PIR Sensor for Garage Door Automation: Vehicle Detection

Project Overview

This project creates a hands-free garage door opener that detects when your car approaches and automatically opens the door. Using a PIR sensor mounted near the driveway, the system detects your vehicle’s heat signature and triggers a relay that simulates pressing the garage door opener button.

Difficulty: Intermediate
Estimated time: 2-3 hours
Estimated cost: $25-35

How It Works

A PIR sensor placed at the driveway entrance detects the heat signature of your approaching car. When a vehicle is detected (after a short delay), the system activates a relay that connects across the garage door opener’s wall button terminals, simulating a button press. An optional reed switch on the garage door can detect whether the door is already open.

Materials Needed

ESP32 or Arduino Uno (1)
HC-SR501 PIR sensor (1) or AM312 for lower power
Relay module (5V, single channel)
Reed switch (normally open) for door position detection (optional)
Magnet for reed switch
12V to 5V converter (if using 12V garage door supply)
Waterproof enclosure (for outdoor PIR sensor)
Jumper wires

Understanding Your Garage Door Opener

Most garage door openers have a wall button that simply shorts two wires together to trigger the door. You can connect a relay across these terminals to simulate a button press. The wires are low voltage (usually 12-24V DC), so it is safe to interface with.

Important: Identify the correct wires before connecting. Use a multimeter to find the pair that shows continuity when the wall button is pressed.

Circuit Diagram

Connection Table

VCC

3.3V or VIN

GND

OUT

GPIO 4

GPIO 5

One side

GPIO 12 (with 10k pull-up)

Other side

GND

表

Arduino Code

// Automatic Garage Door Opener with PIR
#include <WiFi.h>
#include <WebServer.h>

const int pirPin = 4;
const int relayPin = 5;
const int doorSensorPin = 12;

WebServer server(80);

unsigned long lastTriggerTime = 0;
const unsigned long triggerDelay = 1000;
const unsigned long relayDuration = 500;
const unsigned long cooldownPeriod = 30000;

bool motionDetected = false;
bool doorOpen = false;
unsigned long motionStartTime = 0;

void setup() {
  Serial.begin(115200);
  
  pinMode(pirPin, INPUT);
  pinMode(relayPin, OUTPUT);
  pinMode(doorSensorPin, INPUT_PULLUP);
  
  digitalWrite(relayPin, LOW);
  
  WiFi.begin("YourSSID", "YourPassword");
  while (WiFi.status() != WL_CONNECTED) delay(500);
  
  server.on("/", []() {
    String html = "<html><body><h1>Garage Door</h1><p>Status: ";
    html += doorOpen ? "OPEN" : "CLOSED";
    html += "</p><a href='/open'><button>Open</button></a></body></html>";
    server.send(200, "text/html", html);
  });
  server.on("/open", []() {
    triggerDoor();
    server.sendHeader("Location", "/");
    server.send(303);
  });
  server.begin();
  
  doorOpen = digitalRead(doorSensorPin) == LOW;
  delay(60000);
}

void triggerDoor() {
  digitalWrite(relayPin, HIGH);
  delay(relayDuration);
  digitalWrite(relayPin, LOW);
  delay(2000);
  doorOpen = digitalRead(doorSensorPin) == LOW;
  lastTriggerTime = millis();
}

void loop() {
  server.handleClient();
  
  bool pirState = digitalRead(pirPin) == HIGH;
  
  if (pirState && !motionDetected) {
    motionDetected = true;
    motionStartTime = millis();
  }
  
  if (motionDetected && (millis() - motionStartTime > triggerDelay)) {
    if (!doorOpen && (millis() - lastTriggerTime > cooldownPeriod)) {
      triggerDoor();
    }
    motionDetected = false;
  }
  
  if (motionDetected && !pirState && (millis() - motionStartTime < triggerDelay)) {
    motionDetected = false;
  }
  
  bool newDoorState = digitalRead(doorSensorPin) == LOW;
  if (newDoorState != doorOpen) {
    doorOpen = newDoorState;
  }
  
  delay(100);
}

Installation Steps

Identify the wall button terminals on your garage door opener
Wire the relay COM and NO terminals across those terminals
Mount PIR sensor at driveway entrance, 1.5-2m high, angled to detect vehicle approach
Mount reed switch on door frame and magnet on door
Place ESP32 and relay in waterproof enclosure near the garage door opener
Test by driving vehicle toward garage and verifying door opens automatically

Project Extensions

Add Wi-Fi dashboard to monitor door status and manually control
Integrate with Home Assistant via ESPHome
Add ESP32-CAM to capture images when door opens
Add RFID for vehicle-specific control
Add timer to automatically close door if left open

Conclusion

This automatic garage door opener adds convenience and a modern touch to your home. With proper installation, it will reliably open your garage door as you arrive.