Powering a 2.5" hdd from single USB.

[ninjaturtle]

I know of the .5 amps max power draw from a USB port, I have a seagate 2.5" drive that rated at .451 amps.

Do you think the USB to SATA controller will draw more than the difference? USB drive have a JM20329 IC.

At the moment the only problem I see is at spin-up.

What is your opinion?

 

[Joe Average]

I've got several external drives in cases, all of them are 2.5" laptop drives. Some are PATA/IDE, some are straight SATA (inside the case, that is), and the PATA/IDE ones are almost always rated - according to the label - to draw .7 amps and I use them on a pretty wide variety of machines, both desktops and laptops, and I've yet to come across a situation where it's too much of a current load to cause a problem.

The only time I had an issue was years ago using a very old (like, made in 1999 or something) PATA/IDE drive in an external case that was attached to a laptop (from around 2000 or so) with only USB 1.1 ports and that did prompt Windows 2000 to complain about the current draw and there not being enough power on the port.

At this moment I've got a 250GB Toshiba SATA I (MK25555GSX) drive clearly marked as DC +5V 1.0A (yes, it reads a full amp) plugged into this ThinkPad T60 on the left-side USB 2.0 port, just one port in use and it works fine, no complaints or issues. The cord I'm using can be attached to two USB ports using the second line as additional power draw, but so far so good with just using one.

Pretty sure the tolerances for USB ports let them handle higher current loads than the published ratings usually imply. If that Seagate is rated (on the label, etc) at <.5 amps, you'll be fine. That's a pretty low power requirement, in my experience. I've yet to find a 2.5" laptop drive with anything that low... is that an actual external drive "out of the box" as it was when purchased, like one of those SeaGate FreeAgent drives, or is it a 2.5" laptop drive you put in some kind of external case?

Just curious...

 

[hotzen]

The y-connectors are actually the worst solution:
1. the are not allowed by the standard and it's just luck that they don't cause any issues
2. the second cable is not a device registered with the host and as such can only get 0.1 amps, which means the y-cables can get 0.6 (0.5 properly registered + 0.1) amps max in total.
3. you have to connect the y-thing first to support the drive's spin-up with the additional 0.1 amps

there are drives that have a particulary low spin-up power-draw (<0.5 amps), get one of these. yours seems to be perfect.
but after the end of the day: every modern desktop usb-port allows you to get ~1.0 amps from it. on laptops this differs, but usually it is also possible to get way more than the standardized 0.5 amps.

 

[ninjaturtle]

It is the default HD from my new HP DV6 3143us. I swapped it with a WD that draws IIRC about .55 amps w/ the sole purpose of using a single USB cable.