int trigPin = 12;
int echoPin = 11;
long timeperiod, cm;
const int analogOutPin = 9;
int brightness;

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

void loop(){

  if (timeperiod > 50)
  analogWrite(analogOutPin,0);
}
{

  if (timeperiod 10 < 50){
  for(brightness = 0; brightness < 256; brightness++){
    analogWrite(led,brightness);
    delay(10);}
}}
  if (timeperiod < 10)
  analogWrite(analogOutPin,0);

{
  digitalWrite(trigPin, LOW);
  delayMicroseconds(20);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(0);
  digitalWrite(trigPin, LOW);

  timeperiod = pulseIn(echoPin, HIGH);

  cm = microsecondsToCentimeters(timeperiod);
  Serial.print("dist=");
  Serial.print(cm);
  Serial.println();

  delay(10);
}
long microsecondsToInches(long microseconds)
{
  return microseconds / 74 /2;
}
  long microsecondsToCentimeters(long microseconds)
{
  return microseconds / 29/ 2;
}