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Can you guy's help out with a diagram and description for a small project

Discussion in 'Electronic Basics' started by james, Sep 4, 2003.

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  1. james

    james Guest

    problem
    ---------
    1.I fitted a digital dashboard from an Vauxhall Astra GTE into a Ford
    Escort,all works great apart from the speedometer.

    2.The Astra used a Transducer to send a pulse to the speedometer, I'm
    told that the pulse rate is 1474 revs/mile for the Astra and 1000
    revs/mile for the Escort.the escort has a spedometer cable and works
    mechanically (now redundant)

    3.I need a new way to measure speed, a friend suggested using a
    reflective opto switch http://www.isocom.com/datasheets/db92074.pdf to
    read a disk or driveshaft with reflective strips placed on it
    producing the desired amout of pulses.how would i convert a 12v feed
    to the desired input voltage. and what is an NMP amlifier? (i think
    thats it)

    3a Can a simple diagram be drawn up for a brainless twit to accomplish
    this?

    4. if anyone has any other ideas....feel free


    and thanks for your time and some of your big brains\


    James
     
  2. Guest

    Guest Guest

    Hi James

    Please note; I'm not an expert in automotive mechanics.

    If I were in your situation I would try to find an off the shelf solution.

    Getting an optical signal off the drive shaft is possible.
    In an automotive environment this may not be reliable due the possibility
    of mud/dirt getting splattered on the reflective tape.
    The speedometer cable or transducer signal usually comes from the transmission
    in my experience.
    If this is so,would the drive shaft provide an usable pulse per mile?

    Failing an off the shelf solution I would start by removing the transducer
    from the Astra and use the existing cable from the escort to drive it.
    There are configurable ratio adapters (gear boxes) available to calibrate
    the rpm of speedometer cables.
    This may allow you to calibrate your speedometer.

    Good Luck

    Colin
     
  3. james

    james Guest

    thanks colin ill see whats available, but in the meantime i'm looking
    for a quick fix,

    any other suggestions?
     
  4. Colubris

    Colubris Guest

    Maybe to avoid the mud and hostile exterior environment you could hack
    the existing mechanical speedo cable. Attach a magnet to the cable (on
    the free, unused end) and a Hall effect sensor to pick up rotations.
    All the sensitive bits could then be in the cars interior.

    Arch
     
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