[over9k] used his Arduino to set up a laser trip wire. The laser is mounted along side the Arduino, reflects off of a mirror, and shines on a photoresistor that interfaces via a voltage divider. The ...

[Andy] stuffed some more RAM onto an Arduino Mega and his three-part walk through on the design, construction, and software is a great read and one of the more ‘hard core’ Arduino builds we’ve seen.