Misc Hacks

4058 Articles

Building A Hydrogen-Powered Foam Dart Cannon

November 1, 2024 by 18 Comments

Nerf blasters are fun and all, but they’re limited by the fact they have to be safe for children to play with. [Flasutie] faced no such restrictions when building his giant 40 mm foam dart launcher, and it’s all the better for it.

This thing is sizeable—maybe two to four times bigger than your typical Nerf blaster. But that’s no surprise, given the size of the foam ammunition it fires. [Flasutie] shows us the construction process on how the 3D-printed blaster is assembled, covering everything from the barrel and body assembly to the chunky magazine. Loading each round into the chamber is a manual process, vaguely akin to a bolt-action mechanism, but simplified.

It’s the method of firing that really caught our eye, though. Each round has a cartridge and a foam projectile. Inside the cartridge is a quantity of flammable HHO gas generated, presumably, from water via electrolysis. The blaster itself provides power to a spark gap in the cartridge that ignites the gas, propelling the projectile through the barrel and out of the blaster.

We’ve seen plenty of Nerf blasters and similar builds around these parts, including some with a truly impressive rate of fire. Video after the break.

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Word Of The Day Calendar Is Great Use Of E-Paper

October 28, 2024 by 10 Comments

If you’re trying to learn a new language, there are always a lot of words to learn. A word-of-the-day calendar can help, and they’re often readily available off the shelf. Or, you can grab some hardware and build your own, as [daedal-tech] did!

The project was built as a gift to help [daedal-tech]’s partner with their efforts to pick up French. Thus, a Raspberry Pi Zero 2W was employed and paired with a small Waveshare e-Paper display. These were stuffed inside a fancy light switch plate from Hobby Lobby and a small stand, the pair of which act as a pretty nice little frame for the build. The Pi runs a small Python script which employs the BeautifulSoup4 library and the Python Image library. Basically, the script grabs French words and spits them out on the display with a small description such that one might understand their meaning.

It’s a simple build, but one that has some real utility and is fun to boot. We might see more word clocks than calendars around these parts, but we love both all the same!

DIY Air Bearings, No Machining Required

October 20, 2024 by 26 Comments

Seeing a heavy load slide around on nearly frictionless air bearings is pretty cool; it’s a little like how the puck levitates on an air hockey table. Commercial air bearings are available, of course, but when you can build these open-source air bearings, why bother buying?

One of the nice things about [Diffraction Limited]’s design is that these bearings can be built using only simple tools. No machining is needed past what can be easily accomplished with a hand drill, thanks to some clever 3D-printed jigs that allow you to drill holes with precision into stainless steel discs you can buy on the cheap. An extremely flat surface is added to the underside of these discs thanks to another jig, some JB Weld epoxy, and a sheet of float glass to serve as an ultra-flat reference. Yet more jigs make it easy to scribe air channels into the flat surface and connect them to the air holes through a bit of plaster of Paris, which acts as a flow restriction. The video below shows the whole process and a demo of the bearings in action.

[Diffraction Limited] mentions a few applications for these air bearings, but the one that interests us most is their potential use in linear bearings; a big CNC cutter using these air bearings would be pretty cool. We seen similar budget-friendly DIY air bearings before, including a set made from used graphite EDM electrodes.

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Ideal Diodes And How To Build Them

October 19, 2024 by 17 Comments

[Julian] knows that real diodes you can buy don’t work exactly like we say they do. That’s actually pretty common. We routinely ignore things like wire resistance and source resistance in batteries. Diodes have problems that are harder to ignore, such as the forward voltage drop. So, while a real diode will only pass current in one direction, it will also drop some of the voltage. [Julian] shows you how you can get simulated ideal diodes and why you might want them in a recent video you can see below.

The video starts with a simple demonstration and enumerates some of the practical limitations. Then, he pulls out some ideal diode modules. These typically don’t solve every problem, so they aren’t really ideal in the theoretical sense. But they typically appear to have no forward voltage drop.

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Power Supply PCB Redesign

October 19, 2024 by 6 Comments

We’ve often heard you should do everything twice. The first time is to learn what you need to do, and the second time is to do it right. We bet [Ian Carey] would agree after taking his old linear power supply PCB and changing it to a switching regulator design. You can see more about the project in the video below.

The first power-up revealed a problem with the 3.3V output. We’ve often thought it is harder to troubleshoot a new design than it is to repair something that is known to have worked at one time.

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Little RC Car Project Takes Inspiration From Mario Kart

October 18, 2024 by 9 Comments

RC cars used to be pretty simple. They’d go forwards, backwards, and steer if you got a full-function toy. However, with modern technology, it’s pretty trivial to make them more advanced. [Stuck at Prototype] demonstrates that nicely with his little Micro Racer Cars.

Each little RC car has its own ESP32 running the show, hooked up with a motor controller running a small DC gear motor at each wheel. Power is from a lithium-polymer battery on board the car, which is charged via USB C. 3D-printed components form the chassis and body of the vehicle. [Stuck at Prototype] set the cars up so they could be controlled via a smartphone app, or via a custom RC controller of his own design. He liked the latter solution after he realized how hard apps were to maintain. He also gave the cars a little color sensor so they could detect color patches on the ground, so they could change their behavior in turn. This was to create gameplay like Mario Kart, where hitting a color patch might make the car go fast, go slow, or spin out.

The video goes into great detail about everything these tiny tabletop racers can do. The racer cars were initially intended to be a Kickstarter funded project, but it never quite reached its goal. Instead, [Stuck at Prototype] decided to release the designs online instead, putting the relevant files on Github.

We’ve seen some other neat RC projects before, too. Video after the break.

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A stylized image of Haskell code from the article

Alphabet Soup: Haskell’s Single-Letter Naming Quirks

October 14, 2024 by 14 Comments

When you used punch cards or tape to write a computer program, brief variable names were the norm. Your compiler or assembler probably only allowed six letters, anyway. But times change, and people who, by habit, give array indices variable names like I, J, or K get a lot of grief. But [Jack Kelly] points out that for highly polymorphic languages like Haskell, you often don’t know what that variable represents anyway. So how are you supposed to name it? He provides a guide to one-letter variable names commonly used by Haskell developers and, sometimes, others.

Haskell’s conventions are particularly interesting, especially with i, j, and k, which are borrowed from mathematical tradition to signify indices or integers and passed on via Fortran. The article also highlights how m often refers to Monads and Monoidal values, while t can represent both traversables and text values. Perhaps more obscurely, p can denote profunctors and predicates, giving a glimpse into Haskell’s complex yet efficient type system. These naming conventions are not formal standards but have evolved into a grass-roots lexicon.

Of course, you can go too far. We see a lot of interesting and strange things written in Haskell, including this OpenSCAD competitor.