Things used in this project

Schematics

Fritzing Schematics
You can use any general purpose breadboard, including the Starter Kit one which is smaller than the one depicted here (the buzzer can be placed under the yellow wires, see the video and the photos).
Fritzing%20schematics
Fritzing Circuit Diagram
Fritzing%20electric%20diagram

Code

ArduinoSketchArduino
/**************************************************
 * Arduino Kitchen Timer v1.0 - 2016/01/27
 * By Angelo Fiorillo (Rome, IT)
 * This work is distributed under the GNU General 
 * Public License version 3 or later (GPL3+)
 * Please include this credit note if you want to 
 * re-use any part of this sketch. Respect my work 
 * as I'll do with yours.
 * Feel free to contact me: afiorillo@gmail.com
 * ************************************************/
#include <LiquidCrystal.h>
#include <Time.h>
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

const int buzzerPin = 10;
const int resetButtonPin = 6;
const int startStopButtonPin = 7;
const int downButtonPin = 8;
const int upButtonPin = 9;

int setupHours = 0;     // How many hours will count down when started
int setupMinutes = 0;   // How many minutes will count down when started
int setupSeconds = 0;   // How many seconds will count down when started
time_t setupTime = 0;

int currentHours = 0;
int currentMinutes = 0;
int currentSeconds = 0;
time_t currentTime = 0;

time_t startTime = 0;
time_t elapsedTime = 0;

int resetButtonState = LOW;
long resetButtonLongPressCounter = 0;
int startStopButtonState = LOW;
int upButtonState = LOW;
int downButtonState = LOW;
int resetButtonPrevState = LOW;
int startStopButtonPrevState = LOW;
int upButtonPrevState = LOW;
int downButtonPrevState = LOW;
bool resetButtonPressed = false;
bool resetButtonLongPressed = false;
bool startStopButtonPressed = false;
bool upButtonPressed = false;
bool downButtonPressed = false;

const int MODE_IDLE = 0;
const int MODE_SETUP = 1;
const int MODE_RUNNING = 2;
const int MODE_RINGING = 3;

int currentMode = MODE_IDLE;    // 0=idle 1=setup 2=running 3=ringing
                                // Power up --> idle
                                // Reset --> idle
                                //  Start/Stop --> start or stop counter
                                //  Up / Down --> NOP
                                // Reset (long press) --> enter setup
                                //   Start/Stop --> data select
                                //   Up --> increase current data value
                                //   Down --> decrease current data value
                                //   Reset --> exit setup (idle)

int dataSelection = 0;  // Currently selected data for edit (setup mode, changes with Start/Stop)
                        // 0=hours (00-99) 1=minutes (00-59) 2=seconds (00-59)

void setup() {
  // put your setup code here, to run once:
  lcd.begin(16, 2);
  pinMode(resetButtonPin, INPUT);
  pinMode(startStopButtonPin, INPUT);
  pinMode(upButtonPin, INPUT);
  pinMode(downButtonPin, INPUT);
  pinMode(buzzerPin, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  // put your main code here, to run repeatedly:
  startStopButtonPressed = false;
  upButtonPressed = false;
  downButtonPressed = false;

  /*
   * Reset button management
   */
  resetButtonPressed = false;
  resetButtonLongPressed = false;
  resetButtonState = digitalRead(resetButtonPin);
  if(resetButtonState != resetButtonPrevState)
  {
    resetButtonPressed = resetButtonState == HIGH;
    resetButtonPrevState = resetButtonState;
  }
  else  // Long press management...
  {
    if(resetButtonState == HIGH)
    {
      resetButtonLongPressCounter++;
      if(resetButtonLongPressCounter == 100)
      {
        resetButtonPressed = false;
        resetButtonLongPressed = true;
        resetButtonLongPressCounter = 0;
      }
    }
    else
    {
      resetButtonLongPressCounter = 0;
      resetButtonPressed = false;
      resetButtonLongPressed = false;
    }
  }

  /*
   * Start/Stop button management
   */
  startStopButtonPressed = false;
  startStopButtonState = digitalRead(startStopButtonPin);
  if(startStopButtonState != startStopButtonPrevState)
  {
    startStopButtonPressed = startStopButtonState == HIGH;
    startStopButtonPrevState = startStopButtonState;
  }

  /*
   * Down button management
   */
  downButtonPressed = false;
  downButtonState = digitalRead(downButtonPin);
  if(downButtonState != downButtonPrevState)
  {
    downButtonPressed = downButtonState == HIGH;
    downButtonPrevState = downButtonState;
  }

  /*
   * Up button management
   */
  upButtonPressed = false;
  upButtonState = digitalRead(upButtonPin);
  if(upButtonState != upButtonPrevState)
  {
    upButtonPressed = upButtonState == HIGH;
    upButtonPrevState = upButtonState;
  }

