smoke.ino

// Threshold value is the magnitude or intensity that must be
// exceeded for a certain phenomenon too occur. We're keeping it
// sensorThres = 400. The value 400 has been choosen and tested 
// due to reason how the circuit will behave during favourable condition.
// If smoke detection value will be greater than threshold then
// alarm will be activated. If smoke detection value will be less than
// threshold then alarm will remain silent.

int redLed = 12;
int greenLed = 11;
int buzzer = 10;
int smokeA0 = A5;

// Your threshold value
int sensorThres = 400;

void setup() {
  pinMode(redLed, OUTPUT);
  pinMode(greenLed, OUTPUT);
  pinMode(buzzer, OUTPUT);
  pinMode(smokeA0, INPUT);
  Serial.begin(9600);
}

void loop() {
  int analogSensor = analogRead(smokeA0);

  Serial.print("Pin A0: ");
  Serial.println(analogSensor);
  // Checks if it has reached the threshold value
  if (analogSensor > sensorThres) {
    digitalWrite(redLed, HIGH);
    digitalWrite(greenLed, LOW);
    tone(buzzer, 1000, 200);
  } else {
    digitalWrite(redLed, LOW);
    digitalWrite(greenLed, HIGH);
    noTone(buzzer);
  }
  delay(100);
}