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ping)) not consistently reading beyond 5 inches? — Parallax Forums

ping)) not consistently reading beyond 5 inches?

tms1tms1 Posts: 2
edited 2009-04-04 14:14 in Accessories
I am running a ping)) sensor and it seems to 'stick' at a max distance of about 5 inches. I do get varying values back, and occasionally do get a longer value (typically the wall at which the unit is pointed) which seems accurate, but only for a single ping. After that the readings return to values varying from approx 740-800. If I move something closer I do get appropriate variations in distance below 5 inches, but as soon as I remove the near object, it usually returns to the 5 inch reading instead of reading the wall, which is about 40 inches away.

Is this unit defective? Is there any way to test that theory? What are my options?

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2009-03-30 02:02
    1) Could you be reading reflections from a floor or tabletop? That will do what you describe.

    2) You could have an error in your program. You'd have to post it for help on that regard.
  • tms1tms1 Posts: 2
    edited 2009-03-30 17:02
    Moving the sensor to the very edge of the table does give me better results, but I still get periodic 'blips' back to the 5 inch range. Is that normal behavior?

    As to code, this is a pretty simple arduino setup using a a very basic code template, so I don't see any issues there. It's almost as though it's falling back to a default reading in lieu of input?
  • Mike GreenMike Green Posts: 23,101
    edited 2009-03-30 17:10
    What you describe is not normal behavior.

    Now you mention that you're using an Arduino. That may well be your problem. The PING works well with both the Stamps and the Propeller, very different microcontrollers. You might want to re-read the documentation for the PING. It's really quite simple. You produce a brief trigger pulse on the bidirectional I/O line, then wait for the leading edge of a pulse from the PING. You time the width of the pulse from the PING and that's proportional to the round-trip distance from the PING to the nearest object.
  • Old man EarlOld man Earl Posts: 46
    edited 2009-04-01 03:11
    What is the outside range of the ping ? I seem to get reliable results out to about 10 feet. I am going to use it to detect the ground in a uav for landings.
    Earl
  • Mike GreenMike Green Posts: 23,101
    edited 2009-04-01 04:08
    There's no specification for an outside range. It's so dependent on ambient noise and the reflectivity of surfaces that I'm sure it's hard to say.
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2009-04-01 14:57
    How is the PING))) Sensor mounted? Are you using screws through the mounting holes?

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    Chris Savage
    Parallax Engineering
  • JDJD Posts: 570
    edited 2009-04-03 07:07
    tms1,

    It is possible that you have a defective module. You can test by gently shaking the module; can you hear any rattle?

    If you would like to have it tested, you can you send me your customer at support@parallax.com.·I will set up an RMA to have you send the module·and if it turns out to be defective, we will replace the module at no cost; otherwise we·will offer·half off replacement if the module has been damaged somehow.

    If you want to call me to set that up, feel free, the best number to use is 888-997-8267 and you can ask for me.

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    Respectfully,


    Joshua Donelson
    www.parallax.com

    Post Edited (Joshua Donelson (Parallax)) : 4/3/2009 3:17:17 PM GMT
  • Rich GreenRich Green Posts: 11
    edited 2009-04-04 14:14
    I had a similar problem when using a Ping)) unmounted on the end of a servo extension cable.· Seems I was getting some crosstalk between the transmit and receive sensors.· A small bit of foam between the two solved the problem.
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