2025 One Hertz Challenge: 555 Timer Gets A Signal From Above

July 24, 2025 by Adam Zeloof 7 Comments

One of the categories we chose for the One Hertz Challenge is “Could Have Used a 555.” What about when you couldn’t have, but did anyway? The 555 is famously easy to use, but not exactly the most accurate timer out there — one “ticking” at 1 Hz will pulse just about once per second (probably to within a millisecond, depending on the rest of the circuit), but when you need more precise timing, the 555 just won’t cut it. Not on its own, anyway.

An Allan deviation plot — Allan Deviation can be a bit confusing, but generally — lower is more accurate

This entry by [burble] shows us how the humble 555 can hold its own in more demanding systems with some help from a GPS receiver. He used the One Pulse per Second (1PPS) output from a GPS module to discipline the 1 Hz output from a 555 by modulating the control voltage with a microcontroller.

Okay, this sounds a bit like baking a cake by buying a cake, scraping all the icing off, then icing it yourself, but what better way to learn how to ice a cake? The GPS-disciplined 555 is way more accurate than a free running one — just check out that Allan Deviation plot. While the accuracy of the standard 555 begins to decrease as oscillator drift dominates, the GPS-disciplined version just keeps getting better (up to a point — it would also eventually begin to increase, if the data were recorded for long enough). Compared to other high-end oscillators though, [burble] describes the project’s accuracy in one word: “Badly.”

That’s okay though — it really is a fantastic investigation into how GPS-disciplined oscillators work, and does a fantastic job illustrating the accuracy of different types of clocks, and some possible sources of error. This project is a great addition to some of the other precision timekeeping projects we’ve seen here at Hackaday, and a very fitting entry to the competition. Think you can do better? Or much, much worse? You’ve got a few weeks left to enter!

2025 One Hertz Challenge: 16-Bit Tower Blinks At One Hertz

July 23, 2025 by Matt Varian 3 Comments

We’ve seen our share of blinking light projects around here; most are fairly straightforward small projects, but this entry to the 2025 One Hertz Challenge is the polar opposite of that approach. [Peter] sent in this awesome tower of 16bit relay CPU power blinking a light every second.

There’s a lot to take in on this project, so be sure to go look at the ongoing logs of the underlying 16-bit relay CPU project where [Peter] has been showing his progress in creating this clicking and clacking masterpiece. The relay CPU consists of a stack of 5 main levels: the top board is the main control board, the next level down figures out the address calculations for commands, under that is the arithmetic logic unit level, under the ALU is the output register where you’ll see a 220 V lamp blinking at 1 Hz, and finally at the base are a couple of microcontrollers used for a clock signal and memory. [Peter] included oscilloscope readings showing how even with the hundreds of moving parts going on, the light is blinking within 1% of its 1 Hz goal.

It’s worth noting that while [Peter] has the relay CPU blinking a light in this setup, the CPU has 19 commands to program it, enabling much more complex tasks. Thanks for the amazing-sounding entry from [Peter] for our One Hertz Challenge. Be sure to check out some of the other relay computers we’ve featured over the years for more clicking goodness.

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2025 One Hertz Challenge: A 555, But Not As We Know It

July 22, 2025 by Tyler August 2 Comments

We did explicitly ask for projects that use a 555 timer for the One Hertz Challenge, but we weren’t expecting the 555 to be the project. Yet, here we are, with [matt venn]’s Open Source 1Hz Blinky, that blinks a light with a 555 timer… but not one you’d get from Digikey.

Hooking a 555 to blink an LED at one hertz is a bog-simple, first-electronics-project type of exercise, unless you have to make the 555 first. Rather than go big, as we have seen before, [matt venn] goes very small, with a 555 implemented on a tiny sliver of Tiny Tapeout 6.

We’ve covered projects using that tapeout before, but in case you missed it, Tiny Tapeout gives space to anyone to produce ASICs on custom silicon using an open Process Design Kit, and we have [matt venn] to thank for it. The Tiny Tapeout implementation of the 555 was actually designed by [Vincent Fusco].

Of course wiring it up is a bit more complicated than dropping in a 555 timer to the circuit: the Tiny Tapeout ASIC must be configured to use that specific project using its web interface. There’s a demo video embedded below, with some info about the project– it’s not just a blinking LED, so it’s worth seeing. The output isn’t exactly One Hertz, so it might not get the nod in the Timelord category, but it’s going to be a very strong competitor for other 555-based projects– of which we could really use more, hint-hint. You’ve got until August 19th, if you think you can use a 555 to do something more interesting than blink an LED.

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2025 One-Hertz Challenge: Pokémon Alarm Clock Tells You It’s Time To Build The Very Best

July 22, 2025 by Adam Zeloof 3 Comments

We’ve all felt the frustration of cheap consumer electronics — especially when they aren’t actually cheap. How many of us have said “Who designed this crap? I could do better with an Arduino!” while resisting the urge to drop that new smart doorbell in the garbage disposal?

It’s an all-too familiar thought, and when it passed through [Mathieu]’s head while he was resetting the time and changing the batteries in his son’s power-hungry Pokémon alarm clock for the umpteenth time, he decided to do something about it.

