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500mA max for an USB product ?

Forum CPU & Components : Other Components - 500mA max for an USB product ?

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Anonymous   01-13-2001 at 11:02:51 AM

For those SELF-powered USB hubs, they said it can provide up to 500mA for EACH port. Is 500mA adequate for ANY type of USB devices including power hungry digital cameras etc.

Thanks

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HoldenMcGroin   04-12-2006 at 08:00:02 PM
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Yep. Digital cameras are power hungry because of the CCD and LCD. Transferring data to computer is a completely different issue.

Of course, if you still worry, check the power ratings on any USB device before you buy it.

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jap0nes   04-12-2006 at 08:41:54 PM
- 0 +

hmmmmmmmm i guess this 500mA is meant for devices that are not self powered, like a keyboard or mouse.
a power hungry digital camera you mean a webcam or a normal camera?
if it's a normal camera than this 500mA limitation does not apply, as it will use usb for transfer only, not powering the device.

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nigelf   04-12-2006 at 09:31:39 PM
- 0 +

0.5 A is the max current in the USB-standard.

Quote :

The USB connector provides a single nominally 5 volt wire from which connected USB devices may power themselves. In practice, delivered voltage can drop well below 5 V, to only slightly above 4 V. The compliance spec requires no more than 5.25 V anywhere and no less than 4.375 V at the worst case; a low-power function after a bus-powered hub. In typical situations the voltage is close to 5 V.

A given segment of the bus is specified to deliver up to 500 mA. This is often enough to power several devices, although this budget must be shared among all devices downstream of an unpowered hub. A bus-powered device may use as much of that power as allowed by the port it is plugged into.



Googled it: from Wikipedia ( http://en.wikipedia.org/wiki/USB#Power_supply )

power = voltage x current
P=V x I

P max for USB = 5V x 0.5A = 2.5Watts)

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