Psst… Got A Second? Here Are The 2025 One-Hertz Challenge Winners

There are two kinds of people in the world: those who think “once per second” sounds easy, and those who have
ever tried to build a “perfect” one-second tick and watched it slowly drift into chaos like a shopping cart with one
wobbly wheel. Welcome to the 2025 One-Hertz Challenge, where the rule was simple enough to fit on a sticky note:
do something once per secondflash, click, beep, ping, flip, blink, clunk, or otherwise remind the universe you’re still here.

But that “simple” constraint is exactly why this contest is so fun. One hertz (1 Hz) is the heartbeat of timekeeping,
the metronome of microcontrollers, the pace of clocks, and the most polite frequency on Earthuntil you try to make it
accurate, stable, beautiful, weird, or all four at once.

Hackaday’s 2025 challenge pulled in well over a hundred entries, and the judges had to narrow it down to three winners,
plus a buffet of honorable mentions that prove one thing: if you give hackers a single constraint, they will build
an entire universe inside it.

The One-Hertz Challenge in Plain English

The brief: build a device where something happens once per second. Not once-ish. Not “whenever the code feels like it.”
Once per second, at as close to 1 Hz as your design can managewhether you’re using a watch crystal, a GPS reference,
a 555 timer, a pendulum, mains frequency, or (as you’re about to see) fire.

The genius of the format is that it supports wildly different interpretations. A one-hertz project can be:
a clock, a kinetic sculpture, a logic puzzle, a calibration exercise, a noise machine, or an absurd contraption that
should not work… but does, with confidence.

Meet the 2025 One-Hertz Challenge Winners

Hackaday crowned three top projects, each turning “one tick per second” into a distinct personality: one part engineering,
one part artistry, and one part “how did you even think of that?”

1) “the electromechanicalanalogdigitalclock” A Clock With Commitment Issues (In the Best Way)

The overall winner wears its identity crisis like a badge of honor. It’s mechanical and analog and digital, and it doesn’t apologize.
At the heart of the build is a mains-powered stepper motor that generates a 1 Hz signal via a photochopperalready a
delightfully tactile way to say “I don’t just want a second; I want to earn it.”

From there, the signal drives a 12-bit counter built from CMOS logic, which then feeds a digital-to-analog converter that
drives vintage moving-coil meters to display time. So instead of a normal clock face, you get a kind of instrument-panel
vibelike time is something you’re actively piloting.

It’s also a physical object with presence. The brass frame and spring suspension isolate the motor’s noise, and the whole thing
reads like circuit sculpture that just happens to keep time. Bonus points for the retro sci-fi energy in the project photos:
if your clock looks like it belongs on a 1970s spaceship set, you’re doing it right.

2) BEZICRON The Hair-Tie Clock That Somehow Feels… Elegant?

If you ever needed proof that timekeeping can be whimsical without being flimsy, BEZICRON is your exhibit A.
Yes, it uses hair bands. Yes, it forms numerals by bending and stretching them via intricate cams and levers.
And yes, after about five seconds of watching it, your brain goes, “Okay, this is oddly mesmerizing, and I respect it.”

Mechanically, it’s doing the hard thing: repeatedly and reliably shaping a flexible material into legible digits.
Visually, it’s doing the harder thing: looking distinctive without becoming unreadable.
The colon’s smooth one-hertz pulse ties it all together like a tiny metronome that says, “Relax. Time is happening.”

BEZICRON is also a reminder that a one-hertz project doesn’t have to be about chasing the last decimal place.
Sometimes the win is creating a display that nobody has seen beforethen making it work like it’s always existed.

3) Deriving 1 Hz from Candle Flame Oscillations A Clock Powered by “Please Don’t Spill Wax on the PCB”

Most of us see a candle flame and think: ambience, scent, maybe a little fire hazard if the cat is feeling curious.
This project looked at a flickering flame and thought: timebase.

