Ultrasonic sensors are distance sensors that use sound waves to detect how far away an object is. They send out high frequency bursts of sound and listen for its echo. They then determine how far away the object is based on how long it takes for the sound to return to the sensor. This variety requires an Arduino library to operate.

#include <NewPing.h>

#include <Servo.h>

Servo myservo;  // create servo object to control a servo

NewPing mysensor(5, 6, 200);

void setup() {

  myservo.attach(11);  // attaches the servo on pin 9 to the servo object

  Serial.begin(9600);

}

void loop() {

  int pingTime = mysensor.ping();

  int distance = mysensor.ping_in();

  int distance_cm = mysensor.ping_cm();

  if (distance < 2){

    myservo.write(179);

  }

  else{

    myservo.write(0);

  }

  Serial.println(distance);

}