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🔶 HC-SR501 PIR Motion Sensor Module — Infrared Pyroelectric Detector for ESP32 / Arduino — Motion / Presence Detection

📦 Overview

The HC-SR501 is a low-cost PIR (Passive Infrared) motion sensor module that detects changes in infrared energy (movement of warm bodies). The module includes on-board potentiometers to adjust sensitivity and delay time, and a jumper to switch retrigger mode (repeatable / non-repeatable). Ideal for motion sensing, lighting control, intrusion detection, and presence automation.

Typical supply: 5V (many modules work at 3.3V but check your module's silkscreen). Output is a single digital pulse (HIGH when motion detected). This listing includes example code for an ESP32 (Nano/Dev board) and ESPHome integration.

✅ Key Benefits

Reliable motion detection for humans & animals (infrared based)
Adjustable sensitivity and time delay via onboard potentiometers
Simple digital output — easy to integrate with ESP32/Arduino
Low power, compact module suitable for battery and mains projects
Privacy-friendly presence sensing (no camera)

⚙️ Features & Specifications

Model: HC-SR501 PIR Motion Sensor Module
Sensor type: Pyroelectric infrared (PIR)
Typical supply: 5V (some modules operate at 3.3V — verify your board)
Output: Digital OUT (HIGH on detection)
Adjustments: Sensitivity (distance) & Delay (time-on) potentiometers; retrigger jumper (L or H)
Detection range: up to ~6–7 m depending on sensitivity and environment (walls, temperature)
Mounting: PCB hole or plastic lens housing (module dependent)

🔌 Wiring Diagram (ASCII — eBay Safe)

   HC-SR501 MODULE PINS
   --------------------
   VCC   ---> 5V (or 3.3V on tolerant modules)
   GND   ---> GND
   OUT   ---> Digital input pin on MCU (pull-up not required; module drives output)

   Typical wiring to ESP32 (Nano / Dev board):

   HC-SR501    ESP32
   -------     ------
   VCC    -->  5V (or 3V3 if your module supports it)
   GND    -->  GND
   OUT    -->  GPIO 15  (example - change to any available input)

   Optional: LED indicator on GPIO (for local visual feedback)
   LED+   -->  GPIO 2 (with resistor)
   LED-   -->  GND

Note: Always confirm the VCC range printed on your board. If your MCU is 3.3V-only, prefer a 3.3V-compatible PIR module or use a regulator/level shifter.

Wiring Table (ESP32 example)

HC-SR501 Pin	ESP32 (example)	Notes
VCC	5V (or 3.3V on compatible modules)	Power supply — check board label
GND	GND	Common ground
OUT	GPIO 15 (example)	Digital input — HIGH when motion detected

🧩 ESP32 Arduino Example — Motion Detection

Click to expand ESP32 (Arduino) sketch

// ESP32 Motion Detection Example — HC-SR501
// Shows basic debounced motion detection and toggles an LED.
// Connect HC-SR501 OUT to PIR_PIN (example GPIO 15).
// Optional: connect an LED (with resistor) to LED_PIN for visual feedback.

const int PIR_PIN = 15;    // PIR output
const int LED_PIN = 2;     // On-board LED or external (change if needed)

unsigned long lastTrigger = 0;
const unsigned long debounceMs = 500;  // ignore triggers shorter than this
volatile bool motionFlag = false;

void IRAM_ATTR handlePIR() {
  // ISR sets a flag; keep ISR short
  motionFlag = true;
}

void setup() {
  Serial.begin(115200);
  pinMode(PIR_PIN, INPUT);
  pinMode(LED_PIN, OUTPUT);
  digitalWrite(LED_PIN, LOW);

  // Attach interrupt for rising edge detection
  attachInterrupt(digitalPinToInterrupt(PIR_PIN), handlePIR, RISING);

  Serial.println("HC-SR501 PIR Motion Sensor demo");
}

void loop() {
  if (motionFlag) {
    motionFlag = false; // reset flag
    unsigned long now = millis();

    // Debounce / rate limit
    if (now - lastTrigger > debounceMs) {
      lastTrigger = now;
      Serial.println("Motion detected!");
      // Visual pulse on LED
      digitalWrite(LED_PIN, HIGH);
      delay(200);                 // short flash
      digitalWrite(LED_PIN, LOW);

      // Here you can add actions: MQTT publish, GPIO toggle, web request, etc.
    }
  }
  // low CPU usage; add sleep or other tasks here
  delay(10);
}

Tip: You can increase the PIR's built-in delay potentiometer to keep OUT HIGH longer, or decrease sensitivity to avoid false positives.

🧩 ESPHome — Binary Sensor (PIR)

Click to expand ESPHome YAML

esphome:
  name: pir_room
  platform: ESP32
  board: esp32dev

wifi:
  ssid: "YOUR_SSID"
  password: "YOUR_PASS"

binary_sensor:
  - platform: gpio
    pin:
      number: GPIO15
      mode: INPUT
      inverted: false
    name: "PIR Motion"
    device_class: motion
    filters:
      - delayed_on: 50ms   # short debounce
      - delayed_off: 10s   # treat as motion for 10s after last detection
    on_press:
      then:
        - logger.log: "PIR triggered"

logger:
  level: INFO

Note: Adjust `delayed_off` to control how long the sensor reports motion after trigger (or use the onboard delay pot).

💡 Possible Uses

Automatic lighting (corridors, closets, stairways)
Security / intrusion detection (indoor zones)
Bathroom / toilet vacancy sensor
Energy-saving presence detection for HVAC / fans
Smart doorbell or porch motion trigger
Interactive installations & motion-triggered effects
Robotics: simple presence or obstacle triggers
Wake-on-motion for battery-powered devices

🛠 Troubleshooting & Notes

If you see false triggers, lower sensitivity (pot) and ensure sensor is not facing moving heat sources (vents, sunlight).
Mount sensor behind a diffuser (thin plastic) to slightly broaden detection cone and reduce spurious triggers.
Allow 30–60 seconds for the PIR to stabilize after power-up (warm-up period).
Check retrigger jumper: one position makes output pulse only once per detection (non-retrigger), the other allows repeated triggers while motion persists.

📦 Package Includes

1 × HC-SR501 PIR Motion Sensor Module

📝

HC-SR501 PIR Motion Sensor Module — Infrared PIR Detector for ESP32 / Arduino — Motion Presence Detector

🔍 Keywords

HC-SR501, PIR motion sensor, infrared detector, PIR module, motion detector, ESP32 sensor, Arduino PIR, occupancy sensor, presence detector, home automation.

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