const int trigPin = 7;
const int echoPin = A0;
int led = 13;
int buzz = 8;
int d = 500;


void setup() {
  pinMode(led, OUTPUT);
  pinMode(buzz, OUTPUT);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  Serial.begin(9600);
}
void loop() {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  long duration = pulseIn(echoPin, HIGH);
  long distance = duration * 0.034 / 2.0;
  Serial.print("distance:");
  Serial.print(distance);
  Serial.print(" cm");
  Serial.println();
  if (distance  <= 100) {
    digitalWrite(led, HIGH);
    digitalWrite(buzz, HIGH);
    delay(d);
    digitalWrite(led, LOW);
    digitalWrite(buzz, LOW);
    delay(d);
  }
  else {
    digitalWrite(led, LOW);
    digitalWrite(buzz, LOW);
    delay(d);
  }
  delay(500);
}