Neighborhood Bulletin Boards, Circa 1982

July 27, 2026 by 2 Comments

When the Internet first started gaining mainstream popularity in the late 90s, many optimists claimed that it would bring people together by reducing barriers to communication. That ideal hasn’t exactly come to pass yet, as anyone who has been on the Nextdoor neighborhood social network can likely attest to. Before social media, neighbors weren’t completely in the dark about their local communities, though. Besides word-of-mouth communication, there were also local access channels on cable TV, which had none of the downsides of modern social media. And [Hans] is bringing this style channel back.

[Hans]’s project is called CABLE 82, a bulletin board channel that matches the style of these channels from the 1980s. There’s better technology available for these types of systems now, though, so instead of relying on something like a character generator he’s using a Raspberry Pi running custom software to produce the video feed. The Pi hosts a web server so the 4:3 video feed can be reserved for the bulletin board display, but users who have older Pis with the yellow composite video output can skip using something like an HDMI to RF converter on their period-appropriate CRT displays. The software also adds sound functionality, as these channels always had some sort of elevator music playing while they were scrolling through local community news.

For those looking to recreate some of the nostalgia of 1980s community and technology, [Hans] has made this project open source, with all of the files on a GitHub page. Part of the reason [Hans] got interested in building something like this is that he had been trying to source a CRT television for retro gaming, and wanted to reproduce more of that era than just a few video games. A channel like this would be a great addition to a complete cable TV recreation build like this one, which even includes a preview channel of everything playing.

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A Music Box With A Very Modern Heart

July 27, 2026 by No comments

A ballerina music box is a charming ornament, but it remains one that is limited by its mechanism to a very short performance. [ShielaDixon] has one, and decided to make so much more with it.

The music box mechanism is a simple clockwork motor with a comb that’s picked by a drum to make the notes. Her box retains the mechanism to give the ballerina her performance, but replaces the comb with a microcontroller and audio channel. This is no mere MP3 player though, instead it’s a music box in itself. Each note of the comb was sampled, and the board plays them just as the music box would, under instruction from a text file containing the music. The repertoire can now go on for far longer, and contain many more compositions.

We like this hack, for its effectiveness, and for its recreation of the music box rather than simply playing a recording. Meanwhile if you recognise [ShieldDixon] from these pages, we’ve in the past featured another musical project of hers, a MIDI recorder.

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Scanwheel

Scanwheel: A Pocket-Sized POV TV

July 26, 2026 by 5 Comments

When you hear the word TV, you probably think of a big LED screen, maybe even the old CRT TVs, but in either case it’s something large and fairly complicated. However, thanks to the persistence of vision, it doesn’t have to be. In this handheld-sized project from [Ancient], the Scanwheel is born, a miniature mechanical TV that uses a spinning disk and some LEDs to produce an image.

The electronics of the Scanwheel are pretty straightforward. The smarts come from a Raspberry Pi Pico, an A4988 motor driver, a couple of LEDs, and a small 21-02485 stepper motor. The Raspberry Pi Pico is used to command the motor speed as well as coordinate the LEDs to turn on at the right time. The case is 3D printed; the base includes space for the various support electronics as well as some small light baffles to ensure the LEDs don’t bleed over outside their intended area. The top of the case is a disk that includes 20 small holes spaced evenly around the perimeter at varying heights, allowing light to only leave the disk when one of these holes is in front of the LEDs.

When you put all these pieces together, spin the motor up to roughly 900 RPM, and turn the LEDs on in a precise order, you end up with a really cool result: a miniature TV. And due to the five different LEDs in this build, you actually have a color 20×20 pixel display in the center and, on either side of that, two more 20×20 black-and-white displays capable of showing different images. Thanks [Ancient] for sharing this awesome build that takes advantage of the persistence of vision effect to create a unique display. Be sure to check out the video below as well as the instructions on how to build your own. And if you enjoy this sort of thing, check out some of our other persistence-of-vision projects as well.

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A plastic device sits on a desk, with a computer display and an oscilloscope behind it. A fiber-optic cable runs from the device to a laser diode source.

2026 Frikkin Lasers Challenge: Measuring Nanometer-Scale Displacements With An Optical Cavity

July 26, 2026 by 1 Comment

Optical cavities – two mirrors arranged to reflect light multiple times between them – form the basis of lasers and certain optical filters. Since any angle between the two mirrors results in light being scattered away, parallel alignment is essential, yet difficult to maintain. Nevertheless, [Timothy Giles] managed to 3D-print and align such an optical cavity, and used it to detect minute shifts in space and wavelength.

The cavity has two semi-transparent mirrors facing towards each other. One mirror is held in a 3D-printed mount, and the other is attached to the diaphragm of a speaker with a hole drilled through the center. The hole avoids the speaker coil, and allows light exiting the optical cavity through the semi-transparent mirror to appear on a paper target, which is monitored by a webcam. On the other side of the optical cavity, a laser diode coupled to a single-mode fiber shines in through the other mirror. Alignment is challenging, but the webcam makes it easier; as the mirrors tilt relative to each other, the pattern seen on the paper target changes, providing feedback for more precise adjustment.

