Creating a driverless car using Arduino is a complex but rewarding project. Below is a step-by-step guide to building a basic autonomous car using Arduino, sensors, and motors. This project will use an ultrasonic sensor for obstacle detection and an L298N motor driver to control the motors.



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### **Components Required**
1. **Arduino Uno** (or any compatible board)
2. **Ultrasonic Sensor (HC-SR04)** - For obstacle detection
3. **L298N Motor Driver** - To control DC motors
4. **DC Motors (2 or 4)** - For movement
5. **Chassis with Wheels** - For the car body
6. **Battery Pack (6V or 9V)** - To power the motors and Arduino
7. **Jumper Wires** - For connections
8. **Breadboard** - For prototyping
9. **Wheel Encoders (Optional)** - For precise movement control
10. **Servo Motor (Optional)** - For rotating the ultrasonic sensor

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### **Circuit Diagram**
1. **L298N Motor Driver Connections**:
   - Connect `IN1`, `IN2`, `IN3`, and `IN4` to Arduino digital pins (e.g., 8, 9, 10, 11).
   - Connect `ENA` and `ENB` to PWM pins (e.g., 5, 6) for speed control.
   - Connect the motor terminals to the L298N output pins.
   - Connect the L298N `VCC` to the battery pack and `GND` to the common ground.
   - Connect the L298N `5V` pin to the Arduino `5V` pin.

2. **Ultrasonic Sensor Connections**:
   - Connect `VCC` to Arduino `5V`.
   - Connect `GND` to Arduino `GND`.
   - Connect `Trig` to Arduino digital pin (e.g., 12).
   - Connect `Echo` to Arduino digital pin (e.g., 13).

3. **Power Connections**:
   - Connect the battery pack to the L298N motor driver and Arduino (via Vin or external power jack).

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### **Arduino Code**
Below is the Arduino code for a basic obstacle-avoiding car:

```cpp
// Define motor control pins
#define IN1 8
#define IN2 9
#define IN3 10
#define IN4 11
#define ENA 5
#define ENB 6

// Define ultrasonic sensor pins
#define TRIG 12
#define ECHO 13

// Define distance threshold (in cm)
#define DISTANCE_THRESHOLD 20

void setup() {
  // Set motor control pins as output
  pinMode(IN1, OUTPUT);
  pinMode(IN2, OUTPUT);
  pinMode(IN3, OUTPUT);
  pinMode(IN4, OUTPUT);
  pinMode(ENA, OUTPUT);
  pinMode(ENB, OUTPUT);

  // Set ultrasonic sensor pins
  pinMode(TRIG, OUTPUT);
  pinMode(ECHO, INPUT);

  // Initialize serial communication
  Serial.begin(9600);
}

void loop() {
  // Measure distance
  long distance = measureDistance();

  // If obstacle is detected, stop and turn
  if (distance < DISTANCE_THRESHOLD) {
    stopCar();
    delay(500);
    turnRight();
    delay(500);
  } else {
    moveForward();
  }
}

// Function to measure distance using ultrasonic sensor
long measureDistance() {
  digitalWrite(TRIG, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG, LOW);

  long duration = pulseIn(ECHO, HIGH);
  long distance = duration * 0.034 / 2; // Convert to cm

  Serial.print("Distance: ");
  Serial.println(distance);

  return distance;
}

// Function to move forward
void moveForward() {
  digitalWrite(IN1, HIGH);
  digitalWrite(IN2, LOW);
  digitalWrite(IN3, HIGH);
  digitalWrite(IN4, LOW);
  analogWrite(ENA, 200); // Set speed
  analogWrite(ENB, 200);
}

// Function to stop the car
void stopCar() {
  digitalWrite(IN1, LOW);
  digitalWrite(IN2, LOW);
  digitalWrite(IN3, LOW);
  digitalWrite(IN4, LOW);
}

// Function to turn right
void turnRight() {
  digitalWrite(IN1, HIGH);
  digitalWrite(IN2, LOW);
  digitalWrite(IN3, LOW);
  digitalWrite(IN4, HIGH);
  analogWrite(ENA, 200);
  analogWrite(ENB, 200);
  delay(500); // Adjust delay for turning angle
}
```

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### **How It Works**
1. **Ultrasonic Sensor**:
   - The sensor measures the distance to obstacles in front of the car.
   - If an obstacle is detected within the threshold distance (e.g., 20 cm), the car stops and turns right.

2. **Motor Control**:
   - The L298N motor driver controls the direction and speed of the motors.
   - The car moves forward by default and turns when an obstacle is detected.

3. **Power Supply**:
   - The battery pack powers both the Arduino and the motors.

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### **Enhancements**
1. **Add More Sensors**:
   - Use multiple ultrasonic sensors or IR sensors for better obstacle detection.
   - Add a line-following sensor for path tracking.

2. **Use a Servo Motor**:
   - Attach the ultrasonic sensor to a servo motor to scan the environment in multiple directions.

3. **Implement PID Control**:
   - Use wheel encoders and PID control for precise movement and turning.

4. **Bluetooth/WiFi Control**:
   - Add a Bluetooth or WiFi module (e.g., HC-05 or ESP8266) for remote control.

5. **Mapping and Navigation**:
   - Use an advanced microcontroller (e.g., Raspberry Pi) for mapping and navigation algorithms.

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### **Testing and Calibration**
1. Test the car in an open area with no obstacles.
2. Adjust the distance threshold and turning delay for better performance.
3. Calibrate the motor speeds to ensure smooth movement.

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