You can buy a ready-made Drawdio pencil that just works, or you can build it yourself with a kit of parts from places like Adafruit Industries. I decided to build it. As this was my first time soldering in a long time, it's a good project because there aren't too many places to mess up! Adafruit provides a very detailed tutorial on how to build Drawdio, so that's what I used.
The concept is pretty straight forward. You have a speaker powered by one AAA battery, set up in an open circuit. The second you close the circuit with your body, the speaker sounds. Your body closes the circuit because you are touching the conductive tape with your drawing hand. The tape is connected to the circuit board/speaker, then out to the top of the pencil where it connects to the graphite inside the pencil using a thumbtack. You draw with the pencil, and touch the drawing with your other hand, thereby closing the circuit. Okay, it might be easier just to watch! Notice how the pitch adjusts depending on distance between hand and pencil.
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