Cheap, easy-to-control Arduino boards are the bread and butter of garage inventors the world over. Regular Arduinos are already pretty small, but the AAduino design shrinks things down to the size of—you guessed it—an AA battery.
DIYer Johan Kanflo was looking for a way to shrink down the (already small) Tiny328 board he was using, and find a battery housing for self-contained power at the same time.
His solution: make an Arduino board the size of an AA battery, invert the battery terminals, and stick it in a housing alongside two normal AA batteries. The result is a tiny board that’s perfect for basic wireless communications, without needing any kind of power source.
The complete build of materials and instructions are available on GitHub. It’s a little beyond a novice DIYer, but then again, if you’re the kind of person to get excited about a tiny open-source board, you can probably handle a little soldering.