Building A 7-Segment Shadow Clock

August 10, 2025 by Lewin Day 6 Comments

There are plenty of conventional timepieces out there in the world; we’ve also featured a great many that are aesthetically beautiful while being unreadably esoteric. This neat “shadow clock” from [Smart Solutions for Home] is not conventional, but it’s still a clock you could use every day.

The display is made of four seven-segment digits, which have a subtle appearance. Each segment uses a solenoid to extend it forward out of the display, or to retract it flush with the faceplate. This creates a numerical display in all one color, with the physical protrusion doing the job of making the numbers visible. This is perhaps where the “shadow clock” name comes from, though you notice the protruding segments moreso than the shadows they cast on the faceplate.

Running the show is an ESP32, paired with H-bridges to drive the solenoids that make up the 7-segment displays. The H-bridges are driven via shift registers to reduce the number of GPIO pins needed. Unlike many other ESP32 clock builds, this one uses a DS3231 real-time clock module to keep accurate time, rather than solely relying on Internet-based NTP time servers. Configuring the clock can be done via a web interface. Design files are available online.

If you think you’ve seen this recently, maybe you’re thinkig of this prototype for a very similar display by [indoorgeek]. And that’s not the only way to make shadow clocks either. After all, the term is not enforced or defined by any global horological organization. Maybe that’s a good thing! Video after the break.

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2025 One Hertz Challenge: The Real-Time Clock The VIC-20 Never Had

August 8, 2025 by Lewin Day 5 Comments

Like many early microcomputers, the Commodore VIC-20 did not come with an interna real-time clock built into the system. [David Hunter] has seen fit to rectify that with an add-on module as his entry to the 2025 One Hertz Challenge.

[David]’s project was inspired by a product that Hayes produced in the 1980s, which provided a serial-port based real-time clock solution for computers that lacked one on board. The heart of the project is an Arduino Uno, which itself uses a Dallas DS3231 RTC module to keep accurate time. [David] then drew from an IEC driver developed by [Lars Pontoppidan] for the MM2IEC project. This enables the Arduino to report the time to the VIC-20 via its IEC port.

The project is a neat way to provide a real-time clock source to programs written in Commodore BASIC. It’s also perfectly compatible with the IEC bus, so it can be daisy chained along with printers and disk drives without issue. [David] hasn’t tested it with a Commodore 64, but he suspects it should work just as well on that platform, too.

If you’ve ever wanted to build something clock-based for the VIC-20 but didn’t know how, this is a great piece of hardware to solve that problem. Meanwhile, you might find joy in reading about real-time clock hacks for other systems like the Raspberry Pi. Meanwhile, if you’re working on your own nifty timekeeping projects, don’t hesitate to let us know!

Educational Arduino Clock Uses Analog Meters For Display

March 1, 2024 by Lewin Day 13 Comments

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.

Hackable OSHW CardClock Demands Attention

July 12, 2022 by Ryan Flowers 12 Comments

When examining a project, it’s easy to be jaded by a raw parts list. When the main component is an ESP8266, we might say “oh, another 8266 project. yawn!” But we’re certain that when you take a look at [Will Fox]’s Foxie CardClock, it’ll surely grab your attention.

As if all those beautiful LEDs weren’t enough, the rest of the device’s specifications are quite impressive. The core components might be common, but what often separates such projects is the software. With Over The Air updates supported via ArduinoOTA, updates are a snap. A light sensor helps to keep all those LEDs at a sane level, and a once-per-minute synchronization via NTP keeps the time accurate. Even if power is lost, a super-capacitor can hold the time accurate for up to two days with the built in RTC module. There’s even provisions for setting the time using the buttons on the front panel should you want to keep the gadget offline.

The entire project is open source, with the hardware released under the CERN Open Hardware Licence Version 2 and the firmware source code distributed as GPLv3. Users are encouraged to hack and modify the design, and all the information you need to build one of your own is available in the project’s GitHub repository. [Will] also offers a pre-assembled version of the clock for just $45 USD, but unfortunately it seems to be out of stock at the time of this writing.

