One Hertz Challenge

Earlier this year, Hackaday launched the 1Hz Challenge: create something that does exactly one thing every second. Right up my alley. Fresh back from summer vacation, I have just six days left to design and submit something. There are four categories: Timelords – how precisely can you hit that heartbeat, Ridiculous – accuracy is nice, but absurdity wins, Clockwork – for the true clockmakers, and Could Have Used a 555 – for any project built around the legendary NE555.

Vacation Sparks Ideas

While on holiday, I mentally browse through my parts drawers. What could happen every second? Ideas flash by: a word clock, a 1Hz useless box, a water dripper (perfect for cafés), a pet-activator launching a treat every second, a tennis ball in a tube driven by a fan, and even an automatic poetry generator typing a new character each second. Back home, I decide to take a different route.

Dice and Inspiration

On vacation, I see couples, families, and groups of kids playing games, dice rolling everywhere. It’s all about luck and reaction time. That sparks an idea. From a past project, I still have a BTR MARk-E08 multifunctional timer relay, programmable via a potentiometer and DIP switches. I also have two electronic dice kits I use in soldering and basic electronics lessons. Together, they form the foundation of my 1Hz Dice.

Timer Meets Dice

The BTR MARk-E08 can act as a start or stop delay, or in a ‘blink’ mode. Its potentiometer ranges from 0–10 seconds. Connected to mains power, I quickly have my 1Hz pulse. The dice run on an STC Micro 8G1K17A microcontroller (8051 core, internal oscillator) with seven green LEDs for the pips, powered by CR2032 coin cells. Normally triggered by a motion sensor with a spring-mounted ball, I bypass that and feed the relay’s contact directly into the dice.

Building in Manhattan Style

I opt for a “Frankenstein–Manhattan” bend-and-solder approach. The link between relay and dice is 1.5 mm² copper wire. I measure carefully, set the dice at a 25° angle, cut and bend the wires symmetrically, and solder them to the activation contacts. The copper wires are stabilized to give the whole build a solid feel.

Fine-Tuning the Beat

From a distance, the dice are easy to read. I configure the relay via the DIP switches to trigger on the falling edge—this proves most reliable for the dice. Using my iPhone’s stopwatch, I calibrate the potentiometer for an exact once-per-second activation.

Finished and Fun

The project is complete. Fun to think up, even more fun to build. Challenges like this fire up my creativity, lead to engaging builds, and make technology approachable and shareable—even with non-nerds.


One Hertz Challenge - Submission 1Hz Double Dice