Posted on May 19

DIY Local Wireless Control System With ESP8266 And Relay - No Internet Required

I think this is one of the most important projects if you are interested in iot. This project connects an ESP8266 (D1 Mini) to a 5-pin relay module, creating a web server that hosts a control interface. I select ESP8266 for this project because of its WIFI and I used D1 mini because it is one of the best ESP8266 variant, it's compact and powerful enough and has many pins.
You can toggle the relay on/off from any device on your local network by accessing the ESP8266's IP address in a web browser. This is a simple and effective solution for controlling devices remotely using a web interface.
I use a transistor(2n2222) and a diod(1n4007) because my relay is 5 volt and d1 mini pins has around 3 volt output and i use transistor to be able to use 5 volt pin of d1 mini to trigger relay coil. ( If you have 3V relays, You only need to connect D1 mini and relay together )

✨ Features

🌐 Web-based control interface
💡 Real-time status updates
🔄 Automatic status refresh
📱 Mobile-friendly responsive design
🔌 Control any device connected to the relay
🏠 Works on your local network (no internet required)

🛠️ Hardware Requirements

ESP8266 D1 Mini (or any ESP8266-based board)
5V Relay Module
NPN Transistor (e.g., 2N2222)
1kΩ Resistor
Jumper Wires
Micro USB Cable
Power Supply (for the relay if needed)

📊 Circuit Diagram

My Wiring

🔧 Setup Instructions

Parts Pinout

5V Relay

2N2222 Transistor

1N4007 Diode

Hardware Setup

Connect the D1 pin of the ESP8266 to the base of the NPN transistor through a 1kΩ resistor
Connect the collector of the transistor to the control pin of the relay module
Connect the emitter of the transistor to ground
Connect the VCC of the relay module to the 5V output of the ESP8266 (or external power supply for larger relays)
Connect the GND of the relay module to the GND of the ESP8266

Sketch

Here is the sketch that you need to upload to your ESP8266 board :
( If you dont know how to upload this sketch to your board, After sketch there is a simple guide to install Arduino IDE and required packages for uploading it )

