Detect Motion with a PIR Sensor

Understand the target result

Tune and read the HC-SR501 PIR sensor for presence detection. The expected result is: Movement changes the sensor output and triggers a visible status.

Prepare the board and parts

Disconnect the ESP32 from USB. Put the ESP32, breadboard, jumper wires, and the listed lesson parts in front of you. Straighten bent pins gently and never force a module into the breadboard.

Make each connection with power off

1. Sensor VCC → the voltage printed on the module (use 3.3V when supported).
2. Sensor GND → ESP32 GND.
3. Sensor digital output DO/OUT → GPIO 27.

Install any library and upload the code

No additional Arduino library is required for this starter sketch. Select your ESP32 board and serial port before clicking Upload.

const int SENSOR = 27, LED = 23;
void setup() { Serial.begin(115200); pinMode(SENSOR, INPUT); pinMode(LED, OUTPUT); }
void loop() {
  bool detected = digitalRead(SENSOR);
  digitalWrite(LED, detected);
  Serial.println(detected ? "DETECTED" : "CLEAR");
  delay(100);
}

Power the circuit and observe

Connect USB power only after the wiring check. Open Serial Monitor at 115200 baud when the sketch prints data. Watch the circuit for at least 20 seconds and compare it with this expected behavior: Movement changes the sensor output and triggers a visible status.

Change one value and test again

Make one small change—such as a delay, threshold, brightness, or displayed message—then upload again. This confirms that you understand which part of the program controls the result.