Misc Hacks

4054 Articles

Your Childhood Inventions Brought To Life

May 12, 2023 by 8 Comments

If you are the kind of person who reads Hackaday, you probably spent time in school doodling little design day dreams. [Allen Pan] gets it, and he’s taken it upon himself to make some of those daydreams into reality. You can see how it worked out — or didn’t — in the video below.

The video starts out with suction cup boots for walking on the ceiling, a laser sword made with a mirror, a plunger gun, and lawnmower boots. Some of these were more successful than others.

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Low-Frequency DC Block Lets You Measure Ripple Better

May 10, 2023 by 12 Comments

We all know how to block the DC offset of an AC signal — that just requires putting a capacitor in series, right? But what if the AC signal doesn’t alternate very often? In that case, things get a little more complicated.

Or at least that’s what [Limpkin] discovered, which led him to design this low-frequency DC block. Having found that commercially available DC blocks typically have a cutoff frequency of 100 kHz, which is far too high to measure power rail ripple in his low-noise amplifier, he hit the books in search of an appropriate design. What he came up with is a  non-polarized capacitor in series followed by a pair of PIN diodes shunted to ground. The diodes are in opposite polarities and serve to limit how much voltage passes out of the filter. The filter was designed for a cutoff frequency of 6.37 Hz, and [Limpkin]’s testing showed a 3-dB cutoff of 6.31 Hz — not bad. After some torture testing to make sure it wouldn’t blow up, he used it to measure the ripple on a bench power supply.

It’s a neat little circuit that ended up being a good learning experience, both for [Limpkin] and for us.

Scorched Moon: Secret Project A119

May 9, 2023 by 35 Comments

In today’s world, it is hard to realize how frightened Americans were at the news of Sputnik orbiting the Earth. Part of it was a fear of what a rival nation could do if they could fly over your country with impunity. Part of it was simply fear generated by propaganda. While America won the race to the moon, that wasn’t clear in the 1950s. The Soviet Union was ahead in the ability to deliver bombs using planes and missiles. They launched Sputnik on a modified ICBM, while American attempts to do the same failed spectacularly. The Air Force wanted ideas about how to respond to Sputnik, and one of the most disturbing ones was project A119, a project we were reminded of recently by a BBC post.

In all fairness, the Soviets had an almost identical plan, code-named E4. Fortunately, both sides eventually realized these plans weren’t a good idea. Oh, did we forget to mention that A119 and E4 were plans to detonate a nuclear device on the moon?

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Tiny Orrery Keeps The Planets In Their Places

May 9, 2023 by 9 Comments

[Frans] claims to have made the world’s smallest wooden orrery. We won’t take a position on that — such things are best left up to the good folks at Guinness. But given that the whole thing is seriously in danger of being dwarfed by a USB-C connector, we’d say he’s got a pretty good shot at that record.

The key to keeping this planetarium so petite while making it largely out of wood is to eschew the complex gear trains that usually bring the Music of the Spheres to life in such devices. The layered base of the orrery, with pieces cut from a sheet of basswood using a laser cutter, contains a single tiny stepper motor and just two gears. A zodiac disc sits atop the base and is the only driven element in the orrery; every other celestial body moves thanks to a pin set into the zodiac disc. An ESP32 C3 contacts a NASA feed once a day to get the relative positions of the planets and uses the zodiac disk to arrange everything nicely for the day. The video below shows the “Planet Spinner” in action.

We love the look of this project; the burnt edges and lightly smoked surface of the laser-cut wooden parts look fantastic, and the contrast with the brass wires is striking. We’ve seen an orrery or two around here, executed in everything from solid brass to Lego, but this one really tickled our fancy. Continue reading “Tiny Orrery Keeps The Planets In Their Places” →

Easter’s Over, But You Can Still Dye Keycaps

May 4, 2023 by 11 Comments

While it’s true that keycap colorways abound these days, one can’t always find exactly what one is looking for. And once found, the set is often either prohibitively expensive, or it doesn’t come in the desired layout, or both. So, why not color your own keycaps?

That’s exactly what [amphiboi] did, while standing on the shoulders of [CrowningKnight]’s imgur post on the subject. Essentially, you use Rit dye and PBT keycaps for best results. Rit has a comprehensive guide to mixing their dyes to achieve pretty much whatever colors you want. Once that’s all squared away, it’s time to gather your cooking supplies.

Starting with a pot you don’t care about and four cups of boiling water. Add about a teaspoon of dish soap, which helps the dye settle evenly across the keycaps. Then you just add the dye(s) and stir with an expendable spoon, then add your keycaps. 5-10 minutes later, depending on your desired outcome, the ‘caps are ready to be rinsed, dried, and pushed on to your switches.

Satisfied with the color of your keycaps, but wish they had cool legends? Check out this waterslide decal tutorial.

Carbon Fiber And Kevlar Make This Linear Actuator Fast And Strong

May 3, 2023 by 9 Comments

When it comes to the “build versus buy” question, “buy” almost always wins. The amount of time you have to put into building something is rarely justified, especially with a world of options available at the click of a mouse.

That’s not always the case, of course. These custom-made linear actuators are a perfect example of when building your own wins. For a planned ball-juggling robot, [Harrison Low] found himself in need of linear actuators with long throw distance, high speed, and stiff construction. Nothing commercially available checked all the boxes, so he set out to design his own.

A few design iterations later, [Harrison] arrived at the actuators you see in the video below. Built mainly from carbon fiber tubing and 3D-printed parts, the actuators have about 30 centimeters of throw, and thanks to their cable-drive design, they’re pretty fast — much faster than his earlier lead screw designs. The stiffness of the actuator comes by way of six bearings to guide the arm, arranged in two tiers of three, each offset by 60 degrees. Along with some clever eccentric spacers to fine-tune positioning, this design provides six points of contact that really lock the tube into place.

The cable drive system [Harrison] used is pretty neat too. A Kevlar kite string is attached to each end of the central tube and then through PTFE tubes to a pulley on an ODrive BLDC, which extends and retracts the actuator. It’s a clever design in that it keeps the weight of the motor away from the actuator, but it does have its problems, as [Harrison] admits. Still, the actuator works great, and it looks pretty cool while doing it. CAD and code are available if you want to roll your own.

These actuators are cool enough, but the real treat here will be the ball juggler [Harrison] is building. We’ve seen a few of those before, but this one looks like it’s going to be mighty impressive.

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The Nuts And Bolts Of Nuts And Bolts

April 28, 2023 by 23 Comments

If you’re a mechanical engineer, the material covered in this video on the basics of bolted joints probably won’t cover any new ground. On the other hand, if you aren’t a mechanical engineer but still need to bring a little of that discipline to your projects, there’s a lot to learn here.

If there’s one takeaway lesson from [The Efficient Engineer]’s excellent examination of the strength of bolted joints, it’s the importance of preload. Preload is the tensile force created by tightening a bolt or a screw, which provides the clamping force that keeps the joined members together. That seems pretty self-obvious, but there’s more to the story, especially with joints that are subject to cycles or loading and unloading. Such joints tend to suffer from fatigue failure, but proper preloading on the bolts in such a joint mitigates fatigue failure because the bolts are only taking up a small fraction of the total cyclical force on the joint. In other words, make sure you pay attention to factory torque specs.

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