const int trigPin = 9;  
const int echoPin = 10; 
const int motionPin = 12;
const int ledPin = 13;           

float duration, distance;
bool motionDetected = false;

void setup() {
  pinMode(trigPin, OUTPUT); 
  pinMode(echoPin, INPUT);  
  pinMode(ledPin, OUTPUT);
  pinMode(motionPin, INPUT);
  Serial.begin(9600);      
}

void loop() {
  // Check for motion
  int motionState = digitalRead(motionPin);
  if (motionState == HIGH) {
    motionDetected = true;
  } else {
    motionDetected = false;
  }

  // If motion is detected, perform distance measurement
  if (motionDetected) {
    digitalWrite(trigPin, LOW);
    delayMicroseconds(2);
    digitalWrite(trigPin, HIGH);
    delayMicroseconds(10);
    digitalWrite(trigPin, LOW);

    duration = pulseIn(echoPin, HIGH);
    distance = (duration * 0.0343) / 2;

    Serial.print("Distance: ");
    Serial.println(distance);

    if (distance <= 50) {
      digitalWrite(ledPin, HIGH);
    } else {
      digitalWrite(ledPin, LOW);
    }
  } else {
    // If no motion is detected, turn off the LED
    digitalWrite(ledPin, LOW);
  }

  delay(100);
}