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Looking for a sensor or devise, that indicates a forward and a reverse movement

Discussion in 'Electronic Basics' started by tecjim, Oct 17, 2006.

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  1. tecjim

    tecjim Guest

    Does anyone know of a devise or sensor that can indicate a signal or no
    signal for a forward movement, but have a signal for a reverse
    movement?
    Or is it impossible to do?
    I am open to any other solutions that someone can tell me

    Description of project is that
    1. It has a flat surface to mount to
    2. It has wheels for mobility for the movement of a forward or reverses
    (push or pull)
    3. Power supplied 12v DC 20amp
    4. To be used for out-door use, subject to extreme weather conditions
    and temperatures.

    Example:
    Take a child's red wagon being pulled or pushed in different
    directions.
    Pull the wagon towards you and walk "prefer a signal
    Stop "prefer a signal
    Push the wagon backwards "signal "
    Now pull the wagon towards you and walk "prefer a signal


    The specs should fall into this area
    Sensor Specifications:

    1. Bi-Directional
    2. 1-3 phase signal, reverse motion and stationary (non movement)
    3. Generate a signal reverse or opposite direction from a forward
    motion
    4. Time delay adjustment
    5. Temperature rating -40°C - +50°
    6. .5v - 12v DC .01amp
    7. Sealed unit
    8. Weather proof
    9. .002% accuracy
    10. Vibration tolerance adjustment
    11. To be used in an external application only
    12. No moving parts or external reference
    13. Non magnetic
    14. PC programmable

    Something like a digital compass? I'm not that experience in this field
     
  2. vic

    vic Guest

    This requirement as I understand it makes it impossible. You want to
    measure movement relative to a surface, then you *need* a reference. You
    could try to use an accelerometer, but it only measures variations of
    speed, not the absolute value.

    vic
     
  3. Greg Neill

    Greg Neill Guest

    ---------------Begin Quote------------------------------------------
    The specs should fall into this area
    Sensor Specifications:

    1. Bi-Directional
    2. 1-3 phase signal, reverse motion and stationary (non movement)
    3. Generate a signal reverse or opposite direction from a forward
    motion
    4. Time delay adjustment
    5. Temperature rating -40°C - +50°
    6. .5v - 12v DC .01amp
    7. Sealed unit
    8. Weather proof
    9. .002% accuracy
    10. Vibration tolerance adjustment
    11. To be used in an external application only
    12. No moving parts or external reference
    13. Non magnetic
    14. PC programmable

    Something like a digital compass? I'm not that experience in this field

    ---------------End Quote------------------------------------------

    That's a lot of specs, but they're not exactly clear.

    In (1) What's Bi-Directional mean? Are you saying that
    your moving object will move only along a straight line
    (linear)?

    In (4), what's the characteristic of the time delay?
    Delay after what, and for how long?

    In (9): .002% accuracy with respect to what? You haven't
    said what your units of measurement are, or what the
    expected range of motions will be (you gave the "example"
    of the red wagon, but that's only an illustrative
    example, right?).

    In (10), what sort of vibrations are you expecting?
     
  4. Greg Hansen

    Greg Hansen Guest

    It has wheels. You've already shot the "no moving parts" condition, so
    you might as well put a speedometer on it. An optical encoder is
    non-magnetic.
     
  5. Chris

    Chris Guest

    Hi, Jim. Your wish list is full -- I'd guess you're going to say you
    want it to be less than $3.50 in single quantity, too. You have a very
    specific and rather generous specification list. Some of your specs
    are kind of obscure. For instance, what do you mean by .002% accuracy?

    Just going from your spec list, I'd suggest you'll get the closest by
    doing a quick wallet biopsy, then calling up the good people at BEI and
    ask about specialty optical encoders. You could power your encoder and
    a special automotive temp range single board computer in a sealed
    enclosure, and program the SBC to provide the logic functions. I'd
    suggest that 5 to 10 watts is a more realistic power budget, though.

    For a real world low current application, you would typically see a
    cheapie optical encoder mounted to one of the wheels or, much more
    likely and more inexpensively, a few magnets mounted on one of the
    wheels with two hall effect sensors mounted out of phase such that you
    could get direction from quadrature.

    Hall effect sensors are pretty much impervious to cold (although -40C
    is a stretch for the rest of the electronics), and would be the device
    of choice. And if there's a chance of dirt or snow gumming up the
    works, you'd pretty much be limited to hall sensors. You obviously
    can't use slotted optointerrupters in an environment where something
    could block the slot.

    Possibly you might want to talk a bit about your application, and we
    can work through the specs and find out what you need and what you can
    live with. And by the way, what do you have against magnets? They're
    noble devices that are impervious to cold, are energy efficient and
    don't wear out.

    Cheers
    Chris
     
  6. Kurt Krueger

    Kurt Krueger Guest

    How about an optical mouse?
     
  7. tecjim

    tecjim Guest

    Unfortantly I cannot use the wheels a a referance point
    No machincal devises
     
  8. Guest

    You sound like my wife. An impossible group of restrictions and won't
    tell me what the real goal is. SO what IS the real goal here?

