Voltage for powering US hub?

[Terry Pinnell]

I've dusted off a 4-port USB hub I had lying but can't find whatever
adapter it came with. What are the specs please? I want to replace a
PC-powered hub with it.

I have several old adapters. This 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?

 

[Gerard Bok]

I've dusted off a 4-port USB hub I had lying but can't find whatever
adapter it came with. What are the specs please? I want to replace a
PC-powered hub with it.

I have several old adapters. This 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?

There is no way to tell from the outside.
Find either the sticker on the hub or the manual

By the way, as a 4 port hub is required to be able to supply at
least 4 times .5 amps neither of the .3 amps adapters will be
suitable
Keep looking for a device that says 2 Amps or more.

 

[GMAN]

There is no way to tell from the outside.
Find either the sticker on the hub or the manual

By the way, as a 4 port hub is required to be able to supply at
least 4 times .5 amps neither of the .3 amps adapters will be
suitable
Keep looking for a device that says 2 Amps or more.

You want a 5V 2Amp adapter

 

[Terry Pinnell]

You want a 5V 2Amp adapter

Thanks both. Hadn't realised such a heavy duty adapter was required, so
glad I asked.

Presumably doesn't matter whether it's a conventional transformer type or
a more compact 'switched' type?

 

[GMAN]

Thanks both. Hadn't realised such a heavy duty adapter was required, so
glad I asked.

Presumably doesn't matter whether it's a conventional transformer type or
a more compact 'switched' type?

If its a 7 port USb 2.0 Powered hub, then you are going to want a supply than
can output 5v 3.5A or slightly higher . But that really would only be
necessary if you were loading each and every port with devices like portable
har drives that draw power from the USB port. If all you are using are mice,
keyboards, webcam, low ppower devices like that or even printers, then you
could get away witha 5v 2A supply. I wouldnt go less than a 2A myself



http://en.wikipedia.org/wiki/USB_hub#Power

http://www.beyondlogic.org/usbnutshell/usb-in-a-nutshell.pdf

Power
A bus-powered hub is a hub that draws all its power from the host computer's
USB interface. It does not need a separate power connection. However, many
devices require more power than this method can provide, and will not work in
this type of hub.

USB current (related to power) is allocated in units of 100 mA up to a maximum
total of 500 mA per port. Therefore a compliant bus powered hub can have no
more than four downstream ports and cannot offer more than four 100 mA units
of current in total to downstream devices (since one unit is needed for the
hub itself). If more units of current are required by a device than can be
supplied by the port it is plugged into, the operating system usually reports
this to the user.

In contrast a self-powered hub is one that takes its power from an external
power supply unit and can therefore provide full power (up to 500 mA) to every
port. Many hubs can operate as either bus powered or self powered hubs.

However, there are many non-compliant hubs on the market which announce
themselves to the host as self-powered despite really being bus-powered.
Equally there are plenty of non-compliant devices that use more than 100 mA
without announcing this fact (or indeed sometimes without identifying
themselves as USB devices at all). These hubs and devices do allow more
flexibility in the use of power (in particular many devices use far less than
100 mA and many USB ports can supply more than 500 mA before going into
overload shut-off) but they are likely to make power problems harder to
diagnose.

Some powered hubs do not supply enough power to support a 500mA load on every
port. For example, many 7 port hubs come with a 1A power adapter, when in fact
seven ports could draw a maximum of 7 x 0.5 = 3.5A, plus power for the hub
itself. The assumption is that the user will most likely connect many low
power devices and only one or two requiring a full 500mA.

 

[Terry Pinnell]

If its a 7 port USb 2.0 Powered hub, then you are going to want a supply than
can output 5v 3.5A or slightly higher . But that really would only be
necessary if you were loading each and every port with devices like portable
har drives that draw power from the USB port. If all you are using are mice,
keyboards, webcam, low ppower devices like that or even printers, then you
could get away witha 5v 2A supply. I wouldnt go less than a 2A myself



http://en.wikipedia.org/wiki/USB_hub#Power

http://www.beyondlogic.org/usbnutshell/usb-in-a-nutshell.pdf

Power
A bus-powered hub is a hub that draws all its power from the host computer's
USB interface. It does not need a separate power connection. However, many
devices require more power than this method can provide, and will not work in
this type of hub.

USB current (related to power) is allocated in units of 100 mA up to a maximum
total of 500 mA per port. Therefore a compliant bus powered hub can have no
more than four downstream ports and cannot offer more than four 100 mA units
of current in total to downstream devices (since one unit is needed for the
hub itself). If more units of current are required by a device than can be
supplied by the port it is plugged into, the operating system usually reports
this to the user.

In contrast a self-powered hub is one that takes its power from an external
power supply unit and can therefore provide full power (up to 500 mA) to every
port. Many hubs can operate as either bus powered or self powered hubs.

