1.Introduction:

                                   ‘Stopwatch using Arduino’ having two functions start and pause. It counts up to 23:59:59. The start button is used to start the stopwatch, pause button for pause the time. It can resume count by pressing the start button again.

2.Arduino Uno:

  Arduino platform offers open-source hardware and software that is easy to use and is used widely for projects.

• Arduino has 14 digital input/output pins that can be used for receiving and transmitting digital data.
• Arduino has 3 ground pins, one 5V, and one 3V pin which is used for providing power to   Bluetooth and relay device.

                                                                 Fig1.Arduino

• Pin no 2,3,4,5,11,12 are used to interface the 16*2 LCD display.
• Pin no 8 used for getting start signal from the push on the button.
• Pin no 7 used for getting a pause signal from the push on the button.

3. 16*2LCD Display:

• It is having 16 pins from that we used 12 pins for interfacing with Arduino.
• It is having 8 data lines (D0-D7) from that we used D0-D3.

                                                        Fig2. 16*2LCD Display

4.Circuit Diagram:

• Make the connection as shown in bellow figure.

                                                            Fig3.Circuit Diagram

• Button on the right side of the display is the start button and the left side is a pause button.
• When start button press then Arduino start the stopwatch and show it on display.
• After pressing pause button time pause until the start button press.

5.Program:

#include <LiquidCrystal.h>                 //includes the library code of LCD in aurdino 
unsigned long time; 
long int seconds=0; 
int minutes=0; 
int hours=0; 
int set=0; 
int reset=0; 
LiquidCrystal LCD(12, 11, 5, 4, 3, 2);  //RS,EN,D4,D5,D6,D7 pin of LCD respectively 
 

void setup() 
{ 
Serial.begin(9600);                   //initiates serial communication 
LCD.begin(16, 2);     //sets the number of columns and rows 
pinMode(8,INPUT); 
pinMode(7,INPUT); 
} 

void loop() 
{ 
//set=digitalRead(8); 
//Serial.println(set); 

if(digitalRead(8)==1) 
{ 
 while(digitalRead(7)==0) 
{   
setClock();         //function 
LCD.setCursor(0,1);     //sets the cursor to 0th column and 1st row,numbering starts from 0 
{ 
if(hours<10)        //suppose 4 
{ 
LCD.print("0");     //LCD first prints 0 and stopwatch shows 0 
LCD.print(hours);       //LCD then prints 4. So value printed is 04 stopwatch shows 04 
} 
else 
{ 
LCD.print(hours); 
} 
} 
LCD.print(":"); 
{ 
if(minutes<10) 
{ 
LCD.print("0"); 
LCD.print(minutes); 
LCD.print(":"); 
} 
else 
{ 
LCD.print(minutes); 
LCD.print(":"); 
} 
} 
{ 
if(seconds<10) 
{ 
LCD.print("0"); 
LCD.print(seconds); 
} 
else 
{ 
LCD.print(seconds); 
} 
} 
} 
}
} 

void setClock() 
{ 
seconds++;       //counts seconds from 0 
delay(1000);     //a delay of 1000 milliseconds is given for each second count 
if (seconds>59) 
{ 
seconds=0;      //whenever second is greater than 59 than second is made equal to 
minutes++;     // zero and a minute is counted for it 
} 
if (minutes>59) 
{hours++; 
minutes=0; 
} 

if(hours>23) 
{ 
hours=0; 
} 
}