Nodemcu ESP8266 web server relay control tutorial | Step by step instructions

Nodemcu ESP8266 webserver relay control

Hello, welcome back. This tutorial includes how to connect Nodemcu ESP8266 with a web server and how to turn a relay ON / OFF using a web server. Also, we can use this project knowledge to create home automation projects.

What is the web server?

A web server is simply a place where a web page can be stored and process. For that, we can connect using a web browser. That is, we can connect to a web server through a smartphone or computer. Also, the HTTP protocol is used for this. An IP address is also required to connect to this web server. For that, we can use the IP address in the Nodemcu board, according to this tutorial. So, we can turn the Relay module ON / OFF by a small website created on a web server. Also, we can easily operate this in the local network.

OK, let’s learn how to connect the Nodemcu board with the webserver step by step. To do this, the required components are given below.

Nodemcu ESP8266 x 1 — Amazon / Our Store

Relay module x 1 — Amazon / Our Store
Breadboard x 1 — Amazon / Our Store
Jumper wires — Amazon /Our Store

Disclosure: These Amazon links are Affiliate links. As an Amazon Associate, I earn from qualifying purchases.

Step 1

Firstly, identify these components.

Nodemcu ESP8266

Relay module

Breadboard

Jumper wires

Step 2

Secondly, connect these components. For that, use the circuit diagram below.

Nodemcu ESP8266 web server relay control circuit diagram

Step 3

Thirdly, we create the program. It is as follows. Also, the code sections of this program are described one by one. Please study this program carefully and use it for your own creations. Also, HTML and CSS are used to create the web page. Understand these things and try to make the web page more beautiful.

WIFI library — Download

The complete program of this project – Download

/*1 Relay module control with the webserver.
  created by the SriTu Tech team.
  Read the code below and use it for any of your creations.
*/
 
#include <ESP8266WiFi.h>
// Replace with your network credentials
const char* ssid     = ""; // Enter your WIFI name
const char* password = ""; // Enter your WIFI password
 
// Set webserver port number to 80
WiFiServer server(80);
 
// Variable to store the HTTP request
String header;
 
// Auxiliar variables to store the current output state
String output1State = "off";
 
// Assign output variables to GPIO pins
const int relay1 = D0;
 
// Current time
unsigned long currentTime = millis();
unsigned long previousTime = 0;
// Define timeout time in milliseconds (example: 2000ms = 2s)
const long timeoutTime = 2000;
 
void setup() {
  Serial.begin(115200);
  // Initialize the output variables as outputs
  pinMode(relay1, OUTPUT);
 
  // Set outputs to LOW
  digitalWrite(relay1, HIGH);
 
  // Connect to Wi-Fi network with SSID and password
  Serial.print("Connecting to ");
  Serial.println(ssid);
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  // Print local IP address and start web server
  Serial.println("");
  Serial.println("WiFi connected.");
  Serial.println("IP address: ");
  Serial.println(WiFi.localIP());
  server.begin();
}
 
void loop() {
  WiFiClient client = server.available();   // Listen for incoming clients
 
  if (client) {                             // If a new client connects,
    Serial.println("New Client.");          // print a message out in the serial port
    String currentLine = "";                // make a String to hold incoming data from the client
    currentTime = millis();
    previousTime = currentTime;
    while (client.connected() && currentTime - previousTime <= timeoutTime) { // loop while the client's connected
      currentTime = millis();
      if (client.available()) {             // if there's bytes to read from the client,
        char c = client.read();             // read a byte, then
        Serial.write(c);                    // print it out the serial monitor
        header += c;
        if (c == 'n') {                    // if the byte is a newline character
          // if the current line is blank, you got two newline characters in a row.
          // that's the end of the client HTTP request, so send a response:
          if (currentLine.length() == 0) {
            // HTTP headers always start with a response code (e.g. HTTP/1.1 200 OK)
            // and a content-type so the client knows what's coming, then a blank line:
            client.println("HTTP/1.1 200 OK");
            client.println("Content-type:text/html");
            client.println("Connection: close");
            client.println();
 
            // turns the GPIOs on and off
            if (header.indexOf("GET /0/on") >= 0) {
              Serial.println("GPIO 0 on");
              output1State = "on";
              digitalWrite(relay1, LOW);
            } else if (header.indexOf("GET /0/off") >= 0) {
              Serial.println("GPIO 0 off");
              output1State = "off";
              digitalWrite(relay1, HIGH);
            }
 
            // Display the HTML web page
            client.println("<!DOCTYPE html><html>");
            client.println("<head><meta name="viewport" content="width=device-width, initial-scale=1">");
            client.println("<link rel="icon" href="data:,">");
            // CSS to style the on/off buttons
            // Feel free to change the background-color and font-size attributes to fit your preferences
            client.println("<style>html { font-family: Helvetica; display: inline-block; margin: 0px auto; text-align: center;}");
            client.println(".button { background-color: #195B6A; border: none; color: white; padding: 16px 40px;");
            client.println("text-decoration: none; font-size: 30px; margin: 2px; cursor: pointer;}");
            client.println(".button2 {background-color: #77878A;}</style></head>");
 
            // Web Page Heading
            client.println("<body><h1>Welcome to IOT system</h1>");
 
            // Display current state, and ON/OFF buttons for GPIO 0
            client.println("<p>Relay 1 " + output1State + "</p>");
            // If the output0State is off, it displays the ON button
            if (output1State == "off") {
              client.println("<p><a href="/0/on"><button class="button">ON</button></a></p>");
            } else {
              client.println("<p><a href="/0/off"><button class="button button2">OFF</button></a></p>");
            }
 
            client.println("</body></html>");
 
            // The HTTP response ends with another blank line
            client.println();
            // Break out of the while loop
            break;
          } else { // if you got a newline, then clear currentLine
            currentLine = "";
          }
        } else if (c != 'r') {  // if you got anything else but a carriage return character,
          currentLine += c;      // add it to the end of the currentLine
        }
      }
    }
    // Clear the header variable
    header = "";
    // Close the connection
    client.stop();
    Serial.println("Client disconnected.");
    Serial.println("");
  }
}

OK. now includes the WIFI connections details. For that, use your information.

// Replace with your network credentials

const char* ssid = “Dialog 4G 025”; // Enter your WIFI name

const char* password = “b2016ee3”; // Enter your WIFI password

Step 4

Now, select board and port. Afterward, upload this code.

Step 5

Then, run the serial monitor and copy this IP address and log in to that address from your web browser. Now you can see the web page we created from the program. This includes one button.

This button allows you to turn the relay module ON / OFF. You can control this from your computer as well as your phone. OK, enjoy this video. The full video guide is given below. So, we will meet in the next tutorial.

Nodemcu ESP8266 web server relay control tutorial | Step by step instructions

Nodemcu ESP8266 web server relay control tutorial | Step by step instructions