Portable usb drive detection problems

vbimport

#1

I have recently bought a new Simpletech 250gb portable usb drive.
When I connect it to my computer it works fine, but when I connect it to my girlfriends computer it does strange things.
It powers up (power light comes on) but doesn’t get detected and doesn’t show up in disk management or device manager even with the extra usb power cable plugged in.
However… if I connect it when the computer’s off and then turn the computer on, the drive gets detected and works fine. It doesn’t really make sense to me.
I assume it’s not a power problem, because it will work from boot, and the computer obviously CAN detect it… but why won’t it work if I plug it in while the computer is on?
I have used portable usb drives on this machine before and they work fine, my old one still works fine on this computer just not my new one.

Can anyone suggest a reason & solution?
Thanks


#2

Hi,

please keep in mind, that host powered USB HDDs are beyond the specs for power supply via USB.
An USB port is specified to deliver up to 500mA @5V if requested by the device. Without device request, an USB port will deliver 100mA @5V. That is 600mA total if an additional USB power cable is attached.

A 250 GB 2.5" needs 900mA during spinup, which is too much for many USB ports.
What can happen:

Connect a power supply with proper connector, polarity, voltage and amperage, and you should be fine.


#3

Thanks for the reply.
I guess that’s bad news for me then.

Why is it that another drive works though? Do smaller drives require less power to spin up? My 80gb lacie portable works fine on that computer.

Also, is it possible to tell the usb port to supply 500ma at all times, not just when requested by a device? Surely there must be a way by going into the bios maybe? or is this a driver or OS related problem?


#4

Hi,[quote=confuzed666;2045925]Thanks for the reply.
I guess that’s bad news for me then.[/quote]:iagree:

Why is it that another drive works though? Do smaller drives require less power to spin up? My 80gb lacie portable works fine on that computer.
Just luck. Or the manufacturer of the enclosure has added some mechanism to reduce the power demand during spinup (something like a buffer, or slowing down the spinup process, there seem to some tricks available)

Also, is it possible to tell the usb port to supply 500ma at all times, not just when requested by a device? Surely there must be a way by going into the bios maybe? or is this a driver or OS related problem?
This behaviour is by specification. The drivers (that are part of the OS mostly) are also designed to meet the specs.

Michael


#5

Hello confuzed666

The problem you described is totally normal, it is like mciahel said. The power consumption of your 250GB drive is too large. I’d assume during the spinum the current is larger than 1A. There are USB Y-adapter cables available, than the drive might work, but I’m not a fan of this y-adapters.

I’d recommend using an external power supply with your drive. With expternal power there should not be any problem.

BTW, there is no 2.5" on the market that reaches the USB specification for buspowered devices. Even 80GB or 40GB need too much power. Some older Toshiba HDDs (40GB, 4200rpm) reached the 500mA. but this drives are not available anymore since 3 years or more… No drive with a spin rate of 5400rpm or faster would reach the USB specification. Maybe a 4200rpm drive would come close, but I guess not close enough…

If you would like to have a drive working buspowered I’d recommend a 1.8" drive. I have a 1.8" USB powered drive (60GB, 4200rpm) and this works fine sinse this special HDD also works with 3.3V as voltage. I never had problems with spin up.


#6

I have a 120GB 2.5" HDD in an enclosure with NO power supply and it works Perfectly in both my PCs n Laptop n a friends PC n his wifes pc…USB/Sata…With USB cable/Sata Cable & USb Power cable…
So you be saying that it should be on a Power Plug!! ?
If So, Why don’t they sell a power supply with them ???


#7

[quote=MrScary;2082953]I have a 120GB 2.5" HDD in an enclosure with NO power supply and it works Perfectly in both my PCs n Laptop n a friends PC n his wifes pc…USB/Sata…With USB cable/Sata Cable & USb Power cable…
So you be saying that it should be on a Power Plug!! ?[/quote]Since USB power specs are not met. Works in many cases, but sometimes does not. Depends on the mainboard.

If So, Why don’t they sell a power supply with them ???
Optimising profit. Also, a unit without additional cables is more attractive for customers (another contribution for more profit).


#8

I own many (8) external USB bus powered hard drives. All of them will work find off the USB bus. Recently, I bought a Simpletech 250 GB USB bus powered drive. It would not work with any machine (desktop or laptop). I used a dual USB cable to get power from an additional USB port and that did not work. This particular external drive did not have provisions for external power.

I rather believe that the problem is the way Simpletech designed the drive or the possibility it was DOA except that the lights came on and the drive would spin up. I took the 250 Simpletech back and got the 320GB WD passport and it works like a champ on anything I connect it to.

No more Simpletech for me.


#9

[quote=mciahel;2083041]Since USB power specs are not met. Works in many cases, but sometimes does not. Depends on the mainboard.
Optimising profit. Also, a unit without additional cables is more attractive for customers (another contribution for more profit).[/quote]

Unfortunately, I suspect that this has a great deal of truth to it - on both counts: it’s nice to have a system that can run without a power cable and it’s great for extra cash for the company is it’s a separate purchase