The Time Clock Has Stood The Test Of Time

January 8, 2026 by Kristina Panos 31 Comments

No matter the item on my list of childhood occupational dreams, one constant ran throughout: I saw myself using an old-fashioned punch clock with the longish time cards and everything. I now realize that I have some trouble with the daily transitions of life. In my childish wisdom, I somehow knew that doing this one thing would be enough to signify the beginning and end of work for the day, effectively putting me in the mood, and then pulling me back out of it.

But that day never came. Well, it sort of did this year. I realized a slightly newer dream of working at a thrift store, and they use something that I feel like I see everywhere now that I’ve left the place — a system called UKG that uses mag-stripe cards to handle punches. No it was not the same as a real punch clock, not that I have experience with a one. And now I just want to use one even more, to track my Hackaday work and other projects. At the moment, I’m torn between wanting to make one that uses mag-stripe cards or something, and just buying an old punch clock from eBay.

I keep calling it a ‘punch clock’, but it has a proper name, and that is the Bundy clock. I soon began to wonder how these things could both keep exact time mechanically, but also create a literal inked stamp of said time and date. I pictured a giant date stamper, not giant in all proportions, but generally larger than your average handheld one because of all the mechanisms that surely must be inside the Bundy clock. So, how do these things work? Let’s find out.

Continue reading “The Time Clock Has Stood The Test Of Time” →

The clock and the rebuilt calculator from which its VFD was donated.

An RPN Calculator And A Bonus VFD Clock From Casio Revival

January 5, 2026 by Tyler August 15 Comments

Have you heard the saying “the problem is the solution”? It seems to originate in the permaculture movement, but it can apply equally well to electronics. Take the problem [shiura] had: a Casio Mini CM-602 that had let out the magic smoke. The solution was a twofer: rebuild the Casio into a modern number cruncher with Reverse Polish Notation (RPN), and save the Vacuum Fluorescent Display (VFD) for a gorgeous WiFi clock.

[shiura]’s write-up includes a helpful guide for reverse engineering the pins on this sort of VFD, if you don’t happen to have the same model calculator (or VFD tube) they’re working with. If you’ve done this sort of thing, you know what to expect: power it up and kill power to the pins, one by one, to map out which segments or characters go out, thereby identifying the anodes and grid electrodes. The cathodes had already been ID’d from looking at the PCB. After that it’s just a matter of wiring the VFD to an ESP32 via a transistor array to get the voltages right, and voila! Clock. The code and case design files for this clock — including an editable .blend — are available via GitHub.

The calculator half of the project is an incredibly elegant hack that relies on the fact that the Casio’s CPU has the same pin pitch as modern micros: 2.54 mm, or 0.1″, so an RP2040 zero can sit in the footprint of the original CPU, scanning the keypads with its GPIO. Then an I2C display is separately wired up to replace the clockified VFD. Perhaps some driver circuitry for the VFD died, or [shiura] salvaged the display before deciding to save the calculator, because otherwise we see no reason why this brain transplant couldn’t be done while keeping the original display. Admittedly having two lines on the display instead of one make the “new” calculator a tad more usable. The code for that is also available on GitHub, and while the readme is in Japanese, machine translations have gotten pretty good and the code is quite readable on its own.

Longtime readers will likely be familiar with [shiura]’s work, with a number of finely crafted clocks having been featured from the Japanese maker, along with vintage pocket computer repairs. Bringing both together makes this twin hack particularly on-brand.

Continue reading “An RPN Calculator And A Bonus VFD Clock From Casio Revival” →

Qron0b: A Minimalist, Low-Power BCD Wristwatch

January 2, 2026 by Maya Posch 19 Comments

Over the decades we have seen many DIY clocks and wrist watches presented, but few are as likely to get you either drawing in the crowds, or quietly snickered at behind your back, as a binary watch of some description does. A wrist watch like [qewer]’s qron0b project which also uses BCD encoding to display the current time is among our more rare project types here, with us having to go all the way back to 2018 for a similar project as well as a BCD desk clock.

As is typical, a single CR2032 coin cell powers the entire PCB, with an ATtiny24A or compatible as the MCU, a DS1302 RTC and the requisite 4×4 LED matrix to display the hours and minutes. Technically three LEDs are unneeded here, but it looks nicely symmetrical this way, and the extra LEDs can be used for other tasks as the firmware is expanded from the current setting and reading of the time.

