2025 One-Hertz Challenge: Fixing The Clock That Once Synced The World

July 29, 2025 by 4 Comments

The HP 115BR is not one of the most well-known products from Hewlett-Packard. And yet, it was remarkably important nonetheless. This hardware once synced time around the world. Now, for our 2025 One-Hertz Challenge, [curiousmarc] has taken on the job of restoring it. 

The HP 115BR itself was not used alone, but in concert with the HP5060A atomic clock. The latter would output a 100 KHz reference output. It was the job of the HP 115BR to divide this frequency down to provide a superbly accurate 1-second tick.

The example on [curiousmarc]’s bench showed up in poor shape. It was “very broken,” and he reported that it had also previously been hacked to some degree. However, he has been able to restore it to proper functionality, including the special modification for continuous tick adjustment, as used in the 1964 flying atomic clock experiment. He was even able to sync it to NIST’s current atomic clock signal from Fort Collins using the WWW radio signal.

We’ve seen plenty of old HP metal restored over the years; it’s always pleasant to see how well things were built back in the day. Video after the break.

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Numbers Station Simulator, Right In Your Browser

July 29, 2025 by 6 Comments

Do you find an odd comfort in the uncanny, regular intonations of a Numbers Station? Then check out [edent]’s numbers station project, which leverages the browser’s speech synthesis engine to deliver a ceaseless flow of (mostly) numbers, calmly-intoned in various languages.

The project is an entry for the annual JavaScript Golfing Competition, in which participants aim to create a cool program in 1024 bytes or less. It cleverly relies on the Web Speech API to deliver the speaking parts, which helps keep the code size tiny. The only thing it’s missing is an occasional shadow of static drifting across the audio.

If you’re new to numbers stations, our own [Al Williams] is here to tell you all about them. But there’s no need to tune into an actual mysterious radio signal just to experience weird numbers; just fire up [edent]’s project, put on some headphones, and relax if you can.

Power Line Patrols: The Grid’s Eye In The Sky

July 29, 2025 by 17 Comments

Those of us who like to monitor air traffic with ADS-B aggregators such as FlightAware and ADS-B Exchange tend to see some interesting flight paths. I’m not talking about the truly ambitious pictures drawn by pilots, or even the more ribald ones, but rather flights that follow paths that seem to make little sense from either a commercial or leisure standpoint.

Most of these mystery flights have long straight stretches interrupted by occasional tight loops, and often cover great distances across rural and urban landscapes alike. A glance at the ADS-B data indicates that these flights are usually pretty close to the ground, and are often completed by helicopters. Occasionally, the registration of the aircraft will even indicate ownership by some “three-letter” federal agency.

Although mystery helicopters flying odd patterns in the sky seems like a good excuse to don a tinfoil hat and head to one’s bunker, chances are pretty good that these aircraft are engaged in a far less nefarious and far more useful endeavour: aerial transmission line patrols. These flights are key to keeping the transmission lines that form the backbone of the grid in tip-top shape, especially at a time of unprecedented growth in load and a shift in the generation profile away from fossil fuels towards renewables.

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Tetris In A Single Line Of Code

July 29, 2025 by 14 Comments

PC gaming in the modern era has become a GPU measuring contest, but back when computers had far fewer resources, every sprite had to be accounted for. To many, this was peak gaming. So let’s look to the greats of [Martin Hollis, David Moore, and Olly Betts], who had the genius (or insanity) to create Tetris in a single BBC BASIC line.

Created in 1992, one-line Tetris serves as a great use of the limited resources available. The entirety of the game fits within 257 bytes. With the age of BASIC, the original intent of the game for BBC BASIC was to be played on computers similar to Acorn’s BBC microcomputer or Archimedes.

One line Tetris has all the core features of the original game. Moving left, right, and rotating all function like the traditional game, most of the time. Being created in a single line, there were a few corners cut with bug fixing. Bugs such as crashing every 136 years of play due to large numbers or holding all keys causing the tetrominoes to freeze make it an interesting play experience. However, as long as our GPUs are long enough to play, we don’t mind.

