Power for US hub?
Terry Pinnell
adapter it came with. What are the standard specs for USB 2.0 please? I
want to replace a PC-powered hub with it.
I have several old adapters at hand. One (which happily has the correct
plug) has switchable outputs of 3V, 4.5V and 6V, with current capacity of
300 mA at 6V. options. Would the 4.5V be OK?
--
Terry, East Grinstead, UK
J. Todd
terry...@DELETEgmail.com says...
type. Linksys routers use them, for one.
D Yuniskis
5V at about 2+A -- for four *powered* ports; less if you
can guarantee the devices plugged into the hub have their
own power source(s). You won't be finding this in an
old-fashioned "transformer" wall wart (you'll need a small
switcher wall-wart)
Most hubs that I have seen, lately, use a ~0.100 dia barrel
connector (center positive) -- though I have seen others.
Geoffrey S. Mendelson
No. You really need 5 volts at 500ma for each port. Most things don't use
5 volts anymore, they use regulators for lower voltages and 4.5 is just at
the border of 3.3 volt regulators working or not.
Besides a 4.5 volt unregulated supply could provide almost anything at no
load (like 8 or 9 volts if it is really bad) which would be a problem.
Lucklily 5 volt supplies are easy to get and cheap. You can get a 5v 1amp
switching supply as a charger for a music player/cell phone. That will do for
2-3 bus powered devices, or all 4 if they are self powered.
Geoff.
--
Geoffrey S. Mendelson N3OWJ/4X1GM
Those who cannot remember the past are condemned to misquote it.
Terry Pinnell
Thanks all, glad I asked, as I hadn't realised it needed such a heavy duty
supply. At worse, I'll get out to the shed and make one.
BTW, if you'll excuse a related question, is it usual for USB ports on the
front of a PC case to be less reliable than ports on the back? Perhaps
with lower current delivery? That's my motive for deploying this powered
hub. An operation that failed from the front worked OK from the back
(connecting an iPad to run an iTunes sync). That wasn't the only thing I
changed, so it's not conclusive. But from subsequent googling I've seen
several suggestions that this difference is a real one.
D Yuniskis
Terry Pinnell wrote:
> Thanks all, glad I asked, as I hadn't realised it needed such a heavy duty
> supply. At worse, I'll get out to the shed and make one.
Again, it only needs that sort of supply if you have devices that
1) need lots of power (e.g., a laptop disk drive powered from
the USB port) and 2) don;t provide it themselves. Some devices
(e.g., the sort of laptop drive I mentioned) have options for
both. Mice, keyboards, etc. usually rely on the USB port for
their (typically modest) power requirements.
> BTW, if you'll excuse a related question, is it usual for USB ports on the
> front of a PC case to be less reliable than ports on the back? Perhaps
> with lower current delivery? That's my motive for deploying this powered
> hub. An operation that failed from the front worked OK from the back
> (connecting an iPad to run an iTunes sync). That wasn't the only thing I
> changed, so it's not conclusive. But from subsequent googling I've seen
> several suggestions that this difference is a real one.
A lot of this depends on the vintage/manufacturer of the PC.
All bets are off when it comes to an "add in" USB card (which
would typically be USB2 or USB3 and most likely "powered" -- but,
could just as easily be an ancient USB1.1 card, etc.)
Some manufacturers put "good" (fast, powered) ports on the front
of the machine leaving slower ports on back for the keyboard/mouse
and giving the user more flexibility in what he can CONVENIENTLY
plug into the front of the machine. Other machines may be the
exact opposite with the philosophy that the fast devices you are
likely to use will be semi-permanently attached and you'll just
need the front ports for things like thumb drives (modest power
requirements).
The ports *in* keyboards are almost never capable of delivering
and sort of power (I've seen some that won't support a thumb drive).
And, of course, you are limited to the speed of the keyboard's
connection to the PC (in addition to the hub/controller within the
keyboard).