If credit card sized hacks are your chosen area of interest, you will appreciate this crystal radio made from an actual Credit Card. Thanks to [Abe] for submitting the Tip!

NTP Server Gets Time From Space

January 20, 2022 by Bryan Cockfield 30 Comments

Cheap GPS units are readily available nowadays, which is great if you have something that needs to be very precisely located. Finding the position of things is one of many uses for GPS, though. There are plenty of ways to take advantage of some of the ancillary tools that the GPS uses to determine location. In this case it’s using the precise timekeeping abilities of the satellites to build a microsecond-accurate network time protocol (NTP) server.

GPS works by triangulating position between a receiver and a number of satellites, but since the satellites are constantly moving an incredibly precise timing signal is needed in order to accurately determine location from all of these variables. This build simply teases out that time information from the satellite network and ignores the location data. There are only two parts to this build, a cheap GPS receiver and a Raspberry Pi, but [Austin] goes into great detail about how to set up the software side as well including installing PPS, GPSd, and then setting up the actual NTP server on the Pi.

While this is an excellent way to self-host your own NTP server if you don’t have Internet access (or just want to do it yourself), [Austin] does note that this is probably overkill on timekeeping as far as accuracy goes. On the other hand, the Raspberry Pi has no built-in real time clock of its own, so this might actually be a cost-competitive way of timekeeping even when compared to something more traditional like a DS3231 RTC module.

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Save Your Original Xbox From A Corrosive Death

December 14, 2020 by Lewin Day 21 Comments

Fans of retro computers from the 8-bit and 16-bit eras will be well aware of the green death that eats these machines from the inside out. A common cause is leaking electrolytic capacitors, with RTC batteries being an even more vicious scourge when it comes to corrosion that destroys motherboards. Of course, time rolls on, and new generations of machines are now prone to this risk. [MattKC] has explored the issue on Microsoft’s original Xbox, built from 2001 to 2009.

Despite looking okay from above, the capacitor inside the Xbox had already started leaking underneath. Leaving this in the console would inevitably cause major damage.

The original Xbox does include a real-time clock, however, it doesn’t rely on a battery. Due to the RTC hardware being included in the bigger NVIDA MCPX X3 sound chip, the current draw on standby was too high to use a standard coin cell as a backup battery. Instead, a fancy high-value capacitor was used, allowing the clock to be maintained for a few hours away from AC power. The problem is that these capacitors were made during the Capacitor Plague in the early 2000s. Over time they leak and deposit corrosive material on the motherboard, which can easily kill the Xbox.

The solution? Removing the capacitor and cleaning off any goop that may have already been left on the board. The fastidious can replace the part, though the Xbox will work just fine without the capacitor in place; you’ll just have to reset the clock every time you unplug the console. [MattKC] also points out that this is a good time to inspect other caps on the board for harmful leakage.

We’ve seen [MattKC] dive into consoles before, burning his own PS1 modchip from sourcecode found online. Video after the break.

Edit: As noted by [Doge Microsystems], this scourage only effects pre-1.6 Xboxes; later models don’t suffer the same problem, and shouldn’t be modified in this way.

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Choosing The Right RTC For Your Project

September 30, 2020 by Lewin Day 27 Comments

When it comes to measuring time on microcontrollers, there’s plenty of ways to go about things. For most quick and dirty purposes, such as debounce delays or other wait states, merely counting away a few cycles of the main clock will serve the purpose. Accurate to the tens of milliseconds, they get the average utility jobs done without too much fuss.

However, many projects are far more exacting in their requirements. When you’re building a clock, or a datalogger, or anything that relies on a stable sense of passing time for more than a few minutes, you’ll want a Real Time Clock. So called due to their nature of dealing with real time, as we humans tend to conceive it, these devices take it upon themselves to provide timekeeping services with a high degree of accuracy. We’ve compiled a guide to common parts and their potential applications so you can get things right the first time, every time.

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