Arduino Nano - Door Sensor - Piezo Buzzer
This tutorial instructs you how to use Arduino Nano and door sensor to trigger piezo buzzer. In detail:
- Arduino Nano produces a sound when the door is opened.
- Arduino Nano stops the sound when the door is closed.
- Arduino Nano plays a melody when the door is opened.
Hardware Preparation
Or you can buy the following kits:
| 1 | × | DIYables Sensor Kit (30 sensors/displays) | |
| 1 | × | DIYables Sensor Kit (18 sensors/displays) | 
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Additionally, some of these links are for products from our own brand, DIYables .
Additionally, some of these links are for products from our own brand, DIYables .
Overview of Piezo Buzzer and Door Sensor
If you are not familiar with piezo buzzer and door sensor (including pinout, functioning, programming, etc.), the following tutorials can help:
Wiring Diagram

This image is created using Fritzing. Click to enlarge image
See The best way to supply power to the Arduino Nano and other components.
Arduino Nano Code - Simple Sound
/*
 * This Arduino Nano code was developed by newbiely.com
 *
 * This Arduino Nano code is made available for public use without any restriction
 *
 * For comprehensive instructions and wiring diagrams, please visit:
 * https://newbiely.com/tutorials/arduino-nano/arduino-nano-door-sensor-piezo-buzzer
 */
#define DOOR_SENSOR_PIN  5 // The Arduino Nano pin connected to the door sensor's pin
#define BUZZER_PIN       2 // The Arduino Nano pin connected to the piezo buzzer
int door_state;
void setup() {
  Serial.begin(9600);                     // Initialize the Serial to communicate with the Serial Monitor.
  pinMode(DOOR_SENSOR_PIN, INPUT_PULLUP); // set arduino pin to input pull-up mode
  pinMode(BUZZER_PIN, OUTPUT);            // set arduino pin to output mode
}
void loop() {
  door_state = digitalRead(DOOR_SENSOR_PIN); // read state
  if (door_state == HIGH) {
    Serial.println("The door is open");;
    digitalWrite(BUZZER_PIN, HIGH); // turn on Piezo Buzzer
  } else {
    Serial.println("The door is closed");
    digitalWrite(BUZZER_PIN, LOW);  // turn off Piezo Buzzer
  }
}
Detailed Instructions
- Connect an Arduino Nano to your computer with a USB cable.
- Open the Arduino IDE, select the correct board and port.
- Copy the code above and open it in the Arduino IDE.
- Click the Upload button in the Arduino IDE to compile and upload the code to the Arduino Nano.
- Bring the magnet close to the reed switch and then move it away.
- Listen to the sound of the piezo buzzer.
Code Explanation
Check out the line-by-line explanation contained in the comments of the source code!
Arduino Nano Code - Melody
/*
 * This Arduino Nano code was developed by newbiely.com
 *
 * This Arduino Nano code is made available for public use without any restriction
 *
 * For comprehensive instructions and wiring diagrams, please visit:
 * https://newbiely.com/tutorials/arduino-nano/arduino-nano-door-sensor-piezo-buzzer
 */
#include "pitches.h"
#define DOOR_SENSOR_PIN  5 // The Arduino Nano pin connected to the door sensor's pin
#define BUZZER_PIN       2 // The Arduino Nano pin connected to the piezo buzzer
int door_state;
// notes in the melody:
int melody[] = {
  NOTE_E5, NOTE_E5, NOTE_E5,
  NOTE_E5, NOTE_E5, NOTE_E5,
  NOTE_E5, NOTE_G5, NOTE_C5, NOTE_D5,
  NOTE_E5,
  NOTE_F5, NOTE_F5, NOTE_F5, NOTE_F5,
  NOTE_F5, NOTE_E5, NOTE_E5, NOTE_E5, NOTE_E5,
  NOTE_E5, NOTE_D5, NOTE_D5, NOTE_E5,
  NOTE_D5, NOTE_G5
};
// note durations: 4 = quarter note, 8 = eighth note, etc, also called tempo:
int noteDurations[] = {
  8, 8, 4,
  8, 8, 4,
  8, 8, 8, 8,
  2,
  8, 8, 8, 8,
  8, 8, 8, 16, 16,
  8, 8, 8, 8,
  4, 4
};
void setup() {
  Serial.begin(9600);                     // Initialize the Serial to communicate with the Serial Monitor.
  pinMode(DOOR_SENSOR_PIN, INPUT_PULLUP); // set arduino pin to input pull-up mode
}
void loop() {
  door_state = digitalRead(DOOR_SENSOR_PIN); // read state
  if (door_state == HIGH) {
    Serial.println("The door is open");
    buzzer();
  }
}
void buzzer() {
  // iterate over the notes of the melody:
  int size = sizeof(noteDurations) / sizeof(int);
  for (int thisNote = 0; thisNote < size; thisNote++) {
    // to calculate the note duration, take one second divided by the note type.
