ESP32 - Door Sensor Toggle Relay

This tutorial instructs you how to use ESP32 to toggle the relay's state each time door is closed.

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	×	USB Cable Type-C
1	×	Door Sensor
1	×	Relay
1	×	(Optional) Solenoid Lock
1	×	(Optional) 12V Active Buzzer
1	×	(Optional) 12V Cooling Fan
1	×	(Optional) 12V Warning Light Bright Waterproof
1	×	12V Power Adapter
1	×	Breadboard
1	×	Jumper Wires
1	×	(Optional) DC Power Jack
1	×	(Recommended) Screw Terminal Expansion Board for ESP32

Or you can buy the following sensor kits:

1	×	DIYables Sensor Kit (30 sensors/displays)
1	×	DIYables Sensor Kit (18 sensors/displays)

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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

This image is created using Fritzing. Click to enlarge image

If you're unfamiliar with how to supply power to the ESP32 and other components, you can find guidance in the following tutorial: How to Power ESP32.

ESP32 Code - Door Sensor Toggles Relay

/* * 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-toggle-relay */ #define DOOR_SENSOR_PIN 16 // ESP32 pin GPIO16 connected to door sensor's pin #define RELAY_PIN 26 // ESP32 pin GPIO26 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, toggles state of relay"); // toggle state of relay relayState = !relayState; // control relay arccoding to the toggled state digitalWrite(RELAY_PIN, relayState); } }

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
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

Line-by-line Code Explanation

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

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

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

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