void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  pinMode(13, OUTPUT);
  pinMode(12, INPUT);
pinMode(7, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
float distance;
digitalWrite(13, LOW);
delayMicroseconds(2);
digitalWrite(13, HIGH);
delayMicroseconds(10);
digitalWrite(13, LOW);
delayMicroseconds(2);
float duration = pulseIn(12,HIGH);
distance = (0.034*duration)/2;
Serial.println(distance);
if(distance<100){
  digitalWrite(7, HIGH);
}
if(distance>100){
  digitalWrite(7,LOW);
}
delay(1000);
}