    //e.g. quarter note = 1000 / 4, eighth note = 1000/8, etc.
    int noteDuration = 1000 / noteDurations[thisNote];
    tone(BUZZER_PIN, melody[thisNote], noteDuration);
    // to distinguish the notes, set a minimum time between them.
    // The note's duration + 30% seems to work well:
    int pauseBetweenNotes = noteDuration * 1.30;
    delay(pauseBetweenNotes);
    // stop the tone playing:
    noTone(BUZZER_PIN);
  }
}
Detailed Instructions
- Copy the code and open it with the Arduino IDE.
- Create the pitches.h file On Arduino IDE by:
- Either click on the button just below the serial monitor icon and choose New Tab, or use Ctrl+Shift+N keys.
- Give file's name pitches.h and click OK button
- Copy the below code and paste it to the created pitches.h file.
- Click the Upload button on the Arduino IDE to compile and upload the code to the Arduino Nano.
- Move the magnet far from the reed switch of door sensor to simulate the door open.
- Hear the tune from the piezo buzzer.


/*************************************************
 * Public Constants
 *************************************************/
#define NOTE_B0  31
#define NOTE_C1  33
#define NOTE_CS1 35
#define NOTE_D1  37
#define NOTE_DS1 39
#define NOTE_E1  41
#define NOTE_F1  44
#define NOTE_FS1 46
#define NOTE_G1  49
#define NOTE_GS1 52
#define NOTE_A1  55
#define NOTE_AS1 58
#define NOTE_B1  62
#define NOTE_C2  65
#define NOTE_CS2 69
#define NOTE_D2  73
#define NOTE_DS2 78
#define NOTE_E2  82
#define NOTE_F2  87
#define NOTE_FS2 93
#define NOTE_G2  98
#define NOTE_GS2 104
#define NOTE_A2  110
#define NOTE_AS2 117
#define NOTE_B2  123
#define NOTE_C3  131
#define NOTE_CS3 139
#define NOTE_D3  147
#define NOTE_DS3 156
#define NOTE_E3  165
#define NOTE_F3  175
#define NOTE_FS3 185
#define NOTE_G3  196
#define NOTE_GS3 208
#define NOTE_A3  220
#define NOTE_AS3 233
#define NOTE_B3  247
#define NOTE_C4  262
#define NOTE_CS4 277
#define NOTE_D4  294
#define NOTE_DS4 311
#define NOTE_E4  330
#define NOTE_F4  349
#define NOTE_FS4 370
#define NOTE_G4  392
#define NOTE_GS4 415
#define NOTE_A4  440
#define NOTE_AS4 466
#define NOTE_B4  494
#define NOTE_C5  523
#define NOTE_CS5 554
#define NOTE_D5  587
#define NOTE_DS5 622
#define NOTE_E5  659
#define NOTE_F5  698
#define NOTE_FS5 740
#define NOTE_G5  784
#define NOTE_GS5 831
#define NOTE_A5  880
#define NOTE_AS5 932
#define NOTE_B5  988
#define NOTE_C6  1047
#define NOTE_CS6 1109
#define NOTE_D6  1175
#define NOTE_DS6 1245
#define NOTE_E6  1319
#define NOTE_F6  1397
#define NOTE_FS6 1480
#define NOTE_G6  1568
#define NOTE_GS6 1661
#define NOTE_A6  1760
#define NOTE_AS6 1865
#define NOTE_B6  1976
#define NOTE_C7  2093
#define NOTE_CS7 2217
#define NOTE_D7  2349
#define NOTE_DS7 2489
#define NOTE_E7  2637
#define NOTE_F7  2794
#define NOTE_FS7 2960
#define NOTE_G7  3136
#define NOTE_GS7 3322
#define NOTE_A7  3520
#define NOTE_AS7 3729
#define NOTE_B7  3951
#define NOTE_C8  4186
#define NOTE_CS8 4435
#define NOTE_D8  4699
#define NOTE_DS8 4978
Code Explanation
Examine the line-by-line description in the comments of the source code!