Arduino Stopwatch





Introduction: Arduino Stopwatch

About: If it moves and it isn't supposed to move, Duct Tape it. If it doesn't move and its supposed to move, WD40 it. Hack with Sugru. Conor is a participant in the Amazon Services LLC Associates Program, an affi...

This Instructable will show you how to make a stop watch out of an Arduino.

Step 1: What You Will Need

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You Will Need:

- 1x Arduino Uno:

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- 1x LCD Keypad Shield:

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- 1x USB A - B Connector Cable:

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What I Recommend:

- Amazon Prime so you can get all your items the next day:

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- You could attach some of these magnets to attach the stopwatch onto nearly anything metal:

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- Arduino For Dummies (very helpful when learning code):

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- Arduino Projects For Dummies:

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Step 2: Slot the LCD Display Onto the Arduino

This step is very simple just slot the LCD display onto the Arduino.

Step 3: Connect and Install the Program

Just connect your Arduino to The Computer and install the program.

Update - Please use the Modified Stopwatch Program.

Step 4: Run Your Stopwatch

Now just run your stopwatch.

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thank you very much

WhatsApp Image 2017-05-20 at 11.10.05 PM.jpeg

Very cool idea and a great starting point, thanks!!!

I did a bit of rewrite to make it more accurate and display the time as it progresses plus other tweaks :


Standalone Arduino StopWatch

By Conor M - 11/05/15

Modified by Elac - 12/05/15


// call the necessary libraries
#include <SPI.h>
#include <LiquidCrystal.h>
// these are the pins used on the shield for this sketch
LiquidCrystal lcd(8, 13, 9, 4, 5, 6, 7);
// variables used on more than 1 function need to be declared here
unsigned long start, finished, elapsed;
boolean r = false;
// Variables for button debounce time
long lastButtonPressTime = 0; // the last time the button was pressed
long debounceDelay = 50; // the debounce time; keep this as low as possible

void setup()
lcd.begin(16, 2); // inicialize the lcd (16 chars, 2 lines)

// a little introduction :)
lcd.setCursor(4, 0); // set the cursor to first character on line 1 - NOT needed (it sets automatically on lcd.begin()
lcd.setCursor(3, 1); // set the cursor to 4th character on line 2
delay(2000); // wait 2 seconds
lcd.clear(); // clear the display
lcd.print("Press select for");
lcd.setCursor(2, 1); // set the cursor to 3rd character on line 2
lcd.print("Start & Stop");

void loop()

void CheckStartStop()
int x = analogRead (0); // assign 'x' to the Arduino's AnalogueInputs (Shield's buttons)
if (x < 800 && x > 600 ) // if the button is SELECT
if ((millis() - lastButtonPressTime) > debounceDelay)

if (r == false)
lcd.setCursor(2, 0); // needed
lcd.print("Elapsed Time");
start = millis(); // saves start time to calculate the elapsed time
else if (r == true)
lcd.setCursor(2, 0); // needed
lcd.print(" Final Time ");
r = !r;
lastButtonPressTime = millis();

void DisplayResult()
if (r == true)
finished = millis(); // saves stop time to calculate the elapsed time
// declare variables
float h, m, s, ms;
unsigned long over;

// MATH time!!!
elapsed = finished - start;

h = int(elapsed / 3600000);
over = elapsed % 3600000;
m = int(over / 60000);
over = over % 60000;
s = int(over / 1000);
ms = over % 1000;
// display the results
lcd.setCursor(0, 1);
lcd.print(h, 0); // display variable 'h' - the 0 after it is the number of algorithms after a comma (ex: lcd.print(h, 2); would print 0,00
lcd.print("h "); // and the letter 'h' after it
lcd.print(m, 0);
lcd.print("m ");
lcd.print(s, 0);
lcd.print("s ");
if (h < 10)
lcd.print(ms, 0);
lcd.print("ms ");

1 reply


I only want to count time while the button or another input is present , how would I go about this?

I'm struggling to get external buttons to work - I want to add a start and stop but keep getting stuck! Anybody done this with the modified code? :)

Welcome to join the group :)

how to install the program I don't see anything on my computer after connecting the arduino to it. do we need some software like matlab or something?

1 reply

Make sure you have downloaded the arduino software from

I want a coding I want to connect ir sensor to micro servo so that if something pass from front of ir sensor servo rotates at a 90 degree angle and returns to its initial position. I have a ARDUINO UNO for the purpose.... Can anybody do coding for this..PLZ PLZ PLZ THANK YOU... HOPE U REPLY...

please reply here --

2 replies

The code is there for you to use

Check out one of my other instructables, how to make an arduino web server, it uses a servo, hope it helps

Outstanding. I am using it and am happy to say it works without problem.

can somebody give me a version for measuring and displaying seconds,miliseconds and microseconds all on 3 digits each . If yes thanks in advance and contact me at

on the line elapsed = finished - start I am getting an error 'start' was not declared in this scope.

Any ideas?

1 reply

is your software up to date?

sorry I don't have a schematic

OK - got it working and it is great! Can you instruct me on how I can replace the SELECT button with an external switch for an experiment I am working on?