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Using nodemcu board with Internet being remotely controlled by any smartphone. As technology is advancing so houses are also getting smarter. Modern houses are gradually shifting from conventional switches to centralized control system, involving remote controlled switches.

Components Required:

  • NodeMCU – Buy
  • Relay Module – Buy

Software Required:

Circuit Diagram:


  • Install Blynk app in your smartphone
  • New users tap create account
  • For existing users login with your username and password
  • Create new project

  • Select NodeMCU as hardware and wifi as connection type

  • Now add button widgets as much as connection you want to connect relay with your NodeMCU

  • Allocate each button widget which pin has to be connected to NodeMCU

  • Output select digital and pin number as (D0, D1, D2,….)
  • Select play button at top right corner of the app it will show your device is offline
  • Add auth token it will be available in new project in Blynk app


 * Blynk is a platform with iOS and Android apps to control
 * Arduino, Raspberry Pi and the likes over the Internet.
 * You can easily build graphic interfaces for all your
 * projects by simply dragging and dropping widgets.
 *   Downloads, docs, tutorials:
 *   Blynk community:  
 *   Social networks:  
 * Blynk library is licensed under MIT license
 * This example code is in public domain.
 * This example runs directly on ESP8266 chip.
 * You need to install this for ESP8266 development:
 * Please be sure to select the right ESP8266 module
 * in the Tools -> Board menu!
 * Change WiFi ssid, pass, and Blynk auth token to run 🙂

#define BLYNK_PRINT Serial    // Comment this out to disable prints and save space
#include <ESP8266WiFi.h>
#include <BlynkSimpleEsp8266.h>

// You should get Auth Token in the Blynk App.
// Go to the Project Settings (nut icon).
char auth[] = "auth token";

// Your WiFi credentials.
// Set password to "" for open networks.
char ssid[] = "ssid";
char pass[] = "pwd";

void setup()
  Blynk.begin(auth, ssid, pass);

void loop()
  • NodeMCU device automatically connects to wifi connection after uploading this progran
  • Tap play icon on your Blynk app
  • Now press button widgets to turn ON/OFF relay switches.
  • All you need is internet connection

I hope this project can help others find their way in the exciting world of electronics and IoT!