LM35

#include <LiquidCrystal.h>
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

int reading = 0;
int sensorPin = A0;
int relay =7;
void setup() {
  analogReference (INTERNAL);
  analogRead (sensorPin);
  lcd.begin(20, 4);
  pinMode(relay,OUTPUT);
  lcd.setCursor(0, 0);
  lcd.print("Temperatura: ");
}

void loop() {
  // float celsius = analogRead(sensorPin)*(1.1F/1024.0F)*100.0F ;
  // equivalente a (fai due operazioni su valori costanti in meno)

  float celsius = averageAnalogRead(sensorPin, 50)*0.107421875F ;
  char lcd_buffer[17];
  dtostrf(celsius, 5, 1, lcd_buffer);

  if (celsius >28) {
    digitalWrite(7,HIGH);
    sprintf(lcd_buffer, "%s %cC - ON ", lcd_buffer, (char)223);
  }
  else {
    digitalWrite(7,LOW);
    sprintf(lcd_buffer, "%s %cC - OFF", lcd_buffer, (char)223);
  }
  lcd.setCursor(0,1);
  lcd.print(lcd_buffer);
  delay(500);
}


long averageAnalogRead(const byte AnChannel, const byte Num) {
  long _val = 0;
  for (int n = 0; n < Num; n++) {
    _val += analogRead(AnChannel);
  }
  return _val / Num;
}