“Introducing a mechanical digital clock with numbers strangely arranged.
- Usually, intermittent motion mechanism such as Geneva drive is necessary to decrease the number of the motors of mechanical digital clock. Contrary, this clock has a constant mesh (permanently engaged reduction gear) between tens and ones places of minute numbers. The ratio of the reduction gear is coprime (7 : 10) and 70 numbers can be shown by one motor.
- The order of the numbers are not random but optimized to minimize the time to update. Average angle of rotation of the central rotor is less than 360 degrees.
- To show the current time correctly when it is powered on, not only the WiFi connection capability but also origin finding mechanism are necessary. This clock has an one-way rotation blocking mechanism. The rotors for minutes are stopped at 00 when it moves backward, but pass through there when rotating forward.
- Herringbone gears are used to hold the rotors without central axes.
- two 28BYJ-48 stepper motors and driver board (around 2USD each)
- one M5Stamp-C3 micro controller with WiFi (5.90 - 6 USD)
- cables for pin headers
- M2 tapping screws with various lengths
- short M3 tapping screws (used to attach the stepper motor)
- lubricant (silicone oil or grease)”