ESP32 - Door Sensor Toggle Relay

In a previous tutorial, We have learned how to turn on the relay if the door is open, and turn off relay if the door is closed. In this tutorial, We are going to learn how to toggle relay each time door is closed.

By connecting relay to light bulb, led strip, motor or actuator... We can use the door sensor to toggle light bulb, led strip, motor or actuator...

Hardware Required

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
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About Relay and Door Sensor

If you do not have knowledge of relay and door sensor (pinout, how they work, how to connect them to ESP32, how to program for them...), learn about them in the following tutorials:

Wiring Diagram

ESP32 Door Sensor Relay Wiring Diagram

Image is developed using Fritzing. Click to enlarge image

ESP32 Code - Door Sensor Toggles Relay

/* * Created by esp32io.com * * This example code is in the public domain * * Tutorial page: https://esp32io.com/tutorials/esp32-door-sensor-toggle-relay */ // constants won't change const int DOOR_SENSOR_PIN = 21; // ESP32 pin GIOP21 connected to door sensor's pin const int RELAY_PIN = 27; // ESP32 pin GIOP27 connects to the IN pin of relay // variables will change: int relayState = LOW; // the current state of relay int lastDoorState; // the previous state of door sensor int currentDoorState; // the current state of door sensor 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 currentDoorState = digitalRead(DOOR_SENSOR_PIN); } void loop() { lastDoorState = currentDoorState; // save the last state currentDoorState = digitalRead(DOOR_SENSOR_PIN); // read new state if (lastDoorState == HIGH && currentDoorState == LOW) { // state change: HIGH -> LOW Serial.println("The door-closing event is detected"); // toggle state of relay relayState = !relayState; // control relay arccoding to the toggled state digitalWrite(RELAY_PIN, relayState); } }

Quick Steps

  • If this is the first time you use ESP32, see how to setup environment for ESP32 on Arduino IDE
  • Connect the ESP32 board to your PC via a micro USB cable
  • Open Arduino IDE, select the right ESP32 board and COM port
  • Copy the above code and paste it to Arduino IDE
  • Click Upload button on Arduino IDE to compile and upload code to ESP32 board
  • Move the magnet close to the reed switch and them move it far from the reed switch. Repeat this several times
  • See the change of relay's state

Code Explanation

Read the line-by-line explanation in comment lines of code!

In the code, relayState = !relayState is equivalent to the following code:

if(relayState == LOW) relayState = HIGH; else relayState = LOW;

Video Tutorial

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