  /*
   * Mode management
   */
  switch(currentMode)
  {
    case MODE_IDLE:
      if(resetButtonPressed)
      {
        Reset();
      }
      if(resetButtonLongPressed)
      {
        currentMode = MODE_SETUP;
      }
      if(startStopButtonPressed)
      {
        currentMode = currentMode == MODE_IDLE ? MODE_RUNNING : MODE_IDLE;
        if(currentMode == MODE_RUNNING)
        {
          // STARTING TIMER!
          startTime = now();
        }
      }
      break;

    case MODE_SETUP:
      if(resetButtonPressed)
      {
        // Exit setup mode
        setupTime = setupSeconds + (60 * setupMinutes) + (3600 * setupHours);
        currentHours = setupHours;
        currentMinutes = setupMinutes;
        currentSeconds = setupSeconds;
        dataSelection = 0;
        currentMode = MODE_IDLE;
      }
      if(startStopButtonPressed)
      {
        // Select next data to adjust
        dataSelection++;
        if(dataSelection == 3)
        {
          dataSelection = 0;
        }
      }
      if(downButtonPressed)
      {
        switch(dataSelection)
        {
          case 0: // hours
            setupHours--;
            if(setupHours == -1)
            {
              setupHours = 99;
            }
            break;
          case 1: // minutes
            setupMinutes--;
            if(setupMinutes == -1)
            {
              setupMinutes = 59;
            }
            break;
          case 2: // seconds
            setupSeconds--;
            if(setupSeconds == -1)
            {
              setupSeconds = 59;
            }
            break;
        }
      }
      if(upButtonPressed)
      {
        switch(dataSelection)
        {
          case 0: // hours
            setupHours++;
            if(setupHours == 100)
            {
              setupHours = 0;
            }
            break;
          case 1: // minutes
            setupMinutes++;
            if(setupMinutes == 60)
            {
              setupMinutes = 0;
            }
            break;
          case 2: // seconds
            setupSeconds++;
            if(setupSeconds == 60)
            {
              setupSeconds = 0;
            }
            break;
        }
      }
      break;
    
    case MODE_RUNNING:
      if(startStopButtonPressed)
      {
        currentMode = MODE_IDLE;
      }
      if(resetButtonPressed)
      {
        Reset();
        currentMode = MODE_IDLE;
      }
      break;

    case MODE_RINGING:
      if(resetButtonPressed || startStopButtonPressed || downButtonPressed || upButtonPressed)
      {
        currentMode = MODE_IDLE;
      }
      break;
  }

  /*
   * Time management
   */
  switch(currentMode)
  {
    case MODE_IDLE:
    case MODE_SETUP:
      // NOP
      break;
    case MODE_RUNNING:
      currentTime = setupTime - (now() - startTime);
      if(currentTime <= 0)
      {
        currentMode = MODE_RINGING;
      }
      break;
    case MODE_RINGING:
      analogWrite(buzzerPin, 20);
      delay(20);
      analogWrite(buzzerPin, 0);
      delay(40);
      break;
  }

  /*
   * LCD management
   */
  //lcd.clear();
  lcd.setCursor(0, 0);
  switch(currentMode)
  {
    case MODE_IDLE:
      lcd.print("Timer ready     ");
      lcd.setCursor(0, 1);
      lcd.print(currentHours);
      lcd.print(" ");
      lcd.print(currentMinutes);
      lcd.print(" ");
      lcd.print(currentSeconds);
      lcd.print("    ");
      break;
    case MODE_SETUP:
      lcd.print("Setup mode: ");
      switch(dataSelection)
      {
        case 0:
          lcd.print("HRS ");
          break;
        case 1:
          lcd.print("MINS");
          break;
        case 2:
          lcd.print("SECS");
          break;
      }
      lcd.setCursor(0, 1);
      lcd.print(setupHours);
      lcd.print(" ");
      lcd.print(setupMinutes);
      lcd.print(" ");
      lcd.print(setupSeconds);
      lcd.print("    ");
      break;
    case MODE_RUNNING:
      lcd.print("Counting down...");
      lcd.setCursor(0, 1);
      if(hour(currentTime) < 10) lcd.print("0");
      lcd.print(hour(currentTime));
      lcd.print(":");
      if(minute(currentTime) < 10) lcd.print("0");
      lcd.print(minute(currentTime));
      lcd.print(":");
      if(second(currentTime) < 10) lcd.print("0");
      lcd.print(second(currentTime));
      break;
    case MODE_RINGING:
      lcd.print("   RING-RING!   ");
      lcd.setCursor(0, 1);
      lcd.print("                ");
      break;
  }
  delay(10);
}

void Reset()
{
  currentMode = MODE_IDLE;
  currentHours = setupHours;
  currentMinutes = setupMinutes;
  currentSeconds = setupSeconds;
}

Credits

P1100942 2 2
Angelo Fiorillo
1 project • 21 followers
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