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Practical 10: Control Bulb ON/OFF using Blynk App

Lesson 10 of 10 in the free Internet of Things (IoT) Lab notes on Siksha Sarovar, written by Rohit Jangra.

Program Statement

Write a program for controlling bulb on/off by using Blynk app.

CO Mapping

CO2, CO3, CO4

Objective

To remotely control a bulb (or relay-connected load) ON and OFF using a Button widget in the Blynk app and NodeMCU (ESP8266).

Components Required

ComponentQuantity
NodeMCU (ESP8266)1
5V Relay Module1
Bulb / LED (as load)1
Breadboard + Jumper WiresAs needed
Smartphone with Blynk App1

Circuit Connection

ComponentNodeMCU Pin
Relay IN (Signal)D2 (GPIO4)
Relay VCCVIN (5V)
Relay GNDGND
Bulb (via relay NO terminal)
Safety Note: If controlling a mains-voltage bulb, ensure proper insulation and do not touch live wires. Prefer using a 5V LED bulb for practice.

Blynk App Setup

  1. Open the Blynk app and open your project.
  2. Add a Button widget.
  3. Set it to Virtual Pin V0.
  4. Set mode to Switch (so it toggles between ON and OFF).
  5. Note your Auth Token from project settings.

Program

Replace YourAuthToken, YourNetworkName, and YourPassword with your actual credentials before uploading.