Introduction

In this project, we will build a WiFi-controlled robotic car using the ESP8266 NodeMCU.
The robot creates its own WiFi network, and you can control it using a mobile browser — no internet required.

This is a perfect beginner-to-intermediate IoT + robotics project.

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Components Required

• ESP8266 NodeMCU
• L298N Motor Driver Module
• DC Motors (2 or 4)
• Robot chassis + wheels
• Battery (7.4V Li-ion or 2×18650)
• Jumper wires
• USB cable

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Circuit Diagram (Connections Explained)

Motor Driver → Motors

• OUT1 → Left Motor
• OUT2 → Left Motor
• OUT3 → Right Motor
• OUT4 → Right Motor

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Motor Driver → ESP8266

L298N	ESP8266
IN1	D1
IN2	D2
IN3	D5
IN4	D6
ENA	D7
ENB	D8

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Power Connections (VERY IMPORTANT)

Correct Way:

• Battery → L298N (12V input)
• ESP8266 → USB power (recommended)
• GND of ESP8266 ↔ GND of L298N

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Wrong Way (Avoid this)

• DO NOT power ESP8266 from L298N 5V
  –> Causes reset, WiFi issues, unstable behavior

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Arduino IDE Setup

1. Install ESP8266 Board

Go to:

• File → Preferences
• Add this URL:

http://arduino.esp8266.com/stable/package_esp8266com_index.json

Then:

• Tools → Board Manager
• Install ESP8266 Boards by ESP8266 Community

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2. Select Board

• Tools → Board → NodeMCU 1.0 (ESP-12E Module)

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Working Principle

• ESP8266 creates a WiFi hotspot: RobotCar
• Phone connects to it
• A web page with buttons is served
• Buttons send commands using AJAX (no page reload)
• Motors move accordingly

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Complete Code

#include <ESP8266WiFi.h>

// ===== MOTOR PINS =====
#define IN1 D1
#define IN2 D2
#define IN3 D5
#define IN4 D6

// ===== SPEED PINS (PWM) =====
#define ENA D7
#define ENB D8

int speedValue = 300; // 0 - 1023

// ===== WIFI =====
const char* ssid = "RobotCar";
const char* password = "12345678";

WiFiServer server(80);

// ===== MOTOR FUNCTIONS =====
void forward() {
  analogWrite(ENA, speedValue);
  analogWrite(ENB, speedValue);

  digitalWrite(IN1, HIGH);
  digitalWrite(IN2, LOW);
  digitalWrite(IN3, HIGH);
  digitalWrite(IN4, LOW);
}

void backward() {
  analogWrite(ENA, speedValue);
  analogWrite(ENB, speedValue);

  digitalWrite(IN1, LOW);
  digitalWrite(IN2, HIGH);
  digitalWrite(IN3, LOW);
  digitalWrite(IN4, HIGH);
}

void left() {
  analogWrite(ENA, speedValue);
  analogWrite(ENB, speedValue);

  digitalWrite(IN1, LOW);
  digitalWrite(IN2, HIGH);
  digitalWrite(IN3, HIGH);
  digitalWrite(IN4, LOW);
}

void right() {
  analogWrite(ENA, speedValue);
  analogWrite(ENB, speedValue);

  digitalWrite(IN1, HIGH);
  digitalWrite(IN2, LOW);
  digitalWrite(IN3, LOW);
  digitalWrite(IN4, HIGH);
}

void stopCar() {
  analogWrite(ENA, 0);
  analogWrite(ENB, 0);

  digitalWrite(IN1, LOW);
  digitalWrite(IN2, LOW);
  digitalWrite(IN3, LOW);
  digitalWrite(IN4, LOW);
}

// ===== SETUP =====
void setup() {
  Serial.begin(115200);

  pinMode(IN1, OUTPUT);
  pinMode(IN2, OUTPUT);
  pinMode(IN3, OUTPUT);
  pinMode(IN4, OUTPUT);

  pinMode(ENA, OUTPUT);
  pinMode(ENB, OUTPUT);

  analogWriteRange(1023);
  analogWriteFreq(1000);

  stopCar();

  WiFi.mode(WIFI_AP);
  WiFi.softAP(ssid, password);

  Serial.println("WiFi Started");
  Serial.println(WiFi.softAPIP());

  server.begin();
}

// ===== LOOP =====
void loop() {
  WiFiClient client = server.available();
  if (!client) return;

  String request = client.readStringUntil('\r');
  client.flush();

