? Ground Wires on Molex Connector (Reverseable?)

  • Thread starter Thread starter Alec S.
  • Start date Start date
A

Alec S.

Hi,

Is there a difference between the two black ground wires on a drive
connector? For example, does one ground the 12v and the other ground
the 5v or do they both go to the same place? Is it bad if they are
reversed?

Thanks a lot.
 
Alec said:
Is there a difference between the two black ground wires on a drive
connector? For example, does one ground the 12v and the other ground
the 5v or do they both go to the same place? Is it bad if they are
reversed?
Click to expand...

In order: No, same place, no.
 
I have no idea what that means. Are you saying that they must put in
the same order, or are you saying that there is no difference.
 
Alec said:
I have no idea what that means. Are you saying that they must put in
the same order, or are you saying that there is no difference.
Click to expand...
He answered your questions in order. Try reading it again.
 
Alec S. said:
Is there a difference between the two black ground wires on a drive connector?
Nope.

For example, does one ground the 12v and the other
ground the 5v or do they both go to the same place?
Click to expand...

Depends on where you mean place wise. They do go to
the same place back in the power supply with the vast
bulk of power supplys. They dont always with hard drives.
Is it bad if they are reversed?
Click to expand...

Nope.
 
Alec S. said:
Hi,

Is there a difference between the two black ground wires on a drive
connector? For example, does one ground the 12v and the other ground
the 5v or do they both go to the same place? Is it bad if they are
reversed?
Click to expand...


All the black wires are the same...
if they are reversed it will not matter
 
Hi,

Is there a difference between the two black ground wires on a drive
connector? For example, does one ground the 12v and the other ground
the 5v or do they both go to the same place? Is it bad if they are
reversed?

Thanks a lot.
Click to expand...

The two black ground wires terminate at the same place in
the power supply, to that extent they are interchangeable.

It is not guaranteed that any particular device will have
both wires/positions used as a ground though - they *should*
do that, it is a poor design if it didn't, but it is
possible a device wouldn't. Reversing them will not be a
problem.
 
Alec S. said:
I have no idea what that means. Are you saying that they must put
in the same order, or are you saying that there is no difference.
Click to expand...

Please don't top-post. I fixed this one. See the following links.

UCLAN gave you one answer per sentence.

--
Some informative links:
<<http://www.geocities.com/nnqweb/>
<http://www.catb.org/~esr/faqs/smart-questions.html>
<http://www.caliburn.nl/topposting.html>
<http://www.netmeister.org/news/learn2quote.html>
<http://cfaj.freeshell.org/google/>
 
Alec said:
I have no idea what that means. Are you saying that they must put in
the same order, or are you saying that there is no difference.
Click to expand...

You asked three questions, and I gave three answers (in the same order
as you asked.) Simple enough.
 
Okay, thanks everyone.

I just wanted to double-check what I assumed to be true because I had
to fix a Molex connector (some of the wires had gotten a little fray),
and it did not occur to me to pay attention to which holes the the two
black wires were connected to (I guess that subconciously I knew them
to be the same for obvious reasons and so hadn't bothered). :)

After I put the yellow and red back in their places, it occurred to me
and I was a little worried that perhaps the grounds were meant to be
specific to the different loads or terminated at different places (for
example one goes to a resistor or something before heading to ground,
etc.)

I've been told that in many cases they actually connect back in the
power supply which is what I figured, but could not be sure of since
there are two distinct wires. My research (which found this subject to
be rather sparse since the focus is mostly on the positive leads and
pinouts), found that the reason there are two is due to older drives
and PSUs in the past which often used wires that could not handle the
combined load and so had separate ground wires. I've been told that
the wires used today can usually handle it just fine (so one could do
but the standard is already set.)

The new question then is, why do the new standards such as SATA cables
still use separate ground wires when they surely could use fewer?
 
Alec S. said:
Okay, thanks everyone.

I just wanted to double-check what I assumed to be true because I had
to fix a Molex connector (some of the wires had gotten a little fray),
and it did not occur to me to pay attention to which holes the the two
black wires were connected to (I guess that subconciously I knew them
to be the same for obvious reasons and so hadn't bothered). :)

After I put the yellow and red back in their places, it occurred to me
and I was a little worried that perhaps the grounds were meant to be
specific to the different loads or terminated at different places (for
example one goes to a resistor or something before heading to ground,
etc.)

I've been told that in many cases they actually connect back in the
power supply which is what I figured, but could not be sure of since
there are two distinct wires. My research (which found this subject
to be rather sparse since the focus is mostly on the positive leads
and pinouts), found that the reason there are two is due to older
drives and PSUs in the past which often used wires that could not
handle the combined load and so had separate ground wires. I've been
told that the wires used today can usually handle it just fine (so
one could do but the standard is already set.)
Click to expand...
The new question then is, why do the new standards such as SATA cables
still use separate ground wires when they surely could use fewer?
Click to expand...

