2025 One Hertz Challenge: A Game Of Life

August 13, 2025 by Zoe Skyforest 6 Comments

The 2025 One Hertz Challenge asks you to build a project that does something once every second. While that has inspired a lot of clock and timekeeping builds, we’re also seeing some that do entirely different things on a 1 Hz period. [junkdust] has entered the contest with a project that does something rather mathematical once every second.

[junkdust] wanted to get better acquainted with the venerable ATtiny85, so decided to implement Conway’s Game of Life on it. The microcontroller is hooked up to a 0.91″ OLED display with a resolution of 128 x 32 pixels, however, [junkdust] only elected to implement a 32 x 32 grid for the game itself, using the rest of the display area to report the vital statistics of the game. On power up, the grid is populated with a random population, and the game proceeds, updating once every second.

It’s a neat little desk toy, but more importantly than that, it served as a nicely complicated test project for [junkdust] to get familiar working inside the limitations of the ATtiny85. It may be a humble part, but it can do great things, as we’ve seen many times before!

2025 One Hertz Challenge: Abstract Aircraft Sculpture Based On Lighting Regulations

August 12, 2025 by Zoe Skyforest 9 Comments

The 2025 One Hertz Challenge is really heating up with all kinds of projects that do something once every second. [The Baiko] has given us a rather abstract entry that looks like a plane…if you squint at it under the right conditions.

It’s actually quite an amusing abstract build. If you’ve ever seen planes flying in the night sky, you’ve probably noticed they all have similar lights. Navigation lights, or position lights as they are known, consist of a red light on the left side and a green light on the right side. [The Baiko] assembled two such LEDs on a small sliver of glass along with an ATtiny85 microcontroller.

Powered by a coin cell, they effectively create a abstract representation of a plane in the night sky, paired with a flashing strobe that meets the requirements of the contest. [The Baiko] isn’t exactly sure of the total power draw, but notes it must be low given the circuit has run for weeks on a 30 mAh coin cell.

It’s an amusing piece of PCB art, though from at least one angle, it does appear the red LED might be on the wrong side to meet FAA regulations. Speculate on that in the comments.

In any case, we’ve had a few flashers submitted to the competition thus far, and you’ve got until August 19 to get your own entry in!

2025 One Hertz Challenge: Using Industrial Relays To Make A Flasher

August 10, 2025 by Zoe Skyforest 8 Comments

These days, if you want to flash some LEDs, you’d probably grab a microcontroller. Maybe you’d go a little more old-school, and grab a 555. However, [Jacob] is even more hardcore than that, as evidenced by this chunky electromechanical flasher build.

[Jacob] goes into great detail on his ancillary write-up, describing how the simple building blocks used by industrial control engineers can be used to make a flasher circuit that cycles once per second. Basically, two relays are paired with two 0.5-second delay timers. The two relays tag each other on and off on delay as their timers start and expire, with the lamp turned on and off in turn.

We’ve had lots of other great entries to our One Hertz Challenge, too — from clocks to not-clocks. There’s still time to get an entry in — the deadline for submission is Tuesday, August 19 at 9:00AM Pacific time. Good luck out there!

2025 One Hertz Challenge: Estimating Pi With An Arduino Nano R4

August 9, 2025 by Zoe Skyforest 10 Comments

Humanity pretty much has Pi figured out at this point. We’ve calculated it many times over and are confident about what it is down to many, many decimal places. However, if you fancy estimating it with some electronic assistance, you might find this project from [Roni Bandini] interesting.

[Roni] programmed an Arduino Nano R4 to estimate Pi using the Monte Carlo method. For this specific case, it involves drawing a circle inscribed inside a square. Points are then randomly scattered inside the square, and checked to see if they lie inside or outside the circle based on their position and distance of the circle’s outline from the center point of the square. By taking the ratio of the points inside the circle to the total number of points, you get an approximation of the ratio of the square and circle’s areas, which is equal to Pi/4. Thus, multiply the ratio by 4, and you’ve got your approximation of Pi.

[Roni] coded a program to run the Monte Carlo simulation on the Arduino Nano R4, taking advantage of the mathematical benefits of its onboard Floating Point Unit. It generates 100 new samples for the Monte Carlo approximation every second, improving the estimation of pi as it goes. It then displays the result on a 7-segment display, and beeps as it goes. [Roni] readily admits the project is a little too close in appearance to a classic Hollywood bomb.

We’ve seen some other neat Pi-calculating projects before, too.

Continue reading “2025 One Hertz Challenge: Estimating Pi With An Arduino Nano R4” →

2025 One Hertz Challenge: The Real-Time Clock The VIC-20 Never Had

August 8, 2025 by Zoe Skyforest 6 Comments

Like many early microcomputers, the Commodore VIC-20 did not come with an interna real-time clock built into the system. [David Hunter] has seen fit to rectify that with an add-on module as his entry to the 2025 One Hertz Challenge.

[David]’s project was inspired by a product that Hayes produced in the 1980s, which provided a serial-port based real-time clock solution for computers that lacked one on board. The heart of the project is an Arduino Uno, which itself uses a Dallas DS3231 RTC module to keep accurate time. [David] then drew from an IEC driver developed by [Lars Pontoppidan] for the MM2IEC project. This enables the Arduino to report the time to the VIC-20 via its IEC port.

The project is a neat way to provide a real-time clock source to programs written in Commodore BASIC. It’s also perfectly compatible with the IEC bus, so it can be daisy chained along with printers and disk drives without issue. [David] hasn’t tested it with a Commodore 64, but he suspects it should work just as well on that platform, too.

If you’ve ever wanted to build something clock-based for the VIC-20 but didn’t know how, this is a great piece of hardware to solve that problem. Meanwhile, you might find joy in reading about real-time clock hacks for other systems like the Raspberry Pi. Meanwhile, if you’re working on your own nifty timekeeping projects, don’t hesitate to let us know!

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

August 7, 2025 by Zoe Skyforest 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!

Continue reading “2025 One Hertz Challenge: The Easy Way To Make A Nixie Tube Clock” →

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.