Multi Stage Ventilation

  // Three stage small extractor fan
  // GAS sensor output pin to Arduino analog A0 pin
  // PWM pins used to drive fans to allow tickover speeds and prevent back flow
  
  
  #define F1 5        // Define DIGITAL pin for Fan 1
  #define F2 6        // Define DIGITAL pin for Fan 2
  #define F3 9        // Define DIGITAL pin for Fan 3
  #define MQ2 A0      // Define ANALOG pin for MQ sensor
  #define gasadj A1   // Define trim pot
  #define Alarm 4     // Define DIGITAL pin for buzzer
  
  int lgl1 = 17;      // lower gas level for Fan 1
  int lgl2 = 19;      // upper gas level for fan 1
  int mgl1 = lgl2;    // lower gas level for fan 2
  int mgl2 = 28;      // upper gas level for fan 2
  int hgl1 = mgl2;    // lower gas level for fan 3
  int hgl2 = 254;     // upper gas level for fan 3
  int gaslevel;       // blank holder
  int settle = 3000;  // Allow settle time to be set here
  int gaschange;      // will be used as a trim adjustment factor
  int tick = 100;     // set tickover speed
  
  void setup()
  {
    
  Serial.begin(9600);   // Initialize serial port - 9600 bps
  pinMode(MQ2,INPUT);   // MQ pin set
  pinMode(F1,OUTPUT);   // Fan 1 pin set
  pinMode(F2,OUTPUT);   // Fan 2 pin set
  pinMode(F3,OUTPUT);   // Fan 3 pin set
  pinMode(Alarm,INPUT); // Alarm pin set
  _delay_ms (10000);    // MQ Heater warm up can be changed to suit.

TCCR0A = _BV(COM0A1) | _BV(COM0B1) | _BV(WGM01) | _BV(WGM00); // Used to reduce motor harmonics
TCCR0B = _BV(CS01); // Used to reduce motor harmonics from PWM
OCR0A = 180;        // Used to reduce motor harmonics from PWM
OCR0B = 180;        // Used to reduce motor harmonics from PWM

    //set up for spreadsheet output
    Serial.println("ClearRange,A,2,d,5000"); // Used to set up PLX-DAQ v2.1
    Serial.println("ROW,SET,2");            //
    Serial.println("LABEL,Date.,Time.,GAS,Trim%");
    
  }
  
  void loop()
  
  {
    
     //gaschange = (analogRead (gasadj));         // read pot to adjust levels
     //gaschange = map(gasadj,0,1023,-20,20);     // mappedValue = +-20
     //lgl1=lgl1+gaschange;lgl2=lgl2+gaschange;   // add to levels
     //mgl1=mgl1+gaschange;mgl2=mgl2+gaschange;   //
     //hgl1=hgl1+gaschange;                       // Move this to its own routine
    
    gaslevel = (analogRead(MQ2));           // Get Gass level
    gaslevel = map(gaslevel,0,1023,0,255);  // Map gas range

             Serial.println((String) "DATA,DATE,TIME," + (gaslevel));//+","+(gaschange)); 
        
    _delay_ms(settle);
   if ( gaslevel > lgl1 && gaslevel <= lgl2 ) 
   {                          // If gaslevel is greater than 20 and less than 30 turn on Fan 1
      analogWrite (F1,tick);  // Fan 1 TICK
      digitalWrite (F2,LOW);  // FAN 2 OFF
      _delay_ms (settle*2);   // Fan settle time extended
      digitalWrite (F3,HIGH); // Fan 3 ON
      _delay_ms (settle);
      
    }
    
    else if ( gaslevel > mgl1 && gaslevel <= mgl2 ) 
    {                             // If gaslevel is greater than 30 and less than 60 Turn on Fan 1 and 2
          analogWrite (F1,tick);  // Fan 1 TICK
          _delay_ms (settle*3);   // Fan settle time extended
          digitalWrite (F2,HIGH); // Fan 2 ON
          digitalWrite (F3,HIGH); // Fan 3 ON
      
        }
        
         else if (gaslevel > hgl1  && gaslevel <= hgl2 ) 
         {                         // IF gaslevel is greater than 60 and less than 90 turn all fans on   && gaslevel <= hgl2
          digitalWrite (F1,HIGH);  // Fan 3 ON
          digitalWrite (F2,HIGH);  // Fan 2 ON
          digitalWrite (F3,HIGH);  // Fan 1 ON
          _delay_ms (settle * 4);  // Fan settle time extended
         if (gaslevel>=100)  {tone (9,900,1000) ;} // Alarm on 
         if (F3==LOW) {noTone(9);}
        }
        
        else
        
        {
           analogWrite (F1,tick);   // Fan 1 TICK
           digitalWrite (F2,LOW);   // Fan 2 OFF
           digitalWrite (F3,LOW);   // Fan 3 OFF
           _delay_ms (settle);      // Fan settle time
        }
  }