#define trigpin 7
#define echopin 6
void setup() {
 Serial.begin(9600); 
pinMode(7, OUTPUT);
pinMode(6, INPUT);
pinMode(8, OUTPUT);
}

void loop() {
  long duration;
  digitalWrite(7, LOW);
  delayMicroseconds(2);
  digitalWrite(7, HIGH);
  delayMicroseconds(10);
  digitalWrite(7, LOW);
  duration = pulseIn(6,HIGH);
  float distance = duration * 0.5 * 343 / 10000 ;
  Serial.println(distance);
  delay(500);
  if(distance<200){
    digitalWrite(8, HIGH);
  }
    else{
      digitalWrite(8, LOW);
    }
  }