#define trigPin 9
#define echoPin 8
#define ledPin 3
void setup() {
  // put your setup code here, to run once:
Serial.begin(9600);
pinMode(trigPin, OUTPUT);
pinMode(echoPin, INPUT);
pinMode(ledPin, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
float duration;
float distance;
 
 digitalWrite(trigPin, LOW);
 delayMicroseconds(2);
 digitalWrite(trigPin, HIGH);
 delayMicroseconds(10);
 digitalWrite(trigPin, LOW);
 duration=pulseIn(echoPin, HIGH);
 distance=(duration/2)/29.1; 
  Serial.print("Distance:");
  Serial.println(distance);
if(distance<50)
{
digitalWrite(ledPin, HIGH);
}
else if(distance>=100 && distance<=150)
{
digitalWrite(ledPin, HIGH);
delay(1000);
digitalWrite(ledPin, LOW);
delay(1000);
}
else
{
digitalWrite(ledPin, LOW);
 }
}