Arduino Based Countdown Timer

A timer is a clock type used for time interval calculation. There are two types for calculating the time elapsed, one counting upward from zero, called a stopwatch. And the second counts from a specified time, typically called the countdown-timer, provided by the user. 

Here we’re going to teach you how to create Arduino for a countdown timer. There is no real-time clock module (RTC) here to get the time. The user with Keypad and 16×2 LCD provides the length. And when the timer reached Zero, the Buzzer warning sound is made.

Hardware Components

The required hardware components for making  Arduino Based Countdown Timer are listed below:

S. No	Component	Value	Qty
1	Potentiometer	10k	1
2	Arduino UNO	–	1
3	Buzzer	–	1
4	Pushbutton	–	1
5	Resistor	10k	1
6	Resistor	100ohm	1
7	Connecting wires	–	–
8	LCD 16*2	–	1
9	4*4 matrix keypad	–	1

CODE

// Arduino Countdown Timer Code
#include <LiquidCrystal.h>
#include <Keypad.h>
const byte ROWS = 4; // Four rows
const byte COLS = 4; // Three columns

long int set1;
long int set2;
long int set3;
long int set4;
long int j;

String hours;
String minutes;
String seconds;
// Define the Keymap

char keys[ROWS][COLS] = {

  {'1','2','3','A'},

  {'4','5','6','B'},

  {'7','8','9','C'},

  {'*','0','#','D'}

};

byte rowPins[ROWS] = { 6, 7, 8, 9 };// Connect keypad ROW0, ROW1, ROW2 and ROW3 to these Arduino pins
byte colPins[COLS] = { 10, 11, 12, 13 };// Connect keypad COL0, COL1 and COL2 to t

Keypad kpd = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS );

LiquidCrystal lcd(A0, A1, 5, 4, 3, 2); // Creates an LC object. Parameters: (rs, enable, d4, d5, d6, d7)

 int t1, t2, t3, t4, t5, t6;
 int r1, r2, r3;
 
boolean feed = true; // condition for alarm

 char key;
 String r[8];

 void setFeedingTime()
{
  feed = true;
   int i=0;

  lcd.clear();
  lcd.setCursor(0,0);
  lcd.print("Set feeding Time");
  lcd.clear();
  lcd.print("HH:MM:SS");
  lcd.setCursor(0,1);

  
  while(1){
    key = kpd.getKey();

    char j;
    
  if(key!=NO_KEY){
    
    lcd.setCursor(j,1);
    
    lcd.print(key);
    
    r[i] = key-48;
    i++;
    j++;

    if (j==2 || j == 5)
    {
      lcd.print(":"); j++;
    }
    delay(500);
  }

  if (key == 'D')
  {key=0; break; }
  }
 lcd.clear();
}
 
 void setup() 
 { 
  lcd.begin(16,2);
  Serial.begin(9600);
  pinMode(A0, OUTPUT);
  pinMode(A1, OUTPUT);
  pinMode(A3, INPUT);
  pinMode(A4, OUTPUT);
 } 
 
 void loop() 
 { 
      lcd.setCursor(0,0);
      lcd.print("Arduino Timer");
      //Serial.println(A3);

      if (digitalRead(A3)==1) //
      {
      lcd.clear();
      setFeedingTime(); 
      for(int i = 0; i < 6; i++)  // this for loop is used to get the value of the feeding time and print it serially
      {
       Serial.print(r[i]);
       Serial.println();
      }
      
   hours = String (r[0]) + String (r[1]) ; //combining two separate int values of r[0] and r[1] into one string and save it to "hours" 
   minutes = String (r[2]) + String (r[3]) ;  //combining two separate int values of r[2] and r[3] into one string and save it to "minutes" 
   seconds = String (r[4]) + String (r[5]) ;  //combining two separate int values of r[4] and r[5] into one string and save it to "seconds" 

  
  set1 = (hours.toInt()*3600); //converting hours into seconds
  set2 = (minutes.toInt() * 60);  //converting minutes into seconds
  set3 = seconds.toInt();
  set4 = (hours.toInt() * 3600)+ (minutes.toInt() * 60) + seconds.toInt(); //adding set1, set2 and set3 together in set4
  Serial.print("set4");
  Serial.print(set4);
  Serial.println();

  lcd.setCursor(0,0);
  lcd.print("Countdown begins");
  delay(1000);
  lcd.clear();
  
  for(long int j = set4; j >= 0; j--) // this for loopis used to decrease the total time in seconds
  {
  Serial.println(j);
  
  lcd.setCursor(0,0);
  lcd.print("HH:MM:SS");
  
  long int HH = j / 3600; // converting the remaining time into remaining hours
  lcd.setCursor(0,1);
  Serial.println(HH);
  if (HH < 10) { lcd.print('0');  }
  lcd.print(HH);
  lcd.print(":");
  
  long int MM = (j - (HH*3600))/60 ; //converting the remaining time into remaining minutes
  lcd.setCursor(3,1);
  Serial.println(MM);
  if (MM < 10) { lcd.print('0');  }
  lcd.print(MM);
  lcd.print(":");
  
  long int SS = j - ((HH*3600)+(MM*60)); //converting the remaining time into remaining seconds
  lcd.setCursor(6,1);
  Serial.println(SS);
  if (SS < 10) { lcd.print('0');  } 
  lcd.print(SS);
  delay(1000);

  if (digitalRead(A3)==1){break;} 

   if (j == 0)
    
    {
      lcd.clear();
      lcd.setCursor(0,0);
      lcd.print("Timer Stop");
      lcd.setCursor(2,1);
      lcd.print("-Ring-Ring-");
      
    for(int k =0; k<= 100; k++) //this for loop is used for the buzzer to beep 100 time as the timer reaches zero
      {
        digitalWrite(A4,HIGH);
        delay(300);
        digitalWrite(A4,LOW);  
        delay(300); 
        if (digitalRead(A3)==1){break;}  
      }
    }
   }
  }
}       

Circuit Diagram

Working Explanation

It’s easy to work with this Arduino Timer, but the code is a little complicated. Notes in the code describe the code. At first, “Arduino Timer” is printed on the LCD display before the push-button is pressed. If you press the button, it will be asked to enter countdown times by naming the feature “Set Feeding Time.”

You will then use Keypad to enter the time duration. Then you must click ‘D’ to save time and start the countdown timer.  We made some calculations here for the void loop() function to decrease the time second to second and display the correct value of Hour, Minutes, and Seconds values (HH:MM: SS) compared to the rest of the time. 

The buzzer begins beeping and beeps up 100 times only until the timer reaches zero, as per the code. Press and hold the button to stop the buzzer. To stop the time between counting, you should still use the Pushbutton.