2025 One Hertz Challenge: Metronalmost Is Gunning For Last Place

July 15, 2025 by Tyler August 9 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 2 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.

2025 One Hertz Challenge: An Ancient Transistor Counts The Seconds

July 12, 2025 by Jenny List 8 Comments

If you’ve worked with germanium transistors, you’ll know that many of them have a disappointingly low maximum frequency of operation. This has more to do with some of the popular ones dating from the earliest years of the transistor age than it does to germanium being inherently a low frequency semiconductor, but it’s fair to say you won’t be using an OC71 in a high frequency RF application. It’s clear that [Ken Yap]’s project is taking no chances though, because he’s using a vintage germanium transistor at a very low frequency — 1 Hz, to be exact.

The circuit is a simple enough phase shift oscillator that flashes a white LED, in which a two transistor amplifier feeds back on itself through an RC phase shift network. The germanium part is a CV7001, while the other transistor is more modern but still pretty old these days silicon part, a BC109. The phase shift network has a higher value resistor than you might expect at 1.8 MOhms, because of the low frequency of operation. Power meanwhile comes from a pair of AA cells.

We like this project not least for its use of very period passive components and stripboard to accompany the vintage semiconductor parts. Perhaps it won’t met atomic standards for timing, but that’s hardly the point.

This project is an entry in the 2025 One Hertz Challenge. Why not enter your own second-accurate project?

Listen To The Sound Of The Crystals

July 11, 2025 by Jenny List 33 Comments

We’re all used to crystal resonators — they provide pretty accurate frequency references for oscillators with low enough drift for most of our purposes. As the quartz equivalent of a tuning fork, they work by vibrating at their physical resonant frequency, which means that just like a tuning fork, it should be possible to listen to them.

A crystal in the MHz might be difficult to listen to, but for a 32,768 Hz watch crystal it’s possible with a standard microphone and sound card. [SimonArchipoff] has written a piece of software that graphs the frequency of a watch crystal oscillator, to enable small adjustments to be made for timekeeping.

Assuming a microphone and sound card that aren’t too awful, it should be easy enough to listen to the oscillation, so the challenge lies in keeping accurate time. The frequency is compared to the sound card clock which is by no means perfect, but the trick lies in using the operating system clock to calibrate that. This master clock can be measured against online NTP sources, and can thus become a known quantity.

We think of quartz clocks as pretty good, but he points out how little it takes to cause a significant drift over month-scale timings. if your quartz clock’s accuracy is important to you, perhaps you should give it a look. You might need it for your time reference.

Header: Multicherry, CC BY-SA 4.0.

Shadow Clock Shows The Time On The Wall

July 5, 2025 by Lewin Day 12 Comments

What if you build a clock that displayed the time not just on its own, but in its shadows as well? [Lewis] from [DIY Machines] has done just that, with a nifty 3D-printed shadow clock build.

The clock itself, based on a design by [shiura], has a hollow rim inside which are the two hands which actually display the time. The hands appear to almost float inside the clock, a tricky visual effect of the design which instantly catches the eye. The trick is simple—the minute hand is physically attached to the outer rotor, which sets its position. Meanwhile, the floating hour hand pivots freely around the center of the clock, with a secret magnet within. This magnet is attracted to a complementary magnet in the hour rotor—as that rotor turns, the hour hand points at the magnets inside.

So far, it’s already a cool clock. The bonus feature is that [Lewis] realized this design could show an even larger clockface on the wall behind, merely by using its shadows. Thus, the clock features an LED light source which can project the clock’s shadows into a much larger display than the desktop timepiece itself.

As for the electronics, it’s straightforward stuff. An ESP8266 devboard runs the show, turning stepper motors and controlling addressable LEDs to make the clock do its thing. It also queries a network time server in order to ensure the displayed time is always accurate to the second.

We’ve featured some other excellent clocks over the years, like this incredible thermochromic build. Video after the break.

