Connecting PIR sensors to a microcontroller is really simple. The PIR acts as a digital output, it can be high voltage or low voltage, so all you need to do is listen for the pin to flip high (detected) or low (not detected) by listening on a digital input on your Arduino
Power the PIR with 5V and connect ground to ground. Then connect the output to a digital pin. In this example we’ll use pin 2.
The code is very simple, and is basically just keeps track of whether the input to pin 2 is high or low. It also tracks the state of the pin, so that it prints out a message when motion has started and stopped.