Happy Birthday

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Kit purchase

Looking for parts? Check out our all-in-one kits below — packed with components, beginner-friendly guides, and tons of fun.

Name	Includes Arduino board	PURCHASE LINK
Ultimate Sensor Kit	Arduino Uno R4 Minima	BUY
Elite Explorer Kit	Arduino Uno R4 WiFi	BUY
3 in 1 Ultimate Starter Kit	Arduino Uno R4 Minima	BUY
Universal Maker Sensor Kit	×	BUY

Course Introduction

In this lesson, you will learn how to use Arduino along with I2C LCD, Active Buzzer, LEDs, and resistors to create a birthday show.

Note

If this is your first time working with an Arduino project, we recommend downloading and reviewing the basic materials first.

Required Components

In this project, we need the following components:

SN	COMPONENT INTRODUCTION	QUANTITY	PURCHASE LINK
1	Arduino UNO R4 Minima/Arduino UNO R4 WIFI	1	BUY
2	USB Type-C cable	1
3	Breadboard	1	BUY
4	Wires	Several	BUY
5	220Ω resistor	Several	BUY
6	I2C LCD 1602	1	BUY
7	LED	Several	BUY
8	Active Buzzer	1

Wiring

Common Connections:

Active Buzzer
- ＋: Connect to 8 on the Arduino.
- －: Connect to breadboard’s negative power bus.
LED
- Connect the LEDs cathode to the negative power bus on the breadboard, and the LEDs anode to a 22Ω resistor then to 3 to 7 on the Arduino.
I2C LCD 1602
- SDA: Connect to SDA on the Arduino.
- SCL: Connect to SCL on the Arduino.
- GND: Connect to breadboard’s negative power bus.
- VCC: Connect to breadboard’s red power bus.

Writing the Code

Note

You can copy this code into Arduino IDE.
To install the library, use the Arduino Library Manager and search for LiquidCrystal I2C and install it.
Don’t forget to select the board(Arduino UNO R4 Minima) and the correct port before clicking the Upload button.

#include <Wire.h>
#include <LiquidCrystal_I2C.h>

// LCD
LiquidCrystal_I2C lcd(0x27, 16, 2);

// LED pins
const int ledPins[] = {3, 4, 5, 6, 7};
const int ledCount = 5;

// Passive buzzer pin
const int BUZZER_PIN = 8;

// Start time
int year = 2026;
int month = 5;
int day = 31;
int hour = 23;
int minute = 59;
int second = 50;

unsigned long lastSecondUpdate = 0;
unsigned long lastLedUpdate = 0;

bool birthdayStarted = false;

int ledIndex = 0;

// Notes
#define NOTE_C4  262
#define NOTE_D4  294
#define NOTE_E4  330
#define NOTE_F4  349
#define NOTE_G4  392
#define NOTE_A4  440
#define NOTE_AS4 466
#define NOTE_B4  494
#define NOTE_C5  523

// Happy Birthday melody
int melody[] = {
  NOTE_C4, NOTE_C4, NOTE_D4, NOTE_C4, NOTE_F4, NOTE_E4,
  NOTE_C4, NOTE_C4, NOTE_D4, NOTE_C4, NOTE_G4, NOTE_F4,
  NOTE_C4, NOTE_C4, NOTE_C5, NOTE_A4, NOTE_F4, NOTE_E4, NOTE_D4,
  NOTE_AS4, NOTE_AS4, NOTE_A4, NOTE_F4, NOTE_G4, NOTE_F4
};

int noteDurations[] = {
  4, 4, 2, 2, 2, 1,
  4, 4, 2, 2, 2, 1,
  4, 4, 2, 2, 2, 2, 1,
  4, 4, 2, 2, 2, 1
};

const int melodyLength = sizeof(melody) / sizeof(melody[0]);

int currentNote = 0;
unsigned long noteStartTime = 0;
bool notePlaying = false;

void setup() {
  lcd.init();
  lcd.backlight();

  for (int i = 0; i < ledCount; i++) {
    pinMode(ledPins[i], OUTPUT);
    digitalWrite(ledPins[i], LOW);
  }

  pinMode(BUZZER_PIN, OUTPUT);

  updateLCD();
}

void loop() {
  updateClock();

  if (year == 2026 && month == 6 && day == 1 && hour == 0 && minute == 0) {
    birthdayStarted = true;
  }

  if (birthdayStarted) {
    lcd.setCursor(0, 1);
    lcd.print("Happy Birthday ");

    runLedEffect();
    playBirthdaySong();
  }
}

void updateClock() {
  if (millis() - lastSecondUpdate >= 1000) {
    lastSecondUpdate = millis();

    second++;

    if (second >= 60) {
      second = 0;
      minute++;
    }

    if (minute >= 60) {
      minute = 0;
      hour++;
    }

    if (hour >= 24) {
      hour = 0;
      day++;
    }

    if (month == 5 && day > 31) {
      month = 6;
      day = 1;
    }

    updateLCD();
  }
}

void updateLCD() {
  lcd.setCursor(0, 0);

  lcd.print(year);
  lcd.print("-");

  printTwoDigits(month);
  lcd.print("-");

  printTwoDigits(day);
  lcd.print(" ");

  printTwoDigits(hour);
  lcd.print(":");

  printTwoDigits(minute);
  lcd.print(" ");

  lcd.setCursor(0, 1);

  if (birthdayStarted) {
    lcd.print("Happy Birthday ");
  } else {
    lcd.print("Time ");

    printTwoDigits(hour);
    lcd.print(":");

    printTwoDigits(minute);
    lcd.print(":");

    printTwoDigits(second);
    lcd.print(" ");
  }
}

void printTwoDigits(int value) {
  if (value < 10) {
    lcd.print("0");
  }
  lcd.print(value);
}

void runLedEffect() {
  if (millis() - lastLedUpdate >= 120) {
    lastLedUpdate = millis();

    for (int i = 0; i < ledCount; i++) {
      digitalWrite(ledPins[i], LOW);
    }

    digitalWrite(ledPins[ledIndex], HIGH);

    ledIndex++;

    if (ledIndex >= ledCount) {
      ledIndex = 0;
    }
  }
}

void playBirthdaySong() {
  if (!notePlaying) {
    int noteDuration = 1000 / noteDurations[currentNote];

    tone(BUZZER_PIN, melody[currentNote], noteDuration);

    noteStartTime = millis();
    notePlaying = true;
  } else {
    int noteDuration = 1000 / noteDurations[currentNote];

    if (millis() - noteStartTime >= noteDuration * 1.3) {
      noTone(BUZZER_PIN);

      currentNote++;

      if (currentNote >= melodyLength) {
        currentNote = 0;
      }

      notePlaying = false;
    }
  }
}