🔥 Lesson 3.2 – Flame Sensor Circuit & ESP32 Connections

In this lesson, we will connect the Flame Sensor with ESP32 and build the hardware setup for our IoT-Based Fire Alert System. We will also connect an LED and a Buzzer that will provide local alerts whenever fire is detected.

🎯 Objective of This Circuit

The purpose of this circuit is to:

✅ Detect the presence of fire using a Flame Sensor

✅ Display alert status using an LED

✅ Generate sound alert using a Buzzer

✅ Send fire detection data to Blynk through ESP32

✅ Build the hardware foundation of the IoT Fire Alert System

🛠️ Components Required

🔌 ESP32 Pin Connections

🔥 Flame Sensor Connection

💡 LED Connection

🔔 Buzzer Connection

📊 Complete Pin Mapping

🔥 How the Circuit Works

The Flame Sensor continuously monitors the surroundings for fire.

Normal Condition

When no flame is detected:

✅ Sensor output remains HIGH

✅ LED remains OFF

✅ Buzzer remains OFF

✅ Blynk Dashboard shows Safe Status

Fire Detection Condition

When flame is detected:

🔥 Sensor output changes

🔥 ESP32 detects the change

💡 LED turns ON

🔔 Buzzer starts beeping

📱 Fire alert is sent to Blynk

⚙️ Understanding Each Component

🔥 Flame Sensor

The Flame Sensor acts as the input device.

Function

✅ Detects infrared radiation emitted by fire.

Output

Digital Output (DO)

HIGH = No Fire
LOW = Fire Detected

💡 Alert LED

The LED acts as a visual indicator.

Purpose

Normal Condition:

❌ LED OFF

Fire Detected:

✅ LED ON

This helps users quickly identify fire status.

🔔 Buzzer

The buzzer acts as an audio alert device.

Purpose

Normal Condition:

🔇 Silent

Fire Detected:

🔊 Alarm Sound

This immediately alerts nearby people.

🌐 ESP32

ESP32 acts as the brain of the project.

Responsibilities

✅ Read flame sensor data

✅ Control LED

✅ Control buzzer

✅ Connect to Wi-Fi

✅ Send data to Blynk Cloud

✅ Generate IoT alerts

🔄 System Working Flow

Flame Appears
       ↓
Flame Sensor Detects Fire
       ↓
ESP32 Reads Sensor Data
       ↓
LED Turns ON
       ↓
Buzzer Activates
       ↓
Data Sent to Blynk
       ↓
User Receives Alert

⚠️ Important Wiring Precautions

🔹 Check Power Supply

Ensure:

Flame Sensor VCC → ESP32 3.3V

Wrong voltage may damage the sensor.

🔹 Verify Ground Connections

All GND pins must be connected together.

ESP32 GND
Flame Sensor GND
LED GND
Buzzer GND

🔹 Use Resistor with LED

Always connect a 220Ω resistor in series with the LED.

This protects the LED from excessive current.

🔹 Secure Jumper Wires

Loose connections may cause:

❌ False fire detection

❌ Sensor reading errors

❌ Unstable system behavior

🧪 Hardware Testing Before Programming

Before uploading code:

Step 1

Connect ESP32 to the computer.

Step 2

Check the power LED on ESP32.

✅ Should turn ON

Step 3

Check Flame Sensor Power LED.

✅ Should turn ON

Step 4

Verify all wiring connections.

✅ VCC connected correctly

✅ GND connected correctly

✅ GPIO pins connected correctly

Step 5

Confirm there are no loose wires.

📌 Key Points to Remember

✅ Flame Sensor is connected to GPIO 27.

✅ LED is connected to GPIO 26.

✅ Buzzer is connected to GPIO 25.

✅ ESP32 reads fire detection data from the sensor.

✅ LED and buzzer provide local alerts.

✅ ESP32 sends real-time data to Blynk Cloud.

✅ Proper wiring is essential for reliable operation.