Mini Battery-Powered Vapor-Compression Air Conditioner

December 26, 2025 by Maya Posch 17 Comments

The brushless DC-powered compressor. (Credit: Hyperspace Pirate, YouTube)

When you think of air conditioners, you tend to think of rather bulky units, with the window-mounted appliances probably among the most compact. There’s however no real minimum size limit to these AC units, as long as you can get an appropriate compressor. If you also manage to pick up a small, DC-powered compressor like [Hyperspace Pirate] did, then you might be tempted to make a hand-portable, battery-powered AC unit.

At their core vapor-compression AC units are very simple, featuring the aforementioned compressor, a condensing coil, expansion valve and the evaporator coil. Or in other words, some radiators looted out of other devices, various plumbing supplies and the refrigerant gas to charge the AC unit with.

Since the compressor uses a BLDC motor, it has three terminals that a typical ESC connects to, along with two 2200 mAh Li-on battery packs that can keep the portable AC unit running for a while.

As for the refrigerant gas, although the compressor lists R134a, this is both quite expensive and illegal in parts of the world like the EU. Alternatives are butane (R600) as well as isobutane (R600a), but due to unfortunate circumstances the use of propane (R290) was forced. Fortunately this worked fine, and after some testing and running of numbers it was found that it had about 42 Watt cooling power, with a coefficient of performance (COP) of around 1.

Considering that most AC units have a COP of 3.5 – 5, this shows that there’s still some room for increased efficiency, but at the very least this portable, battery-powered AC unit provides cold air on one side, and hot air on the other while completely blowing Peltier thermocouples out of the water in terms of efficiency.

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Pocket-sized Test Pattern Generator Helps Check Those CRTs

December 26, 2025 by Donald Papp 21 Comments

[Nicholas Murray]’s Composite Test Pattern Generator is a beautifully-made, palm-sized tool that uses an ESP32-based development board to output different test patterns in PAL/NTSC. If one is checking out old televisions or CRTs, firing up a test pattern can be a pretty handy way to see if the hardware is healthy or not.

The little white add-on you see attached to the yellow portion is a simple circuit (two resistors and an RCA jack) that allows the microcontroller to output a composite video signal. All one needs to do is power on the device, then press the large button to cycle through test patterns. A small switch on the side toggles between NTSC and PAL video formats. It’s adorable, and makes good use of the enclosures that came with the dev board and proto board.

In a pinch a hacker could use an original Raspberry Pi, because the original Pi notably included a composite video output. That feature made it trivial to output NTSC or PAL video to a compatible display. But [Nicholas]’s device has a number of significant advantages: it’s small, it’s fast, it has its own battery and integrated charger, and the little color screen mirroring the chosen test pattern is a great confirmation feature.

This is a slick little device, and it’s not [Nicholas]’s first test pattern generator. He also created a RP2040-based unit with a VGA connector, the code of which inspired a hacker’s home-grown test pattern generator that was used to service a vintage arcade machine.

Retrotechtacular: IBM’s The World Of OCR

December 26, 2025 by Maya Posch 3 Comments

Optical Character Recognition (OCR) forms the bridge between the analog world of paper and the world of machines. The modern-day expectation is that when we point a smartphone camera at some characters it will flawlessly recognize and read them, but OCR technology predates such consumer technology by a considerable amount, with IBM producing OCR systems as early as the 1950s. In a 1960s promotional video on the always delightful Periscope Film channel on YouTube we can get an idea of how this worked back then, in particular the challenge of variable quality input.

What drove OCR was the need to process more paper-based data faster, as the amount of such data increased and computers got more capable. This led to the design of paper forms that made the recognition much easier, as can still be seen today on for example tax forms and on archaic paper payment methods like checks in countries that still use it. This means a paper form optimized for reflectivity, with clearly designated sections and lines, thus limiting the variability of the input forms to be OCR-ed. After that it’s just a matter of writing with clear block letters into the marked boxes, or using a typewriter with a nice fresh ink ribbon.

These days optical scanners are a lot more capable, of course, making many of such considerations no longer as relevant, even if human handwriting remains a challenge for OCR and human brains alike.

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Hackaday Podcast: 2025 Holiday Placeholder Edition

December 26, 2025 by Elliot Williams 3 Comments

This week the Hackaday Podcast is on vacation, but we’d like to wish you all happy holidays and a great 2026. Thanks for tuning in! We’ll be back next week.

This wasn’t a real show, but that doesn’t prevent you from downloading it as an MP3 anyway.

