SENSORS/ACTUATORS

ESP8266 - Door Sensor - LED

This tutorial instructs you how to use the ESP8266 and door sensor to control the LED. We will learn two different applications:

Application 1 - LED is on when door is open and LED is off when door is closed. The LED state is synchronized with the door sensor's state. In detail:

ESP8266 turns on the LED when the door is opened.
ESP8266 turns off the LED when the door is closed.

Application 2 - The LED state is toggled each time the door is opened. More specifically:

If ESP8266 detects that the door has been opened (the sensor state changes from LOW to HIGH), it will turn ON the LED if it's currently OFF, or turn OFF the LED if it's currently ON.
Closing the door sensor does not affect to the LED state.

Hardware Preparation

1	×	ESP8266 NodeMCU
1	×	Micro USB Cable
1	×	Door Sensor
1	×	LED
1	×	220 ohm resistor
1	×	Breadboard
1	×	Jumper Wires
1	×	(Optional) 5V Power Adapter for ESP8266
1	×	(Optional) ESP8266 Screw Terminal Adapter

Or you can buy the following sensor kit:

DIYables Sensor Kit 30 types, 69 units

Disclosure: Some of the links provided in this section are Amazon affiliate links. We may receive a commission for any purchases made through these links at no additional cost to you. We appreciate your support.

Overview of LED and Door Sensor

If you are unfamiliar with LED and door sensor (including pinout, operation, and programming), the following tutorials can help:

Wiring Diagram

This image is created using Fritzing. Click to enlarge image

See more in ESP8266's pinout and how to supply power to the ESP8266 and other components.

Application 1 - The LED state is in sync with the door sensor state

ESP8266 Code

/* * This ESP8266 NodeMCU code was developed by newbiely.com * * This ESP8266 NodeMCU code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/esp8266/esp8266-door-sensor-led */ #define DOOR_SENSOR_PIN D7 // The ESP8266 pin D7 connected to the OUTPUT pin of door sensor #define LED_PIN D2 // The ESP8266 pin D2 connected to LED's pin int door_state; void setup() { Serial.begin(9600); // Initialize the Serial to communicate with the Serial Monitor. pinMode(DOOR_SENSOR_PIN, INPUT_PULLUP); // Configure the ESP8266 pin to the input pull-up mode pinMode(LED_PIN, OUTPUT); // Configure the ESP8266 pin to the output mode } void loop() { door_state = digitalRead(DOOR_SENSOR_PIN); // read state if (door_state == HIGH) { Serial.println("The door is open, turns on LED"); digitalWrite(LED_PIN, HIGH); // turn on LED } else { Serial.println("The door is closed, turns off LED"); digitalWrite(LED_PIN, LOW); // turn off LED } }

Detailed Instructions

To get started with ESP8266 on Arduino IDE, follow these steps:

Check out the how to setup environment for ESP8266 on Arduino IDE tutorial if this is your first time using ESP8266.
Wire the components as shown in the diagram.
Connect the ESP8266 board to your computer using a USB cable.
Open Arduino IDE on your computer.
Choose the correct ESP8266 board, such as (e.g. NodeMCU 1.0 (ESP-12E Module)), and its respective COM port.
Connect an ESP8266 to your computer with a USB cable.
Launch the Arduino IDE, and select the correct board and port.
Copy the code and open it in the Arduino IDE.
Click the Upload button on the Arduino IDE to compile and upload the code to the ESP8266.

Open and close the door
Check out the change in the LED's state.

You will see that the LED state is in sync with the door sensor state.

Code Explanation

Check out the line-by-line explanation contained in the comments of the source code!

Application 2 - Door Sensor toggles LED

ESP8266 Code - Door Sensor toggles LED

/* * This ESP8266 NodeMCU code was developed by newbiely.com * * This ESP8266 NodeMCU code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/esp8266/esp8266-door-sensor-led */ #define DOOR_SENSOR_PIN D7 // The ESP8266 pin D7 connected to the OUTPUT pin of door sensor #define LED_PIN D2 // The ESP8266 pin D2 connected to LED's pin int led_state = LOW; // The current state of LED int prev_door_state; // The previous state of door sensor int door_state; // The current state of door sensor void setup() { Serial.begin(9600); // Initialize the Serial to communicate with the Serial Monitor. pinMode(DOOR_SENSOR_PIN, INPUT_PULLUP); // Configure the ESP8266 pin to the input pull-up mode pinMode(LED_PIN, OUTPUT); // Configure the ESP8266 pin to the output mode door_state = digitalRead(DOOR_SENSOR_PIN); } void loop() { prev_door_state = door_state; // save the last state door_state = digitalRead(DOOR_SENSOR_PIN); // read new state if (prev_door_state == HIGH && door_state == LOW) { // state change: HIGH -> LOW Serial.println("The door-closing event is detected, toggles the state of LED"); // toggle state of LED led_state = !led_state; // control LED according to the toggled state digitalWrite(LED_PIN, led_state); } }

Code Explanation

You can locate the explanation in the comment lines of the ESP8266 code above.

In the code, the expression led_state = !led_state is equal to the following code:

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

Detailed Instructions

Copy the code and open it in the Arduino IDE.
Upload the code to the ESP8266.
Open and close the door several times.
Check out the change in the LED's state.

You will see that the LED state is toggled once each time the door is closed.

Video Tutorial

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