Arduino Alarm Clock Project

// Arduino Alarm Clock Project
// 20x4 LCD, 7 buttons, piezo speaker

// Initialize variables
int hour = 0;           // Current hour
int minute = 0;         // Current minute
int second = 0;         // Current second
int hour_a = 0;         // Alarm hour
int minute_a = 0;       // Alarm minute
bool am_pm = false;     // Current AM/PM (false = AM, true = PM)
bool am_pm_a = false;   // Alarm AM/PM
int set_hr = 13;        // Pin 13: set current hour
int set_min = 12;       // Pin 12: set current minute
int set_am_pm = 11;     // Pin 11: set current AM/PM
int set_hr_a = 10;      // Pin 10: set alarm hour
int set_min_a = 9;      // Pin 9: set alarm minute
int set_am_pm_a = 8;    // Pin 8: set alarm AM/PM
int speaker = 7;        // Pin 7: speaker output
int quiet = 6;          // Pin 6: silence alarm button
bool alarm = false;     // Alarm active flag
bool quieted = false;   // Alarm silenced flag
int cur_time = 0;       // Current millis() snapshot
int etime = 0;          // Elapsed time

void setup() {
  // Initialize LCD at 9600 baud
  Serial.begin(9600);
  Serial.write(17);     // Backlight on
  Serial.write(24);     // Display on, cursor, no blink
  Serial.write(12);     // Clear screen
  Serial.write(128);    // Cursor to top-left
  
  // Set pin modes
  pinMode(set_hr, INPUT);
  pinMode(set_min, INPUT);
  pinMode(set_am_pm, INPUT);
  pinMode(set_hr_a, INPUT);
  pinMode(set_min_a, INPUT);
  pinMode(set_am_pm_a, INPUT);
  pinMode(speaker, OUTPUT);
  pinMode(quiet, INPUT);
  
  // Prompt user to set current time
  Serial.print("Set the current time");
  delay(2000);
  Serial.write(12);
  printTimes();
  cur_time = millis();
}

void loop() {
  // Update time
  keepTime();
  
  // Check if alarm should sound
  if ((hour == hour_a && minute == minute_a && !quieted) || alarm) {
    tone(speaker, 2000, 500);  // 2000 Hz for 500ms
    delay(500);
    if (!alarm) {
      alarm = true;  // Start alarm
    }
  }
  
  // Silence alarm if quiet button pressed
  if (alarm && !quieted && digitalRead(quiet)) {
    alarm = false;
    quieted = true;
  }
  
  // Reset quieted flag when minute changes
  if (!alarm && quieted && minute != minute_a) {
    quieted = false;
  }
  
  // Button inputs: set current hour
  if (digitalRead(set_hr) && hour < 12) {
    hour++;
    printTimes();
    debounce();
  } else if (digitalRead(set_hr) && hour == 12) {
    hour = 1;
    printTimes();
    debounce();
  }
  
  // Set current minute
  if (digitalRead(set_min) && minute < 59) {
    minute++;
    printTimes();
    debounce();
  } else if (digitalRead(set_min) && minute == 59) {
    minute = 0;
    printTimes();
    debounce();
  }
  
  // Set current AM/PM
  if (digitalRead(set_am_pm) && am_pm) {
    am_pm = false;
    printTimes();
    debounce();
  } else if (digitalRead(set_am_pm) && !am_pm) {
    am_pm = true;
    printTimes();
    debounce();
  }
  
  // Set alarm hour
  if (digitalRead(set_hr_a) && hour_a < 12) {
    hour_a++;
    printTimes();
    debounce();
  } else if (digitalRead(set_hr_a) && hour_a == 12) {
    hour_a = 1;
    printTimes();
    debounce();
  }
  
  // Set alarm minute
  if (digitalRead(set_min_a) && minute_a < 59) {
    minute_a++;
    printTimes();
    debounce();
  } else if (digitalRead(set_min_a) && minute_a == 59) {
    minute_a = 0;
    printTimes();
    debounce();
  }
  
  // Set alarm AM/PM
  if (digitalRead(set_am_pm_a) && am_pm_a) {
    am_pm_a = false;
    printTimes();
    debounce();
  } else if (digitalRead(set_am_pm_a) && !am_pm_a) {
    am_pm_a = true;
    printTimes();
    debounce();
  }
}

// Debounce: wait until all buttons released, then delay
void debounce() {
  while (digitalRead(set_hr) || digitalRead(set_min) ||
         digitalRead(set_am_pm) || digitalRead(set_hr_a) ||
         digitalRead(set_min_a) || digitalRead(set_am_pm_a)) {}
  delay(250);
}

// Update LCD display with current time and alarm
void printTimes() {
  Serial.write(12);  // Clear screen
  Serial.print("Current Time:");
  Serial.write(148); // Move cursor to second line
  
  if (hour < 10) Serial.print("0");
  Serial.print(hour);
  Serial.print(":");
  if (minute < 10) Serial.print("0");
  Serial.print(minute);
  Serial.print(":");
  if (second < 10) Serial.print("0");
  Serial.print(second);
  Serial.print(am_pm ? " PM" : " AM");
  
  Serial.write(168); // Move cursor to third line
  Serial.print("Alarm Set for:");
  Serial.write(188); // Move cursor to fourth line
  
  if (hour_a < 10) Serial.print("0");
  Serial.print(hour_a);
  Serial.print(":");
  if (minute_a < 10) Serial.print("0");
  Serial.print(minute_a);
  Serial.print(am_pm_a ? " PM" : " AM");
}

// Keep time using millis()
void keepTime() {
  etime = millis() - cur_time;
  
  if (etime >= 1000 && second < 59) {
    second++;
    cur_time = millis();
    printTimes();
  } else if (etime >= 1000 && second == 59 && minute < 59) {
    second = 0;
    minute++;
    cur_time = millis();
    printTimes();
  } else if (etime >= 1000 && second == 59 && minute == 59 && hour < 12) {
    second = 0;
    minute = 0;
    hour++;
    cur_time = millis();
    printTimes();
  } else if (etime >= 1000 && second == 59 && minute == 59 && hour == 12) {
    second = 0;
    minute = 0;
    hour = 1;
    am_pm = !am_pm;
    cur_time = millis();
    printTimes();
  }
}

This sketch uses Serial communication for the LCD (9600 baud). Button layout from left to right: set hour, set minute, set AM/PM, set alarm hour, set alarm minute, set alarm AM/PM, silence alarm.