Build a Mini Ping Pong Ball Launcher

Build a simple ping pong ball launcher using an Arduino, two DC motors, and an L298N motor driver.

This launcher may not send the ball very far, but that is part of the fun. The goal is to experiment with motor speed, direction, positioning, and launcher design.

Group Photos and Memories

Add group photos here with permission from everyone pictured.

Memories

Add a few notes after the class.

  • What made everyone laugh?
  • What launcher design worked best?
  • Did anyone find a surprising way to improve the distance?
  • What would we change next time?

Project Photo

Project

Video

What It Does

Two spinning motors grip the sides of a ping pong ball and launch it forward.

The Arduino controls the motors through an L298N motor driver. Commands sent through the Serial Monitor control:

  • Which motor runs
  • The motor direction
  • The motor speed
  • When both motors stop

Components

  • Arduino Uno
  • L298N motor driver
  • Two small DC motors
  • Ping pong balls
  • Jumper wires
  • Motor power supply

Wiring

Project

Arduino to L298N

Arduino Pin L298N Pin Purpose
5 ENA Motor 1 speed
8 IN1 Motor 1 direction
7 IN2 Motor 1 direction
6 ENB Motor 2 speed
4 IN3 Motor 2 direction
3 IN4 Motor 2 direction
GND GND Common ground

Motors

L298N Output Connection
OUT1 and OUT2 Motor 1
OUT3 and OUT4 Motor 2

Connect the external motor power source to the L298N motor power input.

Make sure the Arduino and L298N share a common ground.

How It Works

The L298N is a dual motor driver. It allows the Arduino to control two DC motors without powering them directly from the Arduino pins.

Each motor uses:

  • Two direction pins
  • One enable pin for speed control

The Arduino uses PWM values from 0 to 255 to control motor speed.

  • 0 means stopped.
  • 255 means full speed.

Serial Commands

Set the Serial Monitor baud rate to:

115200

Set the line ending to:

Newline

Example commands:

M1 CW 200
M1 CCW 150
M2 CW 255
M2 CCW 200
M1 STOP
M2 STOP
STOP

Command Format

MOTOR DIRECTION SPEED

Example:

M1 CW 200

This tells Motor 1 to rotate clockwise at a speed of 200.

Arduino Code

const int ENA = 5;
const int IN1 = 8;
const int IN2 = 7;

const int ENB = 6;
const int IN3 = 4;
const int IN4 = 3;

String command;

void setup() {
  Serial.begin(115200);

  pinMode(ENA, OUTPUT);
  pinMode(IN1, OUTPUT);
  pinMode(IN2, OUTPUT);

  pinMode(ENB, OUTPUT);
  pinMode(IN3, OUTPUT);
  pinMode(IN4, OUTPUT);

  stopAll();

  Serial.println("Ready");
  Serial.println("Examples:");
  Serial.println("M1 CW 200");
  Serial.println("M1 CCW 150");
  Serial.println("M2 CW 255");
  Serial.println("M2 STOP");
  Serial.println("STOP");
}

void loop() {
  if (Serial.available()) {
    command = Serial.readStringUntil('\n');
    command.trim();

    processCommand(command);
  }
}

void processCommand(String cmd) {
  if (cmd == "STOP") {
    stopAll();
    return;
  }

  int firstSpace = cmd.indexOf(' ');
  int secondSpace = cmd.indexOf(' ', firstSpace + 1);

  if (firstSpace == -1) {
    return;
  }

  String motor = cmd.substring(0, firstSpace);

  String direction;
  int speed = 0;

  if (secondSpace == -1) {
    direction = cmd.substring(firstSpace + 1);
  } else {
    direction = cmd.substring(firstSpace + 1, secondSpace);
    speed = cmd.substring(secondSpace + 1).toInt();
    speed = constrain(speed, 0, 255);
  }

  if (motor == "M1") {
    runMotor(ENA, IN1, IN2, direction, speed);
  } else if (motor == "M2") {
    runMotor(ENB, IN3, IN4, direction, speed);
  }
}

void runMotor(
  int enablePin,
  int pin1,
  int pin2,
  String direction,
  int speed
) {
  if (direction == "CW") {
    digitalWrite(pin1, HIGH);
    digitalWrite(pin2, LOW);
    analogWrite(enablePin, speed);
  } else if (direction == "CCW") {
    digitalWrite(pin1, LOW);
    digitalWrite(pin2, HIGH);
    analogWrite(enablePin, speed);
  } else if (direction == "STOP") {
    analogWrite(enablePin, 0);
  }
}

void stopAll() {
  analogWrite(ENA, 0);
  analogWrite(ENB, 0);
}

Try It!

Open the Serial Monitor and set the baud rate to 115200.

Start by entering:

M1 CW 100
M2 CCW 100

If the ping pong ball does not launch, don't worry! Every launcher is built a little differently.

Try experimenting with:

  • Changing the motor speed (100, 150, 200, 255)
  • Switching CW to CCW
  • Moving the motors closer together or farther apart
  • Adjusting the angle of the motors

Part of the fun is finding the combination that works best for your launcher.