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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 ESP32 Development Board. You’ll learn how to read digital inputs from the sensor to detect motion and output a corresponding message to the serial monitor. We’ll cover the setup and programming required for the ESP32 board to respond when the sensor detects someone’s presence by displaying “Somebody here!”

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
ESP32 & Development Board (ESP32 Board)	BUY
PIR Motion Module (HC-SR501)	-
Breadboard	BUY

Wiring

../_images/Lesson_12_PIR_Module_esp32_bb.png

Code

Code Analysis

Setting up the PIR Sensor Pin. The pin for the PIR sensor is defined as pin 25.
```
const int pirPin = 25;
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.