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Measuring current draw from permanent +12v

Discussion in 'General Electronics Discussion' started by john2k, Sep 29, 2019.

  1. john2k

    john2k

    120
    1
    Jun 13, 2012
    My car has a power folding mirrors which currently have a Ignition/ACC controlled +12v being the main +12v source for folding and unfolding. Problem is that when ignition is turned off I cannot operate the folding function as the +12v from IGN is interupted. So what I am thinking to do is take a permanent +12v from nearby and de-pin the connector and suppy the connector with permanent 12v instead of IGN +12v. My only concern is if this will cause any kind of adverse power draw. So I was thinking could i measure the current draw between the permanent +12v and the mirror connector and see how much if any current it draws when car is off. Will a multimeter do the job?
     
  2. 73's de Edd

    73's de Edd

    2,696
    1,092
    Aug 21, 2015
    Sir john2k . . . . . . . . ( and me and my electronics successfully escaped the 2K dilemmna 19 years ago !)


    Considering that your UNKNOWN model and UNKNOWN brand of car utilized the simple design solution of "Monkey SEE-Monkey DO " . . .
    . . . . . au . . . .

    http://www.ti.com/lit/ug/tidu301a/tidu301a.pdf.
    ( Since its introduction in 2014. )

    That system uses a max of up to 3A per door of INITIAL motor start up current and progressively less on continuing run time, until end of cycle.

    AND THEN . . . . . there is the quiescent state current pull of the electronics in standby of a miniscule 0.000012 amperes per door unit . . . . . I'll write that again, for your other eye . . . . . to ALSO confirm . . . 0.000012 amperes.

    Confirming this should be possible by pulling the existing feeder fuse out from its connector and re installing the two probe tips of a DVM set to DC amps function, and initially, use a range of 10 AMPS.
    That way, upon activation of the mirror retracted / extended feature . . . you can watch the impending current pull variance.

    AND ALSO . . . . . . then, with some possible downscaling of the range to low milliamperes, with the mirrors in their dormant state, be able to see that quiescent leakage pull.

    All, being according to your meter capabilities . . . . I know that one of my Fluke's would accomodate that.

    Thaaaaaaaasssit . . . . .


    73's de Edd . . . . .

    My watch is three hours fast, and I can't fix it. So I'm going to move to Florida and stay with with Hop.



    .


    .
     
  3. Bluejets

    Bluejets

    3,489
    706
    Oct 5, 2014
    It could be the mirror motors operate via a relay and also most automotive switching is earth return switching.
    Point being not much point running extra 12v positive to the motors.
     
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