#include <Wire.h>
#include <LiquidCrystal_I2C.h>

int valeurlue;
float tension;

LiquidCrystal_I2C lcd(0x27,16,2);


void setup()
{
  Serial.begin(9600);
  lcd.begin(0x27,16,2);
pinMode(4, OUTPUT);
  lcd.backlight();

}

void loop() {
valeurlue = analogRead(A0);
tension = valeurlue * 5.0 / 1024;
lcd.print("tension=");
lcd.print(tension);
if (tension <  2.5){
  digitalWrite(4, HIGH);
}
if (tension>=4.5){
  digitalWrite(4, LOW);
}
delay(1000);
lcd.clear();
}