#define ECHOPIN 9

#define TRIGPIN 8

#define RELAY 4


#define MAXIMUMRANGE = 100;


long duration;

int distanceCM;


void setup() {

  Serial.begin (9600);


  pinMode (TRIGPIN, OUTPUT);

  digitalWrite(TRIGPIN,LOW);

  pinMode (ECHOPIN, INPUT);

  pinMode (RELAY, OUTPUT);

}


void loop() {

  digitalWrite(TRIGPIN, HIGH);

  delayMicroseconds(5);

  digitalWrite(TRIGPIN, LOW);

  delayMicroseconds(5);

  duration = pulseIn (ECHOPIN, HIGH, MAXIMUMRANGE*60);


  distanceCM = duration/58.2;

  delay(1300);

  Serial.println(distanceCM);

  Serial.print("Distanza cm.  ");




 if ((distanceCM >= 3) && (distanceCM <= 35))

  digitalWrite(RELAY, HIGH)

 else

  digitalWrite(RELAY, LOW)

}