USB hubs

[mp3jockey]

Re: USB hubs

Everything you (didn't) want to know about USB Hubs...and didn't care if you knew the answer to, either:

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

jock

[buzz1941]

Re: USB hubs

Thumb drives using flash memory are a good example. They don't take much power, and yet many won't work on "powered" hubs. What's the point of the transformer power supply then?

[GeckoGeek]

Re: USB hubs

On the other hand I have a old 1.x powered hub I picked up cheap. I use it to power a couple of Christmas novelties.

[tutusue]

Re: USB hubs

[...]Go ahead and try. You won't blow anything up.

Hey, GG! What are you? A mind reader?

[helen]

Re: USB hubs

Thumb drives using flash memory are a good example. They don't take much power, and yet many won't work on "powered" hubs. What's the point of the transformer power supply then?

The transformer power supply is a just in case thing. The USB hubs I have seen so far have provisions for an external power supply to be hooked up to it but not all USB hubs encountered come shipped with an external power supply, in which case their instructions say you can purchase one from the manufactor.

Have you tried using your stuff without hooking up your power supply?

[craigwatanabe]

Re: USB hubs

Powered USB devices when used with hubs can load down the computer's PSU. Load it down too much and you fry the PSU.

[GeckoGeek]

Re: USB hubs

Powered USB devices when used with hubs can load down the computer's PSU.

Huh? I'm not sure if you're talking about powered or non-powered hubs. Also, I think the USB is current limited, so I don't think it's too likely you can overload the PSU just by drawing on the USB.

Load it down too much and you fry the PSU.

The ones I've seen are good about protecting themselves.

[craigwatanabe]

Re: USB hubs

Huh? I'm not sure if you're talking about powered or non-powered hubs. Also, I think the USB is current limited, so I don't think it's too likely you can overload the PSU just by drawing on the USB.



The ones I've seen are good about protecting themselves.

USB devices use power, they get them from the PSU, powered USB hubs allow the USB device to get their power from a separate power source.

Yes there is a limit to how much current a USB port will dish out however I have seen USB devices overload power supplies when too many powered USB devices are powered by a non-powered USB hub. The power has to come from somewhere if the hub isn't powered so it comes from the PSU. Unless you have a good PSU you really don't want to tax it. Most PSU's in computers sold nowdays have underpowered PSU's already installed. Adding more load to it by using non-powered USB hubs only makes that PSU work harder. Sometimes that USB device simply won't work when it's plugged into a non-powered USB hub that is maxed out.

[GeckoGeek]

Re: USB hubs

From what I can tell, the limit for USB power is .5A. I would assume that's the limit a non-powered hub can draw to power the devices plugged into it.

.5A doesn't sound like much, but might be enough to push a marginal supply over the edge. Of course, that's assuming that anyone bothered following specs and limited the USB.

[craigwatanabe]

Re: USB hubs

500-milliamps isn't a whole lot and with some USB devices powering things such as fans, beverage warmers, right up to more common items such as 2.5" external hard drives, 0.5amps can be reached rather quickly.

[GeckoGeek]

Re: USB hubs

It's 500mA per port. If you've got 4 ports on the CPU, that's up to 2A. That starts adding up for a marginal supply.

You'd hope that the motherboard would have current limiting so in the event of a USB overload, it's the USB device(s) that shut down, but someone somewhere probably just tied the line direct to the +5V.

[craigwatanabe]

Re: USB hubs

It's 500mA per port. If you've got 4 ports on the CPU, that's up to 2A. That starts adding up for a marginal supply.

You'd hope that the motherboard would have current limiting so in the event of a USB overload, it's the USB device(s) that shut down, but someone somewhere probably just tied the line direct to the +5V.

Yes you would hope for current limiting circuits and there probably are in the more expensive mobo's.

Regardless if you want to preserve your motherboard, I'd recommend powered USB hubs so there are no conflicts power wise.