//GAS sensor output pin to Arduino analog A0 pin
#define R 2
#define Y 4

#define MQ3 A0
int gaslevel;

// UltraSonic Sensor interfacing to Arduino .
int buzzer = 9;
int triggerPin = 7; //triggering on pin 7
int echoPin = 8; //echo on pin 8

void setup()
{

Serial.begin(9600); 
//we'll start serial comunication, so we can see the distance on the serial monitor 
Serial.println("Tech Ponder's UltraSonic Sensor Tutorial");
pinMode(triggerPin, OUTPUT); //defining pins
pinMode(echoPin, INPUT);
pinMode(buzzer, OUTPUT);
digitalWrite(buzzer,LOW); 

pinMode(MQ3,INPUT);
pinMode(R,OUTPUT);
pinMode(Y,OUTPUT);


}

void loop()
{ 
int duration, distance; //Adding duration and distance
digitalWrite(triggerPin, HIGH); //triggering the wave(like blinking an LED)
delay(10);
digitalWrite(triggerPin, LOW);
duration = pulseIn(echoPin, HIGH); //a special function for listening and waiting for the wave
distance = (duration/2) / 29.1; //transforming the number to cm(if you want inches, you have to change the 29.1 with a suitable number
delay(1000);
Serial.print(distance); //printing the numbers
Serial.print("cm"); //and the unit
Serial.println(" "); //just printing to a new line
if (distance < 35)
{
     digitalWrite(buzzer,HIGH);
     Serial.println("Buzzer On");
}
digitalWrite(buzzer,LOW);


  gaslevel=(analogRead(MQ3));
  gaslevel=map(gaslevel,0,1023,0,255);
	
 if(gaslevel > 100 && gaslevel <= 300){//gaslevel is greater than 100 and less than 300
    digitalWrite(R,LOW);//RED led is off
    
     _delay_ms(500);//delay
    digitalWrite(Y,HIGH);//YELLOW led is on
  _delay_ms(500);
  }
  else if(gaslevel > 300 && gaslevel <= 600){//gaslevel is greater than 300 and less than 600
        digitalWrite(Y,LOW);//YELLOW led is off
         
         _delay_ms(500);
    digitalWrite(R,HIGH);//RED led is on
    
      }
      
       
      else
      {
         digitalWrite(R,LOW);//red led is off
        digitalWrite(Y,LOW);//YELLOW led is off
    
      }
  Serial.println(gaslevel);//print values on serial monitor
  _delay_ms(100);



}