Arduino UNO Multi-Sensor Obstacle Avoidance & Bluetooth Controlled Robot Car Using L298N

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Arduino UNO Obstacle Avoidance & Bluetooth Controlled Robot Car

A 4WD smart robot with 3 operating modes — autonomous obstacle avoidance, line following, and Bluetooth smartphone control. Full code, wiring & simulation included.

Arduino UNO HC-SR04 Ultrasonic HC-05 Bluetooth L298N Motor Driver SG90 Servo IR Sensors 4WD Platform Intermediate

🚗

Obstacle Avoidance

Send cmd 10 · Fully autonomous

↔️

Line Following

Send cmd 9 · IR sensor guided

📱

Bluetooth Control

Send cmd 8 · Manual via app

📋 Contents

1. Project Overview
2. Components List
3. Wiring Diagram
4. How It Works
5. Command Reference
6. Interactive Demo
7. Full Code
8. diagram.json
9. Simulation Link
10. Applications
11. Related Projects

1

Project Overview

This project combines three intelligent operating modes in a single 4-wheel-drive robot. The Arduino UNO acts as the central controller, reading data from multiple sensors and switching between autonomous and manual operation based on Bluetooth or IR remote commands.

🔊

180° Scanning

SG90 servo sweeps the HC-SR04 ultrasonic sensor left and right to find the clearest path forward.

📡

Dual Input

Both Bluetooth (HC-05) and IR remote control are decoded simultaneously for flexible operation.

⚡

PWM Speed

Motor speed is set via analogWrite(enA/enB) PWM — adjustable from the app in real time.

🔋

18650 Li-ion

Rechargeable 18650 battery pack provides stable 7.4V–8.4V to the L298N motor driver.

2

Components List

🟦

Arduino UNO R3

ATmega328P

×1

🔊

HC-SR04

Ultrasonic sensor

×1

📡

HC-05

Bluetooth module

×1

⚙️

SG90 Servo

Sensor scanning

×1

🔴

IR Sensors

Line detection (×2)

×2

🔌

L298N Driver

Dual H-bridge

×1

🚗

DC Motors

TT gear motors

×4

🔋

18650 Battery

Li-ion 2-cell pack

×1

📻

IR Remote

NEC protocol

×1

🏗️

4WD Chassis

Acrylic robot frame

×1

📦

Install via Sketch → Manage Libraries: SoftwareSerial (built-in) · IRremote by shirriff · No additional libs needed for servo (manual PWM pulses used).

3

Wiring Diagram

All digital and analog pins are used. The servo is driven by manual PWM pulses on A4, and SoftwareSerial uses pins 2 (RX) and 3 (TX) for Bluetooth.

Full Pin Reference

Module	Module Pin	Arduino Pin	Notes
HC-05 Bluetooth	VCC	5V
HC-05 Bluetooth	GND	GND
HC-05 Bluetooth	TXD	D2 (SoftSerial RX)	HC-05 TX → Arduino D2
HC-05 Bluetooth	RXD	D3 (SoftSerial TX)	Use voltage divider for 3.3V
L298N	ENA	D10 (PWM)	Right motor speed
L298N	IN1	D9	Right motor dir A
L298N	IN2	D8	Right motor dir B
L298N	IN3	D7	Left motor dir A
L298N	IN4	D6	Left motor dir B
L298N	ENB	D5 (PWM)	Left motor speed
IR Sensor Right	OUT	A0	Digital read
IR Sensor Left	OUT	A1	Digital read
HC-SR04	Echo	A2	Input
HC-SR04	Trigger	A3	Output
SG90 Servo	Signal	A4	Manual PWM pulses
IR Receiver	OUT	A5	RECV_PIN for IRremote lib

⚠️

HC-05 RXD voltage: The HC-05's RXD pin is 3.3V logic. Use a voltage divider (1kΩ + 2kΩ) between Arduino D3 (TX) and HC-05 RXD to avoid damaging the module.

How It Works — Three Modes

Mode 2 · cmd=10 — Obstacle Avoidance (Autonomous)

• Servo sweeps the HC-SR04 to scan forward continuously.
• If front distance > 20 cm (set variable), robot moves forward.
• Obstacle detected, robot stops, calls Check_side().
• Servo rotates left (140°) reads distance_L, then right (0°) reads distance_R.
• compareDistance(): turns toward the side with more space (350 ms turn). If both blocked, reverse and turn 600 ms.
• Servo returns to 70° (centre) and resumes forward motion.

Mode 1 · cmd=9 — Line Following

• Speed set to 130 (moderate) for smooth line tracking.
• R_S=0, L_S=0 (both on white): forward()
• R_S=1, L_S=0 (right on black): turnRight()
• R_S=0, L_S=1 (left on black): turnLeft()
• R_S=1, L_S=1 (both on black / end of track): Stop()

Mode 0 · cmd=8 — Bluetooth / IR Remote Manual Control

• HC-05 or IR remote sends a numeric command (1–10).
• If value > 20, it is treated as a new PWM speed value (0–255).
• Commands 1–5: Forward / Backward / Left / Right / Stop.
• Commands 6–7: Timed turns (voice control style, auto-stop after 400 ms).
• Commands 8/9/10 switch mode: Stop / Line Follow / Obstacle Avoid.

