Reset Switch GND, RESET#, brown, white

Discussion in 'Asus' started by Skybuck Flying, May 26, 2011.

  1. Hello,

    ASRock's motherboard 939A790GMH mentions the following in the quick
    installation guide/manual:

    Page 23:

    System Panel Header:
    O O O O
    O O O O O - dummy
    | |
    GND RESET#

    Antec 1200's reset switch connector has a brown and a white cable.

    I have some question about this:

    1. What is "RESET#" ? (I can understand "ground" but "RESET#" ???)

    2. How does a reset switch work ? Does it "cut power" ? Does it make all the
    electricity flow away via ground or something ?

    3. How to connect the reset switch ? Should the brown wire go to GND or vice
    versa ?

    I also have a theory how the motherboard might get damage if it's not
    grounded:

    The gnd cables and/or the reset switch somehow makes it possible for the
    chasis voltage and low ampere to briefly flow back into the motherboard,
    this probably weakens the electronics, if this is done often enough
    motherboard death would occur, therefore it would be best to ground the PC
    so this can't happen ?!?

    4. Last question, is this theory possible ? ;)

    Bye,
    Skybuck.
     
    Skybuck Flying, May 26, 2011
    #1
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  2. Skybuck Flying

    Joel Koltner Guest

    It means that the signal is active-low. That is, grounding it (rather than
    applying, e.g., 3.3V to it) is what makes it "active," or resets the computer.
    The switch itself just connects the two wires together when you push the
    switch. It doesn't "cut power." It maybe makes "all the electricity flow TO
    ground," perhaps... although that's an explanation that you would likely only
    get away with in elementary school -- and the lower grades at that. :)
    It doesn't matter -- as long as Reset# ends up physically connected to Ground,
    the color of the wires that do it is irrelevant.
    Um, no, not really.

    ---Joel
     
    Joel Koltner, May 26, 2011
    #2
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  3. Skybuck Flying

    Metspitzer Guest

    I have only bought a handful of compter cases and motherboards.
    Everyone I have ever built has the label side of the connectors facing
    to the edge of the mobo.

    Any exceptions?
     
    Metspitzer, May 26, 2011
    #3
  4. Skybuck Flying

    Paul Guest

    Feel free to throw in any crazy theories you might have.

    The RESET# and PWR# circuits should look similar to this. Neither circuit
    carries heavy currents. The switches are momentary contact type, delivering
    a pulse. It is up to the motherboard logic, to convert the pulse into
    something useful. The signal coming from the circuit, is a logic level
    signal. The "#" on the end, means they're active low, activated when
    the signal level is in the low state.

    You may have noticed, that under some conditions, there is a 4 second delay
    from when you start pressing the front power button, until the computer
    goes off. The motherboard has the ability to measure the duration of the
    pulse, and to enforce a long duration requirement if the computer is up
    and running. This is to avoid the computer switching off, if the power
    switch is bumped for a short interval. The same delay is not applied,
    when you try to turn on the computer in the morning - it starts immediately.
    The motherboard logic takes care of all these tiny details. It
    "conditions" the logic signal.

    +5VSB Volts |
    | +5V | -----+ +-----
    | | | |
    Resistor 0V | +----+
    | ------------------ Time
    +----------> Motherboard Input waveform
    | Logic Active low logic
    Push X Chip (Active Low)
    Button->
    Switch X
    |
    Ground

    The body of the two switches on the front panel, is not connected to the
    chassis. The body of each switches "floats" electrically. It's usually
    insulated with plastic. A benefit of that, is it doesn't matter which
    wire of the switch, goes to the "X" points in the circuit. You can rotate
    the 1x2 connector either way and the circuit works. Either rotation
    of the connector for the switch, works equally well.

    *******

    The LED outputs, such as the Hard Drive LED and the Power LED, use
    a similar looking circuit. (I've removed the control element from
    the picture here for simplicity.) The LED is "polarized" and only
    lights when inserted one way. If you reverse the 1x2 LED connector,
    the LED won't light up. If that happens, simply reverse it. The
    LEDs used can take 5V PIV (peak inverse volts) and won't be harmed
    by being connected in reverse. So if you cannot figure out how to
    connect the two LEDs, you have a 50% chance of getting it right
    on the first try, and if that fails, rotating the connector 180 degrees
    will result in a working circuit.

    +5V
    |
    |
    Resistor
    |
    |
    |
    Power X <--- (+)
    LED
    X <--- (-)
    |
    Ground

    *******

    The motherboard may have a 1x4 position labeled SPKR, which connects to the
    computer case speaker. Not all modern computer cases have a speaker, but many
    do. The circuit driving the speaker, looks like this (this circuit is extracted
    from the Intel reference schematic BXDPDG10).

