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Thread: Relay to cut power to ElmScan?

  1. #1
    Newbie
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    Aug 2005
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    Toronto, ON, Canada
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    Relay to cut power to ElmScan?

    Hi folks,

    I searched. Concerns over the 'always-on' LED on the ElmScan interface tend to draw responses that go a little something like this:

    This little light of mine,
    I'm going to let it shine!


    I guess that's fine for some folks, but I'm not really keen on knowingly introducing a constant power drain into my system, no matter how small. Has anyone ever tried to use a relay to cut power to the ElmScan when the car PC is off? I imagine this would involve intercepting the appropriate lead in the supplied cable, but I don't know enough about cable shielding and such to know if this would have any unintended consequences.

    Any insight would be appreciated.
    -
    8^{D>

  2. #2
    FLAC evandude's Avatar
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    Mar 2005
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    Maine
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    OBDII communication is done at a ridiculously slow data rate and does not involve any large power signals or anything like that, therefore wire shielding is not very important for it. however, it would probably be easiest to simply modify the board itself, by finding the power trace and cutting it, and soldering wires to each piece and then to the relay.

    or if you really want to be non-invasive, get a male and a female DB-9 connector from radio shack or somewhere, and build yourself a little short pass-through cable that can be plugged in between the elmscan board and the OBD cable, that passes all the wires straight through pin-for-pin except intercepts the power wire.
    But don't take it from me! here's a quote from a real, live newbie:
    Quote Originally Posted by Viscouse
    I am learning buttloads just by searching on this forum. I've learned 2 big things so far: 1-it's been done before, and 2-if it hasn't, there is a way to do it.
    eegeek.net

  3. #3
    Newbie
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    Aug 2005
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    Toronto, ON, Canada
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    Say, that's a good idea! Non-invasive is good.

    Thanks for the speedy response!
    -
    8^{D>

  4. #4
    Variable Bitrate proph's Avatar
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    Aug 2005
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    Little Elm, Texas
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    I couldn't see the draw close to what an alarm does. Digimoto wheres the current draw spec.

  5. #5
    Variable Bitrate
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    Rosemount, MN
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  6. #6
    Variable Bitrate
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    Jul 2005
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    I have another diagram of the board laying around here somewhere... I'll search for it today.

  7. #7
    Low Bitrate
    Join Date
    Aug 2004
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    72
    I'm curious about this too. Are most people just leaving their ELM connected?

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