A Non-Split Flap Clock

Split-flap clocks work by sequentially flipping flaps from a rotary mechanism so that the top and bottom combine to show the time in digits. Such displays have been in use for many decades.

As noted by pseudonymous creator shiura, split-flap clocks do have a few disadvantages, such as having a split in the middle of the digit and depending on gravity to do the flipping. Not one, apparently, to complain without having a solution, this hacker got to work building a similar display mechanism that sequences whole-digit flaps. Introducing the Non-Split Flap Digital Clock.

The trick to how this device works is that each flap has a front and a back side. The clock’s internal cavity is designed in such a way that the flaps automatically flip in the back when rotated 360º, while maintaining a forward position in the front viewing window. The one and 10-minute flaps move on their own rotors, as the hours flaps move together.

Each rotor is linked together with a carryover mechanism, allowing a single 28BYJ-48 stepper to move the numbers in sequence. There’s also a hook/ratchet mechanism that enables automatic alignment of the one-minute flaps, is performed automatically every minute and upon power-up/reset.

More info on the build, as well as print files and Arduino code, is available via the project write-up. Shiura implemented the build with both an Arduino Nano and a Waveshare RP2040-Zero, though he notes that you could use any microcontroller to run this clock. You’ll, of course, want to ensure your device is up to the task accuracy-wise, but time adjustment can be done by simply rotating the hour and 10-minute wheels as needed.