Smart Stop 5.0

Note

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Kit purchase

Looking for parts? Check out our all-in-one kits below — packed with components, beginner-friendly guides, and tons of fun.

Name	Includes Arduino board	PURCHASE LINK
Elite Explorer Kit	Arduino Uno R4 WiFi	BUY
3 in 1 Ultimate Starter Kit	Arduino Uno R4 Minima	BUY

Course Introduction

In this lesson, you’ll learn how to use an L9110 Motor Driver Module, an Ultrasonic Sensor Module, an I2C LCD Module, an Buzzer module and a TT motor with the Arduino UNO R4 to create a Smart Stop 5.0 system.

As the obstacle gets closer to the Ultrasonic Sensor Module, the LCD screen displays the distance to obstacles and the servo speed.

Note

If this is your first time working with an Arduino project, we recommend downloading and reviewing the basic materials first.

Required Components

In this project, we need the following components:

SN	COMPONENT INTRODUCTION	QUANTITY	PURCHASE LINK
1	Arduino UNO R4 Minima/Arduino UNO R4 WIFI	1	BUY
2	USB Cable	1
3	Breadboard	1	BUY
4	Wires	Several	BUY
5	L9110 Motor Driver Module	1
6	Ultrasonic Sensor Module	1	BUY
7	TT Motor	1
8	Buzzer Modudle	1	BUY
9	I2C LCD 1602	1	BUY

Wiring

Common Connections:

Ultrasonic Sensor Module
- Trig: Connect to 10 on the Arduino.
- Echo: Connect to 11 on the Arduino.
- GND: Connect to breadboard’s negative power bus.
- VCC: Connect to breadboard’s red power bus.
TT Motor
- Connect to MOTOR B on the L9110 Motor Driver Module.
L9110 Motor Driver Module
- GND: Connect to breadboard’s negative power bus.
- VCC: Connect to breadboard’s red power bus.
- B-1B: Connect to 2 on the Arduino.
- B-1A: Connect to 3 on the Arduino.
Buzzer Module
- I/0: Connect to 4 on the Arduino.
- ＋: Connect to breadboard’s red power bus.
- －: Connect to breadboard’s negative power bus.
I2C LCD 1602
- SDA: Connect to A4 on the Arduino.
- SCL: Connect to A5 on the Arduino.
- GND: Connect to breadboard’s negative power bus.
- VCC: Connect to breadboard’s red power bus.

Writing the Code

Note

You can copy this code into Arduino IDE.
To install the library, use the Arduino Library Manager and search for LiquidCrystal I2C and install it.
Don’t forget to select the board(Arduino UNO R4 WiFi) and the correct port before clicking the Upload button.

#include <Wire.h>
#include <LiquidCrystal_I2C.h>

// I2C LCD (16x2)
LiquidCrystal_I2C lcd(0x27, 16, 2);

// Motor driver pins (L9110)
const int motorPinA = 3;
const int motorPinB = 2;

// Ultrasonic sensor pins
const int trigPin = 10;
const int echoPin = 11;

// Passive buzzer pin
const int buzzerPin = 4;

// Distance thresholds (cm)
const int STOP_DISTANCE = 5;
const int SLOW_DISTANCE = 20;

// Motor speed range (PWM)
const int MIN_MOTOR_PWM = 75;
const int MAX_MOTOR_PWM = 255;

// Variables for non-blocking buzzer
unsigned long previousBeepTime = 0;
bool beepState = false;

void setup() {

  // Set motor pins
  pinMode(motorPinA, OUTPUT);
  pinMode(motorPinB, OUTPUT);

  // Set ultrasonic pins
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);

  // Set buzzer pin
  pinMode(buzzerPin, OUTPUT);

  // Fix motor direction
  digitalWrite(motorPinB, LOW);

  // Initialize LCD
  lcd.init();
  lcd.backlight();

  // Startup message
  lcd.setCursor(0, 0);
  lcd.print("Smart Stop");
  lcd.setCursor(0, 1);
  lcd.print("Ready...");
  delay(1000);
  lcd.clear();
}

void loop() {

  // Read distance (cm)
  int distance = readDistance();

  // Calculate motor speed
  int speed = calculateSpeed(distance);

  // Control motor
  controlMotor(speed);

  // Update buzzer and display
  updateBuzzer(distance);
  updateLCD(distance);

  delay(50);
}

// Measure distance using ultrasonic sensor
int readDistance() {
  long duration;

  // Send trigger pulse
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  // Read echo time (with timeout)
  duration = pulseIn(echoPin, HIGH, 25000);

  // If no signal, return far distance
  if (duration == 0) return 100;

  // Convert to cm
  return duration / 58;
}

// Convert distance to motor speed
int calculateSpeed(int distance) {

  // Stop if too close
  if (distance <= STOP_DISTANCE) {
    return 0;
  }

  // Slow down in warning range
  if (distance <= SLOW_DISTANCE) {
    return map(distance,
              STOP_DISTANCE,
              SLOW_DISTANCE,
              MIN_MOTOR_PWM,
              MAX_MOTOR_PWM);
  }

  // Full speed when safe
  return MAX_MOTOR_PWM;
}

// Control motor speed (PWM)
void controlMotor(int speed) {
  analogWrite(motorPinA, speed);
  digitalWrite(motorPinB, LOW);
}

// Control buzzer without delay()
void updateBuzzer(int distance) {
  unsigned long currentTime = millis();

  // Fast beep when very close
  if (distance <= STOP_DISTANCE) {
    if (currentTime - previousBeepTime >= 100) {
      previousBeepTime = currentTime;
      beepState = !beepState;
      beepState ? tone(buzzerPin, 2000) : noTone(buzzerPin);
    }
  }
  // Slow beep in warning range
  else if (distance <= SLOW_DISTANCE) {
    if (currentTime - previousBeepTime >= 500) {
      previousBeepTime = currentTime;
      beepState = !beepState;
      beepState ? tone(buzzerPin, 800) : noTone(buzzerPin);
    }
  }
  // No sound when safe
  else {
    noTone(buzzerPin);
    beepState = false;
  }
}

// Update LCD display
void updateLCD(int distance) {

  // Line 1: system state
  lcd.setCursor(0, 0);

  if (distance <= STOP_DISTANCE) {
    lcd.print("STOP            ");
  }
  else if (distance <= SLOW_DISTANCE) {
    lcd.print("SLOW            ");
  }
  else {
    lcd.print("SAFE            ");
  }

  // Line 2: distance value
  lcd.setCursor(0, 1);
  lcd.print("Dist:");
  lcd.print(distance);
  lcd.print("cm   ");
}