Interconnected circuits for controlling the clock

Tick, Tock, Train Station Clock

December 31, 2025 by John Elliot V 8 Comments

We’ve seen a few H-bridge circuits around these parts before, and here’s another application. This time we have an Old Train Station Clock which has been refurbished after being picked up for cheap at the flea market. These are big analog clocks which used to be common at railway stations around the world.

This build uses an ESP32 C3-mini microcontroller (PDF) in combination with an A4988 Microstepping Motor Driver (PDF). The logic is handled with MicroPython code. The A4988 provides two H-bridge circuits, one for each of two stepper motors, only one of which is used in this build.

The controller for this clock needs to send an alternating positive then negative DC pulse every minute to register that a minute has passed so the clock can update its hour hand and minute hand as appropriate. The ESP32 and the A4988 H-bridge cooperate to make that happen. The wifi on the ESP32 C3-mini is put to good use by facilitating the fetching of the current time from the internet. On an hourly basis the clock gets the current time with a HTTP call to a time server API, for whatever is suitable for your time zone.

Thanks to [PiotrTopa] for writing in to let us know about his project. If you’re interested in learning more about H-bridge applications be sure to check out Introduction To The H-bridge Motor Controller and A H-Bridge Motor Controller Tutorial Makes It Simple To Understand.

Get To The Games On Time With This Ancient-Style Waterclock

December 3, 2025 by Tyler August 2 Comments

One easy way to make a very accurate clock is with a WiFi-enabled microcontroller like an ESP32 and a display: set up NTP, and you’ll never be off by more than a minute. This water clock project by [Liebregts] is not like that — there are no electronics to speak of, and if the clock is ever in sync to within a single minute, well, we’d be surprised.

We’re impressed to see it working regardless. Sure, it’s not exactly high-tech; the floating siphon mechanism [Liebregts] is using to get a steady flow out of the main reservoir dates back to 250 BC. On the other hand, since this style of time keeper has been out of fashion since the fall of Rome, [Liebregts] couldn’t just grab something off GitHub or ask ChatGPT to design it for them. This is real human engineering. The reservoir is even scaled to the four-hour timing of [Liebregts] workday — it gets refilled at lunch along with its maker.

The water clock in all its glory, plus diagrammatic labels.

In a clever build detail, the floating siphon tube also holds a pointer to an hour indicator. For minutes, his mechanism seems unique, though it’s related to another ancient trick, the Pythagorean cup. Pythagoras’s devious cup had a hidden siphon that spilled its contents if you filled it beyond a set level, and so does the secondary reservoir of [Liebregts] water clock.

Since the secondary reservoir is linked to a counterweight with a pivot, it goes up and down over the course of approximately 5 minutes — but rather than linking that to another linear indicator, [Liebregts] is using that mechanism to advance a saw-toothed gear that is marked with 5-12 in analog-clock fashion for a touch of modernity. See it in action in the demo video below.

That last part might confuse a time traveler from Ancient Rome or Greece, but they’d instantly recognize this creation as a clock, which many modern observers might not. Still, once they learn to read it you can be sure that [Liebergts]’s friends will never be late to a gladiator fight again — and not just because Constantine banned them in 325 AD. Apparently nobody listened to that ban anyway.

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Some renderings of shapes made from lines including triangles and a circle.

2025 One Hertz Challenge: Analog Clock For Microsoft Windows

August 4, 2025 by John Elliot V No comments

Our hacker [glgorman] sent in their submission for the One Hertz Challenge: an analog software clock for Microsoft Windows.

I guess we’d have to say that this particular project is a work-in-progress. There is no final clock, yet. But a number of yak’s have been shaved. For instance, we have code for computing geometric objects without using branch instructions, including points and lines and circles and such.

The notes dive deep into various rabbit holes. At one point we find ourselves computing the angle to the sun in the sky, that we may be able to cast the shadow of the clock hands on our clock face. The notes include miscellaneous source code snippets and various screenshots of geometric renderings which have been achieved so far.

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This Thermochromic Clock Is A Ray Of Sunshine

June 16, 2025 by Tyler August 5 Comments

It’s never a bad time to look at a clock, and one could certainly do worse than this delightful Paper Sunshine Clock by [anneosaur]. The sun-ray display is an interesting take on the analog clock, and its method of operation is not one we see every day, either.

Reading the clock is straightforward: there are twelve rays divided into two segments. Once you figure out that this artful object is a clock, it’s easy enough to guess that the rays give the hours, and half-rays are half-hours. In the photo above, it’s sometime between nine o’clock and nine thirty. Our Swiss readers might not be terribly impressed, but a “fuzzy” clock like this is quite good enough much of the time for many people.

Even the flex PCB holding the resistors looks like a work of art.