    +5V
    |
    X
    SPKR
    X
    |
    Resistor (~34 ohms)
    |
    Transistor
    |
    GND

    A logic chip sends a repetitive square wave, at logic levels, to the
    transistor. The transistor, in turn, turns the current on and off
    to the speaker. The 34 ohm resistor (two 68 ohm resistors in parallel
    in the Intel schematic) limits the current, and helps define how
    loud the speaker will get. Generally, there is no volume control
    for SPKR, as it is intended to just "beep".

    The speaker is not polarized and placing the 1x4 in either orientation
    will work.

    One thing to notice in the above circuit, is one wire of the
    speaker twisted pair, is connected directly to the power supply.
    If the wire is pinched in the removable door of the computer, such
    that the chassis grounds the wire, the wire will start to burn.
    This is a silly "feature", and is about the only safety thing
    to be aware of. When you route the SPKR wires inside your case,
    make sure they don't get pinched inside the case. The wires should
    be loose and the insulation in good condition.

    The reason I know about this, is because a poster in one of
    the groups, actually had the wire burn when it got pinched
    and the plastic insulation on the wire was cut. When that happened,
    I waited until I could look at some schematics, to see
    what mistake had been made.

    *******

    The electronics on the motherboard are robust, even if you
    don't believe it.

    There are still some things about motherboards that are
    mysterious, such as why is there so much trouble with
    making a reliable PS_ON# signal (the signal on the main
    cable of the power supply, that turns the supply on). That
    too is a logic level signal, and seems to fail to work
    properly, more than it should.

    Paul
     
    Paul, May 26, 2011
    #4
  5. There are 4 edges ;)

    Ok two edges can be dismissed.

    This leaves two edges ;)

    So the labels are always facing an edge of a motherboard.

    I swapped the connector just at the last moment to follow your advice of
    facing the edge.

    Brown now goes to ground and white to reset.

    The power button and the other side is facing the other edge and I am 100%
    sure that's how it's supposed to be at least assuming "black is ground" ;)


    Black is ground ?

    Hmm yup at least for the fans so I will assume this is for headers too.

    Bye,
    Skybuck.

    Better check this ;)
     
    Skybuck Flying, May 26, 2011
    #5
  6. Skybuck Flying

    Joel Koltner Guest

    Weeelll... I don't recall seeing an exception, although I have encountered
    cases where the connector didn't match up with the motherboard's header at
    all -- USB connectors, early-on, are one example I recall.

    And I've also put together PCs (in years past) where the connectors weren't
    labeled at all -- sometimes there was a sheet of paper that came with the case
    telling you which colored wires went where, and other times you just had to
    figure it out for yourself, paying careful attention to where the wires
    actually went.

    I thnk it was Intel that was attempting to get a more standardized pin-out
    going so there's just be, e.g., one 2x7 header or whatever rather than 4-7 2-
    or 3-pin headers; I don't know if this was ever all that successful, though.
     
    Joel Koltner, May 26, 2011
    #6
  7. Skybuck Flying

    Shaun Guest

    "Skybuck Flying" wrote in message

    Hello,

    ASRock's motherboard 939A790GMH mentions the following in the quick
    installation guide/manual:

    Page 23:

    System Panel Header:
    O O O O
    O O O O O - dummy
    | |
    GND RESET#

    Antec 1200's reset switch connector has a brown and a white cable.

    I have some question about this:

    1. What is "RESET#" ? (I can understand "ground" but "RESET#" ???)

    2. How does a reset switch work ? Does it "cut power" ? Does it make all the
    electricity flow away via ground or something ?

    3. How to connect the reset switch ? Should the brown wire go to GND or vice
    versa ?

    I also have a theory how the motherboard might get damage if it's not
    grounded:

    The gnd cables and/or the reset switch somehow makes it possible for the
    chasis voltage and low ampere to briefly flow back into the motherboard,
    this probably weakens the electronics, if this is done often enough
    motherboard death would occur, therefore it would be best to ground the PC
    so this can't happen ?!?

    4. Last question, is this theory possible ? ;)

    Bye,
    Skybuck.


    Stick the RESET line up your ass, it will probably work better there on your
    computer.
     
    Shaun, May 26, 2011
    #7
  8. Skybuck Flying

    Jasen Betts Guest

    With motherboard/front-panel connectors usually white is ground and
    colour is active, but polarity only matters for the LEDs. The switches
    and the loudspeaker will function fine with either polarity.
     
    Jasen Betts, May 27, 2011
    #8
  9. You guys make little sense.

    Anyway, something else doesn't make sense.

    Why is there a "gnd" connection for the reset header ?!?!?

    Could it be important ?! ;)

    Bye,
    Skybuck.
     
    Skybuck Flying, May 27, 2011
    #9
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