How many amps do your USB sockets provide?

SiD the Turtle · 14 Jun 2007 at 20:46

I want to get a portable HD to use at home and on the work laptop however (a Western Digital Passport) but some people are warning that the drive needs a lot of juice. According to their support site it needs 1000mA to spin up and in the 'rare case' that this can't be provided they sell an adaptor which takes juice from two ports. This also turns out to be the case for other brands of drive.

So I did a straw poll. Turns out every laptop in the office I checked, the laptop at home, my PC and the family behemoth Core2 Duo ALL have USB ports that only supply 500mA. So where's the rare case? Just to make sure I'm not ranting on about nothing go into computer management and look at the power tab on your usb hubs and tell me how much juice is being provided.

Also if anyone knows of anywhere you can get a 2 USB A to USB mini cable in this country it would be appreciated (or at least acknowledge that such a thing exists).

semi-pro waster · 14 Jun 2007 at 20:58

500mA on any individual port (roughly 10 of them) so I think it is pretty common, however the hard drive manufacturer could expect you to use a powered USB hub I suppose although I'd be a bit dubious of that as it is stretching the example of a "rare case" as you say.

It could also be that your USB ports are capable of being overloaded and would work anyway.

TechnoCorruption · 14 Jun 2007 at 20:59

My Laptop is 500ma per slot, I use 300ma via a hub on one slot (Mouse/Keyboard/Flash Drive) I have never heard of 1000ma slots, do all external hdd's come with out plugs?

SiD the Turtle · 14 Jun 2007 at 21:01

Agr3sive said:
My Laptop is 500ma per slot, I use 300ma via a hub on one slot (Mouse/Keyboard/Flash Drive) I have never heard of 1000ma slots, do all external hdd's come with out plugs?

Some do, the Western Digital one doesnt, and it kinda defeats the point of a portable HD if you have to lug a plug around as well

Edit: this was also happening to a colleague of mine and his Freecom drive. Turns out now Freecom will send you a free plug as so many people are complaining.

TechnoCorruption · 14 Jun 2007 at 21:08

Yeah I guess so, I haver never really looked into portable HDD's, is there other makes that use less power, I spoke to a couple of people in order to find out how much usage my hub could take without it plugged in.

I spoke to Canon as my "all in one" is linked to it too when its in use and also spoke to Belkin and both of them said to stay away from external HDD's.

Sorry im not being much help, but I guess in the area of HDD's it may pay to use an external power source as the last thing you want is problems with data.

SiD the Turtle · 14 Jun 2007 at 21:11

Agr3sive said:
the last thing you want is problems with data.

This is key, I could chance it but if the data corrupts I'm fubared. Might be best to invest the cash in a much larger 3.5 inch HDD rather than a notebook HDD, which spins at normal speeds and so needs a proper plug and power brick. Not quite portable but safer.

TechnoCorruption · 14 Jun 2007 at 21:25

The safer way is always a good idea when it comes down to HDD's and data, that why I wanted to double check just how much my hub (without plug) could use before being overloaded.

Even though its just a 1gb flash drive attached to it, if the hub was being overloaded, anything could have been happening to the data as it was being moved.

I have had a save become corrupt on a games console which wound me up, to have important data corrupt on my pc, well it doesnt bear to think about

Snapshot · 14 Jun 2007 at 21:32

500mA is the specified power supply for a USB port. I've found that desktop PCs will often supply more but not laptops. My older (Hitachi?) 60GB 2.5" drive always needs power from a second USB port but the newer Samsung 120GB drive doesn't.

Amonlym · 15 Jun 2007 at 09:58

so far as i understand:
the usb bus is rated to 500ma, and this is all controlers have to provide to meet spec.
this rating is used to automatically proctect controlers from to-hungry devices (assuming devices are obeying spec, and declair their power eneds to the controler)

however, a lot of boards just hook the +5v line on usb ports up to the +5 rail on pc directly. so your just down to how much current the traces, plug and wire can handle.

for example, plug a usb pen drive in, and the power management probably declairs some tens of ma as used. plug in some "dumb" device, like a usb light, fan, cup heater etc, and you wont find anything on the power tab.

pc's generaly provide more than laptops simply because a pc has a comaritively huge +5v supply for usb, while laptops are likely powering the ports thru the controler chip rather than psu, and running that from a much more limited power supply.

sadly, all you can do is try it and see.
remember, 4200rpm single platter drives will use a lot less current at startup than a 7200 rpm multi-platter drive.

riddlermarc · 15 Jun 2007 at 10:07

I bought a 2.5"->usb adapter so I could run a laptop hdd as a removable storage unit:

The cable that connects to the computer has two usb plugs as one apparently doesn't necessarily supply enough power - it does, however, run perfectly fine on one plug. It obviously isn't as juice-hungry as a "proper" usb hdd

SiD the Turtle · 15 Jun 2007 at 11:32

riddlermarc said:
I bought a 2.5"->usb adapter so I could run a laptop hdd as a removable storage unit:

The cable that connects to the computer has two usb plugs as one apparently doesn't necessarily supply enough power - it does, however, run perfectly fine on one plug. It obviously isn't as juice-hungry as a "proper" usb hdd

Nice idea, though I wouldn't want to carry a bare drive around

More research into the issue seems to show that a lot of these drives say they need the 'standard' 1000mA, on desktops this doesn't look like a problem but laptops struggle to pump out the juice. There is a Segate Freeagent Go that comes with a a double cable as standard, so I think I'm going to get one of those, to be safe.

TheVoice · 15 Jun 2007 at 12:04

I've got the WD Passport drive - never had any problems powering it on my notebook, my PC (front ports), or an iMac. This is using the standard cable it came with (single USB A connector).

My step-dad has one too and I know he uses it on his PC and his notebook, and he's never had problems powering it either.

SiD the Turtle · 15 Jun 2007 at 12:08

TheVoice said:
I've got the WD Passport drive - never had any problems powering it on my notebook, my PC (front ports), or an iMac. This is using the standard cable it came with (single USB A connector).

My step-dad has one too and I know he uses it on his PC and his notebook, and he's never had problems powering it either.

Thanks for the information. Problem I see is that WD themselves say that it needs 1000mA, and because I know from other people in the office the laptops struggle with that, I can't risk losing data by chancing it. The Segate is more expensive and uglier, but the safer option imo. Shame though as I've always found WD drives themselves to be superior to any other I have owned.