Scanwheel

Scanwheel: A Pocket-Sized POV TV

July 26, 2026 by 14 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 2 Comments

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 11 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 14 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 27 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.

Repairing A “for Parts” Canon 7D Mark II DSLR

July 26, 2026 by 16 Comments

The exciting part of buying a ‘broken, for parts’ off a site like EBay is that you rarely know exactly just how ‘broken’ it truly is. Even if the seller insists that it’s thoroughly buggered, you just might be able to eke out a fix with some out-of-the-box thinking and plucky ingenuity. Such was the case for [Dieter Vansteenwegen] who gambled on a cheap Canon 7D Mark II DSLR body that was sold for a mere €180 on account of said broken condition.

After confirming that the DSLR’s condition was basically as described by the seller, with nothing on the LCD or HDMI output and the auto-focus not working while partially pressing the trigger button, but still taking a picture when fully pressed. Sometimes it would also show a standard maintenance message on the LCD, so clearly it ought to be working. Maybe the camera’s processor was just being chronically unhappy about something, in which case an easy fix might be possible.

As anyone who has ever taken a digital camera apart knows, you do not simply pop them open for a quick look. Somewhere in the nightmarish contraption of flatflex cables, PCBs and endless sub-assemblies there might be a fault, but where to start? Fortunately with some support from the custom Canon firmware community Magic Lantern and the website Photo Parts UA for reference images he was able to start tracing a number of pertinent signals.

With the auto-focus hint as guide, this was traced back to the MPU, which turned out to have a floating signal on the auto-focus pin that got interpreted as ‘active’. Likely the internal pull-up got damaged due to the use of an external trigger module as there’s no real protection on these lines. One bodge wire later to create an external 3.3 V pull-up the DSLR happily sprung back to life.

In terms of parts this definitely was a cheap repair, but it comes with the prerequisite of having the skills and equipment to perform said repair. Still, massive props and congratulations to [Dieter] for saving this DSLR from being merely a device to be picked over for parts.

Duplicating Parts Using Silicone Molds

July 26, 2026 by 11 Comments

[Do As I Do] had a simple task to complete. A couple of small parts needed to be duplicated in some quantity, with good dimensional accuracy and surface finish. There are a number of ways you might go about this, particularly if you have the original tooling or a machine shop on hand. In this case, however, the plan was to duplicate the parts with silicone molds.

The first step, naturally, was to produce the silicone molds. Doing this involved some craft supplies, with glossy paper and hot glue used to create a vessel for casting silicone around the original parts. The silicone itself was mixed carefully and poured into the vessels, and soon enough [Do As I Do] had a pair of negative molds that could be used to produce duplicates of the original. The original parts were removed, and the silicone molds were filled with resin over and over again to make as many duplicates as were needed.

This was a simple enough project with straightforward geometry that suited the process. More challenging parts would require more care in mold prep and more advanced techniques. Depending on material choice for the duplicate parts and other factors like intended final application, extra steps like degassing may be necessary, too. Still, for a quick guide on duplicating a simple plastic part, it’s hard to beat.

We’ve featured other silicone mold jobs before, like these impressive recreated tail light lenses. Video after the break.

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