Arduino Obstacle Avoiding Car

Overview

The Arduino Obstacle Avoiding Car is an autonomous robot that can navigate its environment by detecting and avoiding obstacles in real-time. This intelligent vehicle uses a servo-mounted ultrasonic sensor to scan for objects in front, left, and right directions, allowing it to determine the best path forward without colliding with obstacles.

Project Tutorial: Arduino Obstacle Avoiding Car - Circuit Digest

Features

Autonomous Navigation: Real-time obstacle detection and avoidance
360° Scanning: Servo motor rotates ultrasonic sensor to check left, right, and front directions
Visual Indicators: RGB LEDs display movement status (green for forward, red for stop/reverse)
Motor Control: Four-wheel drive with independent speed control using L298N motor driver
Smart Decision Making: Calculates optimal path based on available space

Components Required

Component	Quantity	Description
Arduino Uno	1	Main microcontroller
HC-SR04 Ultrasonic Sensor	1	Distance measurement (40kHz ultrasonic waves)
MG90 Metal Gear Servo Motor	1	Sensor rotation for scanning
L298N Motor Driver	1	DC motor control
RGB LEDs	3	Visual movement indicators
2WD Arduino Car Kit	1	Laser cut chassis with 4 geared motors
12V Li-ion Battery	1	Power source
LM2596 DC-DC Buck Converter	1	Voltage regulation (12V to 5V)
Power Switch	1	On/Off control
Breadboard/PCB	1	Circuit assembly
Jumper Wires	As needed	Connections
Screws, Nuts, Spacers	As needed	Assembly hardware

Pin Configuration

Ultrasonic Sensor (HC-SR04)

VCC → 5V (from LM2596)
GND → GND
TRIG → Digital Pin 2
ECHO → Digital Pin 4

Servo Motor (MG90)

Signal → PWM Pin 5
VCC → 5V (from LM2596)
GND → GND

RGB LEDs

Right LED:
- Green → Pin 9
- Red → A3
- GND → Common Ground
Center LED:
- Green → Pin 13
- Red → A2
- GND → Common Ground
Left LED:
- Green → Pin 10
- Red → A1
- GND → Common Ground

L298N Motor Driver

IN1 → Pin 8 (Left Motor Control)
IN2 → Pin 7 (Left Motor Control)
IN3 → Pin 12 (Right Motor Control)
IN4 → Pin 11 (Right Motor Control)
ENA → PWM Pin 6 (Left Motor Speed)
ENB → PWM Pin 3 (Right Motor Speed)
12V Input → 12V Battery Positive
GND → Battery Negative

Power Supply

12V Li-ion Battery → LM2596 Input & L298N 12V Input
LM2596 5V Output → Arduino 5V & Sensor/Servo Power
Common Ground → All components

Circuit Diagram

The complete circuit connects the ultrasonic sensor for obstacle detection, servo motor for sensor rotation, L298N motor driver for wheel control, and RGB LEDs for status indication. The LM2596 buck converter steps down 12V battery power to 5V for the Arduino, sensors, and servo motor.

How It Works

Operating Principle

Power On: When powered, the Arduino initializes all components
Scanning Phase: The servo motor rotates the ultrasonic sensor to scan three directions:
- Left (180°)
- Front (90°)
- Right (0°)
Distance Measurement: The HC-SR04 sensor emits 40kHz ultrasonic pulses and calculates distance based on echo return time
Decision Making:
- If front distance ≥ threshold (12cm): Move forward
- If obstacle detected: Stop and scan all directions
- Choose direction with most clearance
Navigation: Execute turn (left/right) or continue forward
Visual Feedback:
- All Green: Moving forward
- All Red: Stopped
- Single Green: Turning (green LED indicates turn direction)

Distance Calculation

The ultrasonic sensor calculates distance using the formula:

Distance (cm) = (Pulse Duration / 29) / 2

Where:

Pulse duration is measured in microseconds
Speed of sound: 340 m/s
Division by 29 converts to cm, division by 2 accounts for round trip

Obstacle Detection Logic

If (Front Distance < 12cm):
    Stop()
    Scan Left, Front, Right
    
    If (Both Left & Right ≤ 25cm):
        Move Forward (force through)
    Else If (Left Distance > Right Distance):
        Turn Left
    Else:
        Turn Right

Code Structure

Main Functions

`setup()`

Initializes all pin modes (INPUT/OUTPUT)
Attaches servo motor to Pin 5
Sets initial motor speeds via PWM
Initializes serial communication (9600 baud) for debugging
Sets all LEDs to OFF state

`loop()`

Centers servo to look forward (90°)
Measures front distance
Moves forward if path is clear
Stops when obstacle detected
Calls checkDirection() to find best path
Executes appropriate turn or forward movement

`getDistance()`

Sends 10μs trigger pulse to HC-SR04
Measures echo pulse duration
Calculates and returns distance in cm
Prints distance to serial monitor for debugging

`checkDirection()`

Rotates servo to scan left (180°), front (90°), and right (0°)
Stores distances in array: [left, right, front]
Returns optimal turn direction:
- 0 = Turn Left
- 2 = Turn Right
- 3 = Move Forward

Motor Control Functions

moveForward()

Sets motor speeds (ENA: 60.5, ENB: 52)
Turns all LEDs green
Both motors rotate forward

turnLeft()

