Virtual IoT Lab DEI

Instructions

Objective:

Learn to use the MQ135 air quality sensor to detect harmful gases (CO2, ammonia, benzene, smoke) and display air quality levels with visual indicators (RGB LED) and audio alerts (buzzer).

Steps to Perform:

Click 'Start Simulation' to power the circuit
Click 'Add smoke to activate sensor' button to introduce pollutants
Use the slider to move smoke closer or farther from the MQ135 sensor
Observe the LCD display showing air quality data (0-100 scale)
Watch the RGB LED color changes:
- Green: Air quality acceptable (0-33)
- Yellow/Orange: Air quality exceeded (33-66)
- Red + Buzzer: Air quality dangerous (66-100)
Notice the buzzer activates when pollution reaches dangerous levels

Key Concepts:

MQ135 Sensor: Gas sensor for air quality monitoring (detects CO2, NH3, NOx, alcohol, benzene, smoke)
Analog Reading: analogRead(A0) returns values from 306-756 based on gas concentration
map() Function: Converts sensor range (306-756) to percentage scale (0-100)
Threshold-based Control: Uses if-else conditions to trigger different alerts
LCD Display: 16x2 display shows real-time air quality data and status
RGB LED: Digital pins 2-4 control Red, Green, Blue LEDs for visual feedback
Buzzer Alert: tone() function generates 300Hz warning sound for dangerous levels
I2C Communication: LCD uses I2C protocol (Adafruit_LiquidCrystal library)

Arduino Code

            #include "Wire.h"
#include "Adafruit_LiquidCrystal.h"
Adafruit_LiquidCrystal lcd(0);

#define BUZZER 6
#define RED 4
#define BLUE 3
#define GREEN 2
#define SENSOR A0
byte val;

void setup() 
{
  pinMode(SENSOR,INPUT);
  pinMode(RED,OUTPUT);
  pinMode(GREEN,OUTPUT);
  pinMode(BLUE,OUTPUT);
  
  lcd.begin(16, 2);
  lcd.setCursor(0,0);
  lcd.print("Data:");
}

void loop() 
{
  val = map(analogRead(A0),306,756,0,100);
   lcd.setCursor(5,0);
   lcd.print(val);
    if(val >= 10)lcd.setCursor(7,0);
    else lcd.setCursor(6,0);
     lcd.print("/100 ");
  
 lcd.setCursor(6,1);
    if(val < 33) 
     { 
      digitalWrite(GREEN,1);
      digitalWrite(BLUE,0); 
      digitalWrite(RED,0); 
       noTone(BUZZER); 
        lcd.print("acceptable");
     }
      else if(val < 66)
       { 
        digitalWrite(GREEN,1);
        digitalWrite(BLUE,0); 
        digitalWrite(RED,1); 
         noTone(BUZZER); 
          lcd.print("  exceeded");
       }
        else
         {
          digitalWrite(GREEN,0); 
          digitalWrite(BLUE,0);
          digitalWrite(RED,1);
           tone(BUZZER,300);
            lcd.print(" dangerous");
         }
  delay(500);
}
            
          