When it comes to educational electronic projects, it’s hard to go past building a clock. You learn tons about everything from circuit concepts and assembly skills to insights about the very nature of time itself. And you get a clock at the end of it! [hamblin.joe] wanted to do a simple project for kids along these lines, so whipped up a neat design using analog meters to display the time.

The build relies on that old stalwart, the Arduino Uno, to run the show. It’s hooked up to a DS3231 real-time clock module so it can keep accurate time for long periods, as is befitting a clock. Displaying the time is done via the use of two analog meters, each fitted with a custom backing card. One displays hours, the other, minutes. The analog meters are simply driven by the PWM outputs of the Arduino.

It’s not a hugely complex project, but it teaches so much. It provides an opportunity to educate the builders about real-time clocks, microcontroller programming, and even the concepts behind pulse width modulation. To say nothing of the physical skills, like learning to solder or how to assemble the laser-cut enclosure. Ultimately, it looks like a really great way for [hamblin.joe] and his students to dive into the world of modern electronics.

[Build Some Stuff] created an unusual spiral clock that’s almost entirely made from laser-cut wood, even the curved and bendy parts.

The clock works by using a stepper motor and gear to rotate the clock’s face, which consists of a large dial with a spiral structure. Upon this spiral ramp rolls a ball, whose position relative to the printed numbers indicates the time. Each number is an hour, so if the ball is halfway between six and seven, it’s 6:30. At the center of the spiral is a hole, which drops the ball back down to the twelve at the beginning of the spiral so the cycle can repeat.

The video (embedded below) demonstrates the design elements and construction of the clock in greater detail, and of particular interest is how the curved wall of the spiral structure consists of a big living hinge, a way to allow mostly rigid materials to flex far beyond what they are used to. Laser cutting is well-suited to creating living hinges, but it’s a technique applicable to 3D printing, as well.

Thanks to [Kelton] for the tip!

You have to be pretty ambitious to modify a clock to run for 50 years on a single battery. You also should probably be pretty young if you think you’re going to verify your power estimates, at least in person. According to [Josh EJ], this modified quartz analog clock, which ticks off the date rather than the time, is one of those “The March of Time” projects that’s intended to terrify incentivize you by showing how much of the year is left.

Making a regular clock movement slow down so that what normally takes an hour takes a month without making any mechanical changes requires some clever hacks. [Josh] decided to use an Arduino to send digital pulses to the quartz movement to advance the minute hand, rather than let it run free. Two pulses a day would be perfect for making a 30-day month fit into a 60-minute hour, but that only works for four months out of the year. [Josh]’s solution was to mark the first 28 even-numbered minutes, cram 29, 30, and 31 into the last four minutes of the hour, and sort the details out in code.

As for the low-power mods, there’s some cool wizardry involved with that, like flashing the Arduino Pro Mini with a new bootloader that reduces the clock speed to 1 MHz. This allows the microcontroller and RTC module to run from the clock movement’s 1.5 V AA battery. [Josh] estimates a current draw of about 6 μA per day, which works out to about 50 years from a single cell. That’s to be taken with a huge grain of salt, of course, but we expect the battery will last a long, long time.

[Josh] built this clock as part of the Low-Power Challenge contest, which wrapped up this week. We’re looking forward to the results of the contest — good luck to all the entrants!

That big grandfather clock in the library might be an impressive piece of mechanical ingenuity, and an even better example of fine cabinetry, but we’d expect that the accuracy of a pendulum timepiece would be limited to a sizable fraction of a minute per day. Unless, of course, you work at CERN and built  “the most accurate pendulum clock on the planet.”

While we’re in no position to judge [Daniel Valuch]’s claim, we’re certainly inclined to believe him, mainly because the 1950s-era Czechoslovakian pendulum clock his project was based on, the Elektročas HH3, was built specifically as a master clock for labs, power plants, and broadcast use. The pendulum of this mid-century beauty is made of the alloy invar, selected for its exceptionally low coefficient of thermal expansion. This ensures the pendulum doesn’t change length with temperature, but it still only brings the clock into the 0.1 second/day range.

