Reset Switch GND, RESET#, brown, white

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.

 

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

 

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?

 

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

 

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

 

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.

 

"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.

 

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.

 

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.

 

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.

Better check this