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3D Printed PC Case Focuses On Ease Of Access

December 26, 2025 by Lewin Day 19 Comments

There are all kinds of fun, glowing PC cases on the market these days. However, if you want something that focuses on serviceability over flash while still looking stylish, you might like the Makeyo MK01. It’s a PC case that you can print yourself, and [Marst_art] has published a video on what it’s like to whip one up at home.

The MK01 is assembled from lots of smaller parts, so the components can be made on any 3D printer that has a print area of 210 x 210 mm or more. All the outer panels are affixed to the main chassis with magnets, which makes servicing easy. You can just pop off panels when you need to get inside without undoing any fasteners or clips.

Plus, the cool thing about the MK01 is that since you’re printing it yourself, you can easily make whatever mods you like prior to printing it out. [Marst_art] notes that he threw in a USB-C port to the front panel for easy access, and a few internal mounts for 2.5″ SSDs. He also made some mods to the power switch assembly. It also bears noting—you get to choose your own color scheme when you make one of these. This level of customization is something you simply don’t get when you buy off the shelf!

[Marst_art]’s video is a useful guide if you’re planning to undertake such a build yourself. It outlines what it’s like to actually print one of these things on a consumer printer, and how the settings will influence the final look and feel. It’s worth noting that you’ll probably want to print this in ABS or another filament that can handle high heat, unless you’re building a very cool running machine.

It’s not just a great looking case, it’s a highly functional one, too. Files are available on Printables if you’d like to make your own. We’ve featured other printed cases before, too.

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NVIDIA Drops Pascal Support On Linux, Causing Chaos On Arch Linux

December 26, 2025 by Maya Posch 64 Comments

It’s no surprise that NVIDIA is gradually dropping support for older videocards, with the Pascal (GTX 10xx) GPUs most recently getting axed. What’s more surprising is the terrible way that this is being handled by certain Linux distributions, with Arch Linux currently a prime example.

On these systems, updating the OS with a Pascal, Maxwell or similarly unsupported GPU will result in the new driver failing to load and thus the user getting kicked back to the CLI to try and sort things back out there. This issue is summarized by [Brodie Robertson] in a recent video.

Here the ‘solution’ is to switch to a legacy option that comes from the Arch User Repository (AUR), which feels somewhat sketchy. Worse is that using this legacy option breaks Steam as it relies on official NVIDIA dependencies, which requires an additional series of hacks to hopefully restore this functionality. Fortunately the Arch Wiki provides a starting point on what to do.

It’s also worth noting that this legacy driver on the AUR is being maintained by [ventureo] of the CachyOS project, whose efforts are the sole reason why these older NVIDIA cards are still supported at all on Linux with the official drivers. While there’s also the Nouveau driver, this is effectively a reverse-engineering project with all of the problems that come with such an effort, even if it may be ‘good enough’ for older GPUs.

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PC Watercooling Uses Everything But CNC Machining

December 26, 2025 by Tyler August No comments

Names and labels are difficult. Take this “3D Printed” water-cooling loop by [Visual Thinker] on YouTube. It undeniably uses 3D printing — but it also uses silicone casting and laser-cut acrylic, too. All of these are essential parts, yet only 3D printing gets top billing in his thumbnail. At least the version we saw, anyway; the A/B testing game YouTubers play means that may change.

Perhaps that’s simply due to the contrast with [Visual Thinker]’s last build, where the “distro plate” that acts to plumb most of the coolant was made of layers of CNC-routed acrylic, held water-tight with O-rings. Not wanting to wait for his next build to be fabricated, and not wanting to take up CNC machining himself, [Visual Thinker] fell back on tools many of us have and know: the 3D printer and laser cutter.

In this project, the end plates of the cooling loop are still clear acrylic, but he’s using a laser cutter to shape them. That means he cannot route out gaps for o-rings like in the last project, so that part gets 3D printed. Sort of. Not trusting the seal a 3D printed gasket would be able to give him, [Visual Thinker] opts to use his 3D printer to create a mold to cast a seal in silicone. Or perhaps “injection-mold” would be a better word than cast; he’s using a large syringe to force the degassed silicone into the mold. The end part is three pieces: a 3D printed spacer holding two acrylic plates, with the cast-silicone gasket keeping the whole thing water-tight to at least 50 psi, 10x the operating pressure of his PC.

After that success, he tries replacing the printed spacer with acrylic for a more transparent look. In that version only temporary shims that are used to form the mold are 3D printed at all, and the rest is acrylic. Even if you’re not building a water-cooled art PC, it’s still a great technique to keep in your back pocket for fluid channeling.

In some ways, this technique is the exact opposite of the copper-pipe steampunk builds we’ve featured previously. Those were all about pretty plumbing, while with a distro plate you hardly need pipes at all. Like any water-cooled project, it’ll need a radiator, which could be a hack in and of itself.

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