I just received my package from parallax yesterday, as excited as i was i started assembling a robot that i've got under construction, but when i finally came to actually test the ping sensor itself it came up with false readings.
The pingsensor seems to have a problem detecting objects further away than 14cms, as long as an object is within 14cm's it gives correct readings, but as soon as i turn it away (maybe facing a wall that is 40cms away) it comes up with the reading "14cms". I have the sensor connected to a Arduino Duemilanove board and im using port 7.
The code that im using is from arduinos own website showing you how to use the parallax ping sensor with arduino..
// this constant won't change. It's the pin number
// of the sensor's output:
const int pingPin =7;
// initialize serial communication:
// 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:
// 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.
// convert the time into a distance
inches = microsecondsToInches(duration);
cm = microsecondsToCentimeters(duration);
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;