#define echoPin 6 // Echo Pin
#define trigPin 7 // Trigger Pin
#define LEDPin 13 // Onboard LED
int maximumRange = 200;
int minimumRange = 0;
long duration, distance;
void setup() {
Serial.begin (9600);
pinMode(trigPin, OUTPUT);
pinMode(echoPin, INPUT);
pinMode(LEDPin, OUTPUT);
}
void loop() {
digitalWrite(trigPin, LOW);
delayMicroseconds(2); 
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin, LOW);
duration = pulseIn(echoPin, HIGH);
distance = duration/58.2;
if (distance >= maximumRange || distance <= minimumRange){
Serial.println("-1");
digitalWrite(LEDPin, HIGH);
}
else {
Serial.println(distance);
digitalWrite(LEDPin, LOW);
}
delay(50);
}