The core idea is delightfully strange: candle flames “gutter” and oscillate, and while it looks random, those oscillations
can be more stable than you’d expect. A wire placed into the flame is used to trigger a capacitive sensor input on a CH32xxx
microcontroller, measuring the flame’s frequency. Then the measured oscillation is divided down to drive an LED blinking at 1 Hz.

This is the contest in a nutshell: physics meets electronics, and something that feels chaotic gets tamed into a steady tick.
Also: it’s the only clock concept that comes with an implied warning label that reads “do not time travel while your curtains are nearby.”

Honorable Mentions: The Side Quests That Made the Contest

Hackaday contests are famous for their “mini-games”categories that encourage builders to optimize for a specific flavor of madness.
In the One-Hertz Challenge, those honorable mention categories produced a greatest-hits playlist of “you did what once per second?”

Ridiculous: The Least Practical Way to Make a Second

This category celebrates the kind of engineering that looks like a Rube Goldberg machine built by someone with an oscilloscope and a deadline.
Notable runners-up included:

• An electromechanical function generatorbecause why generate a waveform digitally when you could make it physical and loud?
• A pitchblende-powered “atomic” clockbecause “I used a rock” is objectively the funniest possible bill of materials.
• A “Nothing but NAND” Nixie clocka love letter to logic gates and the joy of doing things the hard way.

Timelords: Chasing Zeros After the Decimal Point

For the accuracy crowd, the mission was clear: make your one-hertz tick so precise it feels like it’s wearing a lab coat.
Highlights included an atomic clock restoration project, clever GPS syncing for quartz wall clocks, and a GPS-disciplined crystal-oven oscillator.
In other words: if your idea of fun is disciplining oscillators, you found your people.

Clockwork: Timepieces With Personality

This category was for anyone who hears “one hertz” and immediately pictures gears, numerals, and that satisfying “tick” that makes humans feel safe.
Honorable mentions ranged from a Nixie-based frequency counter clock to a DCF77-based timepiece built from a repurposed conference badge,
plus an eye-catching clock built around bubble displays (because if your clock doesn’t look like treasure, what are we even doing?).

Could Have Used a 555: The Chip That Never Leaves the Party

Of course the 555 showed up. It always does. This category was a respectful nod to the fact that the 555 timer is basically the
Swiss Army knife of “make it blink,” and it’s still beloved even when it’s not the most accurate option.
Favorites included a Bletchley-inspired logic “Bombe,” a capacitor-free timer concept, and an especially cursed “One Hurts” clock
that sounds like it was designed to end friendships.

What These Builds Teach Us About One Hertz

The one-hertz constraint looks simple, but it forces you to answer questions every timekeeper eventually faces:

• Where does your “second” come from? A crystal? Mains frequency? A disciplined reference like GPS? A physical oscillator?
• How do you divide, measure, or correct it? Counters, PLLs, calibration routines, feedback loops, or clever mechanical ratios.
• How do you display it? LEDs are easy. Making it beautiful, legible, and novel is hard.

If you want a practical example of why “good enough” timing is a slippery slope: even a common 32.768 kHz watch crystal with a modest parts-per-million
accuracy can drift enough to be noticeably wrong over time. That’s why some builders chase calibration, temperature stability, and disciplined references,
while others shrug and say, “It blinks. That’s the point.”

Why the Winners Won

The top projects weren’t just accurate or complicatedthey were complete ideas.

• The electromechanicalanalogdigitalclock turned timing into an aesthetic, mixing methods in a way that felt intentional rather than chaotic.
• BEZICRON proved that novelty can be engineered: a display concept that’s both mechanical and surprisingly readable.
• The candle-flame build captured the spirit of hacking: extracting order from something that appears random and turning it into a steady beat.

Taken together, they show three paths to a great one-hertz project: craft, character, and concept.
Preferably all at once.

