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!

The code is an Arduino project for the Digispark Attiny85 to turn on a light source when the PIR sensor detects something. Note that after powering the PIR sensor module, it needs about 10 to 60 ...

Present consists of just a PIR sensor and Arduino in a 3D printed enclosure to snap onto your monitor.