Project 3: Love-o-meter in Celcius?

Hardware The Arduino Starter Kit
3

I immediately had the same question, but ended up figuring it out. I also added a fourth LED and the addition of a buzzer so that when the fourth LED lights up the buzzer goes off. The kids really get a kick out of this because the buzzer adds and extra element of excitement. I told them if they are really love struck then the buzzer will go off. I was surprised how easy it was to set up the buzzer. I set it up on pin 6 in this variation:

//Addition of 4th LED and a buzzer to go off with 4th LED
 */

// named constant for the pin the sensor is connected to
const int sensorPin = A0;
  // room temperature in Celcius
const float baselineTemp = 78;


void setup(){
  // open a serial connection to display values
  Serial.begin(9600);
  // set the LED pins as outputs
  // the for() loop saves some extra coding
  for(int pinNumber = 2; pinNumber<6; pinNumber++){
    pinMode(pinNumber,OUTPUT);
    digitalWrite(pinNumber, LOW);
   
  }
}

void loop(){
  // read the value on AnalogIn pin 0 
  // and store it in a variable
  int sensorVal = analogRead(sensorPin);
  //define alarm pitch

  // send the 10-bit sensor value out the serial port
  Serial.print("sensor Value: ");
  Serial.print(sensorVal); 

  // convert the ADC reading to voltage
  float voltage = (sensorVal/1024.0) * 5.0;

  // Send the voltage level out the Serial port
  Serial.print(", Volts: ");
  Serial.print(voltage);

  // convert the voltage to temperature in degrees C
  // the sensor changes 10 mV per degree
  // the datasheet says there's a 500 mV offset
  // ((volatge - 500mV) times 100)
  Serial.print(", degrees C: "); 
  float temperature = (voltage - .5) * 100;
  Serial.print(temperature);
  float degF = (temperature*9/5+32);
  Serial.print(", degrees F: ");
  Serial.println(degF);

  // if the current temperature is lower than the baseline
  // turn off all LEDs
  if(degF < baselineTemp){
    digitalWrite(2, LOW);
    digitalWrite(3, LOW);
    digitalWrite(4, LOW);
    digitalWrite(5, LOW);
  } // if the temperature rises 2-4 degrees, turn an LED on 
  else if(degF >= baselineTemp +2 && degF < baselineTemp+4){
    digitalWrite(2, HIGH);
    digitalWrite(3, LOW);
    digitalWrite(4, LOW);
    digitalWrite(5, LOW);
  } // if the temperature rises 4-6 degrees, turn a second LED on  
  else if(degF >= baselineTemp+4 && degF < baselineTemp+6){
    digitalWrite(2, HIGH);
    digitalWrite(3, HIGH);
    digitalWrite(4, LOW);
    digitalWrite(5, LOW);
  } // if the temperature rises more than 6 degrees, turn all LEDs on
  else if(degF >= baselineTemp+6 && degF < baselineTemp+8){
    digitalWrite(2, HIGH);
    digitalWrite(3, HIGH);
    digitalWrite(4, HIGH);
    digitalWrite(5, LOW);
    } // if the temperature rises more than 6 degrees, turn all LEDs on and sends tone to speaker
  else if(degF >= baselineTemp+8){
    digitalWrite(2, HIGH);
    digitalWrite(3, HIGH);
    digitalWrite(4, HIGH);
    digitalWrite(5, HIGH);
    tone(6,2000,50);
  }
  delay(10);
}