If You Want to Build Your Own One-Hertz Project

The easiest route is to pick a reference and a display:

• Beginner-friendly: a 555 timer blinking an LED (simple, classic, not ultra-precise).
• Practical clockwork: a 32.768 kHz crystal feeding a divider chain to get 1 Hz (quiet, low-power, widely used).
• Accuracy-hungry: a GPS 1PPS signal disciplining a local oscillator (excellent long-term stability, more complexity).
• Art-school hacker: pick any physical phenomenon that repeats and figure out how to sense it reliably (bonus points if it freaks out your friends).

And if you enter a contest like this? Document everything. Not just the final build, but the “why is it doing that?” moments,
the “oh wow, breadboards are tiny antennas” realizations, and the “I thought the second was constant until I met temperature drift” epiphanies.

Extra : Real-World Maker Experiences When You Chase One Hertz

Ask ten builders what it feels like to design a one-hertz device, and you’ll get ten variations of the same story:
it starts as a quick weekend project and ends with you staring at a blinking LED like it owes you money.
The reason is psychological as much as technicalone second is a human-scale unit. You can feel it.
You can notice when it’s wrong. And once you notice, you can’t un-notice.

A common early experience goes like this: you wire up a simple oscillator, set it to 1 Hz, and celebrate because the LED blinks.
Then you come back later, and the blink is… different. Not dramatically, not “broken,” but just enough to make your brain whisper,
“Is it faster now?” That tiny doubt sends you down the rabbit hole of component tolerances. Resistors aren’t perfect. Capacitors are
often less perfect. Temperature changes values. Even the way you touch the circuit (hello, stray capacitance) can nudge timing.

Then comes the measurement phase, which is half science and half self-control. If you have a frequency counter or a scope,
you learn to stop trusting your eyeballs. If you don’t, you invent comparison tricks: record video and count frames, compare against a phone stopwatch,
or build a reference tick from something you trust more. That’s when many makers “graduate” from relaxed oscillators to a watch crystal,
because dividing 32,768 Hz down to 1 Hz feels like using a ruler instead of guessing with your thumb.

But even the watch-crystal path has its own rite of passage: you discover drift. Not “it’s totally wrong,” but “it’s off by seconds over days.”
That’s when calibration enters the chat. Some builders trim load capacitance. Some add software correction. Others shrug and decide that being
slightly wrong is still charmingespecially if the display is delightful enough to distract people from doing math.

If you go the “accuracy hero” route, you run into a different experience: short-term stability versus long-term correctness.
A disciplined reference (like GPS 1PPS) can nail long-term time alignment, but you still have to manage jitter, signal integrity, and the fact that
clean timing signals don’t always live happily on a messy bench. Suddenly you care about grounding, cable routing, shielding, and whether your LED driver
is injecting noise back into your reference. The project stops being “blink an LED” and becomes “build a tiny timing ecosystem that doesn’t sabotage itself.”

And then there are the “creative physics” buildswhere the experience is less about trimming ppm and more about taming reality.
A candle flame, a pendulum, a mechanical escapement, a motor with a chopper wheelthese force you to confront real-world variability:
airflow, friction, vibration, sensor thresholds, ambient light, and the occasional cat-related interference event. The breakthrough moment usually happens
when you stop demanding perfection from the phenomenon and start designing a system that can measure, filter, and interpret it reliably.

The best part? Regardless of approach, one-hertz projects tend to teach the same lesson: time is a system problem.
The oscillator is only the start. What matters is the chain from reference to logic to output, and the story you tell with that once-per-second moment.
In a contest like Hackaday’s, that storyplus a little stylecan be the difference between “nice blink” and “I can’t stop watching this thing.”

Conclusion

The 2025 One-Hertz Challenge winners are a perfect snapshot of what makes hardware hacking special:
a simple prompt that explodes into hundreds of interpretations, from elegant electromechanical artistry to hair-band numerals to a candle-flame timebase.
Whether you build for precision, absurdity, aesthetics, or pure curiosity, one hertz is a surprisingly rich playground.

And if you’re thinking about building your own one-second machine, here’s the best advice the contest quietly teaches:
start simple, measure honestly, iterate shamelessly, and never underestimate how much personality you can fit into a single second.