Parallax Ping Interface

Forum 2005-2010 (read only) Hardware Interfacing
1

I currently have a Parallax ping sensor, and some code I found and modified to actually return accurate results... well as accurate as i can get without being able to print Floats..
the Ping is supposed to read out to 3m..

It works great out to about 12-16" however after that my echo jumps to ~21000 ms

Do I have a problem with my code or hardware ...
I have adjusted my holdoff from 0 to 500 with no effect
I have removed the Pullup and used while to wait for LOW
I have increased and decreased my trigger to both acceptable extremes.

Any help would be appreciated.

I've turned this in a function that is called every delay(250);

unsigned long ping(){

pinMode(ultraSoundSignal, OUTPUT); // Switch signalpin to output
digitalWrite(ultraSoundSignal, LOW); // Send low pulse
delayMicroseconds(2); // Wait for 2 microseconds
digitalWrite(ultraSoundSignal, HIGH); // Send high pulse
delayMicroseconds(5); // Wait for 5 microseconds
digitalWrite(ultraSoundSignal, LOW); // Holdoff
delayMicroseconds(400); // Wait for 4 microseconds
pinMode(ultraSoundSignal, INPUT); // Switch signalpin to input
digitalWrite(ultraSoundSignal, HIGH); // Turn on pullup resister
echo = pulseIn(ultraSoundSignal, HIGH); //Listen for echo
//cursorSet(1,0); // from my LCD conroller lib
// Serial.print(" ");
//cursorSet(1,0); // from my LCD conroller lib
//Serial.print(echo); // used for debug...
ultrasoundValue = (echo / 58.138) * .39; //convert to CM then to inches
return ultrasoundValue;
}

2

what does a ping sensor sense?

3

I used to work for Parallax and have a lot of experience with the Ping -- give this program a try, it seems to work correctly (please note that I'm new with Arduino, so I'm not as good with C as I am with PBASIC).

// Parallax Ping Demo
// -- Jon McPhalen
// -- www.jonmcphalen.com
// -- 27 DEC 2007

#define pingPin 8

void setup()
{
Serial.begin(9600);
delay(5);
Serial.println("Parallax Ping Demo");
}

void loop()
{
long distance = 0;

delay(500);
distance = getPing();
Serial.print("Raw distance is ");
Serial.println(distance, DEC);
}

long getPing()
{
long measure = 0;

digitalWrite(pingPin, LOW); // ensure output starts low
pinMode(pingPin, OUTPUT); // make it output
delayMicroseconds(1); // let it settle
digitalWrite(pingPin, HIGH); // ping!
delayMicroseconds(5);
digitalWrite(pingPin, LOW); // remove ping
delayMicroseconds(1);
pinMode(pingPin, INPUT); // configure to measure return

measure = pulseIn(pingPin, HIGH);

measure >>= 1; // reduce to one-way trip
return measure;
}