Doorbell¶

The “doorbell” project aims to simulate the function of a doorbell. When a button is pressed, the Arduino plays a predefined melody using a passive buzzer module.

1. Build the Circuit¶

2. Code¶

Open the 07-Doorbell.ino file under the path of ultimate-sensor-kit\fun_project\07-Doorbell, or copy this code into Arduino IDE.

3. Code explanation¶

The main idea behind this project is to use the Arduino Uno board to detect a button press and, in response, play a melody on the passive buzzer. The melody consists of a sequence of notes (defined by their pitches) and their durations.

Setting up necessary libraries and global variables

#include "pitches.h"  // This library provides the frequency values for musical notes.

const int buttonPin = 7;  // Button connected to digital pin 7
const int buzzerPin = 8;  // Buzzer connected to digital pin 8

// Arrays to define the melody and the corresponding note durations
int melody[] = {...};
int noteDurations[] = {...};

This segment includes the necessary library for musical notes and sets up the pins for our components. Additionally, the melody and its durations are defined in arrays.

Initializing the button and starting serial communication

void setup() {
  Serial.begin(9600);           // Start serial communication at 9600 baud rate
  pinMode(buttonPin, INPUT);    // Set the button pin as an input
}

In the setup() function, we start serial communication and configure the buttonPin to act as an input.

Monitoring the button press to play the melody

void loop() {
  int buttonState = digitalRead(buttonPin);  // Read the state of the button

  if (buttonState == LOW) {                  // Check if the button is pressed
    Serial.println("Button pressed");        // Send a message to serial monitor
    buzzer();                                // Play the buzzer melody
  }
}

Here, we continuously check the state of the button in the loop. If pressed, a message is sent to the serial monitor, and the buzzer() function (which plays the melody) is called.

The buzzer() function to play the melody

void buzzer() {
  int size = sizeof(noteDurations) / sizeof(int);   // Calculate the number of notes

  for (int thisNote = 0; thisNote < size; thisNote++) {
    int noteDuration = 1000 / noteDurations[thisNote];   // Calculate note's play duration
    tone(buzzerPin, melody[thisNote], noteDuration);    // Play the note on the buzzer

    int pauseBetweenNotes = noteDuration * 1.30;        // Calculate pause between notes
    delay(pauseBetweenNotes);                           // Introduce the pause
    noTone(buzzerPin);                                  // Stop playing the note
  }
}

In the buzzer() function, the melody’s notes are played sequentially. The tone() function generates a tone on the buzzer for a specified duration. After playing each note, there’s a brief pause before playing the next note.