// "Smoke Detector"

const int smokePin = A0;
const int triggerPin = A1;
const int buzzerPin = 13;

void setup() 
{
  Serial.begin(115200);

  pinMode(buzzerPin,OUTPUT);
}

void loop() 
{
  int triggerValue = analogRead(triggerPin);
  int smokeValue = analogRead(smokePin);

  // Use the next second to either 
  // sound the buzzer or a silent delay.
  int bps = 3;  // beeps per second
  if(smokeValue > triggerValue)
  {
    for(int i=0; i<bps; i++)
    {
      tone(buzzerPin,800);
      delay(1000/(2*bps));
      noTone(buzzerPin);
      delay(1000/(2*bps));
    }
  }
  else
  {
    delay(1000);
  }
}