You’ll see PIRPin defined as “2” and OutPin defined as “3”—these correspond to where you plugged the PIR sensor and power relay into the Arduino. With your fan unplugged, turn it on ...

Get close enough to this raven and you’ll set off the PIR sensor, which triggers lighting ... This bird’s brain is an Arduino Nano, which is protected from the 12V supply with a boost converter.

The device collected dust in his room for some a while until he recently unearthed it, and noticed that a perfectly good PIR ... sensor’s signals, allowing him to easily wire it up to an Arduino.