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!

But there are really just the two speeds with the current programming. Inside the cool laser-cut box is an Arduino Uno and a 9V battery, plus a current-limiting resistor and the all-important buzzer.

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 ...