The title gives away its method of operation: it’s thermochromic paint! The paint is printed onto a piece of Japanese awagami paper, which is pressed against a flexible PCB holding an array of resistors. Large copper pads act as heat spreaders for the resistors. For timekeeping and control, an Atmega328PB is paired with a DS3231MZ RTC, with a coin cell for backup power when the unit is unplugged. (When plugged in, the unit uses USB-C, as all things should.) That’s probably overkill for a +/-30 minute display, but we’re not complaining.

The Atmega328PB does not have quite enough outputs to drive all those resistors, so a multiplexing circuit is used to let the 10 available GIPO control current to 24 rays. Everything is fused for safety, and [anneosaur] even includes a temperature sensor on the control board. The resistors are driven by a temperature-compensated PWM signal to keep them from overheating or warming up too slowly, regardless of room temperature. The attention to detail here is as impressive as the aesthetics.

[annenosaur] has even thought of those poor people for whom such a fuzzy clock would never do (be they Swiss or otherwise) — the Paper Sunshine Clock has a lovely “sparkle mode” that turns the rays on and off at random, turning the clock into an art piece. A demo video of that is below. If you find this clock to be a ray of sunshine, everything you need to reproduce it is on GitHub under an MIT or CC4.0 license.

This is not the first thermochromic clock we’ve featured, though the last one was numeric. If you must have minute accuracy in a thermochromic analog clock, we’ve got you covered there, too.

Special thanks to [anneosaur] for submitting the hack. If you’ve seen (or made) a neat clock, let us know! You won’t catch us at a bad time; it’s always clock time at Hackaday.

A Clock Made Out Of Electromechanical Relays

February 13, 2024 by Maya Posch 11 Comments

Electromechanical circuits using relays are mostly a lost art these days, but sometimes you get people like [Aart] who can’t resist to turn a stack of clackity-clack relays into a functional design, like in this case a clock (article in Dutch, Google Translate).

It was made using components that [Aart] had come in possession of over the years, with each salvaged part requiring the usual removal of old solder, before being mounted on prototype boards. The resulting design uses the 1 Hz time signal from a Hörz DCF77 master clock which he set up to drive a clock network in his house, as he describes in a forum post at Circuits Online (also in Dutch).

The digital pulses from this time signal are used by the relay network to create the minutes and hours count, which are read out via a resistor ladder made using 0.1% resistors that drive two analog meters, one for the minutes and the other for the hours.

Sadly, [Aart] did not draw up a schematic yet, and there are a few issues he would like to resolve regarding the meter indicators that will be put in front of the analog dials. These currently have weird transitions between sections on the hour side, and the 59 – 00 transition on the minute dial happens in the middle of the scale. But as [Aart] says, this gives the meter its own character, which is an assessment that is hard to argue with.

Thanks to [Lucas] for the tip.

Circle Full Of LEDs Becomes A Clock

February 27, 2021 by Rich Hawkes 5 Comments

Building a clock of some sorts seems to be a time honored tradition for hackers and LED clocks seem one of the most popular. You can build anything from a seven-segment display to a binary clock or something even more fancy. [Clueless] found a circle of LED rings online and with made an LED version of an analog clock.

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Vintage Meters Reborn As Steam Punk Clock

January 3, 2021 by Anool Mahidharia 30 Comments

[Build Comics], purveyors of comic strips “where tools are heroes”, have saved another pair of old, vintage, analog meters from the junkyard by converting them into a Meter Clock. The real heroes of the story are their trusty tools – Mac X the knife, Mr. TS the table saw and his trusty band of clamps, G. Rinder the angle grinder, Weldy the welder, Sharp Eye the marker, rounded up by Sandy the Sander and Jiggy Saw. The Drake & Gorham (London) meters going under the knife appear similar to vintage hardware from just after the end of World War II, such as this Ferranti Ammeter found at the Science Museum Group, making them at least 75 years old.

A small cam is used to engage the DST switch.

As you might expect, the conversion process is reminiscent of their previous projects. The original moving-coil movements are discarded, and the pointer is attached to a servo which will act as the new movement. Fresh dials are prepared to replace the original ampere markings with hours and minutes. To retain some of the original charm, the new dials have discoloration and blemishes replicated from the old dials.

The set screw which was once used to align the pointer with the zero mark on the dial is now used to activate a micro switch that enables daylight savings time. Two additional buttons provide a convenient interface to adjust the time. Precision time signals are derived from a DS3231 RTC module connected to an Arduino. A pair of seven segment displays are connected to the Arduino to make it easier to set the time. A piece of oak plank, surrounded by a metal angled frame, is used as a base for mounting the two meters so that the clock can be hung up on the wall.

If you’d like to build some more vintage inspired instrumentation, [Build Comics] have you covered with a Classy Weather Display or a Plant Moisture Gauge.

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