This Device Turns Your Wristwatch Into a Desktop Clock While Winding It

Back in ye olden days, even checking the time took labor. If you wanted your watch to work, you had to regularly wind up the main spring that drove the various gears. Then a miracle happened: the self-winding watch came along. A self-winding watch includes a weight that moves around as the user walks and gesticulates, which keeps the spring under tension. The problem is that you have to wear the watch to keep it wound — take it off for a day or two and you'll have to reset the time. To avoid that hassle, shiura designed this Watch Winder Clock.

This is a pretty clever design and it probably doesn't work in the way you're thinking. When I first saw it, I assumed that it used the watch itself to show the time and occasionally rotated to wind the watch spring. But that isn't the case. Instead, it displays the time with hands like a normal analog clock. To set those hands to the correct positions, the center of the clock rotates. That rotation keeps the watch wound. It can either update 20 times an hour (showing only hours and minutes) or 200 times an hour (showing seconds, too).

The mechanism to set the hand positions is quite interesting. The center is the only motorized part and contains the seconds hand. It spins clockwise, with the second hand pushing on the minutes hand. The minutes hand then pushes on the hours hand. It rotates clockwise until the hours hand is where it should be, then reverses to counterclockwise to move the minutes hand where it should be, then clockwise again until the seconds hand is where it should be. This sequence means the mechanism only needs a single motor and the elaborate movement does a good job of winding the watch.

An M5Stamp C3 Mate ESP32-based development board keeps track of the time using WiFi and controls the operation of the 28BYJ-48 geared stepper motor. The mechanical parts were all 3D-printed and even the bearings were DIY (made with airsoft BBs). All of the STL files and code are available for download and this will work with most watches, but may require some tweaking for unusual watch sizes. The only configuration necessary is setting your timezone and WiFi credentials in the code.