of rare earth permanent magnets is as simple as bringing in another set of magnets to cancel out the magnetic fields of the first set.

[Andrew]’s magnetic pucks are formed from two thick plywood discs with magnets set into the edges. These magnets alternate in polarity around the discs, and they match up with mild steel pole pieces set into the face of the discs. The two discs swivel on a common axis; when the top disc is swiveled so that the polarity of the top and bottom magnets align, the magnet is switched on. Swiveling the top 60° puts the opposing fields in line with each other, canceling out the powerful combined pull of all the magnets and releasing the fixture.

[Andrew] sells a set of plans for the magswitches, which he built using standard woodshop tools. We think the design is perfect for a CNC router, though, where the fussy boring and counterboring operations might be a little easier. Perhaps even a 3D-printed version would be possible. This isn’t the first switchable magnet we’ve seen, of course, but we like this one because it’s all mechanical.

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Hiding Messages In Magnets

April 4, 2019 by 12 Comments

Magnets have always been fun, particularly since the super-powerful neodymium type became readily available. You can stack them up, pull them apart, or, if you really want, use them for something practical. Now [Adric] has shown us a new use for them entirely – by writing hidden messages on them.

It’s a remarkably simple hack, but ingenious all the same. [Adric] was pretty sure that the Quelab hackerspace laser wasn’t powerful enough to cut or etch a nickel-plated neodymium magnet. However, they suspected it would have just enough power to heat localised parts of the magnet above the Curie temperature, where the magnetic properties of the material break down.

Thus, the laser cutter was set up to run a few passes over some neodymium magnets. By placing a magnetic viewing film over the magnet, it’s possible to make the etched pattern visible. There was also some incidental visible marking of the magnet surface, which [Adric] thinks is due to the tape applied to the magnet before the laser processing.

For those of you operating spy rings in deep cover, you’ve now got a new way to send them secret messages. Just be sure to check in with the local postal service as to their policies regarding giant magnets in the post. Then you can contemplate whether you have the ability to sense magnetic fields.

Maybe You Really Can Sense Magnetic Fields

March 23, 2019 by 42 Comments

We’ve known for years that many animals can somehow sense magnetic fields. Birds apparently use the Earth’s magnetic field to navigate. Dogs can find a box containing a magnet better than they can find a similar box with a food treat in it. But humans, apparently, can’t visualize magnetic fields without help. Several scientists at California, New Jersey, and Japan have done experiments that seem to show that people’s brains do have changes when a magnetic field rotates. If the paper, titled “Transduction of the Geomagnetic Field as Evidenced from Alpha-band Activity in the Human Brain” is a bit much for you, might enjoy the video from Veritasium, below, which is much easier to parse than the paper.

To see it work, a subject sits in a dark isolated room with an electrode cap that picks up the subject’s EEG. The study shows that different people have different sensitivity to the field. Also, picking up a magnetic field in an isolated chamber is different from picking it up on the sidewalk and using it to navigate with. Continue reading “Maybe You Really Can Sense Magnetic Fields” →