However, there are many non-compliant hubs on the market which announce
themselves to the host as self-powered despite really being bus-powered.
Equally there are plenty of non-compliant devices that use more than 100 mA
without announcing this fact (or indeed sometimes without identifying
themselves as USB devices at all). These hubs and devices do allow more
flexibility in the use of power (in particular many devices use far less than
100 mA and many USB ports can supply more than 500 mA before going into
overload shut-off) but they are likely to make power problems harder to
diagnose.

Some powered hubs do not supply enough power to support a 500mA load on every
port. For example, many 7 port hubs come with a 1A power adapter, when in fact
seven ports could draw a maximum of 7 x 0.5 = 3.5A, plus power for the hub
itself. The assumption is that the user will most likely connect many low
power devices and only one or two requiring a full 500mA.

Thanks. (This is a 4-port hub, as mentioned.)

 

[Gerard Bok]

You want a 5V 2Amp adapter

No, he wants an adapter that fits his needs

Some hubs just distribute 5 volts from the input to the outlets.
And thus require a fully stabilized 5 volts from the adapter.

Most (?) hubs have their own onboard stabilizer, and therefore
require more than 5 volt to operate.
(And there is even an expensive option around, stabilizer that
are capable of providing 5 volt stabilized from a 5 volt input.)

So: label or manual, no guesswork please ;-)

 

[Paul]

I've dusted off a 4-port USB hub I had lying but can't find whatever
adapter it came with. What are the specs please? I want to replace a
PC-powered hub with it.

I have several old adapters. This 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?

Bus powered USB devices run at 5V.

And you can see this hub, has "DC 5V" printed on it. If your
hub is made from black plastic, it's possible the voltage
is printed in raised black letters near the barrel connector.

http://www.greennet.ca/productimages/live/7-hub-alu/IMG_6714.JPG

If you ran the hub at 4.5V, chances are, the hub itself would run
OK, and be detectable from the computer side. But things downstream
of the hub might have a problem. If you can find a copy of the USB
spec, it might have details on the max voltage drop for power
distribution. I thought it was reasonably tight.

http://www.usb.org/developers/whitepapers/power_delivery_motherboards.pdf

"According to the USB Specification Revision 2.0, the operating
voltage of the range of 4.75V to 5.25V while supplying anywhere
from 0A to 500mA downstream ports meet this requirement, a voltage
drop test verifies the voltage is within the 4.75V to 5.25V range,
when all USB ports in the system are port) loaded, and also when
all USB ports in the system are not loaded."

HTH,
Paul

 

[mike]

Bus powered USB devices run at 5V.

And you can see this hub, has "DC 5V" printed on it. If your
hub is made from black plastic, it's possible the voltage
is printed in raised black letters near the barrel connector.

http://www.greennet.ca/productimages/live/7-hub-alu/IMG_6714.JPG

If you ran the hub at 4.5V, chances are, the hub itself would run
OK, and be detectable from the computer side. But things downstream
of the hub might have a problem. If you can find a copy of the USB
spec, it might have details on the max voltage drop for power
distribution. I thought it was reasonably tight.

http://www.usb.org/developers/whitepapers/power_delivery_motherboards.pdf

"According to the USB Specification Revision 2.0, the operating
voltage of the range of 4.75V to 5.25V while supplying anywhere
from 0A to 500mA downstream ports meet this requirement, a voltage
drop test verifies the voltage is within the 4.75V to 5.25V range,
when all USB ports in the system are port) loaded, and also when
all USB ports in the system are not loaded."

HTH,
Paul

Your question is a lot more complicated than you think.
I assume there are no labels on any of the equipment, or you'd have
disclosed the models so someone might actually be able to help.

There exist voltage-switchable regulated wall-warts.
BUT most older voltage-switchable wall-warts are NOT regulated.
The open circuit voltage is WAY more than 4.5V. Make DARN SURE
your output voltage is what it says on the switch under all load
conditions or you're gonna make smoke.

I'd be interested in learning how they do it these days, but a few years
ago when I worked on the problem, there were several options.

Some hubs had a switch for internal/external power. Those worked well.

Others just put the external power right across the internal power
in parallel with the laptop. The good news is that it usually works.
The bad news is that it sometimes blows up the port in your laptop...
especially when using the WRONG AC adapter...hint...hint!

Third class used diodes to isolate the supplies. Problem with that
was that it dropped the voltage as much as half a volt. Stuff
connected to the hub was erratic. Some brands compensated by using
a 6V wall wart.

Today, it's conceptually trivial to make it all automatic and work.
Question is, whether they're willing to spend the extra 10-cents
(what's 10-cents in Chinese?)
on the hardware to do it.

BTW, although the spec for USB2 says 500mA, it's routinely violated.
External hard drives and CD burners are the most frequent offenders.
And vendors make stupid things like USB-powered coffee warmers
and battery chargers.

