/*
 Voltaat learn (http://learn.voltaat.com/)
 Link for full tutorial:

 Tutorial: Detect smoke and air quality using MQ-135 Sensor

 The function of this sketch is to Detect smoke and air quality using MQ-135 Sensor and Arduino

 Connections from the MQ135 sensor:
 • VCC pin→ Arduino 5V pin
 • GND pin→ Arduino GND pin
 • A0 pin→ Arduino pin A0
*/


// define MQ135 variable with A0 value that represent the input analog pin in the arduino
int MQ135 = A0;

// define standardAir variable with 200 value
int standardAir = 200;


// Commands inside void setup run once
void setup()
{
 // MQ135 is defined as an input
 pinMode(MQ135, INPUT);

 // Start the serial monitor at 9600 baud rate (9600 bits per second)
 Serial.begin(9600);

}

// Commands inside void loop run forever
void loop()
{
 // Read the value of analog input from MQ135 and assign it in the variable sensorRead
 int sensorRead = analogRead(MQ135);

 // print "Sensor Reading: " to the serial monitor at the same line
 Serial.print("Sensor Reading: ");

 // print The sensorRead value to the serial monitor at the same line
 Serial.print(sensorRead);

 // compare the sensor reading value with the standard fresh air value that we set in the code
 if (sensorRead > standardAir)
 {
   // print " ,Gas is detected" to the serial monitor at new line
   Serial.println(" ,Gas is detected");
 }
 else
 {

   // print " ,No gas detected" to the serial monitor at new line
   Serial.println(" ,No gas detected");
 }


}