Door, Window and Push-button Sensor

written by hek

This is a simple but very useful example sketch for sensing binary things; like open/closed doors or the state of a wall switch.

The Arduino Pro Mini board has 13 independent digital input pins that can be used to sense the open/closed state of something.

By enabling the internal pull-up resistor (like we've done in this example) you don't need an external pull-up resistor. Just connect the push-button or reed switch between GND and one of the 13 independent digital inputs.

The sketch also takes advantage of the Debounce-library to filter out false triggers.

Wiring Things Up

Start by connecting the radio module.

Sensor Arduino Comment
Switch GND Black
Switch Digital pin 3 Green


This example uses the external Bounce2 library found here. Please install it and restart the Arduino IDE before trying to compile.

 * The MySensors Arduino library handles the wireless radio link and protocol
 * between your home built sensors/actuators and HA controller of choice.
 * The sensors forms a self healing radio network with optional repeaters. Each
 * repeater and gateway builds a routing tables in EEPROM which keeps track of the
 * network topology allowing messages to be routed to nodes.
 * Created by Henrik Ekblad <[email protected]>
 * Copyright (C) 2013-2015 Sensnology AB
 * Full contributor list:
 * Documentation:
 * Support Forum:
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * version 2 as published by the Free Software Foundation.
 * Simple binary switch example 
 * Connect button or door/window reed switch between 
 * digitial I/O pin 3 (BUTTON_PIN below) and GND.

// Enable debug prints to serial monitor
#define MY_DEBUG 

// Enable and select radio type attached
#define MY_RADIO_RF24
//#define MY_RADIO_RFM69

#include <MySensors.h>
#include <Bounce2.h>

#define CHILD_ID 3
#define BUTTON_PIN  3  // Arduino Digital I/O pin for button/reed switch

Bounce debouncer = Bounce(); 
int oldValue=-1;

// Change to V_LIGHT if you use S_LIGHT in presentation below
MyMessage msg(CHILD_ID,V_TRIPPED);

void setup()  
  // Setup the button
  // Activate internal pull-up
  // After setting up the button, setup debouncer

void presentation() {
  // Register binary input sensor to gw (they will be created as child devices)
  // You can use S_DOOR, S_MOTION or S_LIGHT here depending on your usage. 
  // If S_LIGHT is used, remember to update variable type you send in. See "msg" above.
  present(CHILD_ID, S_DOOR);  

//  Check if digital input has changed and send in new value
void loop() 
  // Get the update value
  int value =;
  if (value != oldValue) {
     // Send in the new value
     send(msg.set(value==HIGH ? 1 : 0));
     oldValue = value;

Shopping Guide

10pcs Magnetic Door Switch Sensor
Reed switch for sensing the open/closed state of doors and windows.
1 available - $17.99   Buy
undefined   Buy
20pcs Push-button
Momentary push-button
Unavailable   Buy
undefined   Buy


Sensors & Actuators

Related Content