Building a linear motor


We admit that this project doesn’t have very many details available, but it was just too neat for us to pass up. It’s a small linear motor which [ligonapProduktion] built after seeing a very brief description of a commercially available version.

The video after the break shows him testing the motor. In this screenshot he’s holding the center shaft while the coil assembly moves back and forth. But it works with a stationary coil moving the rod as well. The motor is basically a modified solenoid. There are sixteen neodymium magnets inside the shaft. The set of four coils is driven by an ATtiny44. Just like a stepper motor, energizing the coils in the correct order pushes against the rare earth magnets creating motion.

We’re not sure if he has any use in mind for this build. For us we just like to see the concept in practice (we feel the same way about a homopolar motor build).

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Hacking grandfather clock accuracy while it’s still ticking


[Keith] got his hands on a few grandfather clocks. Apparently the price tag is greatly reduced if you are able to get them second-hand. The mechanical timepieces require weekly winding, which is a good thing since you’ll also need to correct the time at least that often. But this drift got [Keith] thinking about improving the accuracy of these clocks. He figured out a high-tech way to adjust the timepiece while it’s ticking.

The first thing he needed was a source of super-accurate time. He could have used a temperature compensated RTC chip, but instead went the more traditional route of using the frequency of mains power as a reference. The next part of the puzzle is to figure out how to both monitor the grandfather clock and make small tweaks to its pendulum.

The answer is magnets. By adding a magnet to the bottom of the pendulum, and adjusting the proximity of a metal plate positioned below it, he can speed up or slow down the ticking. The addition of a hall effect sensor lets the Arduino measure the rate of each swing and calculate the accuracy compared to the high voltage frequency reference.

Magnets keep the shower curtain from groping you


We guess we’re glad to hear that other also suffer from the phantom shower curtain liner. On occasion the shower curtain will start closing in on us around the bottom of the shower. We’re not certain of the phenomenon that causes it. Perhaps it’s static electricity like when a comb repels a stream of water. It could be an issue with rising air though… who know. But [Sk84life0129] has had enough of it. He figured out a magnet-based solution to stop the shower curtain from groping him.

You can buy curtain liners that have magnets in the bottom of them to help prevent this. But this is an acrylic tub — not one that’s porcelain-coated cast iron like they used to be — so that’s not going to do any good. Instead, a pair of magnets from an old hard drive were glued to the shower surround. A couple of galvanized bolts had their heads sawn off, and were sewn into pockets in the shower curtain. These hold it taught while you scrub your body, preventing it from reaching out for a close encounter.

[via Reddit]

Tablet interacts with magnets, how does that work?

Making computers interact with physical objects is a favorite of the HCI gurus out there, but these builds usually take the form of image recognition of barcodes or colors. Of course there are new near field communication builds coming down the pipe, but [Andrea Bianchi] has figured out an easier way to provide a physical bridge between computer and user. He’s using magnets to interact with a tablet, and his idea opens up a lot of ideas for future tangible interfaces.

Many tablets currently on the market have a very high-resolution, low latency magnetometer meant for geomagnetic field detection. Yes, it’s basically a compass but Android allows for the detection of magnets, and conveniently provides the orientation and magnitude of magnets around a tablet.

[Andrea] came up with a few different interfaces using magnets. The first is just a magnets of varying strengths embedded into some polymer clay. When these colorful magnetic cubes are placed on the tablet, [Andrea]’s app is able to differentiate between small, medium, and large magnets.

There are a few more things [Andrea]’s app can do; by placing two magnets on an ‘arrow’ token, the app can detect the direction in which the arrow is pointing. It’s a very cool project that borders on genius with its simplicity.

You can check out [Andrea]’s demo video after the break.

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Revolight clone

[Fabian.E] wanted to light up the rims on his bike, but didn’t want to shell out a bunch of clams to get it done. He came up with this system which uses magnets and reed switches to light up one arc or each bicycle wheel.

He calls it the lightrider and it’s based on the revolights concept. That design uses a microcontroller which is capable of animating patterns when the wheels aren’t spinning. [Fabian’s] version can’t do that, but the effect while moving is basically the same. The ring of LEDs around the rim is connected to a battery via a set of reed switches. When these switches move past a magnet on the fork it completes the circuit and switches on that segment of LEDs. The clip after the break gives a demonstration of the finished product, and includes a fast-motion video of the fabrication process.

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Your theme song greets you at the front door

One thing you can look forward to when arriving at home after a long, arduous day at the office is some peppy theme music when you walk in the door. [Sebastian Sommer] built the system, and shows it off in the video after the break by dancing to James Brown’s I feel good.

The setup uses an Arduino as a microcontroller. It monitors a hall effect sensor on the jamb which detects a passing magnet on the door. We guess this means the system doesn’t know if you’re coming or going but perhaps a future upgrade would add an infrared beam to detect your legs as head out the door. The music itself is played by an SparkFun MP3 shield which has a decoder chip, microSD slot, and audio jack for the powered speakers. [Sebastian] grabbed a copy of [Bill Porter’s] mp3 shield library to get the project up and running quickly.

This is a pretty cool addition if you’re already using an Arduino for a door lock or vice versa. Or maybe you’re not home enough to make this hack worth it, in which case you simply must take this music playing Tesla coil hat along on your commute.

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Give yourself a sixth sense on the cheap


Hackaday regular [Mikey Sklar] is no stranger to body modifications. He enjoys tweaking his body in ways that help him with day to day tasks, including a ruler tattoo on his arm and an RFID chip embedded in the web of his hand. Lately, he has been toying around with a less invasive means of getting a better feel for magnetic fields in his surroundings.

Turned on to magnetic rings by a friend, he now wears an epoxy-coated rare earth ring every day, changing the way he interacts with the world. He says that besides the obvious ability to tell when he’s near iron-heavy material, he can also feel cell phone calls, as the speaker draws the ring closer while producing sound.

He says that holding the electric cord of his tea kettle gave him the biggest start, making him feel as if he had been electrocuted, minus the actual shock.

While it’s not the most high-tech hack, [Mikey] is quite happy with the “sixth sense” this reasonably price ring has been able to provide – we just might have to try it out ourselves.