Light reflected within the cavity can interfere constructively or destructively with incoming light, changing the brightness of the emitted beam. [Tim] used the speaker as a linear actuator to vary the cavity’s length, which, by counting the peaks in brightness, allowed him to measure the diaphragm’s displacement. This also demonstrated a laser diode’s wavelength instability: when the cavity was set to a constant length and the laser started up, the output brightness would cycle a few times. As the diode was warming up, its output wavelength was shifting, creating the same changing interference pattern.

To get a Gaussian beam distribution, [Tim] used a fiber-coupled laser; if you’d like to build one, we’ve seen a coupling mechanism built before. Most lasers are built around an internal optical cavity, but some instead use an external cavity.

2026 Hackaday Freaking Lasers Contest
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Hackaday Links: July 26, 2026

July 26, 2026 by 9 Comments

At a time when so-called “artificial intelligence” seems inescapable, we were encouraged to see news that Amazon will be cracking down on third-party sellers that use AI-generated images for their product listings. They won’t be prevented from using the images, but they will need to clearly indicate that they don’t represent reality and were produced via artificial means. This comes in response to a recently enacted New York law that requires the disclosure of AI in advertisements.

Will this be the end of the cat sleeping bag?

But it’s not quite a clear cut as it might seem on the surface, as the New York law is actually about AI-generated people rather than products. Specifically, it’s designed to make it clear when a “synthetic performer” has been used in place of a human actor. As such, it would appear that the easiest way for Amazon sellers to dodge the new rule is to simply not include any humans in their AI slop images and videos. In other words, they can continue to post fake pictures of products without having to inform the consumer so long as they don’t show a fake person holding it.

Under normal circumstances we’d leave something like this next one for our weekly security column, but the utter lack of security in the Pope’s official “Click To Pray” mobile application revealed by researcher BobDaHacker on Friday is just too good a story to pass up. For one thing, who knew that there was an “official” prayer app? We don’t dabble in theology around these parts, but we’re fairly sure the good book didn’t mention anything about requiring a smartphone to give praise.

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Filling High Pressure CO2 Tanks From Sugar Fermentation Gas

July 26, 2026 by 12 Comments

After previously using the fermenting of sugar to obtain ethanol fuel, [Hyperspace Pirate] figured that it’d be a waste to just blast the other half of the yeast production in the form of carbon dioxide into the air. This poses the slight problem that gaseous CO2 is fairly bulky, while compressing it into a liquid isn’t exactly for the faint of heart. This of course means that it’s a fun challenge, involving a beach ball, vapor-compression and various compressors.

Although at room temperature compressing CO2 into a liquid requires quite extreme pressures, if you lower it to freezing temperatures it becomes quite feasible to use more typical off-the-shell compressors.

In the video both oil-less and regular compressors are used, mostly because ultimately you want to get pure CO2 into the bottle, without oil or water. Here a few methods are explored, including a pre-cooler with the oil-less compressor as it cannot quite hit the same pressures. With a typical compressor linked to an oil-separator you can directly fill the tank, which is pretty nice, though even with this removal of water turned out to be a chore.

Desiccating the gas that comes out of the fermentation vat, is attempted using a converted water filter that’s filled with desiccant beads, but as the later tests show, this isn’t quite good enough to prevent moisture to make it into the bottle and clogging its nozzle. Of course, moisture here is more acceptable than oil for most applications, so with some more work this could be quite a feasible method to fill bottles with liquid CO2 for various nefarious applications like paintball guns and more.

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All the parts of a digital clock. Photo by Lee Hutchinson.

Ever Seen Claude Use Fusion 360?

July 26, 2026 by 25 Comments

We’ve all done it before: a simple project that escalated to the point of extreme overengineering.
But what’s less common is [Lee Hutchinson]’s digital clock, whose case is (somewhat-successfully) designed by LLMs!

A clock needs time synchronization, and a digital one needs some code to drive the display. An avid systemd user, [Lee] had no trouble at all setting up all the users and services needed to keep the time synchronized. Some rusty Python skills with some aid of the dreaded Claude Code later, [Lee] had a script to actually show the time too.

But now comes the interesting part: the case. Now, [Lee] isn’t really a mechanical engineer, and he doesn’t really like Autodesk Fusion’s UX. Most projects would see their creators just grit their teeth and get on with it. But here, in an experiment we haven’t often seen before, [Lee] connects LLMs to Fusion’s new MCP server feature! Did it work? Surprisingly enough, yes. Kind of. The local Qwen model got most of the way there on one request, but still made mistakes for the other. However, another pass with the more powerful Claude models got the job done.

But there’s much more to the story; [Lee] goes into more detail, and talks about the assembly process, over at Ars Technica.