2025 One Hertz Challenge: Timekeeping At One Becquerel

August 18, 2025 by Tyler August 23 Comments

The Becquerel (Bq) is an SI unit of radioactivity: one becquerel is equivalent to one radioactive decay per second. That absolutely does not make it equivalent to one hertz — the random nature of radioactive decay means you’ll never get one pulse every second — but it does make it interesting. [mihai.cuciuc] certainly thought so, when he endeavored to create a clock that would tick at one becquerel.

The result is an interesting version of a Vetinari Clock, first conceived of by [Terry Pratchett] in his Discworld books. In the books, the irregular tick of the clock is used by Lord Vetinari as a form of psychological torture. For some reason, imposing this torture on ourselves has long been popular amongst hackers.

Without an impractical amount of shielding, any one-becquerel source would be swamped by background radiation, so [mihai] had to get creative. Luckily, he is the creator of the Pomelo gamma-ray spectroscope, which allowed him to be discriminating. He’s using an Am-241 source, but just looking for the characteristic 59.5 KeV gamma rays was not going to cut it at such a low count rate. Instead he’s using two of the Pomelo solid-state scintillation as a coincidence detector, with one tuned for the Am-241’s alpha emissions. When both detectors go off simultaneously, that counts as an event and triggers the clock to tick.

How he got exactly one becquerel of activity is a clever hack, too. The Am-241 source he has is far more active than one decay per second, but by varying the distance from the gamma detector he was able to cut down to one detection per second using the inverse square law and the shielding provided by Earth’s atmosphere. The result is a time signal that is a stable one hertz… if averaged over a long enough period. For now, anyway. As the Am-241 decays away, its activity decreases, and [mihai] admits the clock loses about 0.4 seconds per day.

While we won’t be giving the prize for accuracy in this contest, we are sure Lord Vetinari would be proud. The Geiger-counter sound effect you can hear in the demo video embedded below is great touch. It absolutely increases the psychic damage this cursed object inflicts.

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Malfunctional Timekeeping With The Vetinari Clock

April 1, 2025 by Lewin Day 26 Comments

Lord Vetinari from the Discworld series is known for many things, but perhaps most of all a clock that doesn’t quite keep continuous time. Instead, it ticks away at random increments to infuriate those that perceive it, whilst keeping regular time over the long term. [iracigt] decided to whip up a real world version of this hilarious fictional timepiece.

The clock itself is an off-the-shelf timepiece purchased from Target for the princely sum of $5. However, it’s been deviously modified with an RP2040 microcontroller hidden away inside. The RP2040 is programmed to tick the clock at an average of once per second. But each tick itself is not so exact. Instead, there’s an erraticness to its beat – some ticks are longer, some shorter, in the classic Vetinari style. [iracigt] explains the nitty gritty of how it all works, from creating chaos with Markov chains to interfacing the RP2040 electronically with the cheap quartz clock movement.

If you’ve ever wanted to build one of these amusements yourself, [iracigt’s] writeup is a great place to start. Even better, it was inspired by an earlier post on these very pages! We love to see the community riff on a theme, and we’d love to see yours, too – so keep the tips coming, yeah? Video after the break.

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Hackaday Prize Entry: A Clock For Alternate Timebases

July 10, 2015 by Brian Benchoff 15 Comments

There is a strange clock in the waiting room of Lord Vetinari, Patrician of Ankh-Morpork. While this clock keeps accurate time overall, the ticks and tocks are out of sync, occasionally missing a tick altogether. The net effect is one of turning one’s brain into a sort of porridge.

Yes, a Vetinari Clock has made its way into The Hackaday Prize. This isn’t a clock that’s random yet accurate over long time spans; this is a complete replacement for run-of-the-mill clock movements you can find at any craft store.

In addition to the Vetinari Clock, [Nick Sayer]’s Crazy Clock can be programmed as a sidereal clock (3m 56s fast per day), a Martian clock (39m 36s slow per day), and a tidal clock (50m 28s slow per day), as well as some ‘novelty’ modes that still have 86400 ticks per day ranging from subtle to ‘clown car’ levels of craziness.

[Nick] is gunning for the ‘best product’ category for the Hackaday Prize, and for that he’s designing a board to be a direct replacement for the board in a Quartex Q80 clock movement. With this new board, [Nick] can replace the electronics in this movement in just a few minutes. Being built around an ATtiny45 means it’s infinitely hackable. A clock with this movement would be a great product, although judging from the video below, not one we would want to be around all day.

The 2015 Hackaday Prize is sponsored by:

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Lord Vetinari’s Clock Strikes Again

February 12, 2013 by Mike Szczys 15 Comments

Inspired by the maddening timepiece from Discworld, this clock keeps time, but anyone watching the seconds tick by may be mentally unstable for it. [Renaud Schleck] built the stuttering clock using very few components. He undertook the build after being inspired by the version which [Simon Inns] built.

The clock itself is a run-of-the-mill item which uses one battery to keep time. We’re always impressed by how these dirt-cheap things remain so accurate over the long haul — but we digress. The method of attack uses coil injection to drive the hands. [Renaud] used one of the microcontrollers from the MSP430 Launchpad, along with the clock crystal which also shipped with the kit, to gain control of the mechanism. The crystal triggers an interrupt which does the actual time-keeping. The seconds hand is driven rather sporadically based on an algorithm explained in his write-up.

You can watch the uneven ticking in the video after the break. Despite that visually disturbing functionality, the short and long ticks balance each other and the correct time continues to be displayed.

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Building A Better Clock To Drive You Insane

October 12, 2011 by Brian Benchoff 24 Comments

[youtube=http://www.youtube.com/watch?v=YpqFU4SGe1Y&w=470]

[Simon] came up with an improved version of Lord Vetinari’s clock that begs to be installed in waiting rooms around the world.

Last week, we were introduced to a real-life Vetinari Clock that keeps regular time but ticks at irregular intervals. It’s a great way to turn someone’s mind into porridge, but the original build broke after a few weeks because of some limitations in the clock drive. [Simon] built a very minimal circuit does away with these problems.

Just as in the first build, a microcontroller pulses the second hand motor once every second. As for the random component of this build, the microcontroller has a puts 32 bytes into a 128 byte array. The array is checked 4 times a second, and if the byte is 1, the second hand is incremented. If the byte is 0, time stops for a little bit. [Simon] included the schematic, board layout and code if you’d like to build one yourself.

There are a few drawbacks to this design; the pattern of ticking and not ticking is hard-coded into the microcontroller. Even though the 32 second long pattern shouldn’t be noticeable by watching the clock, it’s not an entirely random solution. Judging from the comments on the original build, using radioactive decay to increment a second might be a bit uncalled for.

We would like to see a second hand that stops when you look at it though. Facial recognition, anyone?