Clearly that’s not good enough for a clock at CERN, the European Laboratory for Nuclear Research, where [Daniel] works as an RF engineer. With access to a 10-MHz timebase from a cesium fountain atomic clock — no less a clock than the one that’s used to define the SI second, by the way — [Daniel] looked for ways to sync the clock up to it. Now, we know what you’re thinking — he must have used some kind of PLL to give an electromagnetic “kick” to the bob to trim the pendulum’s period. Good guess on the PLL, but the trimming method is a little cruder — [Daniel] uses a stepper motor attached to the clock’s frame to pay out or retract a length of fine chain into a cardboard dish attached to the pendulum’s rod. The change in mass changes the pendulum’s center of gravity, which changes its effective length, and allows the clock to be tuned a couple of seconds per day.

It seems like [Daniel] is claiming that his chain-corrected clock won’t drift more than a second from the cesium clock for 158 million years. Again, we’ll take his word for it, but it’s a wonderfully ad hoc approach to tuning the clock, and we appreciate its simplicity.

Anyone can buy a clock, but building your own lets you express your creative flair along the way. [Edison Science Corner] did just that with this neat sci-fi looking design.

The build relies on an Arduino Pro Mini to run the show, paired with a DS3231 real-time clock module. The latter part is of great importance, as without it, the Arduino would not keep accurate time. The 3D printed enclosure looks nondescript from the outside. However, inside, it’s got a neat triangular structure which allows the time to be displayed in that attractive tessellated triangular fashion. There’s a black plastic separator between all the segments which stop unattractive bleed-through and really help with the final effect. The individual triangles are each lit by a NeoPixel LED, which are both addressable and capable of lighting up in RGB colors. It makes for an attractive and colorful display.

If you want to try something more traditional yet challenging, consider whipping up your own 7-segment displays. Video after the break.

Building a clock from parts is a right of passage for makers, and often represents a sensible introduction into the world of electronics. It’s also hard to beat the warm glow of Nixie tubes in a desktop clock, as [Joshua Coleman] discovered when building a Nixie tube clock for a friend.

The original decision to upcycle the chassis from an unrepairable Heathkit function generator came a little undone after some misaligned cutting, so the front panel ended up being redesigned and 3D printed. This ended up being serendipitous, as the redesigned front panel allowed the Nixie tubes to be inset within the metal chassis. This effect looks great, and it also better protects the tubes from impact damage.

Sourcing clones of the 74141 Nixie driver ICs ended up being easier than anticipated, and the rest of the electronics came together quickly. The decoders are driven by an Arduino, and the IN-4 Nixie tubes are powered by a bespoke 170 volt DC power supply.

Unfortunately four of the tubes were damaged during installation, however replacements were readily available online. The gorgeous IN-4 Nixie tube has a reputation for breaking easily, but is priced accordingly on auction sites and relatively easy to source.

The build video after the break should get any aspiring Nixie clock makers started, but the video description is also full of extra information and links for those needing help getting started.

We’re not short on clock hacks here at Hackaday, so why not check out a couple more? This retro-inspired LED clock looks like its right out of a parallel universe, or maybe this stunning Nixie clock driven by relays will strike your fancy.

Back in the old days, we didn’t have fancy digital clocks. No, we had good analog clocks with a big hand and a little hand, and if you wanted to know the time you had to look at the clock and figure out which number each hand was pointing at, or kind of pointing at. It wasn’t easy, and we liked it that way.

So now, along comes an analog clock that’s nothing but the hands — no dial, no numbers, just hands. How is such a thing possible? The clue is in the clock’s name: AKUROBATTO, and in the video below, which shows the acrobatic movements of the clock’s hands as it does its thing. Serial improbable-clock maker [ekaggrat singh kalsi] clearly put a lot of thought into this mechanism, which consists of the hands and a separate base. The hands are joined together at one end and powered by small stepper motors. The base has two docking areas, where servo-driven claws can grasp the hand assembly, either at the center pivot or at the tip of either hand. With a little bit of shuffling around at transition points, the hands sweep out the hours and minutes in a surprisingly readable way.

