🔰 Introduction

In this lesson, you will learn the most important cloud tool used in this course:
👉 Blynk IoT Platform

Blynk allows your ESP32 to:

• Connect to the internet

• Send sensor data to a mobile app

• Receive control commands from a mobile app

• Create real IoT dashboards

By the end of this lesson, you will clearly understand:

• What Blynk is

• How ESP32 connects to Blynk

• What the Blynk library does

• What virtual pins are

• How to send data to Blynk

• How to receive commands from Blynk

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PART 1 – What is Blynk?

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1️⃣ What is Blynk?

Blynk is a cloud + mobile app platform used to build IoT applications without writing mobile app code.

It provides:

• A mobile app (Android / iOS)

• A cloud server

• A software library for ESP32

Together, these three parts allow your ESP32 to communicate with your phone over the internet.

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2️⃣ Why We Use Blynk in This Course

We use Blynk because:

• No need to build Android apps

• No need to manage servers

• Very beginner-friendly

• Works with ESP32

• Free for basic use

• Supports dashboards, buttons, sliders, displays, alerts

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3️⃣ Basic Working of Blynk (Simple Flow)

• ESP32 sends sensor data to Blynk Cloud

• Blynk Cloud sends data to your phone

• When you press a button in the app:
  → Blynk Cloud sends a command to ESP32

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PART 2 – What is the Blynk Library?

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4️⃣ What is a Library?

In programming, a library is a collection of ready-made code that helps us perform complex tasks easily.

Instead of writing hundreds of lines of networking code, we use a library.

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5️⃣ What is the Blynk Library?

The Blynk library is a software package that:

• Connects ESP32 to Blynk Cloud

• Sends data to the Blynk app

• Receives data from the Blynk app

• Manages authentication and communication

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6️⃣ Why We Need the Blynk Library

Without the Blynk library, you would need to:

• Write WiFi connection code

• Write internet communication code

• Write server communication code

• Handle mobile app data manually

This is very difficult for beginners.

So we use the Blynk library to do all this automatically.

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7️⃣ How Blynk Library Works (Concept)

When your ESP32 runs this function:

The library automatically:

• Connects ESP32 to WiFi

• Connects ESP32 to Blynk Cloud

• Authenticates using your Auth Token

• Keeps the connection alive

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PART 3 – Important Blynk Library Functions

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8️⃣ Blynk.begin()

What it does:

• Connects ESP32 to WiFi

• Connects ESP32 to Blynk server

• Logs in using Auth Token

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9️⃣ Blynk.run()

What it does:

• Keeps ESP32 connected to Blynk

• Listens for commands from app

• Sends data to app

⚠ This must be inside loop().

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🔟 Blynk.virtualWrite()

What it does:

• Sends a value from ESP32 → Blynk app

• Displays it on a widget linked to V5

Example:

Sends number 25 to Blynk.

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PART 4 – What are Virtual Pins?

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1️⃣1️⃣ What is a Pin?

In microcontrollers, a pin is a physical leg used to connect sensors or devices.

Example:
GPIO 2, GPIO 4, GPIO 5, etc.

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1️⃣2️⃣ What is a Virtual Pin?

A virtual pin is a software-only pin created by Blynk.

It does NOT exist physically on ESP32.

It is used to:

• Send data to the app

• Receive commands from the app

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1️⃣3️⃣ Why Virtual Pins Are Needed

We use virtual pins because:

• We don’t want to link app buttons directly to ESP32 GPIO pins

• We want flexible control logic

• We want multiple widgets to talk to code

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1️⃣4️⃣ Virtual Pin Naming

Virtual pins are named like:

• V0

• V1

• V2

• V3

• …

• V255

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PART 5 – Receiving Data from Blynk (App → ESP32)

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1️⃣5️⃣ BLYNK_WRITE() Function

What it does:

• Runs automatically when widget on V1 changes

• Reads value sent from app

• Stores it in value

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1️⃣6️⃣ Example Logic

Meaning:

• Button ON → LED ON

• Button OFF → LED OFF

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PART 6 – Sending Data to Blynk (ESP32 → App)

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1️⃣7️⃣ Sending a Sensor Value

Meaning:

• Send value 30 to widget on V5

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1️⃣8️⃣ Sending Text

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PART 7 – Typical Blynk Program Structure

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1️⃣9️⃣ Basic Blynk Code Template

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2️⃣0️⃣ Where Virtual Pins Fit

Goes outside setup() and loop().

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PART 8 – Common Beginner Mistakes

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❌ Mistake 1: Forgetting Blynk.run()

Result:
App not responding

Fix:
Always add Blynk.run() in loop()

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❌ Mistake 2: Wrong Auth Token

Result:
Device offline

Fix:
Copy correct token from Blynk app

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❌ Mistake 3: Wrong Virtual Pin Number

Result:
Button not working

Fix:
Match V-pin in app and code

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❌ Mistake 4: Blocking Code (delay)

Result:
App becomes slow

Fix:
Avoid long delays in loop()

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PART 9 – Summary

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• Blynk is a cloud + app platform for IoT

• Blynk library connects ESP32 to Blynk

• Virtual pins are software pins

• Blynk.virtualWrite() → ESP32 → App

• BLYNK_WRITE() → App → ESP32

• Blynk.run() keeps everything alive