Ultrasonic Rangefinder

> 2 min read

Today, I’ll be showing you how a ultrasonic sensor can be used to determine the distance of an object from the sensor, which will be displayed on a LCD display. In this tutorial, I’ll be using a Parallax ultrasonic sensor & a parallax serial LCD Display.

Configuration of Serial LCD

In this tutorial, I’ll be using 9600 baud rate, hence you have to switch the Serial LCD mode to 9600 baud. This can be done by switching the 2 DIP switches (on the rear of the panel) as shown below.
lcd_mode_switch

 

How will it look like?

Parts Required

  • Ultrasonic Sensor x 1
  • LCD Display x 1
  • Arduino Uno x 1
  • Jumper wires x 1

 

Schematics

ultrasonic_display

Demo

 

Code

[The code was adapted from the sample PING program found in the Arduino IDE. (Files > Examples > Sensors > Ping) ]

/* Ping))) Sensor

   This sketch reads a PING))) 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 circuit:
    * +V connection of the PING))) attached to +5V
    * GND connection of the PING))) attached to ground
    * SIG connection of the PING))) attached to digital pin 7

   http://www.arduino.cc/en/Tutorial/Ping

   created 3 Nov 2008
   by David A. Mellis
   modified 30 Aug 2011
   by Tom Igoe

   This example code is in the public domain.

 */

// this constant won't change.  It's the pin number
// of the sensor's output:
const int pingPin = 10;
const int TxPin = 6; //LCD Display Setup
#include <SoftwareSerial.h>
SoftwareSerial mySerial = SoftwareSerial(255, TxPin);

void setup() {
  // initialize serial communication:
  mySerial.begin(9600); //Display on LCD Display
}

void loop()
{
  // establish variables for duration of the ping, 
  // and the distance result in inches and centimeters:
  long duration, inches, cm;

  // The PING))) is triggered by a HIGH pulse of 2 or more microseconds.
  // Give a short LOW pulse beforehand to ensure a clean HIGH pulse:
  pinMode(pingPin, OUTPUT);
  digitalWrite(pingPin, LOW);
  delayMicroseconds(2);
  digitalWrite(pingPin, HIGH);
  delayMicroseconds(5);
  digitalWrite(pingPin, LOW);

  // The same pin is used to read the signal from the PING))): 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(pingPin, INPUT);
  duration = pulseIn(pingPin, 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(200);
}


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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