Powered USB question

[birdpic]

This would be the third board I have posted on re this question. If someone here cant answer, it may be un-answerable

I Just bought a Latitude Laptop. It has 3 USB 2.0 ports and one "powered USB D/Bay port." Is this proprietary port?

What I am trying to do is hook up an external mini HDD (G-technology) to one of the 3 USB ports. Can I do this without Ac power to the drive? it needs 5V. I thought all USB 2.0 were "powered". I could find nothing on Dells site wrt max V draw from the 2.0 port.

Thanks for any clarification.

[Ob1]

The USB specification provides a 5 V (volts) supply on a single wire from which connected USB devices may draw power. The specification provides for no more than 5.25 V and no less than 4.35 V between the +ve and -ve bus power lines.

D/bay port is a proprietary port offered only by dell from my understanding, it is used to plug in the cd-rom or floppy to allow the laptop to boot to that type of cd or floppy media.

i have a 40gb laptop h. drive in my external case, and it can be powered from my usb ports, i just connect the usb cable to one of my two ports and its up and running, i got the external case from compusa for like $20 and just put in a laptop hard drive.

[glc]

If the hard drive draws no more than 500ma (milliamps), it can be powered from a USB port without AC power.

[birdpic]

Great explanation from you both. Thank you. I will now endevour to make sure the mini drive draws no more than 5V.

Best.

[glc]

No, voltage is not the issue. It's amperage.

[kilgoretrout]

Some external 2.5 inch hard drive enclosures come with a special usb cord where you have two usb plugs on one end and one usb plug on the other. The single plug end plugs into the hard drive enclosure and the double plug end plugs into two usb ports on the computer. This gives you more than enough amps to power a typical laptop hard drive without an AC adapter since you are drawing power from two usb ports on the computer.