Here's a Make HOWTO for converting a set of wind-up novelty chattering teeth to an electronic tooth-brushing timer and toothbrush holder — take your toothbrush out, start it running, and the teeth will chatter for two minutes (the recommended brushing time).
A switch is mounted under the toothbrush holder. When the toothbrush is lifted, the switch connects the battery to a timer circuit, which powers a servomotor. As the servo spins, it pushes a rod up and down. The rod opens and closes the teeth. When the timer is up the motor stops and the teeth go silent. When the toothbrush his returned to the holder the battery is disconnected.
We could have designed this timer using an Arduino or other microcontroller, but it's so simple that all you really need is that trusty timer chip, the 555. Here's how to make yours.
Toothy Toothbrush Timer [Steve Hoefer/Make]
(via Evil Mad Scientist
