Thinkpads Forum

Hello,

i'm considering ordering an external 2.5" hard disk (Seagate FreeAgent Go) for use with an R40e. The hard drive doesn't have a power adapter of its own; it's powered over the USB cable by the computer. As i don't have the hard drive here, i'm not sure whether the cable that connects to the computer is a Y-cable with two USB plugs or if it has just one USB plug. The manufacturer's homepage isn't clear about this either, the quick start guide shows a picture of a regular USB cable, but the FAQs say that it would use a Y-cable.

The user has a PC-Card with two USB 2.0 sockets on it. This is a D-Link PC-Card and the manufacturer specifies the USB sockets to supply 500 mA each. The PC-Card doesn't have any power jack that could be used in order to supply additional power, its sole power source is the PC-Card slot.

One possible limitation is the PC-Card slot itself. The PCMCIA Association's website specifies the recommended minimum peak current per slot at 5 V to 660 mA. If the R40e just meets these minimum requirements, the PC-Card can't supply 500mA to both sockets simultaneously.

A 2.5" Seagate hard drive needs 1.0 A just in order to spin up. If the PC-Card slot on the R40e just meets the minimum requirements and thus only supplies 660mA, this would not be enough to start up an external 2.5" hard disk, even if one would use a Y-cable. It could still work if the hard disk enclosure contains a capacitor that supplies the additional start-up current, or if the PC-Card slot on the R40e supplies more than the minimum specified current. If a capacitor in the hard disk enclosure should be of any use, the PC-Card's USB sockets would have to supply a voltage even when the computer is turned off. But i have no idea whether this is the case.

Considering these facts, the probability that it would be possible to power a 2.5" external hard drive from a USB 2.0 PC-Card, which doesn't have an additional power jack, seems to be small. Has anyone here tried it? If yes, what were your results?

If you use one of the original USB ports, plus a Y-splitter to connect to one of the PC-Card USB-ports, it should fire up no problem.

RealBlackStuff wrote:If you use one of the original USB ports, plus a Y-splitter to connect to one of the PC-Card USB-ports, it should fire up no problem.

Thanks. In another thread a user wrote that he or she had done so and that it had worked for a while, but then had stopped working. I suppose it will be safer to get an external hard disk that is powered by its own AC adapter.

did some experiments with x31 and travelstar 32GB frm
t22, with this hardware

1. x31 native USB

2. "certified USB 2.0" IDE-USB adapter

3. SIIG pcmcia-2 USB adapter

4. adaptec ACS-120 HD adapter w/ splitter 2 USB cable
with 5v external power (4 amps:-)

drive-2-1 works fine (either native USB)

drive-4-1 OK (either native USB) (with power or without)

drive-4-3-2 only works w/ external 5 volt (splitter not needed)

so the results of my experiments are, that the x31's
USB ports (2.0) supply enough power to spin up the
drive, but that with the pcmcia adapter, only the
external power supply has enough oomph. The splitter
cable was either not necessary, or unhelpful.

tom lightbody wrote:did some experiments... <snipped> ...but that with the pcmcia adapter, only the external power supply has enough oomph.

Thanks. This indicates that the PC-Card slot might not be able to supply the necessary power.

About a year or so ago I made an attempt at using a SimpleTech 2.5" drive and USB PC-Card on my
T21. Even with the splitter it just wasn't enough. The drive would power on but when writing to
it the drive would error as it would lose power.
What bummed me out is the drive has an external power adapter jack but I couldn't for the life of
me find the required adapter anywhere. SimpleTech didn't have them, Radio Shack didn't, nor other
places. I believe it was 5V 1Amp (now available on eBay for $15
http://cgi.ebay.com.sg/ws/eBayISAPI.dll ... 0212299894 ).

Alas, I wound up frying the drive when I tried to use a power adapter that wasn't set right (one of
those universal ones).
A then-brand new 80GB paperweight.