The only real design requirement, imposed by [Mathieu]’s son, was that the clock’s original shell remained. Everything else, including the the controller and “antique” LCD could go. He ripped out the internals and installed an ESP32, allowing the clock to automatically sync to network time in the event of power loss. The old-school LCD was replaced with a modern, full-color TFT LCD which he scored on AliExpress for a couple of Euros.

Rather than just showing the time, the new display sports some beautiful pixel art by Woostarpixels, which [Mathieu] customized to have day and nighttime versions, even including the correct moon phase. He really packed as much into the ESP32 as possible, using 99.6% of its onboard 4 MB of flash. Code is on GitHub for the curious. All in all, the project is a multidisciplinary work of art, and it looks well-built enough to be enjoyed for years to come.

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2025 One-Hertz Challenge: HP Logic Probe Brought Into The Future

July 18, 2025 by Lewin Day 3 Comments

[Robert Morrison] had an ancient HP 545A logic probe, which was great for debugging SMT projects. The only problem was that being 45 years old, it wasn’t quite up to scratch when it came to debugging today’s faster circuitry. Thus, he hacked it to do better, and entered it in our 2025 One Hertz Challenge to boot!

[Robert’s] hack relied on the classic logic probe for its stout build and form factor, which is still useful even on today’s smaller hardware. Where it was lacking was in dealing with circuits running at 100 MHz and above. To rectify this, [Robert] gave the probe a brain transplant with a Sparkfun Alorium FPGA board and a small display. The FPGA is programmed to count pulses while measuring pulse widths and time, and it then drives the display to show this data to the user. There’s also a UART output, and [Robert] is actively developing further logic analyzer features, too.

You might be questioning how this project fits in the One Hertz Challenge, given it’s specifically built for running at quite high speeds. [Robert] snuck it in under the line because it resamples and updates the display on a once-a-second basis. Remember, as per the challenge site—”For this challenge, we want you to design a device where something happens once per second.” We’re giving you a lot of leeway here!

Often, old scopes and probes and other gear are really well built. Sometimes, it’s worth taking the best of the old physical hardware and combining it with modern upgrades to make something stout that’s still useful today. Meanwhile, if you’re cooking up your own neo-retro-logic probes, don’t hesitate to notify the tipsline!

2025 One Hertz Challenge: Metronalmost Is Gunning For Last Place

July 15, 2025 by Tyler August 18 Comments

We’ve just begun to receive entries to the One Hertz Challenge, but we already have an entry by [Mike Coats] that explicitly demands to be awarded last place: the Metronalmost, a metronome that will never, ever, tick at One Hertz.

Unlike a real metronome that has to rely on worldly imperfections to potentially vary the lengths of its ticks, the metronoalmost leaves nothing to chance: it’s driven by a common hobby servo wired directly to a NodeMCU ESP-12E, carefully programmed so that the sweep will never take exactly one second.

This is the distribution. The gap is around the value we explicitly asked for.

The mathematics required to aggressively subvert our contest are actually kind of interesting: start with a gaussian distribution, such as you can expect from a random number generator. Then subtract a second, narrower distribution centered on one (the value we, the judges want to see) to create a notch function. This disribution can be flipped into a mapping function, but rather than compute this on the MCU, it looks like [Mike] has written a lookup table to map values from his random number generator. The output values range from 0.5 to 1.5, but never, ever, ever 1.0.

The whole thing goes into a cardboard box, because you can’t hit last place with a masterfully-crafted enclosure. On the other hand, he did print out and glue on some fake woodgrain that looks as good as some 1970s objects we’ve owned, so there might be room for (un)improvement there.

While we can’t think of a better subversion of this contest’s goals, there’s still time to come up with something that misses the point even more dramatically if you want to compete with [Mike] for last place: the contest deadline is 9:00 AM Pacific time on August 19th.

Or, you know, if you wanted to actually try and win. Whatever ticks your tock.

2025 One Hertz Challenge: Valvano Clock Makes The Seconds Count

July 14, 2025 by Tyler August 3 Comments

A man named [Jim Valvano] once said “There are 86,400 seconds in a day. It’s up to you to decide what to do with them.” — while we couldn’t tell you who [Jim Valvano] was without a google search*, his math checks out. The quote was sufficiently inspirational to inspire [danjovic] to create a clock count those seconds precisely.

It’s a simple project, both conceptually and electrically. All it does is keep time and count the seconds in the day– a button press switches between counting down, counting up, and HH:MM:SS. In every mode, though, the number displayed will change at one Hertz, which we appreciate as being in the spirit of the challenge. There are only four components: an Arduino Nano, a DS3231 RTC module, a SSD1306 128×64 OLED module, and a momentary pushbutton. At the moment it appears this project is only on breadboard, which is a shame– we think it deserves to have a fancy enclosure and pride of place on the wall. Wouldn’t you be more productive if you could watch those 86,400 seconds ticking away in real time? We think it would be motivating.

Perhaps it will motivate you to create something for our One Hertz Challenge. Plenty of seconds to go until the deadline on August 19th, after all. If you’d rather while away the time reading, you can check out some of [danjovic]’s other projects, like this Cistertian-inspired clock, or this equally-inscruitable timekeeper that uses binary-coded octal.

*Following a google search, he was an American college basketball coach in the mid-20th century.