This “Shadow Display” Clock Is Just Plain Cool

I usually start these articles with an introduction that provides some context, but you don’t need that to appreciate this “Shadow Display” clock. It is simply an electromechanical clock that looks really cool.

This is the work of Smart Solutions For Home, which is a website that has a clumsy name and a lot of neat projects. One of those projects is a WiFi-connected electromechanical seven-segment display and it also looks really cool. The Shadow Display is a spin-off of that designed specifically to be used as a clock. And its minimalist monochromatic aesthetic will appeal to a lot of people who consider maximalism to be a travesty.

This is an open source project, but the full build tutorial isn’t yet available. However, it is essentially the same as the aforementioned seven-segment display and that does have a complete tutorial.

The brain of the Shadow Display is an ESP32-WROOM-32 microcontroller. Other ESP32 models would probably also work if they’re pin-compatible, but it is best to use the ESP32-WROOM-32 to avoid potential compilation errors. That goes on a custom PCB and, importantly, each digit of the clock needs its own PCB — though every PCB after the first “main board” is an “extension board” and doesn’t require an ESP32.

Those PCBs have the hardware (namely shift registers and H-bridges) for driving the electromagnets that actuate the segments. There is one electromagnet for each of the seven segments for each of the digits.

The mechanics of the Shadow Display are what set it apart from the older seven-segment display. The seven-segment display had flipping segments, but the Shadow Display has segments that move in and out on arms that are attracted to the electromagnets when active. That’s where the “shadow” part comes in: the protruding segments cast shadows and that’s what makes them visible. Most of the physical parts can be 3D-printed, but the faceplate can also be laser-cut.

You’ll need a programming adapter to flash your ESP32, but afterwards you can use the provided firmware. That’s pretty nifty and gives you a web interface for setting up the clock functionality. That even has a live graphical view showing the segments, which is really polished.