Before we had fancy digital clocks — or even spring-driven mechanical clocks — most methods for measuring short periods of time relied on gravity moving something in a consistent, repeatable way. Both water clocks and hour glasses work under that principle. But it isn’t very fun to watch grains of sand fall, which is why Brett Oliver built a kitchen timer that uses a rolling ball to count the seconds.
This project started with a rolling ball escapement designed by JBV Creative. That mechanism simply flips back and forth as a ball bearing rolls from one side of the track to the other. Perpetual motion is impossible, of course, so this mechanism relies on a weight to turn the gear system that pivots the track. The ball is just there for timing: when it reaches the end of the track, it pushes a lever that releases the mechanism and lets the weight drop a little. This will work until the weight reaches the ground or runs out of cord.
Oliver turned that mechanism into a kitchen timer by replacing the weight with a stepper motor controlled by an Arduino Nano board. Because the motor ultimately drives the mechanism, it can continue operating as long as it has power. An LCD display shows the remaining time and the user can set that with a few buttons. An MP3 module plays a user-configured sound effect when it reaches zero. The speed of the stepper motor determines the time it takes the ball to traverse the track and the default is five seconds, so the timer increments by five seconds with each pass.
This may not be more practical than a standard kitchen timer, but it is much more interesting to watch.
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