2025 One Hertz Challenge: Shoulda Put A Ring Oscillator On It

August 5, 2025 by Tyler August 12 Comments

Entries keep ticking in for the One Hertz Challenge, some more practical than others. [Pierre-Loup M.]’s One Hertz Sculpture has no pretensions of being anything but pretty, but we can absolutely respect the artistic impulse behind it.

The sculpture is a free-form circuit inside of a picture frame. There are 9 LEDs in a ring with a few other components to produce a reverse-chase effect (one going dark at a time) taking about 1 second to circle the sculpture. As far as free-form circuit art goes, it’s handsomely done, but as this is Hackaday it’s probably the electronics, rather that the aesthetics that are of interest.

The circuit is an example of a ring oscillator: a cascading chain of NOT gates, endlessly feeding into and inverting one

An animated gif of the sculpture at work — Without timing it, it looks like 1 Hz, even if we know it’s not.

another. The NOT gates are implemented in resistor-transistor logic with 2N3904 NPN transistors, nine in total. Of course the inverter delay of this sort of handmade logic gate is far too fast for an aesthetically pleasing (or visible) chase, so some extra circuitry is needed to slow down the oscillations to something less than the 5 MHz it would naturally do. This is affected by pairing every transistor with an RC oscillator. Ideally the RC oscillator would have a 0.111..s period (1/9th of a second), but a few things got in the way of that. The RC oscillator isn’t oscillating in a vacuum, and interactions with the rest of the circuit have it running just a little bit fast. That’s really of no matter; a simple oscillator circuit like this wasn’t going to be a shoe in for the accuracy-based Time Lords category of this contest. As a sculpture and not a clock, you’re not going to notice it isn’t running at exactly 1Hz. (Though a ring-oscillator based clock would be a sight indeed.)

We’ve seen ring oscillators before, including inside the venerable 8087 coprocessor and this delightfully romantic beating-heart gift, but this is the first one that seems to have entered the One Hertz Challenge.

If you have a hankering for hertz, the contest is still open, but you’d better get ticking! The contest closes August 19th.

Flex PCB Underlies The Watch Of The Future

August 5, 2025 by Tyler August 8 Comments

If you were at OpenSauce, you may have seen new Youtuber [Sahko] waltzing about with a retrofuturistic peice of jewelery that revealed itself as a very cool watch. If you weren’t, he’s his very first video on YouTube detailing the design and construction of this piece. We’ve embedded it below, and it’s worth a watch. (Pun intended, as always.)

The build was inspired by the delightful amber LED dot-matrix display modules that circle the band of the watch. They go by HCMS2901, but [Sahko] recommends using the HCMS3901 as it’s both more 3.3V-tolerant and easier to find now. A challenge in mounting so many displays was the voltage on the supply rail dropping below the logic level; presumably the newer version does not have this problem to the same degree. Either way we love the look of these little displays and are pondering projects of our own that might include them.

He’s got quite a few wrapped around his wrist, so at full brightness, all these displays draw one amp. That explains why like the LED watches of the 1970s, the default state of the displays is “OFF”. Even with a LiPo pouch salvaged from a disposable vape, the runtime would only be half an hour at full brightness without that periodicity. Luckily [Sahko] included buttons on the band of the watch to activate it and control the brightness so it isn’t always blasting at full. There are also different modes available, including a really cool waterfall effect you can see in the video.

The band is an interesting choice, too: it’s just a flex PCB. There’s nothing backing it, aside from its own stiffeners, which makes us very curious how well this watch would hold up to daily use. There’s no clasp in the traditional sense, either: the band is closed by a 4-pin connector that doubles as both charge and the USB programmer for the stm32u08 microcontroller that runs the displays. Conveniently for a watch, this version of the stm32 has an RTC, so it keeps time as well. We dig the minimalism of this design; it’s a great contrast to the maximalism of wrapping your wrist in displays.

