At one point in time mechanical seven segment displays were ubiquitous, over time many places have replaced them with other types of displays. [Sebastian] has a soft spot for these old mechanically actuated displays and has built an open-source 7-segment display with some very nice features.
We’ve seen a good number of DIY 7-segment displays on this site before, the way [Sebastian] went about it resulted in a beautiful well thought out result. The case is 3D printed, and although there are two colors used it doesn’t require a multicolor 3d printer to make your own. The real magic in this build revolves around the custom PCB he designed. Instead of using a separate electromagnets to move each flap, the PCB has coil traces used to toggle the flaps. The smart placement of a few small screws allows the small magnets in each flap to hold the flap in that position even when the coils are off, greatly cutting down the power needed for this display. He also used a modular design where one block has the ESP32 and RTC, but for the additional blocks those components can remain unpopulated.
The work he put into this project didn’t stop at the hardware, the software also has a great number of thoughtful features. The ESP32 running the display hosts a website which allows you to configure some of the many features: the real-time clock, MQTT support, timer, custom API functions, firmware updates. The end result is a highly customizable, display that sounds awesome every time it updates. Be sure to check out the video below as well as his site to see this awesome display in action. Also check out some of the other 7-segment displays we’ve featured before.
That’s a neat design and the daisy-chaining is awesome.
Really cool features and very polished.
It is, and I assume you could add on a seconds display as well, if you wanted? Wonder if it’s fast enough for tenths or hundredths?
One switch cycle takes about 100 ms, so in theory you could toggle it every tenth of a second. That said, the coils heat up quite a bit, so in practice I usually recommend switching roughly once per second.
Using flip segments that hold their position like latching relays is an old trick in industry, which has been building 7-segment displays this way at least since 1980 or so. One interesting glitch we found was that we had to be careful selling them to scrapyards because the big magnet that picks up cars could flip the digits on the truck scale display from over 100 ft away.
Technically isn’t it a 14-segment display, with that split-segment design? (I know, I know, they can’t be flipped independently…)
Either way it looks awesome!
Thanks! That little divider in the middle of the segments is purely for looks—it just looks so much better. But hey, it’s still only 7 segments :)