TechyMagThings

Well, it depends when you’re going to be househunting– if it’s anytime soon, Betteridge’s law applies, but if your time horizon is a ways further out, [Miana Smith] at MIT wants to make it happen. She’s got a paper out with an open-source inchworm robot designed to assemble structures from voxels– and what is a voxel but a giant, LEGO-esque brick?

There’s a demo video below, and it’s easier to understand the motion of this thing when you see it in action. The 5 degree-of-freedom MILAbot has actuators on both ends, and no traditional base– that’s the inchworm part. It grabs a brick while anchored to one part of the structure, then stays anchored to the new brick to keep building from that locale, so on and so on.

Note that we’re not talking about concrete bricks here, though conceivably you could use an inchworm-style actuator to assemble those. The ‘voxels’ in the study are engineered space-frame blocks which come together very easily, though admittedly would make for a very drafty home– you’d want to fill them with spray foam as a finishing step. So it’s more of a framing technique than a one-and-done thing. Still it is a technique that has something to recommend it compared to the 3D-printed concrete houses that get so much hype— and are already being torn down. 

For instance, the researchers find that weather the voxels are plywood, PLA, or metal, the resulting structure has less embodied energy than any concrete structure, with 3D printed concrete being worst option by that metric– though the balloon-frame stick-build we in North America consider “conventional” is still the lowest of all. On the other hand, that balloon-frame building takes a crew to put together, and labour is expensive compared to robots. At the moment, however, the study admits balloon-framing wins on price, but that doesn’t mean it always will, and it’s a fun hack regardless.

So while your next house might not be made of LEGO by a robot inchworm, we’re still grateful to [Miana] for the tip.

Most building hacks we see here are of the 3D printed variety, but don’t count out plain old dirt. For that matter, as long as someone is willing to live in it, anything can be a house– even an airliner.

The Cheap Yellow Display is a great little module to start a project with, but it wouldn’t necessarily be our first choice for an audio device. That’s because the PWM on the ESP32 isn’t exactly going to put out hi-fi, and the I2C pins needed for the I2S audio protocol aren’t broken out on the CYD board. That didn’t stop [ivans805] AKA [Ill-Town-5623]– he wanted a mod tracker, he had a CYD board, and necessity is the mother of invention.

It isn’t exactly a ground-breaking hack: he’s just tossed a bodge wire to the pin he needs on the ESP32, and run it to the I2S sound module. Still, in this era of endless modules it’s nice to see someone hacking what they have rather than running to AliExpress or somewhere else for a part that has everything the project needs built in.

What really caught our eye when we saw this project on the ESP32 subreddit was the aesthetics. It might be called “Win95-Tracker-CYD” but that interface just screams “Amiga” to us– look at that Boing Ball! Given where MOD files come from, that’s perfect. The UI was made with Lopaka.app, which we haven’t seen before but appears to be a sort of WYSIWYG editor for embedded device interfaces.

While you don’t need an ESP32 to play mod files– the diminutive CH32 can manage the task— there’s no arguing the CYD could make a nice little player. If you actually wanted to push its limits, you might try a 3D engine instead,

Usually, when you want to make glitchy images with lots of colors and things, you have to poke around inside a camera and successfully circuit-bend the thing without bricking it. But [sharkbiscuit101] proves that this isn’t necessary, provided you have a Raspberry Pi 4 and a few other components.

Now we don’t have a lot of detail here, but [sharkbiscuit101] is being heavily encouraged to share the relevant files and a component list. What we do know is that the there’s a screen for previewing images, a portable battery, a shutter button, a rotary encoder to dial in the weirdness, and a game pad for controls. Using the script and a slider, you can tweak different aspects of the image to basically break it down in real time. If you find a nifty combination, you can use the rotary encoder to save and then recall presets.

If you’re wondering about the grip, that’s a Sharge battery from the Bezos Barn. Per [sharkbiscuit101], it is a good size, and since Pi 4 doesn’t have a power button, it can be turned on and off at the battery.

Of course, you can always mess with JPGs on a raw, textual level instead, or produce standard photographs with a pinhole camera.

