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Calling All Accelerometer Gurus

Discussion in 'Electronic Basics' started by DaveK, Aug 2, 2007.

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  1. DaveK

    DaveK Guest

    NEED HELP1

    My ultimate goal is to have an accelerometer and a microprocessor work
    in combination to accomplishing the following:

    Hypothetically: Say I have a rubber ball that contained a two or
    three axis accelerometer & microprocessor and allowed it to roll down
    a slight incline. The incline is so shallow that it would only roll
    approximately 5ft. before it came to a complete stop. The rolling
    surface would be an asphalt pavement, like that of a street witch
    would allow some deviation in one roll compared to the next. I would
    then use the information from the accelerometer as the standard and
    compare it to any number of rolls then after. Each roll would be under
    the same conditions. Then set an adjustable tolerance of the
    deviation from one roll to the next compared to the standard. An alarm
    would go off if the roll was not within the allowable tolerance.

    I have very limited experience in this field. I am familiar with basic
    electronic circuits and components.

    Say it was possible to place a LCD on the ball could it display the
    following:

    1. A plot in-which one roll vs. the other?
    2. A plot in-which each roll against each multiple Plots such as g
    force / time, speed / time, g force / distance, x / y axis?

    Other Questions
    1. Could I download the information to a lap top and plot it from
    there?
    2. Could I have multiple sounds or colored LEDs that would designate
    in which part of the roll (distance) it went out of tolerance?

    3. Is there a package out there for purchase that would comprise of an
    accelerometer, microprocessor and standard code that records the
    speed, distance, g. force, position ect. of an object in motion? This
    would allow me to tweak the code.

    4. If not what would be the closest electronic device that would do
    something similar, besides the individual components that would need
    to be assembled together by myself?

    5. Are there people out there that would put this together for a fee.

    Any information at all on this subject would greatly be appreciated.
    I've been to most of the sites on the web and read as much as I could.

    DaveK
     
  2. BobG

    BobG Guest

    Measurement Computing (and other companies... search for data
    aquisition and analog inputs) has a wireless accelerometer you could
    embed in a ball of some size or another and a graphing package to view
    the data.
     
  3. Try this wireless Bluetooth accelerometer:
    http://www.sparkfun.com/commerce/product_info.php?products_id=254

    Dave.
     
  4. Re.3.
    All those are integrals of acceleration against time. Any guided and
    unguided rocket should have the relevant software included in its computer.
    Try NASA or similar.

    Good luck

    Stanislaw.
     
  5. Bob Masta

    Bob Masta Guest

    Putting accelerometers in a rolling ball is
    going to make for a really messy computation,
    what with all the axes rolling in arbitrary
    directions. Is this really needed?

    You seem to have decided upon a solution
    and are asking for help in implementing it.
    Instead, perhaps if you defined the actual
    problem you want to solve, we could propose
    better approaches.

    Best regards,


    Bob Masta

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    www.daqarta.com
    Scope, Spectrum, Spectrogram, Signal Generator
    Science with your sound card!
     
  6. Tim Wescott

    Tim Wescott Guest

    Yes, but it would have to be a large ball.
    Yes. This would allow you to dispense with the LCD, and make the ball
    smaller. With a bit more development time you could make an inductive
    coupler that would talk to the PC wirelessly and charge the sensor
    board's batteries. With luck, this would let you seal the ball.
    Yes, although getting sounds out of the ball without weakening it may be
    a challenge.
    Not for what you want, I think. Check Spark Fun for the bits, though.
    An IMU would do the measurements, although I think that for what you
    need an 'ordinary' IMU is 100 to 1000 times more expensive than could be
    achieved by building something up from components.

    The 'easy' algorithms to allow you to record distance & speed require
    that you supply three axes worth of rotational information, and gyros
    are more expensive than accelerometers. I think that if you can trust
    the ball to grip the surface you could use just accelerometer input --
    you'd have to do some analysis to verify that theory, though.
    I certainly could, and have fun doing it, too. Contact me via email
    (tim at wescottdesign dot com).

    --

    Tim Wescott
    Wescott Design Services
    http://www.wescottdesign.com

    Do you need to implement control loops in software?
    "Applied Control Theory for Embedded Systems" gives you just what it says.
    See details at http://www.wescottdesign.com/actfes/actfes.html
     
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