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Thread: 12v required when car is moving - for AutoHold tweak

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    12v required when car is moving - for AutoHold tweak

    Hi all

    I am close to an autohold solution for my 16' vRS without EPB, it will require a little piece of hardware.

    For it to work I need to find either:
    A) 12v that becomes live once the car is moving, normally 0v
    B) 12v that becomes live when the vehicle is stationary which is 0v when the car is moving

    So far I've tried the adaption list for the light channels hoping I could use that as a trigger - I thought a few looked promising but I have test them and they don't work
    1) Klemme 15 mit Nachlauf bis Fahrzeugstillstand (Terminal 15 with follow-up vehicle standstill)
    2) Klemme 15 ohne nachlauf (Terminal 15 without running / trailing)

    Ive actually tried all of them and its no good - you can have have a trigger which switches on/off with stop start, and a trigger for handbrake on/off but not vehicle moving/not moving.
    I'm looking for any other ideas of a simple trigger for when the vehicle is 1/2mph+, without having to write code into something like an arduino and have a bliuetooth EOBD dongle and having a decoder to extract the data from the EOBD data protocol

    Thanks

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    Benevolent Dictator Uwe's Avatar
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    Hmm, what reason would there be for a car maker to provide a 12V signal that shows when the car is in motion?

    If I were trying to do this in a "current" car, I'd passively listen on the powetrain CAN. Some message being broadcast on there will have the vehicle speed.

    -Uwe-
    Ceterum censeo, delenda est Daesh.

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    Lightbulb Auto hold solution

    Quote Originally Posted by Xpower View Post
    Hi all

    I am close to an autohold solution for my 16' vRS without EPB, it will require a little piece of hardware.

    For it to work I need to find either:
    A) 12v that becomes live once the car is moving, normally 0v
    B) 12v that becomes live when the vehicle is stationary which is 0v when the car is moving

    So far I've tried the adaption list for the light channels hoping I could use that as a trigger - I thought a few looked promising but I have test them and they don't work
    1) Klemme 15 mit Nachlauf bis Fahrzeugstillstand (Terminal 15 with follow-up vehicle standstill)
    2) Klemme 15 ohne nachlauf (Terminal 15 without running / trailing)

    Ive actually tried all of them and its no good - you can have have a trigger which switches on/off with stop start, and a trigger for handbrake on/off but not vehicle moving/not moving.
    I'm looking for any other ideas of a simple trigger for when the vehicle is 1/2mph+, without having to write code into something like an arduino and have a bliuetooth EOBD dongle and having a decoder to extract the data from the EOBD data protocol

    Thanks
    Have a look at the central locking.........you can set it up so the car locks at about 10 mph so you should be able to find a feed that way.........

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    ^^^^^^^^ So why isn't the trigger for the SS function an acceptable surrogate of vehicle movement?
    VW Golf MkVII (103TSI) my13

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    Quote Originally Posted by Phastazphuk View Post
    Have a look at the central locking.........you can set it up so the car locks at about 10 mph so you should be able to find a feed that way.........
    Interesting, problem is that is done by the door module and doesnt stay live - I'm going to look into that more thanks


    Quote Originally Posted by DV52 View Post
    ^^^^^^^^ So why isn't the trigger for the SS function an acceptable surrogate of vehicle movement?
    Because SS is unpredictable and doesn't always work when the vehicle has stopped. I need something that works every time.

    It would be easier to find the combination for Autohold without EPB - I'm convinced it sits in byte 9 and 19 (I need to check that to 100% on my pc) it maybe quite probable that the coding combination is protected so Autohold cannot be coded without EPB

    thanks for everyones input so far

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    Quote Originally Posted by Xpower View Post
    Because SS is unpredictable and doesn't always work when the vehicle has stopped. I need something that works every time.

    It would be easier to find the combination for Autohold without EPB - I'm convinced it sits in byte 9 and 19 (I need to check that to 100% on my pc) it maybe quite probable that the coding combination is protected so Autohold cannot be coded without EPB

    thanks for everyones input so far
    OK - how about the trace from one of the speed sensors that are connected to the ABS? Regardless whether the speed sensor is variable reluctance, or digital type - since all you need is to detect movement (regardless of speed). it could be a possibility - perhaps?

    You would need to be very careful not to load the sensor too much, but if it's fed into a high impedance device so that the additional parasitic load was undetectable by the ABS, it could work

    Don
    Last edited by DV52; 05-27-2017 at 06:22 PM.
    VW Golf MkVII (103TSI) my13

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  9. #7
    Verified VCDS User Vasco Ferraz's Avatar
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    Uwe already gave you the best tip.

    Sniff the canbus for vehicle's speed.

    A canbus shield and an Arduino will do the job very easy and very cheap.

    Then:

    if (speed >= 1) // You should confirm how speed variable is encoded... This is just an example.
    {
    relay_on(); // 12V
    }

    else relay_off(); // 0V
    Last edited by Vasco Ferraz; 06-13-2017 at 11:23 AM.
    Vasco Ferraz

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