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!

While PIR sensors can be used with Arduino and other microcontroller boards, those best-suited for hobby use are smart enough to perform simple tasks without any programming.

TK has combined a PIR with an Arduino to create a smart safety light for the house or workshop. Follow along as this gets built out into a more extensive project.

A PIR sensor on the front of the can detects when somebody gets close, and plays a message reminding them to make use of the trash cans provided on the playground.