We’ve seen very similar displays on an edge-viewed watch, but a tiny amber LED matrix never gets old. If you wrapping your wrist in all those tiny LEDs is too impractically power-hungry, try using Nixie tubes.

We’re always watching for projects– wrist mounted clocks or otherwise– so if you’ve got the time, please drop us a tip.

Continue reading “Flex PCB Underlies The Watch Of The Future” →

Open Source 5-Axis Printer Has Its Own Slicer

August 4, 2025 by Tyler August 22 Comments

Three-axis 3D printing has been with us long enough that everybody knows the limitations, but so far, adding extra axes has been very much a niche endeavor. [Daniel] at Fractal Robotics wants to change that, with the Fractal 5 Pro 5-axis printer, and its corresponding Fractal Cortex slicer.

The printer looks like an extra-beefy Voron from a distance, which is no surprise as [Daniel] admits to taking heavy inspiration from the Voron Trident. The Fractal 5 shares a core-XY geometry with the Voron, using beefy 30 mm x 30 mm extrusions. Also like the Voron, it runs Klipper on a Raspberry Pi hiding in the base. Under a standard-looking printhead using a BondTech extruder and E3D volcano hotend, we find the extra two axes hiding under the circular build plate. The B axis is a gantry that can pivot the build plate assembly a full 90 degrees; the A axis spins the plate without limit thanks to the slip rings built into the design.

The extruder may look fairly normal, but it has actually been designed very carefully to allow the nozzle to get as close as possible to the build plate when the B-axis is at 90 degrees. It looks like the E3D hotend is actually the limiting factor there, which gives plenty of design freedom when planning prints in the accompanying Fractal Cortex slicer.

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Rebuilt Batteries For The Cutest Clamshell At The Cafe

August 3, 2025 by Tyler August 21 Comments

Keeping retrocomputers going can be tricky enough, but when you’re talking retro laptops, the battery packs add an extra challenge. While one could simply live without the battery, that’s not going to give you the full retro experience. Replacement batteries are long out of stock, so what can one do? Well, one can check out this excellent tutorial by [lazd] on rebuilding an iBook G3 Clamshell battery.

Even if you don’t have this particular laptop, the general process is likely to be similar for PC laptops of similar vintage. (Which we still can’t believe is a whole quarter-century ago.) Luckily for retrocomputer enthusiasts, even Apple used standard 18650 cells in those bygone, halcyon days when computers were allowed to be more than a few atoms thick. They do need to be unprotected, flat-top cells, but that’s easy enough to source.

So it’s really a matter of carefully prying apart the casing (apparently it needs to be Apple-branded; aftermarket cases can’t survive being opened), removing the old batteries, and welding nickel tabs onto the new cells in the proper configuration. One thing that surprised us is that, apparently, Apple did not go in for balancing in those days — so make sure your cells are all in perfect condition and all equally charged before you start, or things won’t end nicely.

As always, battery orientation matters! The cells are welded into two sets in this Clamshell iBook battery.

Assuming you can pull it off (and your battery pack’s control chip has lasted the 300 moons since its manufacture), you’ll get a not-insignificant 5-hour battery run out of what’s sure to be the cutest clamshell computer at the cafe.

If you are repairing an iBook, while you’re at it, why not upgrade the RAM? You might even be able to fix the screen if it’s succumbing to the sadly-too-common vinegar syndrome.

2025 One Hertz Challenge: Learn Morse Code One Second At A Time

August 2, 2025 by Tyler August 3 Comments

Learning Morse Code is no longer a requirement for HAMs in many jurisdictions, but it’s still a nice skill to have. [I_void(warranties)] wanted to learn, but couldn’t find a trainer that fit his style. What to do but build it yourself? Since we’re in the midst of a challenge, he took up the gauntlet and turned his need to learn Morse into a 1 hertz Morse code game.

