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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Clock Mixes Analog, Digital, Retrograde Displays

May 30, 2024 by Bryan Cockfield 6 Comments

Unique clocks are a mainstay around here, and while plenty are “human readable” without any instruction, there are a few that take a bit of practice before someone can glean the current time from them. Word clocks are perhaps on the easier side of non-traditional displays but at the other end are binary clocks or even things like QR code clocks. To get the best of both worlds, though, multiple clock faces can be combined into one large display like this clock build from [imitche3].

The clock is actually three clocks in one. The first was inspired by a binary clock originally found in a kit, which has separate binary “digits” for hour, minute, and second and retains the MAX 7219 LED controller driving the display. A standard analog clock rests at the top, and a third clock called a retrograde clock sits at the bottom with three voltmeters that read out the time in steps. Everything is controlled by an Arduino Nano with the reliable DS3231 keeping track of time. The case can be laser-cut or 3D printed and [imitche3] has provided schematics for both options.

As far as clocks builds go, we always appreciate something which can be used to tell the time without needing any legends, codes, or specialized knowledge. Of course, if you want to take a more complex or difficult clock face some of the ones we’re partial to are this QR code clock which needs a piece of hardware to tell the time that probably already has its own clock on it.

Customizable Bird Clock Sings The Hours By

May 16, 2024 by Bryan Cockfield 7 Comments

For those looking to build their own clocks, one of the easiest ways to get started is with a pre-built module that uses a simple quartz oscillator and drives a set of hands. This generally doesn’t allow for much design of the clock besides the face, and since [core weaver] was building a clock that plays bird songs, a much more hackable clock driver was needed to interface with the rest of the electronics needed to build this project.

The clock hands for this build are driven by a double stepper motor which controls an hour and minute hand coaxially but independently. Originally an H-bridge circuit was designed for driving each of the hands but they draw so little current in this configuration that they could be driven by the microcontroller directly. A DS3231 clock is used for timekeeping connected to an ATMega128a which controls everything else. At the start of each hour the clock plays a corresponding bird song by communicating with an mp3 module, and a remote control can also be used to play the songs on demand.

Bird clocks are not an uncommon thing to find off the shelf, but this one adds a number of customizations that let it fly above those offerings, including customizing the sounds that play on the hour and adding remote control capabilities, a lithium battery charging circuit, and a number of other creature comforts. If you’re looking for even more unique bird clock designs this binary bird clock might fit the bill.

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A two picture montage of the blackout logger, the left picture being the front e-ink display of the data logger in a black case and the second picture of the back of the data logger, with the raspberry pi pico show attached to an e-ink display, both sitting on a wooden table.

Blackout Logger Keeps Track Of Power Outages

November 26, 2022 by Abe Connelly 7 Comments

[Dmytro Panin] lives in Kyiv, Ukraine where there have been rolling blackouts to stabilize the power grid. To help keep track of when the blackouts might happen, be they planned or emergency, and to get more information on how long the blackouts last, [Dmytro] has created a blackout logger.

The build consists of a Raspberry Pi Pico that connects to a DS3231 real time clock (RTC) with a Waveshare 3.7 inch eInk display which [Dmytro] puts into a custom 3D printed case. The RTC has it’s own small power supply, often times from a coin cell battery attached to the module, allowing it to keep time when the module and other devices attached to it are powered off.

The Raspberry Pi Pico is programmed to “poll” every 30 seconds, writing the current time to a file. Should the unit lose power, the last time, within a 30 second window, is available when power is restored and the unit wakes up again. Since the RTC has kept the current time, there is enough information to display the duration of the blackout. The eInk screen ensures that the information is readily available, even when there is no power.

War is not the only reason blackouts can occur and we’ve covered some issues with blackouts in Texas and California in the US.

TshWatch Helps You Learn More About Yourself

April 3, 2022 by Arya Voronova 13 Comments

TshWatch is a project by [Ivan / @pikot] that he’s been working on for the past two years. [Ivan] explains that he aims to create a tool meant to help you understand your body’s state. Noticing when you’re stressed, when you haven’t moved for too long, when your body’s temperature is elevated compared to average values – and later, processing patterns in yourself that you might not be consciously aware of. These are far-reaching goals that commercial products only strive towards.

At a glance it might look like a fitness tracker-like watch, but it’s a sensor-packed logging and measurement wearable – with a beautiful E-Ink screen and a nice orange wristband, equipped with the specific features he needs, capturing the data he’d like to have captured and sending it to a server he owns, and teaching him a whole new world of hardware – the lessons that he shares with us. He takes us through the design process over these two years – now on the fifth revision, with first three revisions breadboarded, the fourth getting its own PCBs and E-Ink along with a, and the fifth now in the works, having received some CAD assistance for battery placement planning. At our request, he has shared some pictures of the recent PCBs, too!

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Careful Cuts Lets Logger Last A Year On A Coin Cell

March 14, 2022 by Bryan Cockfield 21 Comments

Coin cells are great for backup power for things like real-time clocks, or even for powering incredibly small mechanical devices like watches. But for something like a data logger, running on a standard microcontroller, most people would reach for a lithium cell of some sort. Not so with this build, though, which squeezes every joule of energy from a coin cell in order to run a data logger for a full year.

Most of the design and engineering required to improve the efficiency of the data logger involve standard practices for low-power devices such as shutting off unnecessary components and putting the device to sleep when not actively running, but this build goes far beyond that. The Vcc pin on the RTC was clipped which disables some of its internal logic but still keeps its basic functionality intact.

All of the voltage regulators were removed or disabled in favor of custom circuitry that doesn’t waste as much energy. The status and power LEDs were removed where possible, and the entire data logger is equipped with custom energy-efficient code as well.

If you’re starting a low-power project, even one that isn’t a datalogger, it’s worth checking out this build to see just how far you can go if you’re willing to hack at a PCB with cutting tools and a soldering iron. As to why this data logger needed such a low power requirement, it turns out it’s part of a kit being used in classrooms and using a coin cell brought the price of the entire unit down tremendously. Even if you have lithium cells on hand, though, it’s still worthwhile to check out the low power modes of your microcontroller.

Thanks to [Adrian] for the tip!

An orange 3D printed four digit clock with rotating segments

Be Mesmerized By The Latest Time Twister

December 18, 2021 by Chris Wilkinson 16 Comments

[Hans Andersson] has been creating marvelous twisting timepieces for over a decade, and we’re pleased to be able to share his latest mechanical clock contraption with our readers, the Time Twister 5.

In contrast to his previous LEGO-based clocks, version five of the Time Twister uses 3D printed segments, undoubtedly providing greater flexibility in terms of aesthetics and function. Each digit is a mechanical display, five layers vertical and three segments horizontal, with a total of three unique faces. Each layer of each display can be individually rotated by a servo, and this arrangement allows for displaying any number between zero and nine. The whole show is controlled by an Arduino MEGA and a DS3231 real-time clock.

Watching these upended prisms rotate into legible fifteen-segment digits is enjoyable enough already, but the mechanical sound created by this timepiece in motion is arguably even more satisfying. Check out the video below to see (and hear) for yourself. If you want to build one yourself, all the details are here.

We last covered [Hans Andersson] and his very first Time Twister clock way back in November 2011. Since then we’ve come across many impressive mechanical clocks, like this seven-segment work of art. We’re constantly impressed by the outstanding craftsmanship of these mechanical clocks, and it’s inspiring to see one of our OG horologists back in the saddle once more.

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