Misc Hacks

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Mechanical 7-segment display

A One-Servo Mechanical Seven-Segment Display

November 13, 2021 by 21 Comments

The seven-segment display may be a bit prosaic after all these years, but that doesn’t mean there aren’t ways to spice it up. Coming up with a mechanical version of the typical photon-based display is a popular project, of which we’ve seen plenty of examples over the years. But this seven-segment display is quite a mechanical treat, and a unique way to flip through the digits.

With most mechanical displays, we’re used to seeing the state of each segment changed with some kind of actuator, like a solenoid or servo. [Shinsaku Hiura] decided on a sleeker design using a 3D-printed barrel carrying one cam for each segment. Each hinged segment is attached to an arm that acts as a follower, riding on its cam and flipping on or off in a set pattern. Which digit is displayed depends on the position of the barrel, which is controlled with a single servo and a pair of gears. It trades mechanical complexity for electrical simplicity and overall elegance, and as you can see from the video below, it’s pretty snappy.

We think the best part of this build is figuring out the shape of the cams. We wonder how they compare to the cam profiles in [Greg Zumwalt]’s mechanical display; it uses two separate discs with grooves, but the principle is pretty much the same.

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A Guide To Designing A Custom RC Controller

November 12, 2021 by 5 Comments

These days, there are tons of RC controllers out there of all shapes and sizes. However, if you want to build something with just the right amount of buttons and sticks for your application, you might want to design something yourself. That’s precisely what [Sebastian] did. 

The project actually began some time ago, with [Sebastian] sharing his process for building a custom ergonomic enclosure through the use of clay and photogrammetry, which we’ve covered before.

Inside that shapely housing, the build relies on a STM32 microcontroller, hooked up to a series of potentiometers, buttons, and a thumbstick (more potentiometers). A NRF24L01 module is used to handle the radio transmission side of things.

Overall, [Sebastian] has produced a great guide to designing a custom RC controller from the ground up, rather than simply instructing one how to replicate his own build. Armed with these skills, any maker should be able to whip up their own entirely bespoke controllers. Video after the break.

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Is This 12-layer PCB Coil The Next Step In Ferrofluid Displays?

November 12, 2021 by 21 Comments

[Applied Procrastination] is in the business of vertical ferrofluid displays, but struggles somewhat with the electromagnets available off the shelf and the proliferation of wiring that results. [Carl Bugeja] is in the business of making PCB coils, both with rigid and flex PCB substrates, so when the opportunity for a collaboration arose, [AP] jumped at the opportunity.

As [Simen from AP] mentions in the video after the break, they had considered using a large PCB with embedded coils for Fetch their ferrofluid display unit, but the possible magnetic field was just too weak, and attempting to crank up the amps, just overheats them. Some improvements were made, first sticking the coil PCB to a small disk of ferrous metal, which doubled up as a handy heatsink. Next, he tried adding a permanent magnet, which added a bit of bias field. Alone this was not enough to hold the ferrofluid in place, but with the coil powered, it was starting to look encouraging.

Much more progress was made when [Carl] sent over a new design of his, a 12-layer PCB coil. This obviously had a much larger field, but still not enough without the extra boost from permanent magnet.

[Simen] currently doesn’t think the PCB approach is quite there yet, and is looking for help to source PCB-mounted electromagnets of the wired variety. We would imaging prototyping with such a large 12-layer PCB would be rather prohibitively expensive anyway.

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Build Your Own HV Capacitors

November 11, 2021 by 28 Comments

Finding high voltage capacitors can be tricky. Sure, you can buy these capacitors, but they are often expensive and hard to find exactly what you want. [RachelAnne] needed some low-value variable capacitors that would work at 100 kV. So she made some.

Instead of fabricating the plates directly, these capacitors use laminations from a scrap power transformer. These usually have two types of plates, one of which looks like a letter “E” and the other just like a straight bar. For dielectric, the capacitors use common transparency film.

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Kinetic Log Splitter Gets The Job Done Kinetically

November 10, 2021 by 37 Comments

Swinging an axe to split firewood is great exercise and a wonderful way to blow off steam. However, if you’re not a muscled-up Hollywood character that needs to do some emotional processing, it can get pretty dull. Building a powered log splitter could make the work less strenuous, as [Made in Poland] demonstrates. (Video, embedded below.)

The build relies on a big electric motor, which is connected to a set of gears via a big belt drive. Those gears subsequently drive a rack forward when engaged via a lever, which pushes a log towards a splitter blade. The blade itself is a beautifully simple thing, being made out of a flat piece of steel bar carved up with a saw to form a pointy wedge.

The machine is remarkably effective, and greatly reduces the effort required to split even large 30 and 45 cm logs, as demonstrated in the video. We’ve featured a rundown on a few different designs before, too. Video after the break.

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3D Printed Absolute Encoder Is Absolutely Wonderful

November 10, 2021 by 25 Comments

When you need to record the angle of something rotating, whether it’s a knob or a joint in a robotic arm, absolute rotary encoders are almost always the way to go. They’re cheap, they’re readily available, and it turns out you can make a pretty fantastic one out of a magnetic sensor, a zip tie, and a skateboard bearing.

When [Scott Bezek] got his hands on a AS5600 magnet sensor breakout board, that’s just what he did. The sensor itself is an IC situated in the middle of the board, which in Scott’s design sits on a 3D-printed carrier. A bearing mount sits atop it, which holds — you guessed it — a bearing. Specifically a standard 608 skateboard bearing, which is snapped into the mount and held securely by a zip tie cinched around the mount’s tabs. The final part is a 3D-printed knob with a tiny magnet embedded within, perpendicular to the axis of rotation. The knob slides into the bearing and the AS5600 reads the orientation of the magnet.

Of course, if you just wanted a rotary knob you could have just purchased an encoder and been done with it, but this method has its advantages. Maybe you can’t fit a commercially-available encoder in your design. Maybe you need the super-smooth rotation provided by the bearing. Or maybe you’re actually building that robotic arm — custom magnetic encoders like this one are extremely common in actuator design, and while the more industrial versions (usually) have fewer zip ties, [Scott]’s design would fit right in.

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Flip-Dot Oscilloscope Is Flippin’ Awesome

November 9, 2021 by 6 Comments

Oscilloscope displays have come a long way since the round phosphor-coated CRTs that adorned laboratories of old. Most modern scopes ship with huge, high-definition touch screens that, while beautiful, certainly lack a bit of the character that classic scopes brought to the bench. It’s a good thing that hackers like [bitluni] are around to help remedy this. His contribution takes the form of what may be both the world’s coolest and least useful oscilloscope: one with a flip-dot display.

Yup — a flip-dot display, in all it’s clickedy-clacky, 25×16 pixel glory. The scope can’t trigger, its maximum amplitude is only a couple of volts, and its refresh rate is, well, visible, but it looks incredible. The scope is controlled by an ESP32, which reads the analog signal being measured. It then displays the signal via an array of driver ICs, which allow it to update the dots one column at a time by powering the tiny electromagnets that flip over each colored panel.

Even better, [bitluni] live-streamed the entire build. That’s right, if you want to watch approximately 30 hours of video covering everything from first actuating a pixel on the display to designing and assembling a PCB to drive it, then you’re in luck. For the rest of us, he was kind enough to make a much shorter summary video you can watch below. Of course, this scope doesn’t run Doom like some others, but its probably only a matter of time.

Thank to [Zane Atkins] for the tip!

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