HomeAutomation

📡 ESP32 Smart Light Control Using WiFi (4-Channel Relay)

🧠 Introduction

This project demonstrates how to build a simple IoT-based home automation system using an ESP32 microcontroller and a 4-channel relay module. The system allows users to control electrical appliances (like lights) through a web interface hosted on the ESP32, accessible via a mobile phone or computer browser over WiFi.

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🎯 Objectives

• Control up to 4 electrical devices remotely
• Use a mobile browser as the control interface
• Learn basics of IoT, ESP32, and web servers
• Implement a low-cost smart home solution

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🧰 Components Required

Component	Quantity
ESP32 Development Board	1
4-Channel Relay Module	1
Jumper Wires	As needed
WiFi Router	1
Mobile Phone / PC	1

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⚠️ Safety Precautions

• This project involves AC mains voltage, which is dangerous.
• Always disconnect power while wiring.
• If unsure, consult an electrician.
• Ensure proper insulation and secure connections.

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🔌 Hardware Connections

Relay Module to ESP32

Relay Pin	ESP32 Pin
VCC	5V
GND	GND
IN1	GPIO 23
IN2	GPIO 22
IN3	GPIO 21
IN4	GPIO 19

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AC Load Connection

Each relay has:

• COM (Common)
• NO (Normally Open)
• NC (Normally Closed)

Recommended Wiring:

• Phase wire → COM
• NO → Appliance (Light)
• Neutral → Direct to appliance

👉 The appliance turns ON when the relay is activated.

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💻 Software Setup

Step 1: Install Arduino IDE

Download and install Arduino IDE from the official website.

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Step 2: Install ESP32 Board Package

1. Open Arduino IDE
2. Go to File → Preferences
3. Add this URL in "Additional Board Manager URLs":

https://dl.espressif.com/dl/package_esp32_index.json

4. Go to Tools → Board → Board Manager
5. Search for ESP32
6. Install ESP32 by Espressif Systems

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Step 3: Select Board

Go to:

Tools → Board → ESP32 Arduino → DOIT ESP32 DEVKIT V1

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🧾 Program Code

#include <WiFi.h>

// WiFi credentials
const char* ssid = "YOUR_WIFI_NAME";
const char* password = "YOUR_WIFI_PASSWORD";

WiFiServer server(80);

// Relay pins
int relay1 = 23;
int relay2 = 22;
int relay3 = 21;
int relay4 = 19;

void setup() {
  Serial.begin(115200);

  pinMode(relay1, OUTPUT);
  pinMode(relay2, OUTPUT);
  pinMode(relay3, OUTPUT);
  pinMode(relay4, OUTPUT);

  // Turn OFF relays initially
  digitalWrite(relay1, HIGH);
  digitalWrite(relay2, HIGH);
  digitalWrite(relay3, HIGH);
  digitalWrite(relay4, HIGH);

  WiFi.begin(ssid, password);

  Serial.print("Connecting...");
  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.print(".");
  }

  Serial.println("\nConnected!");
  Serial.println(WiFi.localIP());

  server.begin();
}

void loop() {
  WiFiClient client = server.available();

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

    if (request.indexOf("/relay1/on") != -1) digitalWrite(relay1, LOW);
    if (request.indexOf("/relay1/off") != -1) digitalWrite(relay1, HIGH);

    if (request.indexOf("/relay2/on") != -1) digitalWrite(relay2, LOW);
    if (request.indexOf("/relay2/off") != -1) digitalWrite(relay2, HIGH);

    if (request.indexOf("/relay3/on") != -1) digitalWrite(relay3, LOW);
    if (request.indexOf("/relay3/off") != -1) digitalWrite(relay3, HIGH);

    if (request.indexOf("/relay4/on") != -1) digitalWrite(relay4, LOW);
    if (request.indexOf("/relay4/off") != -1) digitalWrite(relay4, HIGH);

    // Web interface
    client.println("HTTP/1.1 200 OK");
    client.println("Content-Type: text/html");
    client.println("");

    client.println("<html><body>");
    client.println("<h2>ESP32 Light Control</h2>");

    client.println("<a href='/relay1/on'>Light 1 ON</a><br>");
    client.println("<a href='/relay1/off'>Light 1 OFF</a><br><br>");

    client.println("<a href='/relay2/on'>Light 2 ON</a><br>");
    client.println("<a href='/relay2/off'>Light 2 OFF</a><br><br>");

    client.println("<a href='/relay3/on'>Light 3 ON</a><br>");
    client.println("<a href='/relay3/off'>Light 3 OFF</a><br><br>");

    client.println("<a href='/relay4/on'>Light 4 ON</a><br>");
    client.println("<a href='/relay4/off'>Light 4 OFF</a><br>");

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

    client.stop();
  }
}

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📱 How It Works

1. ESP32 connects to WiFi network
2. It starts a web server
3. Displays a control page in browser
4. User clicks ON/OFF links
5. ESP32 receives request
6. Relay switches ON/OFF
7. Device (light) responds

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🌐 Accessing the System

1. Upload code to ESP32
2. Open Serial Monitor (115200 baud)
3. Note the IP address (e.g., 192.168.1.5)
4. Open browser on mobile
5. Enter IP address

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🚀 Features

• Wireless control via WiFi
• No external app required
• Supports multiple devices
• Low cost and scalable

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🔧 Troubleshooting

Issue	Solution
ESP32 not connecting	Check WiFi credentials
Upload fails	Press BOOT button while uploading
Page not loading	Verify IP and network
Relay not working	Check HIGH/LOW logic
No Serial output	Press reset button

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🔮 Future Enhancements

• Add modern UI (HTML + CSS)
• Password authentication
• Mobile app integration
• Voice control (Google Assistant)
• Timer-based automation
• Cloud-based remote access

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🧩 Conclusion

This project provides a solid introduction to IoT and home automation using ESP32. With minimal components and basic programming, you can build a functional smart home system and expand it further with advanced features.

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🏷️ Keywords (for SEO)

ESP32 IoT Project, Smart Home Automation, ESP32 Relay Control, WiFi Light Control, Arduino ESP32 Web Server

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🙌 Author Notes

This project is beginner-friendly and can be enhanced into a full-fledged home automation system. Experiment with UI, cloud integration, and voice assistants to take it to the next level.