[ladyada] has a freshly-published and amazingly thorough tutorial on passive infrared (PIR) motion sensors. Most often seen in security floodlights and automatic doors, in creative hands these sensors ...

Building Arduino projects with multiple sensors can unlock powerful environmental monitoring, automation, and IoT applications. From DHT11 temperature sensors to motion, gas, and light detectors, ...

Let me introduce another simple microcontroller-based do-it-yourself circuit that detects motion and excites a light source in a flash. The “snooper” here is an ordinary passive infrared (PIR) motion ...