Stupid Pet Trick

For the Stupid Pet Trick, I made an electric toothbrush whose movements are controlled by a touch sensor.

The project was inspired by an eating machine from Charlie Chaplin’s movie “The Modern Times” – LINK. In the movie, a factory manager pushes for modernization of the production process by introducing an eating machine capable of feeding the workers while they are working. The machine is intended to render lunch breaks obsolete and thus reduce production costs. However, demonstration of the machine’s capabilities goes terribly wrong after a short circuit occurs somewhere in the device. The disorderly machine then starts throwing food at the face of Charlie Chaplin.

I wanted to “modernize” another daily routine – tooth brushing.  I took a toothbrush and attached it to a servo motor. I wanted to leave the control over toothbrush’s movements in the hands of the user, so I connected the servo to a force sensitive resistor. When the touch sensor is pressed, the toothbrush starts to move. The mechanism also includes two toggle switches corresponding to toothpaste and water respectively. The user first has to apply toothpaste on the brush and then turn on one toggle switch to signal that the action was completed. Upon dipping the brush into a glass of water, the user should turn on the other switch.


Indeed, one can cheat and simply turn on the switches without performing the actions tied to the switches, but doing so results in a dry and unpleasant experience. For optimal comfort, the user has to follow the prescribed procedure. Once both switches are turned on, the act of tooth brushing can commence.

So, when was the last time you brushed your teeth?

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