#include <ESP8266WiFi.h> #include <ESP8266WebServer.h> #include <ArduinoJson.h> // WiFi credentials const char* ssid = "YourWifiSSID"; // Replace with your WiFi name const char* password = "YourWifiPassword"; // Replace with your WiFi password // Pin definitions const int relayPin = D1; // D1 pin connected to transistor base via resistor // Web server on port 80 ESP8266WebServer server(80); // LED state bool ledState = false; void setup() { // Initialize serial communication Serial.begin(115200); // Set relay pin as output pinMode(relayPin, OUTPUT); // Initially turn off the relay digitalWrite(relayPin, LOW); // Connect to WiFi WiFi.begin(ssid, password); Serial.print("Connecting to WiFi"); while (WiFi.status() != WL_CONNECTED) { delay(500); Serial.print("."); } Serial.println(); Serial.print("Connected to WiFi. IP address: "); Serial.println(WiFi.localIP()); // Define server routes server.on("/", handleRoot); server.on("/toggle", handleToggle); server.on("/status", handleStatus); server.onNotFound(handleNotFound); // Start the server server.begin(); Serial.println("HTTP server started"); } void loop() { server.handleClient(); } // Handle root page void handleRoot() { String html = R"( <!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <title>LED Control</title> <style> body { font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif; margin: 0; padding: 0; display: flex; justify-content: center; align-items: center; min-height: 100vh; background-color: #f5f5f5; } .container { background-color: white; border-radius: 10px; box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1); padding: 30px; text-align: center; max-width: 400px; width: 100%; } h1 { color: #333; margin-bottom: 30px; } .status { margin: 20px 0; font-size: 18px; } .switch { position: relative; display: inline-block; width: 60px; height: 34px; margin: 20px 0; } .switch input { opacity: 0; width: 0; height: 0; } .slider { position: absolute; cursor: pointer; top: 0; left: 0; right: 0; bottom: 0; background-color: #ccc; transition: .4s; border-radius: 34px; } .slider:before { position: absolute; content: ""; height: 26px; width: 26px; left: 4px; bottom: 4px; background-color: white; transition: .4s; border-radius: 50%; } input:checked + .slider { background-color: #2196F3; } input:checked + .slider:before { transform: translateX(26px); } .led-icon { font-size: 48px; margin: 20px 0; transition: color 0.3s; } .led-off { color: #ccc; } .led-on { color: #ffcc00; text-shadow: 0 0 10px #ffcc00; } </style> </head> <body> <div class="container"> <h1>LED Control Panel</h1> <div class="led-icon" id="ledIcon">💡</div> <div class="status"> LED Status: <span id="ledStatus">OFF</span> </div> <label class="switch"> <input type="checkbox" id="toggleSwitch"> <span class="slider"></span> </label> <div> <p>IP Address: )" + WiFi.localIP().toString() + R"(</p> </div> </div> <script> const toggleSwitch = document.getElementById('toggleSwitch'); const ledStatus = document.getElementById('ledStatus'); const ledIcon = document.getElementById('ledIcon'); // Get initial state fetchStatus(); // Toggle switch event toggleSwitch.addEventListener('change', function() { fetch('/toggle') .then(response => response.json()) .then(data => { updateUI(data.state); }) .catch(error => console.error('Error:', error)); }); // Fetch current status function fetchStatus() { fetch('/status') .then(response => response.json()) .then(data => { updateUI(data.state); }) .catch(error => console.error('Error:', error)); } // Update UI based on state function updateUI(state) { toggleSwitch.checked = state; ledStatus.textContent = state ? 'ON' : 'OFF'; if (state) { ledIcon.classList.add('led-on'); ledIcon.classList.remove('led-off'); } else { ledIcon.classList.add('led-off'); ledIcon.classList.remove('led-on'); } } // Refresh status every 5 seconds setInterval(fetchStatus, 5000); </script> </body> </html> )"; server.send(200, "text/html", html); } // Handle toggle request void handleToggle() { ledState = !ledState; digitalWrite(relayPin, ledState ? HIGH : LOW); DynamicJsonDocument doc(64); doc["state"] = ledState; String response; serializeJson(doc, response); server.send(200, "application/json", response); } // Handle status request void handleStatus() { DynamicJsonDocument doc(64); doc["state"] = ledState; String response; serializeJson(doc, response); server.send(200, "application/json", response); } // Handle 404 Not Found void handleNotFound() { server.send(404, "text/plain", "Not Found"); }

Software Setup

Install the Arduino IDE from arduino.cc
Add ESP8266 board support:
- Open Arduino IDE
- Go to File > Preferences
- Add http://arduino.esp8266.com/stable/package_esp8266com_index.json to Additional Boards Manager URLs
- Go to Tools > Board > Boards Manager
- Search for ESP8266 and install
Install required libraries:
- Go to Sketch > Include Library > Manage Libraries
- Search for and install:
  - ESP8266WiFi
  - ESP8266WebServer
  - ArduinoJson
Open the sketch.ino file in Arduino IDE
Update the WiFi credentials:

 const char* ssid = "YourWifiSSID"; // Replace with your WiFi name const char* password = "YourWifiPassword"; // Replace with your WiFi password

Select your board (Tools > Board > ESP8266 Boards > LOLIN(WEMOS) D1 R2 & mini)
Select the correct port (Tools > Port)
Upload the sketch to your ESP8266

🚀 Usage

Power on your ESP8266
The device will connect to your WiFi network
Check the Serial Monitor (115200 baud) to see the assigned IP address
Open a web browser on any device connected to the same network
Enter the IP address in the address bar
Use the toggle switch on the web interface to control the relay

Sample of LED Control Panel

🔍 Troubleshooting

ESP8266 not connecting to WiFi: Double-check your WiFi credentials in the code
Relay not switching: Verify your wiring connections and ensure the transistor is properly connected
Cannot access web interface: Make sure your device is connected to the same network as the ESP8266
Relay switching erratically: Check for proper grounding and consider adding a flyback diode if not already included in your relay module

If there is any unknown problems, don't hesitate to contact me.

🛡️ Safety Warnings

This project involves working with electricity which can be dangerous
Never connect the relay to mains voltage without proper knowledge and safety precautions
Always disconnect power before making any changes to the circuit
Consider using an optocoupler for additional safety when working with higher voltages