int sensorPin = A0;
float voltage, temperatureC, reading;

void setup() {
pinMode(13, OUTPUT);  
Serial.begin(9600);

}

void loop() {
reading= analogRead(sensorPin);
voltage= reading*5.0/1024;
//Serial.print(voltage);
//Serial.println("volts");
temperatureC=(voltage)*100;
Serial.print(temperatureC);
Serial.println("degrees C");
delay(1000);
if (temperatureC>21)
{   digitalWrite(13, HIGH);   }
 else { digitalWrite(13, LOW);  }
}