TechyMagThings

Last year, we brought you a story about the BhangmeterV2, an internet-of-things nuclear war monitor. With a cold-war-era HSN-1000 nuclear event detector at its heart, it had one job: announce to everything else on the network than an EMP was inbound, hopefully with enough time to shut down electronics. We were shocked to find out that the HSN-1000 detector was still available at the time, but that time has now passed. Fortunately [Bigcrimping] has stepped up to replicate the now-unobtainable component at the heart of his build with his BHG-2000 Nuclear Event Detector — but he needs your help to finish the job.

The HSN-1000, as reported previously, worked by listening for the characteristic prompt gamma ray pulse that is the first sign of a nuclear blast. The Vela Satellites that discovered Gamma Ray Bursts were watching for the same thing, though almost certainly not with that specific component. With the HSN-1000 unavailable, [Bigcrimping] decided he might as well make his own gamma ray detector, using four BPW34S PIN diodes coated with black paint. The paint blocks all visible light that might trigger photocurrent inside diode, but not Gamma Rays, while using four acts increases the area and may inadvertently act as a sort of coincident detector. You wouldn’t want your homemade Dead Hand to be triggered by a cosmic ray, would you?

That tiny photocurrent is then amplified by a transimpedance amplifier based on the LTC6244 op-amp, which then goes into a second-stage based on a LT1797 op amp that drives a LOW pulse to indicate an event has occurred. [Bigcrimping] fit all of this onto a four-layer PCB that is a pin-compatible replacement for the HSN-1000L event detector called for in his BhangmeterV2.

There’s only one problem: without exposing this thing to gamma rays, we really don’t know if it will work. [Bigcrimping] is looking for anyone in Europe with a Cs-137 or Co-60 source willing to help out with that. His contact info is on the GitHub page where the entire project is open sourced. Presumably a nuclear detonation would work for calibration, too, but we at Hackaday are taking the bold and perhaps controversial editorial stance that nuclear explosions are best avoided. If the Bhangmeter– which we wrote up here, if you missed it–or some equivalent does warn you of a blast, do you know where to duck and cover?

Air hockey is one of those sports that’s both incredibly fun, but also incredibly frustrating as playing it by yourself is a rather lonely and unfulfilling experience. This is where an air hockey playing robot like the one by [Basement Builds] could come in handy. After all, after you finished building an air hockey table from scratch, how hard could it be to make a robot that merely moves the paddle around to hit the puck with?

An air hockey table is indeed not extremely complicated, being mostly just a chamber that has lots of small holes on the top through which the air is pushed. This creates the air layer on which the puck appears to float, and allows for super-fast movement. For this part countless chamfered holes were drilled to get smooth airflow, with an inline 12VDC duct fan providing up to 270 CFM (~7.6 m³/minute).

Initially the robot used a CoreXY gantry configuration, which proved to be unreliable and rather cumbersome, so instead two motors were used, each connected to its own gearbox. These manipulate the paddle position by changing the geometry of the arms. Interestingly, the gearbox uses TPU for its gears to absorb any impacts and increase endurance as pure PLA ended up falling apart.

The position of the puck is recorded by an overhead camera, from where a Python script – using the OpenCV library running on a PC – determines how to adjust the arms, which is executed by Arduino C++ code running on a board attached to the robot. All of this is available on GitHub, which as the video makes clear is basically cheating as you don’t get to enjoy doing all the trigonometry and physics-related calculating and debugging fun.

Sound! It’s a thing you hear, moreso than something you see with your eyes. And yet, it is possible to visualize sound with various techniques. [PlasmatronX] demonstrates this well, using a special scanning technique to visually capture the sound field inside an acoustic levitation device. 

If you’re unfamiliar, acoustic levitation devices like this use ultrasound to create standing waves that can hold small, lightweight particles in mid-air. The various nodes of the standing wave are where particles will end up hovering. [PlasmatronX] was trying to calibrate such a device, but it proved difficult without being able to see what was going on with the sound field. Hence, the desire to image it!

Imaging the sound field was achieved with a Schlieren optical setup, which can capture variations in air density as changes in brightness in an image. Normally, Schlieren imaging only works in a two-dimensional slice. However, [PlasmatronX] was able to lean on computed tomography techniques to create a volumetric representation of the sound field in 3D. He refers to this as “computerized acoustical tomography.” Images were captured of the acoustic levitation rig from different angles using the Schlieren optics rig, and then the images were processed in Python to recreate a 3D image of the sound field.

We’ve seen some other entertaining applications of computed tomography techniques before, like inspecting packets of Pokemon cards. Video after the break.

The early history of colour TV had several false starts, of which perhaps one of the most interesting might-have-beens was the CBS field-sequential system. This was a rival to the nascent system which would become NTSC, which instead of encoding red, green, and blue all at once for each pixel, made sequential frames carry them.

The Korean war stopped colour TV development for its duration in the early 1950s, and by the end of hostilities NTSC had matured into what we know today, so field-sequential colour became a historical footnote. But what if it had survived? [Nicole Express] takes into this alternative history, with a look at how a field-sequential 8-bit home computer might have worked.

