🔰 Introduction

In this lesson, we will build the hardware (circuit) part of our first IoT project:

🌦 IoT Based Weather Station

This project measures:

• Temperature

• Humidity

using a DHT11 sensor and sends the data to the ESP32.

Later, this data will be displayed on:

• Serial Monitor

• Blynk mobile app

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🎯 What You Will Learn in This Lesson

By the end of this lesson, you will be able to:

• Understand what the DHT11 sensor is

• Know how the DHT11 works

• Identify DHT11 pins

• Connect DHT11 to ESP32

• Build a complete circuit for the weather station

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PART 1 – What is the DHT11 Sensor?

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1️⃣ What is DHT11?

DHT11 is a digital temperature and humidity sensor.

It measures:

• 🌡 Temperature (in °C)

• 💧 Humidity (in %)

and sends the data in digital format to a microcontroller.

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2️⃣ Why We Use DHT11 in This Course

We use DHT11 because:

• Very cheap

• Easy to use

• Beginner friendly

• Good enough for learning

• Only needs 1 data pin

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3️⃣ What Does DHT11 Measure?

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4️⃣ How DHT11 Works (Simple Explanation)

Inside the DHT11 sensor:

• A humidity sensing element

• A temperature sensing element

• A small chip that converts analog values into digital data

The ESP32:

• Sends a request signal

• DHT11 replies with temperature and humidity values

• Data is sent using 1 single data wire

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PART 2 – Types of DHT11 Modules

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5️⃣ Bare DHT11 vs DHT11 Module

You may see two types:

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🔹 Type 1: Bare DHT11 (4 pins)

Pins:

1. VCC

2. DATA

3. NC (not connected)

4. GND

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🔹 Type 2: DHT11 Module (3 pins)

Pins:

1. VCC

2. DATA

3. GND

This module already has a resistor.

👉 In this course, we use the 3-pin DHT11 module.

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PART 3 – DHT11 Pin Description

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6️⃣ DHT11 Pins (3-Pin Module)

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PART 4 – What is a Weather Station Circuit?

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7️⃣ What Our Circuit Will Do

The circuit will:

• Power the DHT11 sensor

• Read temperature and humidity

• Send values to ESP32

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8️⃣ Components Required

For this lesson, you need:

1. ESP32 Dev Board – 1

2. DHT11 Sensor Module – 1

3. Breadboard – 1

4. Jumper Wires (Male–Female) – 3

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PART 5 – ESP32 Pin Selection

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9️⃣ Which ESP32 Pins We Will Use

👉 You can use other GPIO pins, but we standardize GPIO 4.

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PART 6 – Step-by-Step Circuit Connections

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🔧 Step 1: Place ESP32 on Breadboard

• Insert ESP32 into breadboard

• Make sure pins are accessible

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🔧 Step 2: Connect Power to DHT11

• DHT11 VCC → ESP32 3.3V

• DHT11 GND → ESP32 GND

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🔧 Step 3: Connect Data Pin

• DHT11 DATA → ESP32 GPIO 4

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✅ Final Connection Table

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PART 7 – Circuit Diagram (Text Description)

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1️⃣0️⃣ Logical Circuit View

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PART 8 – Important Electrical Notes

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⚠️ Power Voltage

• DHT11 works at:

  • 3.3V (recommended for ESP32)

  • 5V (also supported)

👉 Use 3.3V to be safe.

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⚠️ Pull-up Resistor

• DHT11 needs a pull-up resistor on DATA line

• The module version already has it built-in

👉 No external resistor needed.

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PART 9 – Common Beginner Mistakes & Fixes

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❌ Mistake 1: Sensor Not Working

Cause:

• Wrong wiring

• VCC and GND reversed

Fix:

• Recheck pin labels

• Match with connection table

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❌ Mistake 2: Always Shows 0 or NaN

Cause:

• Wrong DATA pin number in code

• Loose wire

Fix:

• Use same GPIO number in code

• Press wires firmly

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❌ Mistake 3: ESP32 Resets Randomly

Cause:

• Power short circuit

• Loose connection

Fix:

• Check for wire touching

• Use correct 3.3V pin

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PART 10 – What’s Next?

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In the next lesson:

Lesson 1.2 – Code & Logic (DHT11 Weather Station)

You will learn:

• How to install DHT11 library

• How to read temperature & humidity

• How to print values on Serial Monitor

• How to send data to Blynk