For as cool as the design of AKUROBATTO is, the internals are really something else. There are custom-built slip rings to send power to the motors and the Arduinos controlling them, sensors to determine the position of each hand, and custom gearboxes for the steppers. And the locking mechanisms on the base are worth studying too — getting that right couldn’t have been easy.

All in all, an impressive build. Whether displaying the time on a phosphorescent screen or a field of sequins, it seems like [ekaggrat] has a thing for unique clocks.

Student and hacker [prusteen] recently fell in love with the Pomodoro method of time management. That’s where you concentrate on your task for 25 minutes, then take a five-minute break, and repeat this four times with a longer break at the end. Initially, [prusteen] was keeping track on their phone, but hated having to change the timer value between Pomodoros and break times. In order to keep the flow mode engaged, [prusteen] came up with this darling little study buddy that does it all with the push of a button.

By default, this tomato shows the current time, which we think is a handy and often-overlooked feature of Pomodoro timer builds. Press that momentary switch on the front, and it starts counting upward to 25 minutes. Then it beeps in stereo through a pair of buzzers when the time is up, and automatically starts a five-minute break timer. Press it again and the display goes back to clock mode, although judging by the code, doing this will cancel the timer.

Inside the juicy enclosure is an Arduino Nano, an RTC, and a 7-segment display. We love the attention to detail here, from the little green leaves on top to the anatomically-correct dimple on the underside. And we always like to see lids that snap on with magnets. So satisfying. Check out the brief demo after the break, which unfortunately does not include any lid-snapping action.

Do you need more interaction with your Pomodoro timer? Build yourself a pomo-dachi instead.

When you have a small stock of vacuum fluorescent displays (VFDs) straight out of the 1976 Radio Shack catalog, you might sit around wondering what to do with them. When [stepawayfromthegirls] found out that his stash of seven DT-1704A tubes may be the last in existence, there was no question. They must be displayed! [stepawayfromthegirls]’ mode of display is this captivating clock build. Four VFDs with their aqua colored elements are set against a black background in a bespoke wooden case. Looking under the hood, the beauty only increases.

Keeping the build organized was not an easy task because the tubes are designed in such a way that each segment must be individually controlled. The needed I/O duties are provided by an Arduino Mega 2560 Pro (Embed). 28 2n3904’s each with their two resistors serve as drivers for each VFD segment.

The output of a  24 V AC transformer left over from the 1980s is rectified to 34 V of DC power which is then regulated to 27 V to power the tubes. Switching power supplies provide 6 V to the Arduino and 1.3 V to the filaments. If you look closely, you’ll also see a GPS module so that the clock doesn’t need to be set. To future-proof the clock against daylight savings time adjustments, a potentiometer on the back of the case allows the user to set custom hour offsets without editing any code.

We think the end result is a remarkably clean, simple, and elegant clock that he will be proud of for many years to come!

If VFD clock builds are your thing, then you’ll enjoy this Network Attached VFD Clock and a Mini VFD Clock with floating display.  And while not VFD based, we’d be silly to leave out the Boat Anchor Nixie Clock with enough knobs, switches, and buttons to delight even the fussiest of hacker.

Will Netflix’s nostalgic hit Stranger Things be back for a fourth series anytime soon? We could pull out a Ouija board and ask the spirits, but we’d much rather ask closer to the source, i.e. a spirit in the upside down. And you know that the best way to do that is with LEDs — one for each letter of the alphabet so the spirit can spell out their messages.

Although contact with the Demogorgon’s world isn’t likely with [danjovic]’s open-source Stranger Things board, you are guaranteed to get the time spelled out for you every minute, as in, ‘it’s twenty-five (or six) to four’. And if you want to freak out your unwitting friends, you can covertly send messages to it from your phone.

There are two versions now — the original desktop version, and one that hangs on the wall and uses a high-quality photo print for the background. Both use an ESP-01 and an Arduino to help drive the 26 RGB LEDs, and use a DS2321 real-time clock for timing. We love the enameled wiring job on the wall-mount version, but the coolest part has to be dual language support for English and Brazilian Portuguese. You can check out demos of both after the break.

We’ve seen many a word clock around here, but this is probably one of the few that’s dripping with pop culture. If it’s stunning modernism you want, take a look at this painstakingly-constructed beauty.