const int echoPin=2, triggerPin=3, red=7,buzz=6;
int pulseValue;
float distance;

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

void loop( )
{
 
digitalWrite(triggerPin, LOW);
delayMicroseconds(5);
digitalWrite(triggerPin, HIGH);
delayMicroseconds(10);
pulseValue=pulseIn(echoPin, HIGH);
distance=(pulseValue*0.0001657*39.37);
 


if (distance<=50)
{
  digitalWrite(red, HIGH);
  tone(buzz,500);
}
 
else 
{
  digitalWrite(red, LOW);
  noTone(buzz);
}
Serial.print(distance);
Serial.println(" inch/es");
delay(500);
}