ESP8266 - Door Sensor - Relay

This tutorial instructs you how to use the ESP8266 and door sensor to control the relay. By connecting the relay to a soleniod lock, light bulb, LED strip, motor, or actuator..., we can use a door sensor to control the them. We will learn two different applications:

Application 1 - The relay is activated when door is open and the relay is deactivated when door is closed. The relay state is synchronized with the door sensor state. In detail:

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

Hardware Preparation

1×ESP8266 NodeMCU
1×Micro USB Cable
1×Door Sensor
1×Relay
1×Breadboard
1×Jumper Wires
1×(Optional) Solenoid Lock
1×(Optional) 12V Power Adapter
1×(Optional) DC Power Jack
1×(Optional) 5V Power Adapter for ESP8266
1×(Optional) ESP8266 Screw Terminal Adapter

Or you can buy the following sensor kit:

1×DIYables Sensor Kit 30 types, 69 units
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Overview of Relay and Door Sensor

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

Wiring Diagram

The wiring diagram between ESP8266 NodeMCU and Door Sensor relay

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 relay 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-relay */ #define DOOR_SENSOR_PIN D3 // The ESP8266 pin D3 connected to door sensor's pin #define RELAY_PIN D7 // The ESP8266 pin D7 connects to the IN pin of relay 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(RELAY_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 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 } }

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.
Arduino IDE Upload Code
  • Open and close the door
  • Check out the change in the relay's condition.

You will see that the relay 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 Relay

ESP8266 Code - Door Sensor toggles Relay

/* * 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-relay */ #define DOOR_SENSOR_PIN D3 // The ESP8266 pin D3 connected to door sensor's pin #define RELAY_PIN D7 // The ESP8266 pin D7 connects to the IN pin of relay int relay_state = LOW; // The current state of relay 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(RELAY_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 state of relay"); // toggle state of relay relay_state = !relay_state; // control relay according to the toggled state digitalWrite(RELAY_PIN, relay_state); } }

Code Explanation

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

In the code, the expression relay_state = !relay_state is equivalent to the following code:

if(relay_state == LOW) relay_state = HIGH; else relay_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 relay's state.

You'll notice that the relay will switch on or off one time whenever you close the door.

Video Tutorial