const int mq135=26;
const int ledpin=25;
const int goodth=1364;
const int modth=2729;
void setup()
{
  Serial.begin(115200);
  delay(1000);
  pinMode(ledpin,OUTPUT);
  Serial.println("MQ135 Air quality sensor with LED indication");
}
void loop()
{
  int sv=analogRead(mq135);
  Serial.print("Sensor Value:");
  Serial.println(sv);
  if(sv<=goodth)
  {
    digitalWrite(ledpin,LOW);
    Serial.println("Air quality good,LED OFF");

  }
  else if(sv<=modth){
    digitalWrite(ledpin,HIGH);
    delay(500);
    digitalWrite(ledpin,LOW);
    delay(500);
    Serial.println("Air quality mod,LED BLINK");
  }
  else{
    digitalWrite(ledpin,HIGH);
    Serial.println("AIR quality severe,LED ON");
  }
  delay(1000);
}