Part 13 – Distance Sensing with Ultrasonic Sensor and Arduino

Part 13 was a variation of some of the work we had done in some of the previous labs. In this lab we got to use a good bit of pre-formatted code to test the operation of an Ultra Sonic or sound wave based sensor. The lab was just getting the sensor to work with some pre-created code. Here is the code I used to test …

/* HC-SR04 Sensor
 * Date: 1/31/2017
 * Author: Unknown/Leslie Scott Kerfoot
 * 
 */

// Define the global variables we will use.

const int trigPin = 2; // Assign the trigger pin for the sensor.
const int echoPin = 4; // Assign the echo reading pin for the sensor.
long duration,inches,cm; // These will be variables we’ll use in the main loop.
int distance; // As well as this…

// Note: I changed the pre-formatted code a little be because of the “cost”

//  associated with creating the variable each time through the loop.

void setup() {
  Serial.begin(9600); // I also setup debugging
  pinMode(trigPin,OUTPUT); // We’re sending the echo to the trigPin
  pinMode(echoPin,INPUT); // We’re going to receive the distance from the echoPin
}

long microsecondsToInches(long microseconds) {

  // According to the datasheet for the PING, there are
  //   73.746 microseconds per inch (Sound travels at 1130 feet per 
  //   second).  This gives the distance travelled by the ping, outbound
  //   and return. so we divide by 2 to get the distance of the obstacle which is half.
  //  
  long myResult = ((microseconds / 72) / 2); 
  return myResult;
}

long microsecondsToCentimeters(long microseconds) {

  // Using the same logic as the Inches sound travels at a speed of 340 meters/second
  //   or 29 microseconds per centimeter. Since the ping goes out and back we divide by 2
  //   to get just the distance to the ping
  long myResult = ((microseconds / 29) / 2);
  return myResult;
}

void loop() {

  // Setup variable for measuring the duration of the ping
  //   and the return in inches and cm.
    

  // The sensor is triggered by a HIGH pulse of 10 or more microseconds.

  // Give a short LOW pulse beforehand to make sure the sensor is ready.
  // for a clean HIGH pulse.
  digitalWrite(trigPin,LOW); // get the trigger to low.
  delayMicroseconds(2); // wait a little bit.
  digitalWrite(trigPin,HIGH); // Send the echo.
  delayMicroseconds(10); // Pulse it for 10 Microseconds. 
  digitalWrite(trigPin,LOW); // End the echo pulse.

  // Now we need to read the signal to measure the distance

  duration = 0;
  distance = 0;
  duration = pulseIn(echoPin,HIGH); 
  distance = ((duration/2) / 29.1); // This is the raw distance in CM.

  // Converte the time into a distance.

  inches = microsecondsToInches(duration); // Run our function for converting to inches.
  cm = microsecondsToCentimeters(duration); // Run our function for getting the CM.

  // Output my results for testing purposes.

  Serial.print(“Ping duration “);
  Serial.print(duration);
  Serial.print(” Inches “);
  Serial.print(inches);
  Serial.print(” cm “);
  Serial.println(cm);

  delay(100);

  
}

The additional part of the lab was to add code to the sensor to have the sensor run the a motor. Here is a picture of the circuit.

Here is the code that I used to do that….

/* HC-SR04 Sensor
 * Date: 1/31/2017
 * Author: Unknown/Leslie Scott Kerfoot
 * 
 */

// Define the global variables we will use.

#define motorPin 9 // Define the pin we’ll use to run the motor.
const int trigPin = 2; // Which pin is the trigger on the sensor.
const int echoPin = 4; // Which pin is the echo return on the sensor.
long duration,inches,cm; // Variables we’ll use in the main loop.
int distance;

void setup() {
  Serial.begin(9600);j // Prepare for serial output/debugging.
  pinMode(trigPin,OUTPUT); // We’re sending the echo to the trigPin
  pinMode(echoPin,INPUT); // We’re going to receive the distance from the echoPin
  pinMode(motorPin,OUTPUT); // Setup our motor pin for ourput.
}

long microsecondsToInches(long microseconds) {

  // According to the datasheet for the PING, there are
  //   73.746 microseconds per inch (Sound travels at 1130 feet per 
  //   second).  This gives the distance travelled by the ping, outbound
  //   and return. so we divide by 2 to get the distance of the obstacle which is half.
  //  
  long myResult = ((microseconds / 72) / 2); 
  return myResult;
}

long microsecondsToCentimeters(long microseconds) {

  // Using the same logic as the Inches sound travels at a speed of 340 meters/second
  //   or 29 microseconds per centimeter. Since the ping goes out and back we divide by 2
  //   to get just the distance to the ping
  long myResult = ((microseconds / 29) / 2);
  return myResult;
}

void loop() {

  // Setup variable for measuring the duration of the ping
  //   and the return in inches and cm.
    

  // The sensor is triggered by a HIGH pulse of 10 or more microseconds.

  // Give a short LOW pulse beforehand to make sure the sensor is ready.
  // for a clean HIGH pulse.
  digitalWrite(trigPin,LOW); // get the trigger to low.
  delayMicroseconds(2); // wait a little bit.
  digitalWrite(trigPin,HIGH); // Send the echo.
  delayMicroseconds(10); // Pulse it for 10 Microseconds. 
  digitalWrite(trigPin,LOW); // End the echo pulse.

  // Now we need to read the signal to measure the distance

  duration = 0;
  distance = 0;
  duration = pulseIn(echoPin,HIGH); 
  distance = ((duration/2) / 29.1); // This is the raw distance in CM.

  // Converte the time into a distance.

  inches = microsecondsToInches(duration); // Run our function for converting to inches.
  cm = microsecondsToCentimeters(duration); // Run our function for getting the CM.

  // Output our sensor results.

  Serial.print(“Ping duration “);
  Serial.print(duration);
  Serial.print(” Inches “);
  Serial.print(inches);
  Serial.print(” cm “);
  Serial.print(cm);
  
  // Now run the motor and output debugging if detect something less than 5 in.
  if (inches < 6) {
    digitalWrite(motorPin,HIGH);
    Serial.println(” Motor ON!”);
  } else {
    digitalWrite(motorPin,LOW);
    Serial.println(” Motor OFF!”);
  }

  delay(100);

  

}

Here is a video of the circuit working. I put my hand in front. Note that the motor will run for at least 100 microseconds because of the delay at the end of the loop.

I also wrote some separate test code for Lab 13

const int trigPin = 2;
const int echoPin = 4;

void setup() {

  // initialize serial communication:
  Serial.begin(9600);
}

void loop()

{
  // establish variables for 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);
  
  Serial.print(inches);
  Serial.print(“in, “);
  Serial.print(cm);
  Serial.print(“cm”);
  Serial.println();
  
  delay(500);
}

long microsecondsToInches(long microseconds)

{
  // According to Parallax’s datasheet for the PING))), there are
  // 73.746 microseconds per inch (i.e. sound travels at 1130 feet per
  // second).  This gives the distance travelled 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;
}

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 travelled.
  return microseconds / 29 / 2;

}

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