Using A PIR W/Arduino | PIR Motion Sensor - Adafruit Learning System

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• Overview
• How PIRs Work
• Connecting to a PIR
• Testing a PIR
• Using a PIR w/Arduino
• CircuitPython Code
• Example Projects
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Using a PIR w/Arduino

Reading PIR Sensors

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

Its likely that you'll want retriggering, so be sure to put the jumper in the H position!

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. Download File Copy Code /* * PIR sensor tester */ int ledPin = 13; // choose the pin for the LED int inputPin = 2; // choose the input pin (for PIR sensor) int pirState = LOW; // we start, assuming no motion detected int val = 0; // variable for reading the pin status void setup() { pinMode(ledPin, OUTPUT); // declare LED as output pinMode(inputPin, INPUT); // declare sensor as input Serial.begin(9600); } void loop(){ val = digitalRead(inputPin); // read input value if (val == HIGH) { // check if the input is HIGH digitalWrite(ledPin, HIGH); // turn LED ON if (pirState == LOW) { // we have just turned on Serial.println("Motion detected!"); // We only want to print on the output change, not state pirState = HIGH; } } else { digitalWrite(ledPin, LOW); // turn LED OFF if (pirState == HIGH){ // we have just turned of Serial.println("Motion ended!"); // We only want to print on the output change, not state pirState = LOW; } } } /* * PIR sensor tester */ int ledPin = 13; // choose the pin for the LED int inputPin = 2; // choose the input pin (for PIR sensor) int pirState = LOW; // we start, assuming no motion detected int val = 0; // variable for reading the pin status void setup() { pinMode(ledPin, OUTPUT); // declare LED as output pinMode(inputPin, INPUT); // declare sensor as input Serial.begin(9600); } void loop(){ val = digitalRead(inputPin); // read input value if (val == HIGH) { // check if the input is HIGH digitalWrite(ledPin, HIGH); // turn LED ON if (pirState == LOW) { // we have just turned on Serial.println("Motion detected!"); // We only want to print on the output change, not state pirState = HIGH; } } else { digitalWrite(ledPin, LOW); // turn LED OFF if (pirState == HIGH){ // we have just turned of Serial.println("Motion ended!"); // We only want to print on the output change, not state pirState = LOW; } } } Don't forget that there are some times when you don't need a microcontroller. A PIR sensor can be connected to a relay (perhaps with a transistor buffer) without a micro!

Page last edited March 08, 2024

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