Recently we featured an unusual Commodore 8-bit computer on the bench of [Tynemouth Software] — a Commodore 64 in a PET case. One of the unique parts it had was a board which took the composite output from the mainboard and split out the sync pulses for the monitor, and now they’re back to give it a full reverse engineer.

Perhaps the first surprise is why this board is necessary at all, after all one might expect an 8-bit machine to have those signals already at hand. It seems that the VIC chip inside the 64 did the combination to composite internally, so no such luck for the Commodore engineers. The board they designed then is a complete and very well-engineered sync splitter.

The technology of a video signal has its origins in the 1930s, so it’s not hard to extract both vertical and horizontal sync pulses with little more than a few passive components and a couple of transistors. The trouble with such a simple approach is that the output will work, but it will be messy and crucially, not have quite the required timing. The Commodore board uses the same approach as a simple discrete circuit of having a pair of filters with a time constant selected to catch the relevant sync, but extends it with extra logic. There are one-shots designed to provide clean pulses of exactly the right length, and gates that provide blanking to remove the chance of pulses ending up where they shouldn’t. The video path is the only part which might differ from a conventional sync splitter, because as the output from the 64 is all-digital, it takes a TTL-level through a gate rather than a more conventional analogue path.

You can see the rest of the machine in our original write-up, and we’re reminded that the boards haven’t been cleaned at their owner’s request, to preserve their patina.

Screws are useful fasteners for 3D prints, but the effectiveness of a screw (not to mention the ease or hassle of insertion) depends on the hole itself. This comprehensive guide on how to design screw holes in 3D printed parts takes guesswork out by providing reference tables as well as useful general tips.

The guide provides handy tables saying exactly how big to design a hole depending on screw type, material (PLA, PETG, or high-flow PETG) and whether the hole is printed in a vertical or horizontal orientation. This takes the guesswork out of screw hole design.

The reason for different numbers is because multiple (but predictable) variables affect a 3D-printed hole’s final dimensions. Shrinkage, filament properties, and printing orientation can all measurably affect small features like screw holes; accounting for these is the difference between a good fit, and cracking or stripping.

In addition to the tables, there are loads of other useful tips. Designing lead-ins makes screws easier to insert and engage, and while increasing walls is an easy way to add strength it’s also possible to use 3D-printed microfeatures which are more resistant to distortion and don’t depend on slicer settings. There’s even suggested torque amounts for different screw and material types.

Sure, the most reliable way to get a hole of a known size is to drill it out yourself. But that’s an extra step, and drill bits aren’t always at hand in the desired sizes. The guide shows that it is entirely possible to print an ideal screw hole by taking a few variables into account.

If your design calls for screws, be sure to check it out and see if there’s anything you can use in your own designs.

The age of steam is long gone, but there are few railfans who don’t have a soft spot for the old rolling kettles. So you’d best believe when [AeroKoi] talks about 3D printed train whistles, that’s steam whistles. Generally speaking, Diesels have horns.

You would not expect printed plastic to hold up to live steam– but that’s why [AeroKoi] uses compressed air. Besides, it’s a lot easier to both justify and maintain an air compressor than a boiler in the shop. At least some hobbyists say it doesn’t make a huge difference with brass whistles, so it should be good enough for plastic. What’s interesting is that even with 120 PSI blasting through them, these multi-part prints held together and sounded amazing.

[AeroKoi] does demonstrate there was a learning curve to climb before he had a good whistle design, and shows you what features worked best. He shared two successes on Thingiverse: A 6-Chime whistle from the Sante Fe Railroad, and a Northern Pacific 5-chime whistle, both 4″ in diameter and printed in vertically sectioned parts. The Northern Pacific is not to be confused with the totally different Union Pacific Railroad, whose famous “Big Boy” also had a whistle feature in the video — though evidently he’s not as happy with it, since he did not share the design.

Those are all North American designs, but there’s no reason this technique wouldn’t work to replicate a more European sound; one of his early experiments was kind of going in that direction already. Of course if you want a perfect replica, the old ways are the best ways: cast brass and live steam. We’ve had a few articles about train whistles in the past, one of which was a doorbell. 

