It watches both buttons and keeps two numbers.
Arduino
The brain
Loading part…
Lap Counter
multiple counter variables
Track total presses and laps with two int variables.
Pin connections
| Part 1 | Part 2 | |
|---|---|---|
Pushbutton pin 1 | → | Arduino pin 2 |
Pushbutton pin 2 | → | Arduino GND |
Pushbutton pin 1 | → | Arduino pin 3 |
Pushbutton pin 2 | → | Arduino GND |
See it
Two counters, one race!
Green button adds a lap, red button resets everything — two number boxes working together.
Running apps track your lap number and your total steps with different numbers, just like this.
The story
The problem
Sometimes one number is not enough — the lap count and the total presses are two different ideas.
Think of it like
It's like a lap board at a race: one sign shows "lap 3" and another shows the total.
Meet the parts
How it works
1
Did you press red?
The red button sets both numbers back to zero — a fresh start.
if (digitalRead(RESET_BUTTON) == LOW) {
totalPresses = 0;
lapNumber = 0;
}2
Did you press green?
The green button means count one more lap.
if (digitalRead(LAP_BUTTON) == LOW)
3
Add to both boxes
Both numbers grow by 1 — lapNumber is the lap, totalPresses counts every press.
totalPresses = totalPresses + 1; lapNumber = lapNumber + 1;
4
Show and wait
Show both numbers on the screen, then loop() checks the buttons again.
Serial.print("Lap ");
Serial.println(totalPresses);Then loop back to step 1
Build the circuit
Follow these steps in order. Match the wires to the colors shown.
- 1
Place Arduino
Place the Arduino (uno) on the breadboard.
Arduino placed — ready to count laps!
Loading part…
Try it
- Green button = new lap. Red button = reset both numbers.
- Watch the screen for Lap 1 | Total presses: 1
Peek at code
Two counter boxes
const int LAP_BUTTON = 2; const int RESET_BUTTON = 3; int totalPresses = 0; int lapNumber = 0;
totalPresses and lapNumber are two separate boxes — reset clears them both.
The reset button
lapNumber = 0;
Serial.println("Counters reset!");
while (digitalRead(RESET_BUTTON) == LOW) {
delay(20);
}
}
if (digitalRead(LAP_BUTTON) == LOW) {The red button sets both boxes back to 0 and says Counters reset!
The lap button
lapNumber = lapNumber + 1;
Serial.print("Lap ");
Serial.print(lapNumber);
Serial.print(" | Total presses: ");
Serial.println(totalPresses);
while (digitalRead(LAP_BUTTON) == LOW) {
delay(20);
}
}
delay(20);The green button adds 1 to each box and shows the lap and the total.
Show full sketch (lap-counter.ino)
const int LAP_BUTTON = 2;
const int RESET_BUTTON = 3;
int totalPresses = 0;
int lapNumber = 0;
void setup() {
pinMode(LAP_BUTTON, INPUT_PULLUP);
pinMode(RESET_BUTTON, INPUT_PULLUP);
Serial.begin(9600);
Serial.println("Lap Counter — green = lap, red = reset");
}
void loop() {
if (digitalRead(RESET_BUTTON) == LOW) {
totalPresses = 0;
lapNumber = 0;
Serial.println("Counters reset!");
while (digitalRead(RESET_BUTTON) == LOW) {
delay(20);
}
}
if (digitalRead(LAP_BUTTON) == LOW) {
totalPresses = totalPresses + 1;
lapNumber = lapNumber + 1;
Serial.print("Lap ");
Serial.print(lapNumber);
Serial.print(" | Total presses: ");
Serial.println(totalPresses);
while (digitalRead(LAP_BUTTON) == LOW) {
delay(20);
}
}
delay(20);
}
Quick quiz
Q1. What is a variable?
- A. A named box that stores a number ✓
- B. A kind of wire
- C. Just a wait
Why: Yes! int lapNumber = 0; makes a box named lapNumber.
Q2. What happens when you press the red reset button?
- A. Both totalPresses and lapNumber go back to 0 ✓
- B. Only lapNumber goes back to 0
- C. The Arduino restarts
Why: Yes! The red button sets totalPresses and lapNumber back to 0 together.
Code lab — try on your own
Start at lap 3 — change int lapNumber = 0 to int lapNumber = 3.
Hint: Line 4.
Add a note (comment) on the lapNumber line that says "next lap".
Hint: Line 24.
Code walkthrough
A line-by-line tour of the sketch — the same steps as in Robot Gurukul Studio.
Program overview
Big idea
Every Arduino program has a top part, a setup() part that runs once, and a loop() part that runs again and again.
In this project
A green button adds a lap and a red button sets everything back to zero, using two number boxes.
Tip
Read from the top to the bottom. Tap any word or line if you need help!
const int LAP_BUTTON = 2; const int RESET_BUTTON = 3; int totalPresses = 0; int lapNumber = 0;
setup()
Big idea
setup() runs one time when the board turns on.
In this project
It gets the green button (pin 2) and red button (pin 3) ready and opens the message screen.
Why here
Things we do only once go inside setup().
void setup() {
pinMode(LAP_BUTTON, INPUT_PULLUP);
pinMode(RESET_BUTTON, INPUT_PULLUP);
Serial.begin(9600);
Serial.println("Lap Counter — green = lap, red = reset");
}loop()
Big idea
loop() runs again and again, forever.
In this project
This is where we watch both buttons and update the numbers.
Why here
Things that repeat go inside loop().
void loop() {
if (digitalRead(RESET_BUTTON) == LOW) {
totalPresses = 0;
lapNumber = 0;
Serial.println("Counters reset!");
while (digitalRead(RESET_BUTTON) == LOW) {
delay(20);
}
}
if (digitalRead(LAP_BUTTON) == LOW) {
totalPresses = totalPresses + 1;
lapNumber = lapNumber + 1;
Serial.print("Lap ");
Serial.print(lapNumber);
Serial.print(" | Total presses: ");
Serial.println(totalPresses);
while (digitalRead(LAP_BUTTON) == LOW) {
delay(20);
}
}
delay(20);
}
Try this: Change a number inside loop(), then press Run to see what happens.
pinMode
Big idea
pinMode tells a pin if it will listen or push power out.
In this project
It sets the button pins to listen for presses.
Why here
It goes in setup() because we only set them once.
pinMode(LAP_BUTTON, INPUT_PULLUP);
digitalRead
Big idea
digitalRead checks if a pin is ON or OFF.
In this project
It checks if the red reset button is being pressed.
Why here
It goes in loop() so we can react the moment you press.
if (digitalRead(RESET_BUTTON) == LOW) {delay
Big idea
delay means wait. Nothing else happens while it waits.
In this project
A tiny wait helps the buttons read cleanly.
Why here
Right after we check a button.
delay(20);
begin
Big idea
Serial.begin opens a message screen so the board can talk to the computer.
In this project
It lets us print the lap and the total.
Why here
It goes in setup() once, before we print anything.
Serial.begin(9600);
Big idea
Serial.print writes words or a number on the screen and stays on the same line.
In this project
It writes "Lap " right before the lap number.
Why here
In loop() so the lap and total show on one line.
Serial.print("Lap ");println
Big idea
Serial.println writes on the screen and then jumps to a new line.
In this project
It prints a friendly hello when the board turns on.
Why here
So each message gets its own line.
Serial.println("Lap Counter — green = lap, red = reset");