Even though Attiny85 is fitting here, I opted for Digispark just because of its plethora of features like USB programming interface, on-board voltage regulator, and Arduino IDE compatibility. The code ...

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!

If you’re new to the Arduino, you should read Brian McLaughlin’s introductory articles about the Arduino. The Sparkfun PIR Sensor can be found on the Sparkfun Website as well as the the datasheet.

It should also be possible to shrink the device to the size of the PIR module, with a small custom PCB or one of the many tiny Arduino compatible dev boards. For quick manual muting, check out the ...

It can optionally turn these back on when you are seated again. The cheap HC-SR501 PIR module’s range can also be adjusted with a trimpot for your specific scenario.