Increases motor speed (100, 90) for sharper turn
Left LED green, center & right red
Left motor backward, right motor forward

turnRight()

Increases motor speed (100, 90)
Right LED green, center & left red
Left motor forward, right motor backward

Stop()

All LEDs turn red
Brief reverse pulse for immediate stop
Sets all motor speeds to 0

Installation & Setup

1. Hardware Assembly

Mount Components:
- Secure Arduino Uno to chassis using spacers
- Mount L298N motor driver
- Install ultrasonic sensor on servo motor
- Position servo at front of chassis
- Attach RGB LEDs to underside
Wire Connections:
- Follow pin configuration table above
- Use jumper wires or solder to PCB for permanent connections
- Ensure proper polarity for motors and LEDs
Power System:
- Connect 12V battery to LM2596 input
- Wire LM2596 5V output to Arduino and sensors
- Install power switch in battery positive line
- Add optional battery level indicator and charging port
Final Checks:
- Verify all connections against circuit diagram
- Check for loose wires or potential short circuits
- Ensure motors are securely mounted
- Test servo rotation range

2. Software Installation

Install Arduino IDE:
- Download from arduino.cc
- Install appropriate version for your OS

Install Required Library:

Servo.h (usually pre-installed with Arduino IDE)

Upload Code:
- Open Arduino IDE
- Copy the complete code (provided in repository)
- Select Board: Arduino Uno
- Select Port: Correct COM port
- IMPORTANT: Turn OFF power switch before uploading
- Click Upload button
- Wait for "Done uploading" message

3. Testing & Calibration

Motor Speed Calibration:
- Adjust ENA and ENB values in code for balanced movement
- Default values: ENA=53.5, ENB=45 (idle), ENA=60.5, ENB=52 (forward)
Distance Threshold:
- Modify MIN_DISTANCE_BACK (default: 12cm) based on your requirements
- Larger value = more cautious navigation
Turn Timing:
- Adjust delay values in turnLeft() and turnRight() functions
- Default: 425ms (left), 415ms (right)
- Test on different surfaces for optimal turns

Code Customization

Adjustable Parameters

// Distance threshold (line 21)
#define MIN_DISTANCE_BACK 12  // Change based on obstacle size

// Motor speeds (lines 57-58 for idle)
analogWrite(ENA, 53.5);  // Left motor idle speed
analogWrite(ENB, 45);    // Right motor idle speed

// Forward speeds (lines 155-156)
analogWrite(ENA, 60.5);  // Left motor forward speed
analogWrite(ENB, 52);    // Right motor forward speed

// Turn speeds (lines 171, 185)
analogWrite(ENA, 100);   // Turn speed
analogWrite(ENB, 90);

// Turn duration (lines 99, 105)
delay(425);  // Left turn duration in milliseconds
delay(415);  // Right turn duration in milliseconds

Enhancements

This project includes several upgrades beyond basic functionality:

Power Management:
- Power on/off switch
- 12V DC charging socket
- Li-ion battery level indicator
- Slider switch for battery monitoring when power is off
Visual Indicators:
- RGB LEDs show real-time movement status
- Color-coded feedback for easy monitoring
Modular Design:
- Easy component replacement
- Expandable for additional sensors
- Clean cable management

Troubleshooting

Problem	Possible Cause	Solution
Motors not running	Power issue	Check battery charge and connections
Car only turns one direction	Motor speed imbalance	Calibrate ENA/ENB values
Sensor not detecting	Wrong wiring	Verify TRIG/ECHO pin connections
Servo not moving	Power or signal issue	Check 5V supply and Pin 5 connection
LEDs not lighting	Incorrect polarity	Verify anode/cathode connections
Car hits obstacles	Distance threshold too low	Increase MIN_DISTANCE_BACK value
Erratic movement	Loose connections	Secure all wire connections

Applications

This obstacle-avoiding car demonstrates fundamental autonomous robotics principles and can be adapted for:

Educational Purposes: Teaching robotics, sensors, and programming
Warehouse Automation: Goods transport in confined spaces
Food Delivery Robots: Autonomous indoor navigation
Telemetric Robots: Remote exploration and monitoring
Maze Solving: Algorithm development and testing
Home Automation: Mobile sensor platforms

Future Improvements

Add Bluetooth/WiFi control for manual override
Implement line-following capability
Add camera for computer vision
Include GPS for outdoor navigation
Integrate multiple ultrasonic sensors for better coverage
Add pick-and-place mechanism
Implement maze-mapping algorithms

Safety Notes

⚠️ Important Safety Guidelines:

Always disconnect power when uploading code or modifying hardware
Ensure proper battery polarity to avoid damage
Use appropriate voltage regulators (LM2596)
Monitor battery temperature during charging
Keep electronics away from water
Test in controlled environment before autonomous operation
Add bumpers for additional protection

License

This project is open-source and available for educational and personal use. Please credit Circuit Digest when sharing or modifying this project.

Credits

Original Tutorial: Circuit Digest
Platform: Arduino
Sensors: HC-SR04 Ultrasonic Sensor
Motor Control: L298N Driver Module

Additional Resources

Project Source: https://circuitdigest.com/microcontroller-projects/arduino-obstacle-avoiding-car

Last Updated: October 2025

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