external hard drive

[garyuk2]

does a usb external hard drive get its power from the usb cable

thanks gary

[irisred]

As you're aksing, I'm guessing it doesn't have an alternative power source and therefore the answer would be yes.

Clever little things aren't they these USB bits?!

[vehelpfulguy]

EVERY USB device gets is power from the USB connection.

That is how you can have small USB lights to light the keyboard or even USB coffee heaters, as well as it powering devices like printers etc.

[gen2]

Your computer may not be able to provide enough power if you have too many power hungry USB devices attached.  You may need to use a powered hub to supply the extra devices.  I believe that Apple Macs have less power available from the computer than most Windows PCs.

[tomd]

USB ports can give +5v, which is enough to power some devices, including an external hard drive using a 2.5" style laptop hard drive, but as gen2 says, this isn't enough to power everything. It's quite rare that external hards drive using a 3.5" (desktop style) can be powered solely by the output from the USB port, usually they have a seperate power supply unit, like a laptop power supply.

I'm not sure how Macs and PCs compare - the voltage is standard at +5v across all USB, but the power (amps / milliamps) doesn't seem to be.

[kempie]

3.5" hard drives and cd/dvd-rom drives (&rewriters) require a power source that supplies a 5V and a 12V line. Since the USB port cannot supply the 12V required by these devices any external models will need a separate supply.

[bruce5755]

I have a 250Gb Western Digital external hard drive that is powered from the mains!