It is also not uncommon for connectors to be flakey -- the "pins"
*in* the USB connector as well as the pigtail that invariably connects
the "front connectors" to the motherboard (the rear panel connectors
are more often than not directly soldered to the motherboard).
And, of course, iPod cables are also notoriously flakey
(not to mention the &*^!@#*&$% "charge only" cables!)
HTH
Baron
Open up the machine and unplug the ten pin cable header for the front
USB ports at the mainboard then plug it back in ! Could be the pins
are dirty. Its surprising what a little oxidisation can do !
Don't forget to take anti static precautions !!
--
Best Regards:
Baron.
whit3rd
> I've dusted off a 4-port USB hub I had lying but can't find whatever
> adapter it came with. What are the standard specs for USB 2.0
Well, it's 5V at 500 mA max on the USB pins; the
power adapter could be 5V, 5.1V, 6V, and anything (for
the max output power) from 2A to 2.5A (the hub could
need some internal power, but probably not much).
The various hubs use different input voltages because
the power-supply USB features are implemented in
several different ways.
Terry Pinnell
Thanks for those helpful follow-ups.
The good news is that after more rooting around in the shed I found the
adapter. A 6V, 2.1 A unit.
Not so good is that the 'New Hardware Wizard' on my XP PC now reckons it's
found new hardware and wants to install the darn thing. Why! The same USB
devices are plugged into it as before, when it was running under PC power.
And I'm darned if I have an installation CD for it. I thought USB hubs
were simply plug'n play?
Michael A. Terrell
Did you change the configuration? Is the hub plugged nto the same
port on the PC, and are the otherUSB devices plugged into the same ports
on the hub?
--
For the last time: I am not a mad scientist, I'm just a very ticked off
scientist!!!
Bob
unless it was provided by the manufacturer. I had a strange problem
on my system. I powered it down with a powered usb hub connected.
When I powered it back up a few minutes later it wouldn't boot. It
wouldn't even boot from a cdrom drive. Then I noticed the usb hub was
still on (power led on) when my machine was off. So I unplugged the
hub's power supply (which was 5.0 volt at 2.6 amp regulated) and the
machine then booted up correctly. Apparently the powered hub was
feeding 5 volts back on to the motherboard and not allowing all the
circuits to reset properly on power down. I hate to think what a
unregulated 5 or 6 volt power supply would have done to the 5 volt
circuits on the motherboard.
YMMV
--
...Bob
Michael A. Terrell
Bob wrote:
>
> I wouldn't use any power supply that was not 5.0 volts regulated
> unless it was provided by the manufacturer.
I've seen several USB hubs that use a 6 volt supply. The hub has a
built in LDO 5 V regulator. Terry said it was the supply that came with
the hub.
> I had a strange problem
> on my system. I powered it down with a powered usb hub connected.
> When I powered it back up a few minutes later it wouldn't boot. It
> wouldn't even boot from a cdrom drive. Then I noticed the usb hub was
> still on (power led on) when my machine was off. So I unplugged the
> hub's power supply (which was 5.0 volt at 2.6 amp regulated) and the
> machine then booted up correctly. Apparently the powered hub was
> feeding 5 volts back on to the motherboard and not allowing all the
> circuits to reset properly on power down. I hate to think what a
> unregulated 5 or 6 volt power supply would have done to the 5 volt
> circuits on the motherboard.
The hub isn't supposed to put 5 volts to the input port. Either it
was defective, or it was designed by a retired school teacher.
PeterD
They are, it's trying to play it... So let it install and you'll
probably do just fine.
D Yuniskis
It will "install" support for the (external) hub.
In turn, that may (silently?) reinstall the devices
that you plug into that hub as they are now connected
"differently".
This shouldn't be a problem.
Be sure to note/verify any power indicator on the hub.
Some will only illuminate when a device is plugged
*into* the hub.
You can also check in "Device Manager" to see where
the hub appears (by connection) and whether it is
seen as a 1.1 or 2.0 hub.