The AVR C firmware can be found in the above linked GitHub repository, along with the KiCad PCB project and FreeCAD design files for the watch body. The body accepts a 22 mm GT2/GT3-style watch strap to complete the assembly. With a single CR2032 you’re assured of at least a few months of runtime.

Interconnected circuits for controlling the clock

Tick, Tock, Train Station Clock

December 31, 2025 by John Elliot V 9 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.

How Wind Nearly Took Down Boulder NTP

December 29, 2025 by Fenix Guthrie 28 Comments

NTP is one of the most interesting and important, but all too forgotten, protocols that makes the internet tick. Accurate clock synchronization is required for everything ranging from cryptography to business and science. NTP is closely tied around a handful of atomic clocks, some in orbit on GPS satellites, and some in laboratories. So the near-failure of one such atomic clock sparked a rather large, and nerdy, internet debate.

On December 17, 2025, the Colorado front range experience a massive wind storm. The National Center for Atmospheric Reassure in Boulder recorded gusts in excess of 100 mph (about 85 knots or 160 kph). This storm was a real doozy, but gusts this strong are not unheard of in Boulder either. That is no small reason the National Renewable Energy Laboratory (now the National Laboratory of the Rockies) has a wind turbine testing facility in the neighborhood.

Continue reading “How Wind Nearly Took Down Boulder NTP” →

Silicon-Based MEMS Resonators Offer Accuracy In Little Space

December 24, 2025 by Maya Posch 2 Comments

Currently quartz crystal-based oscillators are among the most common type of clock source in electronics, providing a reasonably accurate source in a cheap and small package. Unfortunately for high accuracy applications, atomic clocks aren’t quite compact enough to fit into the typical quartz-based temperature-compensated crystal oscillators (TCXOs) and even quartz-based solutions are rather large. The focus therefore has been on developing doped silicon MEMS solutions that can provide a similar low-drift solution as the best compensated quartz crystal oscillators, with the IEEE Spectrum magazine recently covering one such solution.

Part of the DARPA H6 program, [Everestus Ezike] et al. developed a solution that was stable to ±25 parts per billion (ppb) over the course of eight hours. This can be contrasted with a commercially available TCXO like the Microchip MX-503, which boasts a frequency stability of ±30 ppb.

Higher accuracy is achievable by swapping the TCXO for an oven-controlled crystal oscillator (OCXO), with the internal temperature of the oscillator not compensated for, but rather controlled with an active heater. There are many existing OCXOs that offer down to sub-1 ppb stability, albeit in quite a big package, such as the OX-171 with a sizable 28×38 mm footprint.

With a MEMS silicon-based oscillator in OXCO configuration [Yutao Xu] et al. were able to achieve a frequency stability of ±14 ppb, which puts it pretty close to the better quartz-based oscillators, yet within a fraction of the space. As these devices mature, we may see them eventually compete with even the traditional OCXO offerings, though the hyperbolic premise of the IEEE Spectrum article of them competing with atomic clocks should be taken with at least a few kilograms of salt.

Thanks to [anfractuosity] for the tip.

Reverse Sundial Still Tells Time

December 10, 2025 by Tyler August 11 Comments

The Dutch word for sundial, zonnewijzer, can be literally translated into “Sun Pointer” according to [illusionmanager] — and he took that literal translation literally, building a reverse sundial so he would always know the precise location of our local star, even when it is occluded by clouds or the rest of the planet.

The electronics aren’t hugely complicated: an ESP32 dev board, an RTC board, and a couple of steppers. But the craftsmanship is, as usual for [illusionmanager], impeccable. You might guess that one motor controls the altitude and the other the azimuth of the LED-filament pointer (a neat find from AliExpress), but you’d be wrong.

This is more like an equatorial mount, in that the shaft the arrow spins upon is bent at a 23.5 degree angle. Through that hollow shaft a spring-steel wire connects the arrow to one stepper, to drive it through the day. The second stepper turns the shaft to keep the axis pointed correctly as Earth orbits the sun. See the demo video embedded below for full details.

Either way you can get an arrow that always points at the sun, but this is lot more elegant than an alt-az mount would have been, at the expense of a fiddlier build. Given the existence of the orrery clock we featured from him previously, it’s safe to say that [illusionmanager] is not afraid of a fiddly build. Doing it this way also lets you read the ticks on the base just as you would a real sundial, which takes this from discussion piece to (semi) usable clock.

Continue reading “Reverse Sundial Still Tells Time” →