SENSORS/ACTUATORS

INTERNET OF THING (IoT)

ESP32 - Door Sensor

The door sensor (also known as entry sensor, contact sensor, or window sensor) is widely used in many kinds of application, especially for security. It is used to detect/monitor entrances (such as door, window ...). This tutorial instructs you how to use ESP32 with the door sensor.

Hardware Used In This Tutorial

1	×	ESP-WROOM-32 Dev Module
1	×	USB Cable Type-C
1	×	Door Sensor
1	×	(Optional) DC Power Jack
1	×	Breadboard
1	×	Jumper Wires
1	×	(Recommended) ESP32 Screw Terminal Adapter

Or you can buy the following sensor kit:

DIYables Sensor Kit 30 types, 69 units

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Introduction to Door Sensor

Door Sensor Pinout

The door sensor has two components:

One magnet
One reed switch, which has two wires

Just like the switch/button, we do NOT need to differentiate the two wires of the reed switch.

How Door Sensor Works

The magnet and the reed switch are installed on the door/windows as follows:

The magnet is the movable part. It should be attached to the door/window
The reed switch is the fixed part. It should be attached to the door frame

The two components are in contact when the door is closed.

The reed switch circuit is closed when it is near to the magnet
The reed switch circuit is open when it is far from the magnet

※ NOTE THAT:

Just like a button, we MUST use the pull-up or pull-down resistor on the ESP32 pin, which connects to the reed switch

If we connect reed switch as follows: one wire to GND, the other to ESP32's input pin with a pull-up resistor:

The ESP32's input pin is LOW when the magnet is near to the reed switch
The ESP32's input pin is HIGH when the magnet is far from the reed switch

So:

If the ESP32's input pin is LOW, the door is closed
If the ESP32's input pin is HIGH, the door is opened
If the ESP32's input pin changes from LOW to HIGH, the door is opening
If the ESP32's input pin changes from HIGH to LOW, the door is closing

Wiring Diagram between Door Sensor and ESP32

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.

How To Program Door Sensor

Initializes the ESP32 pin to the digital input mode by using pinMode() function. For example, pin GPIO19

pinMode(19, INPUT_PULLUP);

Reads the state of the ESP32 pin by using digitalRead() function.

int doorState = digitalRead(19);

ESP32 Code - Check Door Open and Close State

Quick Instructions

If this is the first time you use ESP32, see how to setup environment for ESP32 on Arduino IDE.
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.
See the result on Serial Monitor. It looks like the below:.

COM6

Send

The door is open The door is open The door is closed The door is closed The door is closed The door is closed The door is closed The door is open The door is open

Autoscroll Show timestamp

Clear output

9600 baud

Newline

ESP32 Code - Detect Door-opening and Door-closing Events

/* * 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 */ #define DOOR_SENSOR_PIN 19 // ESP32 pin GPIO19 connected to door sensor's pin int currentDoorState; // current state of door sensor int lastDoorState; // previous 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 currentDoorState = digitalRead(DOOR_SENSOR_PIN); // read state } void loop() { lastDoorState = currentDoorState; // save the last state currentDoorState = digitalRead(DOOR_SENSOR_PIN); // read new state if (lastDoorState == LOW && currentDoorState == HIGH) { // state change: LOW -> HIGH Serial.println("The door-opening event is detected"); // TODO: turn on alarm, light or send notification ... } else if (lastDoorState == HIGH && currentDoorState == LOW) { // state change: HIGH -> LOW Serial.println("The door-closing event is detected"); // TODO: turn off alarm, light or send notification ... } }

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.
See the result on Serial Monitor. It looks like the below:.

COM6

Send

The door-closing event is detected The door-opening event is detected

Autoscroll Show timestamp

Clear output

9600 baud

Newline

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