For this challenge, we asked you to show off your hacks that power themselves sustainably from the environment around them. After all, nobody likes wires, and changing batteries is just a hassle. What’s better than an autonomous gizmo? Nothing.

Because this is Hackaday, we expected to see some finished-looking projects, some absolutely zany concepts, and basically everything in-between, and you did not disappoint! So without further ado, let’s have a look at the 2026 Green Powered Challenge winners, each of whom will be going on a $150 shopping spree at DigiKey, our contest’s sponsor.

LightInk Solar Watch

LightInk is a beautiful wristwatch, and e-ink is a natural companion to the small power budget that you get with a wrist-mounted solar panel. But don’t be fooled by its good looks! The real beauty of this hack is the way that [Daniel Ansorregui] crammed the screen-updating routine into the wakeup stub in the RTC peripheral. This means that the ESP32 doesn’t have to access the SPI flash every time it wakes up, saving precious milliseconds of wake time, and cutting average power in half. This is a trick you’ll want to know even if you don’t need a sexy e-ink wristwatch. (Which you do.)

Supercapacitor Solar IoT

[Nelectra]’s “Heliotrax” solar supercapacitor charger stores up the sun’s power in low-maintenance supercapacitors until it’s time to wake up your device. But supercaps have an output voltage that depends dramatically on their state of charge, so [Nelectra] added a high-efficiency and low-leakage boost converter to get a nice constant voltage out. Depending on your current needs, it can charge up in the sun and run for a few dark days without any problems. It’s a one-stop shop for solar-powered IoT devices, and it should make a whole range of projects easier to realize.

powerTimer

[Juan Flores]’s powerTimer is another module that enables your small off-grid hacks. In this case, it’s a simple latching electronic switch, designed for ultra-low quiescent power. Maybe your project has a microcontroller with a good sleep mode, but the peripherals are leaky hogs? Put the powerTimer in the middle and get your whole system’s power budget down without much extra thought. And if you don’t want to wake the microcontroller, it’s got a low-power RTC on board that can handle periodic wakeups. It’s a sweet, simple design that solves a real problem, and our judges loved that.

Honorable Mentions

• Solar: We knew there would be some great solar-powered projects here, and [Jake Wachlin]’s Ultra Low Power Feather Development Board is a great example. He pairs a low-power accelerometer and barometer with a power-sipping microcontroller to almost achieve ambient-room-lighting capability. [Jake] says you have to put it directly under a light, or in indirect sunlight. But if you have full sun at your disposal, [Arnov Sharma]’s SolMate is a lovely DIY solar power bank that we’d love to bring to the park with us.
• Anything But PV: OK, enough solar. [Ethan]’s Gravity-Powered Digital Clock is exactly the sort of out-of-the-box idea we were hoping to see. He pairs a Casio F91W with an insane gear train, a homebrew electrical generator, and a dumbbell to gather up all of the gravity that makes it work. Or should do so. The gear train ended up having so many stages that it wouldn’t turn under its own magnified friction, and the project doesn’t quite spin. But we love the idea of a wind-up electrical clock, and we hope [Ethan] doesn’t give up!
• Least Power: [caspar]’s Harvesting NFC Energy to Transmit Commands includes a stock Pi Pico dev board and some AA batteries, so you might be thinking “where is the low power element?” It’s the NFC wakeup circuit that reads in some data and writes it directly to the Pico’s EEPROM, before it wakes the chip up, which then reads the command out of EEPROM and does whatever it does under normal battery power, and then shuts itself down again. We love the idea of surreptitious NFC-powered data insertion while the microcontroller is still sleeping.
• Most Power: We initially expected this honorable mention to go to an over-sized solar install, but in the end [alnwlsn]’s Practical Power Cycling won over our judges with an unbeatable display of human determination: over five years, [alnwlsn] has generated 38 kWh on his generator bike, has powered a 3D printer through a Benchy, and even toasted a piece of toast. Maybe the real power here is the human spirit? Check out [alnwlsn]’s great build logs and diary.

Thanks to All!

Much thanks to everyone who entered into this challenge. We had more great entries than we have space to feature, so be sure to check them all out on Hackaday.io. And of course, thanks again to DigiKey for sponsoring the contest, and for providing our three finalists with the parts they need!