The CBS system had a much higher line frequency in order to squeeze in those extra frames without lowering the overall frame rate, so given the clock speeds of the 8-bit era it rapidly becomes obvious that a field-sequential computer would be restricted to a lower pixel resolution than its NTSC cousin. The fantasy computer discussed leans heavily on the Apple II, and we explore in depth the clock scheme of that machine.

While it would have been possible with the faster memory chips of the day to achieve a higher resolution, the conclusion is that the processor itself wasn’t up to matching the required speed. So the field-sequential computer would end up with wide pixels. After a look at a Breakout clone and how a field-sequential Atari 2600 might have worked, there’s a conclusion that field-sequential 8-bit machines would not be as practical as their NTSC cousins. From where we’re sitting we’d expect them to have used dedicated field-sequential CRT controller chips to take away some of the heartache, but such fantasy silicon really is pushing the boundaries.

Meanwhile, while field-sequential broadcast TV never made it, we do have field-sequential TV here in 2026, in the form of DLP projectors. We’ve seen their spinning filter disks in a project or two.

1950 CBS color logo: Archive.org, CC0.

Ever since 3D printing has become a popular tool, the question of waste has been looming in the background. The sad reality of rapid prototyping is that you’re going to generate a lot of prints that just don’t aren’t fit for purpose, even if your printer runs them off perfectly every time. Creality has some products on the way aimed at solving that problem, and [Embrace Making] on YouTube has got his hands on a pre-production prototype of the Creality M1 Filament Maker to give the community a first look.

The M1 is actually only half of the system; Creality is also working on an R1 shredder to reduce your prints into re-usable shreds. [Embrace Making] hasn’t gotten his hands on that, but shredding prints isn’t the hard part. We’ve featured plenty of DIY shredders in the past. Extruding filament reliably at home has traditionally proven much more difficult, which is why we mostly outsource it to professionals.

Lacking the matching shredder, and wanting to give the M1 the fairest possible shake, [Embrace] tests the machine out first using Creality-supplied PLA pellets. The filament diameter isn’t as stable as we’ve gotten used to, and the spool rolling setup needs a bit more work.

Again, this is an early prototype. Creality says they’re working on it and claims they’ll get to ±0.05 mm precision in the production models. Doubtless they’ll also fix the errors that led to [Embrace]’s messy spool. That’s probably just software given that the winding mechanism did a pretty good job on the Creality-supplied spool.

Most importantly, the M1-produced filament does print. The prints aren’t perfect due to the variation in diameter, but they turn out surprisingly well for home-made filament. [Embrace] also shows off the ability to mix custom colors and gradients, but, again, using raw PLA rather than shredded material. Hopefully Creality lets him test drive the R1 shredder once its design is further along.

This is hardly the first time we’ve seen a filament extruder. The goal of this product is to pair with a shredder and use it for recycling, but if you’re going to stick with raw plastic pellets, you may as well print them directly.

Old-school diving helmets are deceivingly simple, even if they are – as [Hyperspace Pirate] puts it in a recent video – essentially the equivalent of an upside-down bucket with an air hose supplying air into it. While working on a 3D-printed diving helmet, he therefore made sure to run through all the requisite calculations prior to testing out said diving helmet in his pool.

The 3D model for the diving helmet can be found over at Thingiverse if you too feel like getting wet, just make sure that you size it to fit your own head. In the video CAD (cardboard-aided design) was used to determine the rough bounding box for the head, but everyone’s head is of course different. The helmet was printed in ABS, with the sections glued together before being covered in fiberglass and epoxy resin. Note that polyester resin dissolves ABS, so don’t use that.

On the helmet is a 1/4″ SAE fitting for the air hose, with the air provided from an oil-less compressor that in the final iteration is strapped to a floatation device along with an inverter and batteries. Of note is that you do not want to use a gas-powered compressor, as it’ll happily use any CO2 and CO it exhausts to send down the air hose to your lungs. This would be bad, much as having vaporized oil ending up in your lungs would be bad.

Although in the video the system is only tested in a backyard pool, it should be able to handle depths of up to ten meters, assuming the compressor can supply at least 41 L/minute. With some compressor-side miniaturization and waterproofing, [Hyperspace Pirate] reckons it would work fine for some actual ocean exploration, which while we’re sure everyone is dying to see. Perhaps don’t try this one at home, kids.

Cycloidal drives are a type of speed reducer that are significantly more compact than gearboxes, but they still come with a fair number of components. In comparison, the harmonic pin-ring drive that [Raph] recently came across as used in some TQ electric bicycles manages to significantly reduce the number of parts to just two discs. Naturally he had to 3D model his own version for printing a physical model to play with.

How exactly this pin-ring cycloidal drive works is explained well in the referenced [Pinkbike] article. Traditional cycloidal drives use load pins that help deal with the rather wobbly rotation from the eccentric input, but this makes for bulkier package that’s harder to shrink down. The change here is that the input force is transferred via two teethed discs that are 180° out of sync, thus not only cancelling out the wobble, but also being much more compact.

It appears to be a kind of strain wave gearing, which was first patented in 1957 by C.W. Musser and became famous under the Harmonic Drive name, seeing use by NASA in the Lunar Rover and beyond. Although not new technology by any means, having it get some more well-deserved attention is always worth it. If you want to play with the 3D model yourself, files are available both on GitHub and on MakerWorld.