Servo Sweep Logic — Manual PWM Pulse Generation

• No Servo library used, pulses are generated manually via servoPulse(pin, angle).
• Formula: pwm = (angle x 11) + 500 microseconds.
• At 70° = 1270 µs, At 0° = 500 µs, At 140° = 2040 µs.
• 50 ms delay between pulses provides the refresh cycle.

5

Bluetooth / IR Command Reference

Send these integer values from your Bluetooth app (e.g. Arduino Bluetooth Controller on Android). IR remote codes are mapped to the same numbers via IRremote_data().

1

Forward

Move ahead

2

Backward

Reverse

3

Left

Turn left

4

Right

Turn right

5

Stop

Halt motors

6

Timed Left

400 ms turn

7

Timed Right

400 ms turn

8

Manual Mode

mode = 0

9

Line Follow

mode = 1

10

Avoid Mode

mode = 2

>20

Set Speed

PWM 0–255

📱

Recommended app: "Arduino Bluetooth Controller" or "Bluetooth RC Car" on Android. Set button values to the integers above. For speed, send any number like 150 or 200.

6

Interactive Robot Simulator

🎮 Mini Control Demo

🧱

🧱

🧱

🤖

Mode: Manual · Status: Ready

7

Full Arduino Code

Arduino / C++

#include <SoftwareSerial.h>
SoftwareSerial BT_Serial(2, 3); // RX=D2, TX=D3

#include <IRremote.h>
const int RECV_PIN = A5;
IRrecv irrecv(RECV_PIN);
decode_results results;

// ── L298N Motor Driver Pins ──
#define enA  10  // Enable Right motors (PWM)
#define in1   9  // Right motor forward
#define in2   8  // Right motor backward
#define in3   7  // Left motor backward
#define in4   6  // Left motor forward
#define enB   5  // Enable Left motors (PWM)

#define servo   A4  // SG90 Servo signal
#define R_S     A0  // IR sensor Right
#define L_S     A1  // IR sensor Left
#define echo    A2  // HC-SR04 Echo
#define trigger A3  // HC-SR04 Trigger

int distance_L, distance_F = 30, distance_R;
long distance;
int set = 20;          // obstacle threshold (cm)
int bt_ir_data;
int Speed = 130;
int mode = 0;
int IR_data;

void setup() {
  pinMode(R_S, INPUT);  pinMode(L_S, INPUT);
  pinMode(echo, INPUT); pinMode(trigger, OUTPUT);
  pinMode(enA, OUTPUT); pinMode(enB, OUTPUT);
  pinMode(in1, OUTPUT); pinMode(in2, OUTPUT);
  pinMode(in3, OUTPUT); pinMode(in4, OUTPUT);
  pinMode(servo, OUTPUT);

  irrecv.enableIRIn();
  irrecv.blink13(true);

  Serial.begin(9600);
  BT_Serial.begin(9600);

  // Servo startup sweep (calibration)
  for (int a = 70; a <= 140; a += 5) servoPulse(servo, a);
  for (int a = 140; a >= 0; a -= 5)  servoPulse(servo, a);
  for (int a = 0; a <= 70; a += 5)   servoPulse(servo, a);
  delay(500);
}

void loop() {
  // Read Bluetooth
  if (BT_Serial.available() > 0) {
    bt_ir_data = BT_Serial.read();
    Serial.println(bt_ir_data);
    if (bt_ir_data > 20) { Speed = bt_ir_data; } // speed update
  }

  // Read IR Remote
  if (irrecv.decode(&results)) {
    bt_ir_data = IRremote_data();
    irrecv.resume();
    delay(100);
  }

  // Mode switching
  if      (bt_ir_data == 8)  { mode = 0; Stop(); }
  else if (bt_ir_data == 9)  { mode = 1; Speed = 130; }
  else if (bt_ir_data == 10) { mode = 2; Speed = 255; }

  analogWrite(enA, Speed);
  analogWrite(enB, Speed);

  if (mode == 0) {
    // ── Manual / Bluetooth control ──
    if      (bt_ir_data == 1) forword();
    else if (bt_ir_data == 2) backword();
    else if (bt_ir_data == 3) turnLeft();
    else if (bt_ir_data == 4) turnRight();
    else if (bt_ir_data == 5) Stop();
    else if (bt_ir_data == 6) { turnLeft();  delay(400); bt_ir_data = 5; }
    else if (bt_ir_data == 7) { turnRight(); delay(400); bt_ir_data = 5; }
  }

  if (mode == 1) {
    // ── Line Following ──
    if      (!digitalRead(R_S) && !digitalRead(L_S)) forword();
    else if ( digitalRead(R_S) && !digitalRead(L_S)) turnRight();
    else if (!digitalRead(R_S) &&  digitalRead(L_S)) turnLeft();
    else if ( digitalRead(R_S) &&  digitalRead(L_S)) Stop();
  }

  if (mode == 2) {
    // ── Obstacle Avoidance ──
    distance_F = Ultrasonic_read();
    if (distance_F > set) forword();
    else Check_side();
  }