Continue reading “Shadow Clock Shows The Time On The Wall” →

CIS-4 Is A Monkish Clock Inside A Ceiling Lamp

July 4, 2025 by Tyler August 2 Comments

It’s always clock time at Hackaday, and this time we have an interesting hack of a clock by [danjovic]– the CIS4, a Cistercian digital clock.

The Cistertians, in case you weren’t paying close attention to European holy orders during the 13th to 15th centuries were the group of monks you’d most likely have found us in. They were the hackers of the middle ages, establishing monestaries across western Europe that were chock full of hacks– including their own numeral system. Cistercian numerals were much more efficient (in spaces and penstrokes) than the Roman numerals they replaced, and even the “Arabic” numerals that replaced them. A single glyph could record anything from 1 to 9,999. (The Europeans hadn’t yet cottoned on to zero.)

The Cistertian glyphs reduced to a 4×4 display.

Depending how you wanted to count time, a single glyph could be used; it looks like [danjovic] is using the thousands and hundreds portions of the glyph for hours and the tens and ones for minutes. This is all accomplished with a 4×4 neopixel matrix, run by an Attiny85 Digispark with a DS3231 RTC module keeping time. A slight simplification is required to reduce the glyphs to 4×4, but we don’t think the monks would mind. For those of us who don’t wear tonsures, an easy read mode scrolls the time in Arabic numerals. (Which still aren’t super easy,with only 4×4 LEDs to display them. See the demo video embedded below and try and guess the time.)

One nice quality of life feature is an LDR for ambient light detection, to automatically adjust the neopixels’ brightness. The hackiest part, which we thought was really clever, is the enclosure: it’s a cheap LED ceiling light. This provides a diffuser, housing and mounting hardware with decent design for no effort. A 3D-printed mask sits between the diffuser and the LEDs and doubles as a PCB holder. All very elegant.

[danjovic] did include a buzzer in the design, but does say if its been programed to sound off for matins, nones and vespers. In any case, at least it’s easier to read than his binary-coded-octal clock that we featured a few years back. This isn’t our first look at this number system,so evidently people can read them with practice.

Have you made or seen a cool clock? Send us a tip. We always have time for clocks. Continue reading “CIS-4 Is A Monkish Clock Inside A Ceiling Lamp” →

2025 One Hertz Challenge: Electromechanical CMOS Clock Keeps In Step With Mains Frequency

July 4, 2025 by Tyler August 12 Comments

Some people can’t be bothered to read the analog face of a traditional clock. Some people cannot stand the low frequency “hum” of mains current. If you are in either of those categories, you probably don’t want to make [Christian]’s handsome and well-documented electromechanical CMOS clock.

As you might guess from the name, the clock uses CMOS logic, based around a 12 bit counter, to provide the divider circuits 24 (daily) and 60 (minutes and seconds). Specifically, the circuits are based around a CD4040 twelve-bit adder. Those signals go through DAC circuits based around DAC0808 chips to drive some very nice coil meters for hours and minutes in lieu of the traditional clock face. Taking the time to make a CMOS clock circuit from adder chips is respectable enough in this era of instant-gratification through micro-controllers, and we dig the blinkenlights built into the circuits, but it’s what is being added that is where things get really interesting.

[Christian] had the bright idea that a stepper motor could be driven via the mains, simply by using a capacitor to offset the waveforms on the coils by 90 degrees. With a 200-step stepper motor, [Christian] gets one revolution per second out of the 50 Hz grid; this generates the seconds signal for his CMOS chips by the simple expedient of a 3D printed arm and a light barrier. Once per second, the light is interrupted by the spinning arm, creating a pulse for the clock circuits to add up. Check it out in action in the demo video below.

This project also seems to have the distinction of being the first project submitted to our One Hertz Challenge. It’s not just for clocks, but keep an eye on your clock because entries are only open until 9:00 AM Pacific time on August 19th.

Continue reading “2025 One Hertz Challenge: Electromechanical CMOS Clock Keeps In Step With Mains Frequency” →