When it is running, this mechanical seven-segment display steps through the digits 0 to 9, each segment sliding out or sinking flush into the white faceplate with an audible click. IndoorGeek calls the project useless but fun, and that is exactly my favourite kind of build.
The whole electromagnetic side is homemade. Seven segment blocks move inside a frame, each one pushed and pulled by its own coil. The maker wound the solenoids from scratch, spinning enamelled copper wire onto orange plastic bobbins with a handheld Bosch drill, and each electromagnet has a central machine screw with a magnet sitting behind its segment. Energize a coil and the two magnets repel, pushing the segment out; cut the power and attraction to the core pulls it back in. Control signals come from an Arduino Nano on a solderless breadboard, switching through a custom protoboard driver built with IRFZ44N MOSFETs, flyback diodes, resistors and bus wiring. A modified 450W ATX computer supply feeds it through binding posts at 3.3V, 5V, 12V and ground. Every printed part came off an Ender-3 and was cleaned up with side cutters and sanded smooth.
The orange segments carry metal plates and ride in white guide blocks, and the maker says the motion is subtle and smooth and genuinely enjoyable to watch. A standard electronic seven-segment LED module appears alongside the mechanical unit for comparison.
Two open points stand out. The digits read well only when light strikes at a particular angle, and an improved version with LED backlighting is planned. Every coil also has to remain powered to keep its segment extended, and the maker thinks a latching mechanism would help. Current draw per digit is too high for the original four-digit clock plan; the maker plans thinner wire with more turns and a smaller electromagnet to bring consumption down. A detailed guide with STLs, schematics and code is published on Instructables.
Project by IndoorGeek. Watch it on their YouTube channel: