Counter-rotating clock
By Andrew Gregory. Posted
If you’re ever stuck for a bit of inspiration and you need something to spark your imagination, you could do a lot worse than try your hand at building a clock. They combine as much or as little mathematics as you’re comfortable with, physical, moving parts, LCD/OLED/otherwise pixellated displays, audio feedback, and require a means of setting the time as well as adjusting it for daylight savings time. There’s a lot to get your teeth into, plus there’s the fact that the internet is awash with brilliant designs that, even though they’re constrained by the same set of requirements, all seem to be slightly different.
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This project was inspired by one of maker Joren’s students, who was trying to program an analogue clock in Java. Somehow a bug was causing the numbers to rotate rather than the hands; Joren saw this and decided to make the image on screen a reality.
Rather than start from scratch, Joren’s device takes a standard wall clock and clamps it into a geared ring with 216 teeth. This balances on top of two 36-tooth gears, which rotate the clock so that the hour hand is always pointing in the same direction. The other two hands move as normal.
The electronics in this creation are simple: there’s a single stepper motor to drive one of the 36T gears, an L298 motor driver, a DS3231 real-time clock, and an Arduino Nano, which calculates how quickly the gears should rotate. For bonus points, the user can set the minute or second hand to be the static hand – though we’re not sure this would make the clock any easier to read.
Features Editor Andrew trawls the internet for Cool Stuff while keeping the magazine running smoothly.
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