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Arduino UNO-Based Obstacle-Avoiding Robot with Ultrasonic Sensors and DC Motors

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Circuit Documentation

Summary

This circuit is designed to control two DC motors using an L298N motor driver and an Arduino UNO. It also includes three HC-SR04 ultrasonic sensors for obstacle detection. The power is supplied by a 3xAAA battery pack with a switch.

Component List

  1. DC Motor

    • Description: A standard DC motor.
    • Pins: pin 1, pin 2

  2. L298N DC Motor Driver

    • Description: A dual H-Bridge motor driver that allows control of two DC motors.
    • Pins: OUT1, OUT2, 12V, GND, 5V, OUT3, OUT4, 5V-ENA-JMP-I, 5V-ENA-JMP-O, +5V-J1, +5V-J2, ENA, IN1, IN2, IN3, IN4, ENB

  3. HC-SR04 Ultrasonic Sensor

    • Description: An ultrasonic distance sensor.
    • Pins: VCC, TRIG, ECHO, GND

  4. Arduino UNO

    • Description: A microcontroller board based on the ATmega328P.
    • Pins: UNUSED, IOREF, Reset, 3.3V, 5V, GND, Vin, A0, A1, A2, A3, A4, A5, SCL, SDA, AREF, D13, D12, D11, D10, D9, D8, D7, D6, D5, D4, D3, D2, D1, D0

  5. 3xAAA Battery Pack with Switch and JST

    • Description: A battery pack that holds three AAA batteries and includes a switch.
    • Pins: POS, NEG

Wiring Details

DC Motor 1

DC Motor 2

L298N DC Motor Driver

HC-SR04 Ultrasonic Sensor 1

HC-SR04 Ultrasonic Sensor 2

HC-SR04 Ultrasonic Sensor 3

Arduino UNO

3xAAA Battery Pack with Switch and JST

Documented Code

#include <NewPing.h>

// Motor Pins
const int IN_LEFT_F = 12; // Motor Left 
const int IN_LEFT_R = 13; // Motor Left control pin

const int IN_RIGHT_F = 8; // Motor Right control pin
const int IN_RIGHT_R = 9; // Motor Right control pin

const int EN_LEFT = 11; // PWM control for Motor Left
const int EN_RIGHT = 10; // PWM control for Motor Right

// Ultrasonic Sensor Pins and Settings
const int TRIG_FRONT = 4; 
const int ECHO_FRONT = 3;

// Ultrasonic Sensor Pins and Settings

const int TRIG_LEFT = 6; 
const int ECHO_LEFT = 5;

// Ultrasonic Sensor Pins and Settings
const int TRIG_RIGHT = 15; 
const int ECHO_RIGHT = 14;

/*Define RX and TX pins for SoftwareSerial
SoftwareSerial BTSerial(1, 0); // RX, TX
String incomingData = "";
*/
const int motorSpeed_RIGHT = 100; // (max PWM value 255)
const int motorSpeed_LEFT = 100;  // (max PWM value 255, 25 to support)

// Max distance to measure in cm
const int MAX_DISTANCE = 250; 

//Create NewPing objects for each sensor
NewPing sonarFront(TRIG_FRONT, ECHO_FRONT, MAX_DISTANCE); 
NewPing sonarRight(TRIG_RIGHT, ECHO_RIGHT, MAX_DISTANCE);
NewPing sonarLeft(TRIG_LEFT, ECHO_LEFT, MAX_DISTANCE);

const int distanceFThreshold = 15; // Distance in cm for obstacle detection
const int distanceRThreshold = 8; // Distance in cm for obstacle detection
const int distanceLThreshold = 8; // Distance in cm for obstacle detection

int distanceFront=0;
int distanceLeft=0;
int distanceRight=0;
int hitCounter = 0;

void setup() {
  // Motor pins setup
  pinMode(IN_RIGHT_F, OUTPUT);
  pinMode(IN_RIGHT_R, OUTPUT);
  pinMode(IN_LEFT_F, OUTPUT);
  pinMode(IN_LEFT_R, OUTPUT);
  
  pinMode(EN_RIGHT, OUTPUT);
  pinMode(EN_LEFT, OUTPUT);
  
  analogWrite(EN_RIGHT, motorSpeed_RIGHT); // Set motor speed to 10%
  analogWrite(EN_LEFT, motorSpeed_LEFT); // Set motor speed to 10%
/*
  BTSerial.begin(9600); // Default baud rate of HC-05/HC-06
  Serial.println("Bluetooth module ready.");
*/
  Serial.begin(9600); // Initialize Serial for debugging
}

void loop() {

  distanceFront = sonarFront.convert_cm(sonarFront.ping_median(5));
  distanceRight = sonarRight.convert_cm(sonarRight.ping_median(5));
  distanceLeft = sonarLeft.convert_cm(sonarLeft.ping_median(5));

  Serial.print("Front: ");
  Serial.print(distanceFront);
  Serial.print(" cm | Left: ");
  Serial.print(distanceLeft);
  Serial.print(" cm | Right: ");
  Serial.print(distanceRight);
  Serial.println(" cm");

  if (distanceFront == 0 || distanceLeft == 0 || distanceRight == 0) {
    Serial.println(" ------ Sensor issue or I am hit");
    stopMotors();
    delay(200);
    hitCounter = hitCounter + 1;
    if (hitCounter > 5){
      moveBackward();
      delay