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 ...

PIR module usually requires an initial warm-up period for the sensing elements to come up to the operating mode. This usually takes not less than 30 seconds. So a 30 seconds delay is intentionally ...

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 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.

You’ll see PIRPin defined as “2” and OutPin defined as “3”—these correspond to where you plugged the PIR sensor and power relay into the Arduino.