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Passing signals with no current.

Discussion in 'General Electronics Discussion' started by eem2am, Dec 5, 2012.

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  1. eem2am

    eem2am

    414
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    Aug 3, 2009
    Hello,

    I have a microcontroller which is connected via a connector to signals from another PCB.

    The header used is the following one......
    http://www.molex.com/molex/products/datasheet.jsp?part=active/0022112062_PCB_HEADERS.xml

    ......the microcontroller input , as you know, draws no current, as its an input...so therefore no current is passing through this header (connector).

    I believe that there are minimum current levels for metal to metal connectors?

    Since my connection passes no current, will it be OK?....(the connection surface is made of gold)
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,448
    2,809
    Jan 21, 2010
    Some current will always pass, although it may be very small.

    At such low currents contact resistance is generally not an issue.

    You should be fine.
     
  3. davenn

    davenn Moderator

    13,717
    1,911
    Sep 5, 2009
    If you have a signal you have a current flow, you cannot have one without the other :)

    Dave
     
  4. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,270
    Nov 28, 2011
    As Dave and Steve have already pointed out, there will be SOME current flow, even if it's just a few microamps.

    AFAIK, low-current gold-plated connectors, switches, and relay contacts don't have minimum wetting current requirements, because gold doesn't oxidise. AFAIK.

    These requirements are more applicable to medium-power and high-power relays and switches, due to the possibility of oxidation of the contacts.

    http://en.wikipedia.org/wiki/Wetting_current

    It's good practice to put a pull-up or pull-down resistor on any logic input that is being fed from off-board so that if the interconnection fails, the signal will assume a consistent and safe level. This resistor will also cause some current flow while the signal is in the opposite state.
     
  5. Harald Kapp

    Harald Kapp Moderator Moderator

    10,793
    2,435
    Nov 17, 2011
    The contacts are gold plated, whic is always a good sign for low currents, since no oxide barrier can reduce the current flow.
    The data sheet says Application: Signal, Wire-to-Board

    So it should be fine.
     
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