#define trigPin 9
#define echoPin 10
#define buzzerPin 8
#define ledPin 7

long duration;
int distance;
int lastDistance = 0;
int threshold = 10; // Minimum change in cm to consider as motion

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

void loop() {
  // Trigger ultrasonic pulse
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  // Measure duration and calculate distance
  duration = pulseIn(echoPin, HIGH);
  distance = duration * 0.034 / 2;

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

  if (abs(distance - lastDistance) > threshold) {
    // Motion Detected
    digitalWrite(buzzerPin, HIGH);
    digitalWrite(ledPin, HIGH);
    delay(1000); // Alert duration
  } else {
    // No Motion
    digitalWrite(buzzerPin, LOW);
    digitalWrite(ledPin, LOW);
  }

  lastDistance = distance;
  delay(500); // Adjust sensitivity
}