  delay(10);
}

long IRremote_data() {
  if      (results.value == 0xFF02FD) IR_data = 1;
  else if (results.value == 0xFF9867) IR_data = 2;
  else if (results.value == 0xFFE01F) IR_data = 3;
  else if (results.value == 0xFF906F) IR_data = 4;
  else if (results.value == 0xFF629D || results.value == 0xFFA857) IR_data = 5;
  else if (results.value == 0xFF30CF) IR_data = 8;
  else if (results.value == 0xFF18E7) IR_data = 9;
  else if (results.value == 0xFF7A85) IR_data = 10;
  return IR_data;
}

void servoPulse(int pin, int angle) {
  int pwm = (angle * 11) + 500;
  digitalWrite(pin, HIGH);
  delayMicroseconds(pwm);
  digitalWrite(pin, LOW);
  delay(50);
}

long Ultrasonic_read() {
  digitalWrite(trigger, LOW);  delayMicroseconds(2);
  digitalWrite(trigger, HIGH); delayMicroseconds(10);
  digitalWrite(trigger, LOW);
  distance = pulseIn(echo, HIGH);
  return distance / 29 / 2;
}

void compareDistance() {
  if      (distance_L > distance_R) { turnLeft();  delay(350); }
  else if (distance_R > distance_L) { turnRight(); delay(350); }
  else                               { backword();  delay(300); turnRight(); delay(600); }
}

void Check_side() {
  Stop(); delay(100);
  for (int a = 70;  a <= 140; a += 5) servoPulse(servo, a);
  delay(300); distance_L = Ultrasonic_read(); delay(100);
  for (int a = 140; a >= 0;   a -= 5) servoPulse(servo, a);
  delay(500); distance_R = Ultrasonic_read(); delay(100);
  for (int a = 0;   a <= 70;  a += 5) servoPulse(servo, a);
  delay(300); compareDistance();
}

// ── Motor Control Functions ──
void forword()   { digitalWrite(in1,HIGH); digitalWrite(in2,LOW); digitalWrite(in3,LOW);  digitalWrite(in4,HIGH); }
void backword()  { digitalWrite(in1,LOW);  digitalWrite(in2,HIGH);digitalWrite(in3,HIGH); digitalWrite(in4,LOW);  }
void turnRight() { digitalWrite(in1,LOW);  digitalWrite(in2,HIGH);digitalWrite(in3,LOW);  digitalWrite(in4,HIGH); }
void turnLeft()  { digitalWrite(in1,HIGH); digitalWrite(in2,LOW); digitalWrite(in3,HIGH); digitalWrite(in4,LOW);  }
void Stop()       { digitalWrite(in1,LOW);  digitalWrite(in2,LOW); digitalWrite(in3,LOW);  digitalWrite(in4,LOW);  }

9

Online Simulation

▶ Try it in CirkitDesigner

Simulate the full 4WD robot circuit online — test all three modes without any hardware. Use the serial monitor to send Bluetooth commands.

Open CirkitDesigner

Step-by-Step Simulation Guide

#	Step
1	Open CirkitDesigner, create a new project, add Arduino UNO.
2	Add HC-SR04, SG90 Servo, 2× IR sensors, IR receiver, 4× DC motors, and L298N from the library.
3	Wire all modules per the pin table above. Use the diagram.json to auto-import connections.
4	Paste the code above into the Arduino editor. Install IRremote library.
5	Click Simulate. Open Serial Monitor — type 10 to enter obstacle avoidance mode.
6	Move a virtual object in front of the HC-SR04 to trigger avoidance. Watch servo sweep and motors respond.
7	Type 9 to switch to line-following mode; toggle IR sensor inputs HIGH/LOW to test steering logic.
8	Type 8 for manual mode, then 1–5 to drive forward/backward/turn/stop manually.

10

Applications & Upgrades

🏆Robotics competitions

🎓Final year projects

🏭Warehouse navigation

🔬Autonomous research

📦Object delivery bots

🌿Agricultural robots

🏠Smart home rover

🎪STEM exhibitions

Possible Upgrades

📷

ESP32-CAM

Add live video streaming to monitor the robot's path remotely from a browser.

🗺️

GPS Navigation

Add a NEO-6M GPS module for outdoor waypoint navigation and route tracking.

🎙️

Voice Control

Use Google Assistant via an ESP8266 + IFTTT bridge to control the robot with voice commands.

🧠

AI Object Recognition

Swap to a Raspberry Pi + camera and add TensorFlow Lite for real-time object detection.

11

Related Robotics Projects

Robotics Arduino UNO Smart Obstacle Avoiding Robot (Ultrasonic + IR + GSM) → Robotics Arduino Nano Bluetooth Controlled Line Follower Robot → Robotics Arduino UNO Bluetooth Controlled 4WD Robot Car Using L298N → Robotics ESP32-Based 4WD Robot Car Using Dual L298N Motor Drivers → Simulation RC Car Simulation with L298N Motor Driver and Joystick Control → Robotics Arduino-Powered Autonomous Obstacle Avoidance Robot with Servo →

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