const int sensorPin = A0;
const int R1 = 2;
const int R2 = 3;
const int R3 = 4;

const float baselineTemp = 20.0;
void setup(){
  Serial.begin(9600); // open a serial port

  for(int pinNumber = 2; pinNumber<5; pinNumber++){
    pinMode(pinNumber,OUTPUT);
    digitalWrite(pinNumber, LOW);
  }
}

void loop(){
  int sensorVal = analogRead(sensorPin);
  Serial.print("Sensor Value: ");
  Serial.print(sensorVal);

  // convert the voltage to temperature in degrees
  const float BETA = 3950;
  float temperature = 1 / (log(1 / (1023. / sensorVal - 1)) / BETA + 1.0 / 298.15) - 273.15;
  Serial.print(", degrees C: ");
  Serial.println(temperature);
  if(temperature < baselineTemp){
    digitalWrite(R1, LOW);
    digitalWrite(R2, LOW);
    digitalWrite(R3, LOW);
  }else if(temperature >= baselineTemp+2 &&temperature < baselineTemp+4){
    digitalWrite(R1, HIGH);
    digitalWrite(R2, LOW);
    digitalWrite(R3, LOW);
  }else if(temperature >= baselineTemp+4 &&temperature < baselineTemp+6){
    digitalWrite(R1, HIGH);
    digitalWrite(R2, HIGH);
    digitalWrite(R3, LOW);
  }else if(temperature >= baselineTemp+6){
    digitalWrite(R1, HIGH);
    digitalWrite(R2, HIGH);
    digitalWrite(R3, HIGH);
  }
  delay(1);
}