int TRIG = D9;      // pin for the ultrasonic sensor trigger
int ECO = D8;       // pin for the ultrasonic sensor echo
int LED = D0;       // pin that controls the MOSFET for the LED

long time;        // variable to store echo time
int distance;      // variable to store distance

void setup() {
  pinMode(TRIG, OUTPUT);
  pinMode(ECO, INPUT);
  pinMode(LED, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  // Send trigger pulse
  digitalWrite(TRIG, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG, LOW);

  // Read echo time
  time = pulseIn(ECO, HIGH);

  Serial.print("Time: ");
  Serial.println(time);

  // Calculate distance (speed of sound: 340 m/s, divided by 2 and converted to cm)
  distance = time * 0.034 / 2;

  // Show distance on the serial monitor
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");

  // If the distance is less than 20 cm, turn on the LED
  if (distance < 20) {
    digitalWrite(LED, HIGH);
  } else {
    digitalWrite(LED, LOW);
  }

  delay(500); 
}