#define echoPin 6
#define trigPin 7
#define fanPin  5

long duration;
int distance;

void setup() {
  pinMode(fanPin, OUTPUT);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  digitalWrite(fanPin, LOW);
  Serial.begin(9600);
}
void loop() {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  duration = pulseIn(echoPin, HIGH);
  distance = duration * 0.034 / 2;
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");

  if (distance<70) {
    digitalWrite(fanPin, HIGH);
    delay(1000);
  }
  else {
    digitalWrite(fanPin, LOW);
  }
}