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.

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

Circuit Diagram (Connections Explained)

Motor Driver → Motors

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

Motor Driver → ESP8266

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

Power Connections (VERY IMPORTANT)

Battery → L298N (12V input)
Battery → L298N GND
GND of ESP8266 ↔ GND of L298N
VV of ESP8266 ↔ 5V Output of L298N

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

2. Select Board

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

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

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();
}

How to Use

Upload code
Power ESP8266
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

Troubleshooting Guide

1. WiFi not visible

Causes:

Code not uploaded properly
ESP not powered

Fix:

Press RESET button
Check Serial Monitor (115200 baud)

2. Connected but page not opening

Fix:

Turn OFF mobile data
Use:

192.168.4.1

(Do not put this in Google search)

3. Buttons work only once

Cause:

Page reload issue

Fix:

Already solved using AJAX in this code

4. Weird symbols on buttons

Cause:

Unicode not supported

Fix:

Use text (Forward, Left, etc.)

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

6. Robot not moving correctly

Fix:

Swap motor wires
Adjust logic in code

7. ESP resets when motor runs

Cause:

Voltage drop

Fix:

Use separate power supply
Use buck converter (LM2596 recommended)

Improvements You Can Add

Voice control
Obstacle avoidance
Camera streaming using ESP32-CAM

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.