USB Y or powered hub

I wondered what USB Y and powered USB hub devices actually are used for above and beyond extending the number of USB ports available. Ive seen people mention to only hook up "bus powered" USB devices to a USB Y or powered hub to give it the neccesary power. So why is this, and what types of devices fall into "bus powered" USB drives, and why is hooking them directly to a PC's USB port not sufficient?
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pma111Asked:
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CallandorCommented:
Typical USB ports are limited to 500ma current and sometimes don't even provide that much.  If you connect a device that draws a lot of current to a motherboard port, you risk blowing out the port or the entire motherboard.  With a powered USB hub, there is an external power source that can provide the current needed, especially if you have multiple devices connected.

Typical high-draw USB devices have motors, such as hard drives.  For an article about USB power capabilities, see http://www.girr.org/mac_stuff/usb_stuff.html
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pma111Author Commented:
How do I pick out a good "powered USB hub", what am I looking for?

I assume a typical USB pen drive doesnt fall under ""bus powered USB drives", but an external camera, card reader, external USB HDD would?
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pma111Author Commented:
And does a USB Y cable have "power" - or what does a Y cable offer that a typicaly USB cable doest?
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CallandorCommented:
A good powered USB hub will have a separate transformer that outputs high current - here's a good one: http://www.amazon.com/CyberPower-High-Speed-7-Port-USB-Hub/dp/B0006TIA8Y

A USB Y cable is a "splitter" - it is essentially a 2-port USB hub, and suffers from low current limits.
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nobusCommented:
i use the belkin hub : http://www.belkin.com/IWCatProductPage.process?Product_Id=158910
also, i doubt the motherboard can handle eg 6 external drives using around 500 mA at the same time - the usb can be overloaded, and burn out
that is why i always recommend powered devices, or a powered hub
same applies to Y cable
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pma111Author Commented:
I assume a typical USB pen drive doesnt fall under ""bus powered USB drives", but an external camera, card reader, external USB HDD would?
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CallandorCommented:
USB memory sticks are very low-powered and would not put a drain on a USB port.  Card readers and cameras (these have their own batteries) are in the same category - they read memory devices.  USB devices with motors, heating elements, and that recharge batteries are high current consumers.
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