Same reason, basically, with a bit more complexity to allow for hot plugging.

There's actually 3 separate 12V, 5V and 3.3V volt lines, total of 9 wires
for those. Thats due to the limited current per pin of the connector used.
You dont have 9 ground wires, because its assumed that a particular
drive wont be loading all those rail pins to their maximum capacity. Its
likely that a single ground line could have its current capacity exceeded tho.
 
Alec S. said:
.... snip ...

The new question then is, why do the new standards such as SATA cables
still use separate ground wires when they surely could use fewer?
Click to expand...

Please don't top-post. Your answer belongs after, or intermixed
with, the material you quote, after snipping anything immaterial to
your answer.

When signals are high speed (which depends on many factors) you
can't look on wires as pure interconnects. They are transmission
lines, with characteristic impedances, propagation times, frequency
responses, etc. The intermixed ground lines make the cables
characteristics better controlled, and preserve the integrity of
the signals at the other end. You can generally be fairly close by
assuming signals propagate at 0.6 to 0.8 C (C is the speed of
light) and that the line approximates 100 ohm impedance. The
impedence is especially importance because matching it at the
driver and receiver will minimize signal reflections and the
associated distortions. That impedance is what is much better
controlled with the additional ground wires.
 
CBFalconer said:
Alec S wrote
Click to expand...
Please don't top-post.
Click to expand...

Take your request and shove it where the sun dont shine.
Your answer belongs after, or intermixed with, the material you quote,
Click to expand...

You get no say what so ever on that or anything else at all, ever.
after snipping anything immaterial to your answer.
Click to expand...

And that in spades.
When signals are high speed (which depends on many factors)
you can't look on wires as pure interconnects. They are
transmission lines, with characteristic impedances,
propagation times, frequency responses, etc.
Click to expand...

The ground lines in the power lines being discussed arent.
The intermixed ground lines
Click to expand...

There arent any of those in the power lines being discussed.
make the cables characteristics better controlled, and
preserve the integrity of the signals at the other end.
Click to expand...

There are no 'signals' in the power lines being discussed.
You can generally be fairly close by assuming signals propagate at
Click to expand...

There are no 'signals' in the power lines being discussed.
0.6 to 0.8 C (C is the speed of light) and that
the line approximates 100 ohm impedance.
Click to expand...

Wrong with the power lines being discussed.
The impedence is especially importance
because matching it at the driver and receiver
Click to expand...

There are none of those in the power lines being discussed.
will minimize signal reflections and the associated distortions. That impedance
is what is much better controlled with the additional ground wires.
Click to expand...

Wrong with the power lines being discussed.

The number of ground lines in the power lines being discussed is entirely
determined by the current carrying capacity of the pins in the connectors used.
 
I've been told that
the wires used today can usually handle it just fine (so one could do
but the standard is already set.)
Click to expand...


A well engineered system will not have any single lead
supplying enough current that a single wire per voltage rail
is maxed out, BUT remember that these are standards set by
engineers for laymen to follow and use. There is no
guarantee someone won't daisey-chain Y splitters or hook up
a video card and two drives to a cable with 3 plugs on it.


Thus, if you have a supply lead capable of X amount of
current, it is prudent to supply sufficient ground capacity
(wiring) to return (reasonably close to) same amount of
current. The more supply leads you have, the less likely
all would carry maximum current (and past a certain point
the supply itself may make it impossible) and less likely
you would need (even planning for a worst case scenario) a
ground for each, BUT with only two power leads (5V and 12V
in this case), it would be an unreasonable ratio to have
only one ground return.
 
You get no say what so ever on that or anything else at all, ever.
Click to expand...

Please use "whatsoever" as opposed to "what so ever". It is grammatically
correct and saves spaces.
 
One additional reason for two black wires - not mentioned by others.
Electronics that use multiple voltages can suffer hardware damage if
ground wire disconnects or becomes intermittent. Two ground wires
guarantee that a rare intermittent break on one black wire does not
cause disk drive electronics failure.

Better bus designs also used this principle. Ground was always
assigned to end pins so that any accidentally disconnected peripheral
board would disconnect ground last. Some would even lengthen that
ground pin for same reasons. Early HP computers used this reliability
technique. Ground must always exist when a device is powered by
multiple voltages.

Meanwhile ignore the nonsense about top posting. Either is
acceptable. But top posters tend to be tolerant people. Those who
complain have this itch they cannot scratch. Your posts were easiest
to read and comprehend - and that (not bottom posting) is what RFC1855
demands.
 
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