If you want to experience the most densely coded gaming experience possible but don’t have one of the BBC BASIC computers of old, make sure to try this emulator with a copy of the game. Considering the amount done in a single line of BBC BASIC, the thought may come into mind on what could be done with MORE than a SINGLE line of code. For those with this thought, check out the capabilities of the coding language with modern hardware.

Thanks to [Keith Olson] for the tip!

Solar Light? Mains Light? Yes!

July 29, 2025 by 21 Comments

So you want a light that runs off solar power. But you don’t want it to go dark if your batteries discharge. The answer? A solar-mains hybrid lamp. You could use solar-charged batteries until they fall below a certain point and then switch to mains, but that’s not nearly cool enough. [Vijay Deshpande] shows how to make a lamp that draws only the power it needs from the mains.

The circuit uses DC operation and does not feed power back into the electric grid. It still works if the mains is down, assuming the solar power supply is still able to power the lamp. In addition, according to [Vijay], it will last up to 15 years with little maintenance.

The circuit was developed in response to an earlier project that utilized solar power to directly drive the light, when possible. If the light was off, the solar power went to waste. Also, if the mains power failed at night, no light.

The answer, of course, is to add a battery to the system and appropriate switching to drive the lights or charge the battery and only draw power from the mains when needed. Since the battery can take up the slack, it becomes easier to load balance. In periods of low sunlight, the battery provides the missing power until it can’t and then the mains supply takes over.

Comparators determine whether there is an under-voltage or over-voltage and use this information to decide whether the battery charges or if the main supply takes over. Some beefy MOSFETs take care of the switching duties. Overall, a good way to save and reuse solar cell output while still drawing from the grid when necessary.

Small solar lights don’t take much, but won’t draw from commercial power. Solar “generators” are all the rage right now, and you could probably adapt this idea for that use, too.

2025 One Hertz Challenge: Drop The Beat (But Only At 60 BPM)

July 28, 2025 by 1 Comment

Mankind has been using water to mark the passage of time for thousands of years. From dripping stone pots in Ancient Egypt to the more mechanically-complicated Greco-Roman Clepsydrae, the history of timekeeping is a wet one — and it makes sense. As an incompressible fluid, water flows in very predictable patterns. If you fill a leaky pot with water and it takes an hour to drain, it will also take an hour the next time you try. One Hertz Challenge entrant [johnowhitaker] took this idea in a different direction, however, with an electromechanical clock that uses dripping water as an indicator.

This clock uses a solenoid to briefly pop the plunger out of a water-filled syringe. This allows a drop to fall from the tip, into a waiting beaker. In addition to the satisfying audio indication this produces, [johnowhitaker] added a bit of food coloring to the dripping water for visual flair. The entire thing is controlled by a Raspberry Pi Pico and a motor driver board, so if you’ve got some spare parts lying about and would like to build your own be sure to head over to the project page and grab the source code.

While this clock isn’t exactly here for a long time (either the syringe will eventually empty or the beaker will overflow), it’s certainly here for a good time. [John] and commenters on his project even have ideas for the next steps: a 1/60 Hz beaker changer, and a 1/600 Hz spill cleaner. Even so, the first couple of drops hitting the beaker produce a lovely lava lamp-esque cloud that is a joy to watch and has us thinking about other microfluidics projects we’ve seen.

And remember — it’s not too late to enter the 2025 One Hertz Challenge!

Models Of Wave Propagation

July 28, 2025 by 7 Comments

[Stoppi] always has interesting blog posts and videos, even when we don’t understand all the German in them. The latest? Computer simulation of wave propagation (Google Translate link), which, if nothing else, makes pretty pictures that work in any language. Check out the video below.

Luckily, most browsers will translate for you these days, or you can use a website. We’ve seen waves modeled with springs before, but between the explanations and the accompanying Turbo Pascal source code, this is worth checking out.

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