Here is an ultra simple Arduino Night Alarm project wired around a handful of inexpensive and easily available components. One advantage of using Arduino as a security system is the flexibility!

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 ...

We’re still not sure exactly how [connornishijima]’s motion detector works, though many readers offered plausible explanations in the comments the last time we covered it. It works well… ...

What he came up with is a light-sensitive motion sensor that uses very little power. He knew that an Arduino would be overkill, and decided to try his hand at using the Arduino to develop code for ...

Make sure the adjustment knobs for sensitivity and on-time for the motion sensor are facing up so you can modify how sensitive your device is and how long it stays on to signal your Arduino.