In concept it is quite simple: a message beeps out in Morse, with a corresponding LED flash, all in one second. The player then has one second to type think they heard. Get it done fast enough, and a character LCD will tell you if you scored.

The project is based around an Arduino Nano; thanks to easily-available libraries, a PS/2 keyboard can serve as input and a 2×16 LCD as feedback with no real effort expended. For the audible component of the Morse challenge, an 8-ohm speaker is driven right off a pin on the Arduino. We won’t claim this efficient design only took one second to put together, but it probably didn’t take too long.

Of course this trainer, unlike some we’ve seen, only helps you learn to listen to the stream of dots and dashes. None of the others ever tried to fit a One Hertz theme, or [I_void(warranties)]’s particular learning style. For some, decoupling send and receive might be just the ticket to finally learning Morse one second at a time.

This Plane Flies Slow Because Its Wings Really Blow

August 2, 2025 by Tyler August 19 Comments

The key to Short Takeoff and Landing (STOL) operations is the ability to fly slow– really slow. That’s how you get up fast without a long takeoff roll to build up speed. Usually, this involves layers of large flaps and/or leading edge slats, but [rctestflight] on YouTube decided he wanted to take a more active approach with a fully blown wing.

The airplane in question is R/C, of course, and good thing: these wings would be a safety nightmare for a manned aircraft. With a blown wing, air is blown out of a slot on the top end of the wing, producing a high-speed, high-pressure zone that keeps the wing flying when it would otherwise be completely stalled out. As long as everything works, that’s great! If an engine fails, well, suddenly you aren’t flying anymore — and you’re going too slow to glide. It ends badly.

[rctestflight] doesn’t have to worry about that, though, because this foamboard and pink styro R/C aircraft carries nothing that can’t survive a crash. (A couple of electric ducted fans (EDCs), an Ardupilot, a radio, and a battery are all pretty shock-resistant.) The EDCs sit midway down the chord of the wings, and blow air into a plenum carved into the foam. On each wing, the exhaust from the fans is driven rearward from a slot created by a piece of carbon fiber. This air serves not only as a lift-enhancement but also as the plane’s sole propulsion and a component of its control system.

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Universal Control For The Last Mac You’d Ever Expect

August 1, 2025 by Tyler August 8 Comments

Universal control is a neat feature on Macintosh computers, allowing you to slide your mouse seamlessly from device to device. Of course you need a relatively recent version of MacOS to make it work, right? Not necessarily– thanks to [Bart Jackobs] MacFriends, universal control has come to the Macintosh Classic.

The Arduino is perfect for this purpose, but choosing it ruined a perfectly good pun and we can never forgive that.

Well, not exactly universal control, but similar functionality at any rate. [Bart] can slide his mouse from one side of his retina display over onto the glorious 512 x 342, 1-bit display of his Macintosh Classic, just as if the 68k powered antique was a modern device. As you might expect, the Motorola 68000 in that old Mac is getting a teensy bit of help– though sadly for our love of puns, from an Arduino Nano and not any kind of Teensy.

The Arduino is emulating a mouse and keyboard on the Apple Desktop Bus using code based on the abduino by [akuker]. [Bart]’s custom software on the modern Mac captures the mouse and keyboard inputs to pipe to the Arduino via USB serial. Apple’s Universal control doesn’t require a wired connection between the two machines, of course, but then, it doesn’t work on the Classic. One could imagine redoing this project for Bluetooth communication to have that a same Clarkian feeling of technological magic Apple has always wanted to convey– but nothing was wireless in 1990 except for telegrams and a handful of telephones, so the project is appropriate as-is.

As much as we might resent that micro-controller for ruining a pun, if you want to hook into the ADB– perhaps to use old peripherals with an emulated Macintosh— an Arduino will do the job. So would a Teensy, though, and then we’d have our pun.

Our thanks to [Bart Jakobs] for the tip. Don’t forget to send in your own: the endless maw of the tipsline is always hungry.