Hardware question again


R

rfdjr1

I posted a question a few days ago about USB add-on cards. To answer one
question I was asked, why I need so many USB connections, well, I have two USB
external drives, wireless headphones which have a USB transmitter, wireless
keyboard and mouse which use a USB port, printer, etc, etc. So yes, believe it
or not, I'm maxing out and I just want backup. I figure a board only costs
around twenty bucks, so no big deal, and I have an empty PCI express slot on my
mobo that I don't see using for anything else.

That being said, this is probably a stupid question, but I found what appears to
be a decent USB adapter card. It needs to be powered. That would be by a molex
connector. I just got through poking around inside my case and see one lone
unused molex connector sitting there. So, I assume it would alright to plug that
into the USB card? I mean, I won't overload the power supply by adding it? I
need to get a molex extension to reach the card, but I found one of those with
no problem. Thanks for any replies. I appreciate it.
 
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K

Ken Blake

I posted a question a few days ago about USB add-on cards. To answer one
question I was asked, why I need so many USB connections, well, I have two USB
external drives, wireless headphones which have a USB transmitter, wireless
keyboard and mouse which use a USB port, printer, etc, etc. So yes, believe it
or not, I'm maxing out and I just want backup. I figure a board only costs
around twenty bucks, so no big deal, and I have an empty PCI express slot on my
mobo that I don't see using for anything else.

Two points/questions:

1. Have you tried a USB hub (making one USB port into four) instead of
a card? They are cheaper and one might work for you.

2. If you have two external hard drives, are they always kept plugged
in into USB ports? If so, why? I have about six external drives, but
none of them are kept plugged in.
 
P

Paul

I posted a question a few days ago about USB add-on cards. To answer one
question I was asked, why I need so many USB connections, well, I have two USB
external drives, wireless headphones which have a USB transmitter, wireless
keyboard and mouse which use a USB port, printer, etc, etc. So yes, believe it
or not, I'm maxing out and I just want backup. I figure a board only costs
around twenty bucks, so no big deal, and I have an empty PCI express slot on my
mobo that I don't see using for anything else.

That being said, this is probably a stupid question, but I found what appears to
be a decent USB adapter card. It needs to be powered. That would be by a molex
connector. I just got through poking around inside my case and see one lone
unused molex connector sitting there. So, I assume it would alright to plug that
into the USB card? I mean, I won't overload the power supply by adding it? I
need to get a molex extension to reach the card, but I found one of those with
no problem. Thanks for any replies. I appreciate it.
USB ports are fuse-protected, and that places an
upper limit on how much current can be drawn.

You don't have anything to worry about, with a two port USB3 add-on card.

The USB3 current is 900mA. Two ports is 1.8 amps. Double
it again, to leave some room for the fusing scheme. So perhaps
3.6 amps might flow for a short time. The Molex is rated for 8 amps
or so. The power supply, you can read the rating off the label. A
good modern supply (active PFC, 80+ efficiency) will offer 20 amps
on the 5V rail. So chances are good there is not an issue there.
(The 5V rail may not have a lot of loads on it, except
for peripherals like HDD and ODD. And your USB3 card.)

The motherboard connectors on the other hand, run USB ports from
+5VSB. At least, the USB2 ports are that way. I don't know if
they want the USB3 ports used for waking functions or not (waking
up is the reason for using +5VSB instead of +5V). Usually
the supply is weak on +5VSB. Things run off +5VSB won't be using
a Molex, and the wiring is already done via the motherboard. A decent
supply now, offers +5VSB @ 3A, and that isn't nearly enough if
you're running a "USB zoo" (coffee warmer, iPhone charger, lamp).

On older motherboards, the motherboard USB power source was jumper
selectable. But for the last five years or so, all the ports
run from +5VSB and so there is a risk of overload. If you do
overload that rail, then the computer shuts off instantly.

Your USB3 add-on card won't be doing that. By using the Molex,
you get a much stronger 5V source for this job. No worries.

Quad port cards are available. And USB3 hubs exist. With an
active hub, you might even get a stout wall adapter for
powering all sorts of junk on your bench. This is an example
of an active hub with its own power source.

Rosewill RHB-630 4-Port USB 3.0 Hub Power Adapter (5V, 3.5A) $30

http://www.newegg.com/Product/Product.aspx?Item=N82E16817182275

http://images17.newegg.com/is/image/newegg/17-182-275-Z06?$S640W$

Always read the reviews carefully on any USB3 stuff. The
data rate is very high - only skilled engineers get that
stuff right. When I see products in the $20 to $30 range,
I expect them to cut corners, and the customer reviews
will tell you whether they're junk or not.

Paul
 
C

choro

Two points/questions:

1. Have you tried a USB hub (making one USB port into four) instead of
a card? They are cheaper and one might work for you.
This might seem sensible but it has certain drawbacks. A card inserted
into a slot on the motherboard is a far better solution.--
choro
*****
 
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K

Ken Blake

This might seem sensible but it has certain drawbacks.

Sometimes yes, sometimes no. That's why I said "*might* work.:
A card inserted
into a slot on the motherboard is a far better solution.

Often, but not always.
 

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