ESP32 - Door Sensor - Relay

This tutorial instructs you how to use ESP32 with door sensor and relay. In detail, ESP32 automatically turn relay on if the door is open and turn relay off if the door is closed.

For toggling relay each time door is closed, See ESP32 - Door Sensor Toggles Relay tutorial.

We can extend this tutorial to use the door sensor to control a led strip, siren, light bulb, or actuator... by connnecting them to the relay.

Hardware Used In This Tutorial

1×ESP-WROOM-32 Dev Module
1×Micro USB Cable
1×Door Sensor
1×Relay
1×Warning Light Bright Waterproof
1×12V Power Adapter
n×Jumper Wires
Disclosure: some of these links are affiliate links. We may earn a commission on your purchase at no extra cost to you. We appreciate it.

Introduction to Relay and Door Sensor

We have specific tutorials about relay and door sensor. Each tutorial contains detailed information and step-by-step instructions about hardware pinout, working principle, wiring connection to ESP32, ESP32 code... Learn more about them at the following links:

Wiring Diagram

wiring diagram between esp32 door sensor relay

This image is created using Fritzing. Click to enlarge image

ESP32 Code

/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-door-sensor-relay */ #define DOOR_SENSOR_PIN 21 // ESP32 pin GIOP21 connected to door sensor's pin #define RELAY_PIN 27 // ESP32 pin GIOP27 connects to the IN pin of relay int doorState; void setup() { Serial.begin(9600); // initialize serial pinMode(DOOR_SENSOR_PIN, INPUT_PULLUP); // set ESP32 pin to input pull-up mode pinMode(RELAY_PIN, OUTPUT); // set ESP32 pin to output mode } void loop() { doorState = digitalRead(DOOR_SENSOR_PIN); // read state if (doorState == HIGH) { Serial.println("The door is open!, turns the relay ON"); digitalWrite(RELAY_PIN, HIGH); // turn on relay } else { Serial.println("The door is closed, turns the relay OFF"); digitalWrite(RELAY_PIN, LOW); // turn off relay } }

Quick Instructions

  • If this is the first time you use ESP32, see how to setup environment for ESP32 on Arduino IDE.
  • Do the wiring as above image.
  • Connect the ESP32 board to your PC via a micro USB cable
  • Open Arduino IDE on your PC.
  • Select the right ESP32 board (e.g. ESP32 Dev Module) and COM port.
  • Copy the above code and paste it to Arduino IDE.
  • Compile and upload code to ESP32 board by clicking Upload button on Arduino IDE
  • Arduino IDE Upload Code
  • Move the magnet close to the reed switch and them move it far from the reed switch.
  • See the change of relay's state

Line-by-line Code Explanation

The above ESP32 code contains line-by-line explanation. Please read the comments in the code!

Video Tutorial

Making video is a time-consuming work. If the video tutorial is necessary for your learning, please let us know by subscribing to our YouTube channel , If the demand for video is high, we will make the video tutorial.

※ NOTICES