int new_v;
int old_v;
int pin =A0;


void setup() {
  // put your setup code here, to run once:
pinMode(A0, INPUT);
Serial.begin(9600);
}

void loop() {
  // put your main code here, to run repeatedly:
new_v = analogRead(pin);
}


if (new_v !=old_v) {
  Serial.println(new_v);
old_v= new_v;