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Lesson 12: PIR Motion Module (HC-SR501)

In this lesson, you will learn how to use a PIR (Passive Infrared) motion sensor with an Arduino Uno. We’ll see how the sensor detects movement and sends a signal to the Arduino, which then triggers a response. This project is ideal for beginners as it provides hands-on experience with digital inputs, serial communication, and conditional programming on the Arduino platform.

Required Components

In this project, we need the following components.

It’s definitely convenient to buy a whole kit, here’s the link:

Name	ITEMS IN THIS KIT	LINK
Universal Maker Sensor Kit	94	Universal Maker Sensor Kit

You can also buy them separately from the links below.

Component Introduction	Purchase Link
Arduino UNO R3 or R4	BUY
PIR Motion Module (HC-SR501)	-

Wiring

../_images/Lesson_12_pir_module_uno_bb.png

Code

Code Analysis

Setting up the PIR Sensor Pin. The pin for the PIR sensor is defined as pin 2.
```
const int pirPin = 2;
int state = 0;
```
Initializing the PIR Sensor. In the setup() function, the PIR sensor pin is set as an input. This allows the Arduino to read the state of the PIR sensor.
```
void setup() {
  pinMode(pirPin, INPUT);
  Serial.begin(9600);
}
```
Reading from the PIR Sensor and Displaying the Results. In the loop() function, the state of the PIR sensor is continuously read.
```
void loop() {
  state = digitalRead(pirPin);
  if (state == HIGH) {
    Serial.println("Somebody here!");
  } else {
    Serial.println("Monitoring...");
    delay(100);
  }
}
```
If the state is HIGH, meaning motion is detected, a message “Somebody here!” is printed to the serial monitor. Otherwise, “Monitoring…” is printed.