  // ===== MOVEMENT COMMANDS =====
  if (request.indexOf("GET /forward") != -1) forward();
  else if (request.indexOf("GET /backward") != -1) backward();
  else if (request.indexOf("GET /left") != -1) left();
  else if (request.indexOf("GET /right") != -1) right();
  else if (request.indexOf("GET /stop") != -1) stopCar();

  // ===== SPEED COMMANDS =====
  else if (request.indexOf("GET /speedlow") != -1) speedValue = 400;
  else if (request.indexOf("GET /speedmed") != -1) speedValue = 700;
  else if (request.indexOf("GET /speedhigh") != -1) speedValue = 1023;

  // ===== RESPONSE =====
  client.println("HTTP/1.1 200 OK");
  client.println("Content-Type: text/html");
  client.println("Connection: close");
  client.println();

  client.println("<!DOCTYPE html><html><head>");
  client.println("<meta name='viewport' content='width=device-width, initial-scale=1'>");

  // ===== STYLE =====
  client.println("<style>");
  client.println("body { text-align:center; font-family: Arial; background:#111; color:white; }");
  client.println("button { width:100px; height:100px; font-size:18px; margin:10px; border-radius:50%; border:none; }");
  client.println(".f { background:green; }");
  client.println(".b { background:blue; }");
  client.println(".l { background:orange; }");
  client.println(".r { background:orange; }");
  client.println(".s { background:red; }");
  client.println(".sp { width:80px; height:50px; border-radius:10px; }");
  client.println("</style>");

  // ===== JAVASCRIPT =====
  client.println("<script>");
  client.println("function send(cmd){");
  client.println("var x=new XMLHttpRequest();");
  client.println("x.open('GET','/'+cmd,true);");
  client.println("x.send();");
  client.println("}");
  client.println("</script>");

  client.println("</head><body>");

  client.println("<h2>Robot Control</h2>");

  // ===== SPEED BUTTONS =====
  client.println("<p>Speed Control</p>");
  client.println("<button class='sp' onclick=\"send('speedlow')\">Slow</button>");
  client.println("<button class='sp' onclick=\"send('speedmed')\">Medium</button>");
  client.println("<button class='sp' onclick=\"send('speedhigh')\">Fast</button><br><br>");

  // ===== MOVEMENT BUTTONS =====
  client.println("<button class='f' onclick=\"send('forward')\">Forward</button><br>");
  client.println("<button class='l' onclick=\"send('left')\">Left</button>");
  client.println("<button class='s' onclick=\"send('stop')\">Stop</button>");
  client.println("<button class='r' onclick=\"send('right')\">Right</button><br>");
  client.println("<button class='b' onclick=\"send('backward')\">Backward</button>");

  client.println("</body></html>");

  client.stop();
}

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How to Use

1. Upload code
2. Power ESP8266
3. Open Settings in your mobile, then go to WiFi and select “RobotCar”. Then type password “12345678”:

RobotCar

4. Open browser and type:

192.168.4.1

5. Use buttons to control the robot

Important Tips

• Turn OFF mobile data
• Use Chrome browser
• Keep ESP powered properly
• Keep motors and ESP power separate

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Troubleshooting Guide

1. WiFi not visible

Causes:

• Code not uploaded properly
• ESP not powered

Fix:

• Press RESET button
• Check Serial Monitor (115200 baud)

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2. Connected but page not opening

Fix:

• Turn OFF mobile data
• Use:

192.168.4.1

(Do not put this in Google search)

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3. Buttons work only once

Cause:

• Page reload issue

Fix:

• Already solved using AJAX in this code

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4. Weird symbols on buttons

Cause:

• Unicode not supported

Fix:

• Use text (Forward, Left, etc.)

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5. ESP8266 not detected

Causes:

• Power issue
• USB driver issue

Fix:

• Use USB cable
• Check drivers:
  • CP2102 USB to UART Bridge
  • CH340 USB to Serial

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6. Robot not moving correctly

Fix:

• Swap motor wires
• Adjust logic in code

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7. ESP resets when motor runs

Cause:

• Voltage drop

Fix:

• Use separate power supply
• Use buck converter (LM2596 recommended)

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Improvements You Can Add

• Voice control
• Obstacle avoidance
• Camera streaming using ESP32-CAM

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Conclusion

This project demonstrates how to build a simple yet powerful IoT robot using ESP8266.
With proper power management and AJAX-based control, you get a smooth and responsive robotic car.