📘Gas Detection (Bluetooth Serial Terminal Version)

🎯 Objective of This Lesson

Students will learn:

• How to enable Bluetooth in ESP32

• How to send gas sensor data to mobile

• How to monitor gas levels wirelessly

• How to detect gas leakage using Bluetooth

📱 Required Mobile App

Install on Android:

• Serial Bluetooth Terminal
  OR

• Any Bluetooth Terminal App

🔌 Hardware Reminder

No extra components.

🧾 Complete ESP32 Bluetooth Code (Copy–Paste Ready)

#include "BluetoothSerial.h"

BluetoothSerial SerialBT;

#define MQ3_PIN 34

int gasValue = 0;
int threshold = 1200; // Adjust after calibration

void setup() {

Serial.begin(115200);
SerialBT.begin("Gas_Detector"); // Bluetooth device name

pinMode(MQ3_PIN, INPUT);

Serial.println("Bluetooth Gas Detection System Started...");
SerialBT.println("Connected to Gas Detection System");

Serial.println("Warming up sensor...");
SerialBT.println("Warming up sensor...");
delay(30000); // 30 seconds warm-up

Serial.println("Sensor Ready!");
SerialBT.println("Sensor Ready!");
}

void loop() {

gasValue = analogRead(MQ3_PIN);

Serial.print("Gas Value: ");
Serial.println(gasValue);

SerialBT.print("Gas Value: ");
SerialBT.println(gasValue);

if (gasValue > threshold) {

Serial.println("⚠ GAS LEAK DETECTED!");
SerialBT.println("⚠ GAS LEAK DETECTED!");

} else {

Serial.println("Environment Safe");
SerialBT.println("Environment Safe");
}

SerialBT.println("----------------------");

delay(1000);
}

🧠 Code Explanation (Step-by-Step)

1️⃣ Include Bluetooth Library

This enables Bluetooth functionality in ESP32.

2️⃣ Create Bluetooth Object

This object is used to send and receive Bluetooth data.

3️⃣ Start Bluetooth

This sets the device name visible in mobile Bluetooth list.

Students will see:

👉 Gas_Detector

4️⃣ Warm-Up Delay

Sensor needs heating time for stable readings.

5️⃣ Reading Gas Value

Reads analog voltage from MQ3.

Range:

0 – 4095

6️⃣ Sending Data to Mobile

This sends data to the Bluetooth terminal app.

Difference:

• Serial.print() → Computer

• SerialBT.print() → Mobile

7️⃣ Gas Detection Logic

If gas level exceeds threshold:

Display:

⚠ GAS LEAK DETECTED!

Else:

Environment Safe

📱 How to Connect Mobile

1️⃣ Upload code
2️⃣ Turn ON Bluetooth in phone
3️⃣ Open Serial Bluetooth Terminal app
4️⃣ Search for device
5️⃣ Select Gas_Detector
6️⃣ Connect

Now you will see live gas readings.

📊 Example Bluetooth Output

Gas Value: 380
Environment Safe

Gas Value: 1600
GAS LEAK DETECTED!

🔧 Threshold Calibration Reminder

Clean air → Note value
Expose to alcohol vapor → Note value

Set threshold between both values.

Example:

Clean air: 400
Gas present: 1800

Set threshold = 1000

🎓 Learning Outcomes

After this lesson, students understand:

• Wireless sensor monitoring

• Bluetooth communication

• Difference between Serial & SerialBT

• Real-time alert system

• Practical IoT foundation