And there are still a LOT of USB1 ports out there.

My solution to the problem was to cut up a USB extension cable
to disconnect the 5V from the USB1 (100mA) laptop and supply
external 5V 1A
to my external hard drive. Drive became reliable after that.

Another thing I've done for usb1 laptops is to modify the docking
station. I disconnected the 5V to the USB socket in the docking
station and wired it thru
a fuse to the keyboard 5V. Worked well for an external hard drive on
the docking station.

Are we having fun yet?

 

[Terry Pinnell]

No, he wants an adapter that fits his needs

Some hubs just distribute 5 volts from the input to the outlets.
And thus require a fully stabilized 5 volts from the adapter.

Most (?) hubs have their own onboard stabilizer, and therefore
require more than 5 volt to operate.
(And there is even an expensive option around, stabilizer that
are capable of providing 5 volt stabilized from a 5 volt input.)

So: label or manual, no guesswork please ;-)

Unfortunately it's not clear to me who manufactured this unit, or I'd have
provided that, but maybe someone recognises the logo? There's nothing
else.
http://dl.dropbox.com/u/4019461/USB Hub.jpg

 

[Terry Pinnell]

Your question is a lot more complicated than you think.
I assume there are no labels on any of the equipment, or you'd have
disclosed the models so someone might actually be able to help.

There exist voltage-switchable regulated wall-warts.
BUT most older voltage-switchable wall-warts are NOT regulated.
The open circuit voltage is WAY more than 4.5V. Make DARN SURE
your output voltage is what it says on the switch under all load
conditions or you're gonna make smoke.

I'd be interested in learning how they do it these days, but a few years
ago when I worked on the problem, there were several options.

Some hubs had a switch for internal/external power. Those worked well.

Others just put the external power right across the internal power
in parallel with the laptop. The good news is that it usually works.
The bad news is that it sometimes blows up the port in your laptop...
especially when using the WRONG AC adapter...hint...hint!

Third class used diodes to isolate the supplies. Problem with that
was that it dropped the voltage as much as half a volt. Stuff
connected to the hub was erratic. Some brands compensated by using
a 6V wall wart.

Today, it's conceptually trivial to make it all automatic and work.
Question is, whether they're willing to spend the extra 10-cents
(what's 10-cents in Chinese?)
on the hardware to do it.

BTW, although the spec for USB2 says 500mA, it's routinely violated.
External hard drives and CD burners are the most frequent offenders.
And vendors make stupid things like USB-powered coffee warmers
and battery chargers.

And there are still a LOT of USB1 ports out there.

My solution to the problem was to cut up a USB extension cable
to disconnect the 5V from the USB1 (100mA) laptop and supply
external 5V 1A
to my external hard drive. Drive became reliable after that.

Another thing I've done for usb1 laptops is to modify the docking
station. I disconnected the 5V to the USB socket in the docking
station and wired it thru
a fuse to the keyboard 5V. Worked well for an external hard drive on
the docking station.

Are we having fun yet?

Thanks for those follow-ups. I'm now sufficiently nervous! I'll search the
shed again for the original adapter.

Too cold here to get back in the shed, remind myself of the electronic
basics and build one myself. So next step will be to just buy another!

 

[Brian Cryer]

I've dusted off a 4-port USB hub I had lying but can't find whatever
adapter it came with. What are the specs please? I want to replace a
PC-powered hub with it.

Most devices indicate the required voltage and polarity next to the power
socket on the device. Do look carefully, because otherwise you are into
guessing - guess a little wrong and it will still work, guess a lot wrong
and you could break something.

Failing that, it should have the device type/code printed on it somewhere
together with the name of the manufacturer. If you post that informatino
then someone may be able to help further.

The suggestion by others that it may be 5volts, may well be correct - there
are a lot of knowledgeable people in this group so I'm not questioning their
advice, personally I simply don't know.

I have several old adapters. This 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?

If its a usb hub then does it need to be powered? I have a "powered" usb
hub, but it will still work when not powered. The only thing it looses when
not being powered is that you can't plug usb devices in which need
powering - so without power it won't work with say a usb cd drive but is
fine for mice and keyboards. Your usb hub might be different, but its worth
a shot.

 

[GMAN]

Thanks for those follow-ups. I'm now sufficiently nervous! I'll search the
shed again for the original adapter.

Too cold here to get back in the shed, remind myself of the electronic
basics and build one myself. So next step will be to just buy another!

Show us a photo of the bottom of the unit and the rear

 

[Terry Pinnell]

Show us a photo of the bottom of the unit and the rear

As I said, there's nothing of any help there.

Anyway, I've come to the conclusion that it must be a USB 1.0 type, as it
doesn't explicitly mention '2.0'. So I'll abandon the idea of using it.
New 10-port unit on order.