2025 One Hertz Challenge: The Easy Way To Make A Nixie Tube Clock

August 7, 2025 by Lewin Day 3 Comments

Let’s say you want to build a Nixie clock. You could go out and find some tubes, source a good power supply design, start whipping up a PCB, and working on a custom enclosure. Or, you could skip all that, and just follow [Simon]’s example instead.

The trick to building a Nixie clock fast is quite simple — just get yourself a frequency counter that uses Nixie tubes for the display. [Simon] sourced a great example from American Machine and Foundry, also known as AMF, the company most commonly associated with America’s love of bowling.

The frequency counter does one thing, it counts the number of pulses in a second. Thus, if you squirt the right number of pulses to represent the time — say, 173118 pulses to represent 5:31 PM and 18 seconds — the frequency counter effectively becomes a clock. To achieve this, [Simon] just hooked an ESP32 up to the frequency counter and programmed it to get the current time from an NTP time server. It then spits out a certain number of pulses every second corresponding to the current time. The frequency counter displays the count… and there you have your Nixie clock!

It’s quick, dirty, and effective, and a sweet entry to our 2025 One Hertz Challenge. We’ve had some other great entries, too, like this nifty hexadecimal Unix clock, and even some non-horological projects, too!

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2025 One Hertz Challenge: Square Waves The Way You Want ‘Em

August 6, 2025 by Jenny List 8 Comments

On an old fashioned bench a signal generator was once an indispensable instrument, but has now largely been supplanted by the more versatile function generator. Sometimes there’s a less demanding need for a clock signal though, and one way that might be served comes from [Rupin Chheda]’s square wave generator. It’s a small PCB designed to sit at the end of a breadboard and provide handy access to a range of clocks.

On the board is a crystal oscillator running at the usual digital clock frequency of 32.768 kHz, and a CMOS divider chain. This provides frequencies from 2048 Hz down to 0.5 Hz for good measure. It’s a simple but oh-so-useful board, and we can imagine more than a few of you finding space for it on your own benches.

This project is part of our awesome 2025 One Hertz Challenge, celebrating all the things which strut their stuff once a second. It’s by no means the first to feature a 32.768 kHz divider chain, and if you have a similar project there’s still time to enter.

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.

2025 One Hertz Challenge: Blinking An LED The Very Old Fashioned Way

August 5, 2025 by Jenny List 10 Comments

Making an LED blink is usually achieved by interrupting its power supply, This can be achieved through any number of oscillator circuits, or even by means of a mechanical system and a switch. For the 2025 One Hertz Challenge though, [jeremy.geppert] has eschewed such means. Instead his LED is always on, and is made to flash by interrupting its light beam with a gap once a second.

This mechanical solution is achieved via a disk with a hole in it, rotating once a second. This is driven from a gear mounted on a 4.8 RPM geared synchronous motor, and the hack lies in getting those gears right. They’re laser cut from ply, from an SVG generated using an online gear designer. The large gear sits on the motor and the small gear on the back of the disk, which is mounted on a bearing. When powered up it spins at 60 RPM, and the LED flashes thus once a second.

We like this entry for its lateral thinking simplicity. The awesome 2025 One Hertz Challenge is still ongoing, so there is still plenty of time for you to join the fun!

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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.

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

July 28, 2025 by Adam Zeloof 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!

2025 One-Hertz Challenge: Clock Calibrator

July 28, 2025 by Lewin Day 8 Comments

Wall clocks! Are they very accurate? Well, sometimes they are, and sometimes they lose minutes a day. If you’ve got one that needs calibrating, you might like this device from [Lauri Pirttiaho].

Most cheap wall clocks use very similar mechanisms based around the Lavet-type stepper motor. These are usually driven by a chip-on-board oscillator that may or may not be particularly accurate.

[Lauri] desired a way to tune up these cheap clocks by using GPS-level timing accuracy. Thus began a project based around a CY8KIT evaluation board from Cypress. The microcontroller is paired with a small character LCD as a user interface, and hooked up to a cheap GPS module with an accurate 1-pulse-per-second (1PPS) timing output. The concept is simple enough. Clock drift is measured by using counters in the microcontroller to compare the timing of the GPS 1PPS output and the pulses driving the Lavet-type stepper motor. The difference between the two can be read off the device, and used to determine if the wall clock is fast or slow. Then one need only use a trimmer capacitor to tweak the wall clock’s pulse rate in order to make it more accurate.

Few of us spend much time calibrating low-cost wall clocks to high levels of accuracy. If that sounds like a fun hobby to you, or your name is Garrus, you would probably find [Lauri]’s device remarkably useful. Believe it or not, this isn’t the first clock calibrator we’ve seen, either. Meanwhile, if you’ve brewed up your own high-accuracy timing hardware, feel free to let us know on the tipsline.