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Thread: Vehicle speed converter

  1. #11
    Newbie
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    Jan 2009
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    this is getting interesting.... I'm following along. What are the odds this goes nowhere?

  2. #12
    Raw Wave
    Join Date
    Nov 2009
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    What do you mean goes nowhere? It never got anywhere! (LOL!)

    I would have thought an Electrical and Electronic Engineer could have envisaged the many signals that exist and that it is simply a matter of determining which it is and interfacing appropriately. (Then again, after seeing 3rd year Electrical & Electronic Engineering students that couldn't connect a DMM, or text-book authors that still thought electricity had a "direction" (ie, EITHER positive ions/holes OR electrons!) and thought of Maxwell's Equation(s) as something fantastic, I'm not surprised.)


    Maybe kirupa wants to design a universal interface? But in that case, I have already provided the info kirupa requires (for most systems).


    Maybe when kirupa provides appropriate info, we can progress.
    (Maybe kirupa will find his ECUs do NOT provide speed information. After all, why would they?


    I don't mind going nowhere - that's like many dreams.
    It's going in circles, costing a fortune, trial&erroring that which is already known... (Especially since finding the true & correct info is so easy.... LOL - that's a joke - no chance of that these days! Progress? - yes, if you understand for what.)

  3. #13
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    Apr 2009
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    Tap into an ABS tone ring, that should give you a PWM output that increases in frequency as the vehicle's speed increases. Tap all 4 and you can also check if the car is in a skid.

    If it doesn't have one of those, you'll need to tap into the sensor in the transmission, or, if it were a truck, the center diff. Those are probably also PWM, but an oscilloscope will tell you for certain.

  4. #14
    Raw Wave
    Join Date
    Nov 2009
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    2,118
    So is it a tone, or PWM, or a frequency thing?


    Answer: Frequency.

    If any have pwm or tone, let me know.


    But this thread was a dead end, or rather - a dead start. The OP simply had no idea...

  5. #15
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    Apr 2009
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    ABS tone ring will be frequency modulated, yes. Although the pulses will be longer as the vehicle slows, they will still be the same percentage duration.

    And it's the PART that's called a tone ring, it's just part of the name of the part, has nothing to do with the signal.

  6. #16
    Raw Wave
    Join Date
    Nov 2009
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    2,118
    And an ABS tone ring is the name of a part. It has nothing to do with its output being a tone - it is a frequency (and square wave).

    ERGO: Frequency (again).

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