HC_SR04_Ping_Servo.ino

// AServo activated by an HC-SR04 via Arduino.

/*
  This sketch reads a HC-SR04 ultrasonic rangefinder and returns
  the distance to the closest object in range. To do this, it sends
  a pulse to the sensor to initiate a reading, then listens for a
  pulse to return. The length of the returning pulse is proportional
  to the distance of the object from the sensor.

  The Arduino then takes this information and initiates a series of
  sweeps. A sweep is defined as the servo moving its horn from
  the 0 position to 180 and back to 0 then to -180 and back to 0.

  This code was developed partially from Ping))) code found in the
  public domain is written by David A. Mellis and adapted to the HC-SRO4
  by Tautvidas Sipavicius, servo code was provided the sweep example
  that is included in the Arduino IDE, while other portions were written
  by Charles Gantt and Curtis Gauger from
  http://www.themakersworkbench.com.

  This code was written for a tutorial on http://www.themakersworkbench.com,
  and was designed for use in a project built by
  The Young Makers of Greater Augusta. */

/*Tell the Arduino Ide to include the Servo.h library. */
#include <Servo.h>

/*Setup the variables for the HC-SR04 */
const int trigPin = 6;
const int echoPin = 7;

/*create servo object to control a servo
  a maximum of eight servo objects can be created */
Servo myservo;

/*variable to store the servo position */
int pos = 0;

void setup() {
  /*initialize serial communication: */
  Serial.begin(9600);

  /* attaches the servo on pin 9 to the servo object */
  myservo.attach(9);
}
void loop()
{
  /*establish variables for the duration of the ping,
    and the distance result in inches and centimeters: */
  long duration, inches, cm;

  /*The sensor is triggered by a HIGH pulse of 10 or
     more microseconds.
    Give a short LOW pulse beforehand to ensure a clean HIGH pulse:*/
  pinMode(trigPin, OUTPUT);
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  /*Read the signal from the sensor: a HIGH pulse whose
     duration is the time (in microseconds) from the sending
    of the ping to the reception of its echo off of an object.*/
  pinMode(echoPin, INPUT);
  duration = pulseIn(echoPin, HIGH);

  /*convert the time into a distance*/
  inches = microsecondsToInches(duration);
  cm = microsecondsToCentimeters(duration);

  /*Tell the Arduino to print the measurement in the serial console*/
  Serial.print(inches);
  Serial.print("in, ");
  Serial.print(cm);
  Serial.print("cm");
  Serial.println();

  /* This if-else statement tells the Arduino at what distance
    it should trigger the servo, what the servo should do,
    and what it should do if the distance is too far away.*/
  if (inches <= 24) {
    sweep(3);
  }
  else if (inches >= 24) {
    myservo.write(pos);
  }

  /*Tell the Arduino to wait 0.10 seconds before pinging the
    Ultrasonic Sensor again.*/
  delay(100);
}

/*Converts the microseconds reading to Inches*/
long microsecondsToInches(long microseconds)
{

  /*According to Parallax datasheet for the PING sensor, there are
     73.746 microseconds per inch (i.e. sound travels at 1130 feet per
     second). This gives the distance traveled by the ping, outbound
     and return, so we divide by 2 to get the distance of the obstacle.
    See: http://www.parallax.com/dl/docs/prod/acc/28015-PING-v1.3.pdf */
  return microseconds / 74 / 2;
}

/*Converts the Microseconds Reading to Centimeters */
long microsecondsToCentimeters(long microseconds)
{

  /* The speed of sound is 340 m/s or 29 microseconds per centimeter.
      The ping travels out and back, so to find the distance of the
    object we take half of the distance traveled. */
  return microseconds / 29 / 2;
}

/*This sub-routine is what dictates the movement of the servo */
void sweep(int NUM_OF_CYCLES)
{

  /* Tells the Arduino to start this loop at 0 and increment it by 1
       each time the loop completes. This is how the Arduino knows to
       stop the loop when a specific number of the
    Sweep routine has been run. */
  for (int j = 0; j < NUM_OF_CYCLES; j++)

    /*goes from 0 degrees to 180 degrees */
    for (pos = 0; pos < 180; pos += 1)
    { // in steps of 1 degree

      /*tell servo to go to position in variable 'pos' */
      myservo.write(pos);

      /*waits 15ms for the servo to reach the position delay(10); }
        goes from 180 degrees to 0 degrees */
      for (pos = 180; pos >= 1; pos -= 1) {

        /*tell servo to go to position in variable 'pos' */
        myservo.write(pos);

        /*waits 15ms for the servo to reach the position */
        delay(10);
      }
    }