How it works: When something triggers the sensor, the Arduino records that moment as triggerTime in Line 23, and compares it with the current time based on conditions in lines 26, 29, and 34.

Using motion detectors and an Arduino you can trigger lights, fans, or even an pneumatically controlled cleaver-wielding clown to help add your house to the “if you dare” list.

For his sensor, [Felix] is using a Moteino, a very tiny Arduino compatible board with solder pads for an RFM12B and RFM69 radio transceivers.

If you've always wanted to try to build an Arduino project, this may be a great way to start. Matt Williamson built a tiny, Arduino-based motion sensor that will SMS you when something moves by ...