    GG
     
  9. Chris

    Chris Guest

    Second the motion. tecjim has given a poorly defined set of
    requirements without describing anything about his application.

    The plain fact is, there isn't any magic blivet that will do everything
    on his list, even with a generous interpretation of his requirements.
    It's his part here to pony up and describe a bit about what he's doing,
    and why none of these ideas are valid. Possibly then someone on one of
    the ngs can walk through some of the tradeoffs, and he might get
    directed toward a best fit, whether it's quadrature hall effect
    sensors, quadrature optical encoder, GPS, ultrasonic ranging sensor or
    capacitive/inductive sensor. He hasn't given the distance range, or a
    real number for the resolution (0.002% of 100 miles on a railroad
    track, 0.002% of one revolution of a 1" dia. wheel). To be honest, I'm
    not even sure from his description if the device is supposed to be
    mounted on the "wagon" or externally, what kind of output he wants, or
    where it's supposed to go.

    If he doesn't want to take that step, he'll just have to accept that he
    can't be helped here. I don't believe anyone on the sci.electronics.*
    newsgroups is forced to help on a query where someone just demands
    something that doesn't exist, without explaining why he needs it.

    And if it's proprietary, he'll have to hire somebody instead of casting
    about for free suggestions. There are several well-qualified engineers
    who post regularly on both s.e.b. and s.e.d. that are capable of
    helping him design a solution. He can have them sign a non-disclosure
    agreement, which will keep them from spilling the beans about his idea.
    But he will have to give more information to the engineer, and I
    pretty much guarantee that there will be some tradeoffs and he won't
    get everything on his shopping list.

    Since tecjim seems to be new to this, he should know that it's
    considered good
    form to bottom post, and also good form to crosspost to several groups
    (if you must) rather than individually post to several groups. There's
    no point in making this several conflicting conversations when one will
    do. He should please check out Google Groups Help Topic "What's good
    'netiquette' when posting to Usenet?"

    http://groups.google.com/support/bin/answer.py?answer=12348&topic=250

    Cheers
    Chris
     
  10. tecjim

    tecjim Guest

    Due too this application, I realy can't give you much more
    then,,,,,,,,,,,I want to place a devise or senor on several moving
    applications. I need to recieve a signal of any type when this (wagon)
    is moving in the opposite direction, Would also like a foward or netual
    signal. I will program the rest of the board and software myself. I
    know it has wheels, but due to different manufactures and Liablities
    are a consered, I can't use the wheels. Believe me, I wouldn't be
    asking for help. It has to be a universal devise!

    Thanks for your info.
    Jim
     
  11. Chris

    Chris Guest

    Well, Jim, then I guess we're stuck. One of the basic ideas of a
    sensor (the center of what you're asking) is that it has to have
    something to sense.

    If you've got a "wagon", and have to mount a device to sense movement,
    it really has to be movement in relation to something. If you don't
    have anything at all, GPS (Global Positioning Satellie) information is
    available, but that would only have accuracy to yards or meters.
    You're the "something", and the sensor is in geosynchronous orbit --
    too far away for any real accuracy, unless as I said you're talking
    about miles here instead of inches. No precision.

    The other option you might want to consider is using a video camera and
    doing a video capture of the ground immediately below the "wagon". But
    that would have limitations on a uniform surface or on snow, and be
    very processor-intensive.

    Both of these blow your 120mW (.01A * 12V) power budget out of the
    water, of course.

    You might want to consider spending a few bucks and setting up an
    appointment with an electronics engineer. For a couple of billable
    hours time, he can sign a standard legally binding non-disclosure
    agreement (downloadable from many sources), you can explain your idea
    in detail, show them your sketches, and they can tell you what you can
    realistically expect from the world of today's modern electronics.
    You'll be able to get an expert opinion on this in one morning, and pay
    less than $300 USD with change for coffee. And you'll get a
    comprehensive answer you can trust.

    Good luck
    Chris
     
  12. Guest

    Gyration has a wireless mouse that the user simply waves around in the
    air.
    http://www.gyration.com/en-US/Products.html
    http://www.extremetech.com/article2/0,1697,1128548,00.asp

    It looks like the IEEE has done at least one paper on cost-effective
    inertial motion sensors that might be informative. You might want to
    spend a few days in your local, university library and see what you can
    find out.
    http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=303402
     
  13. Jamie

    Jamie Guest

    i know i mentioned this before, "Doppler type unit"
    i don't know your surface area's below the wagon how ever,
    have you thought about using a motion a motion detector where
    is, it aims a Transmitter of Ultrasonic to the floor and then
    a receiver picks it up.
    something simple, like a LM1496 chip (Double balance Modulator) can
    reproduce phase angle output results depending on the direction of
    movement.

    but like i said, i don't know your surface's that your riding on.
     
  14. Randy Day

    Randy Day Guest

    Jamie wrote:

    [snip]
    I know! Strap an optical mouse to the underside!
    That way he can get side-to-side *as well as*
    forward-reverse! :p

    <g>
     
  15. Jamie

    Jamie Guest

    yeah rite!
    :)
     
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