If you have a YouTube page, you probably check your subscriber stats more than you really need to. In response to the issue of wanting to keep on top of this metric, quite a few makers have come up with their own sub counter that puts things on display at all times, sort of like a wall clock. This device, however, by YouTuber Zack’s Lab puts a different spin on things using an electromechanical seven-segment displays for numerical output.
Zack notes that not only do these displays look cool, but they don’t need power to maintain state once switched — and make a satisfying clicking sound when something has changed. The trick, though, is that each of these segments must be changed individually, by reversing the positive and negative voltages. While an H-bridge could be used to power such a device, this would mean four MOSFETs per segment, times seven segments, times five digits, meaning 140 components. Naturally, this wasn’t going to work, and the video goes over how the process can be simplified into something manageable, then reduced down to a four-layer PCB, actuated by MC338800 octal serial switches.
The system is run by an ESP32, and uses the YouTube API to extract subscriber data, then updates the segments only when there is a change. The build process is explained in the clip below, and schematics, code, and an explanation of how an interference issue was fixed are also available for your perusal.