Step-Up 4.9-5.0V to 5.1V

[Steven G.]

I have just purchased a 2.5" USB HDD Enclosure, with 20GB HDD - Very nice !

However, on some systems, it seems the voltage is slightly too low to get
the Hard Disk to spin up, it just goes click-click-click.

What is the best way to step up USB Voltage just a tad, as by the time the
5V gets to the end of the USB Cable it must have dropped just enough, to be
annoying.

Obviously efficiency is of major concern, being USB, so even a Switchmode
reg with ~80% eff. is possibly not good enough as this will load down the
USB Power output even more, and possibly cause even more problems.

Any input appreciated.

 

[Rod Speed]

Steven G <georgste@geocities.com.NOSPAM> wrote in message
news:Ln8Qa.2742$wU5.359@news-server.bigpond.net.au...

I have just purchased a 2.5" USB HDD Enclosure, with 20GB HDD - Very nice !

However, on some systems, it seems the voltage is slightly too
low to get the Hard Disk to spin up, it just goes click-click-click.

What is the best way to step up USB Voltage just a tad,
as by the time the 5V gets to the end of the USB Cable
it must have dropped just enough, to be annoying.

Your problem is that the USB port cant provide
enough CURRENT. The problem isnt the voltage.

Obviously efficiency is of major concern, being USB, so even a Switchmode
reg with ~80% eff. is possibly not good enough as this will load down the
USB Power output even more, and possibly cause even more problems.

Yep, if the USB port cant provide enough current,
nothing you try voltage regulator wise will help.

Simplest approach is to use a powered USB hub
that can provide the current the drive needs.

 

[Peter Jetson]

Craig Hart wrote:

Try a thicker USB cable (i.e. heavier gague wire, not ticker plastic )
to minimise losses, check the drive itself - for example in a laptop or by
replacement, and try an assortment of different computers to eliminate lack
of current from the USB port.

Or perhaps a powered hub, on the problem computer(s)?

Peter

 

[Brenden Ede]

Steven,
The primary problem is that all USB ports are not created equal.

Most use a current limiting device set to 500mA and the drive tries to
use more than this during spin up, this current protection device acts
and limits the current and thus voltage to the port. ( click , click ,
click )

Many laptops have ports limited to 100mA MAX so these won't work at all.

Use a Powered USB hub and most of your problems will go away.

This however ruins the idea of just taking a small little 20GB hdd with
you as you've ghot to cart around a powered hub and AC adapter with you.

Best Regards,
Brenden Ede
Gigatechnology.com (USB specialists)



Steven G. wrote:

I have just purchased a 2.5" USB HDD Enclosure, with 20GB HDD - Very nice !

However, on some systems, it seems the voltage is slightly too low to get
the Hard Disk to spin up, it just goes click-click-click.

What is the best way to step up USB Voltage just a tad, as by the time the
5V gets to the end of the USB Cable it must have dropped just enough, to be
annoying.

Obviously efficiency is of major concern, being USB, so even a Switchmode
reg with ~80% eff. is possibly not good enough as this will load down the
USB Power output even more, and possibly cause even more problems.

Any input appreciated.

 

[Steven G.]

Thanks to all above who replied.

It seems that the quality of the USB cable that came with this unit is not
so good. When using the USB Cable that came with my Digital Camera, the unit
works fine.

* However, the unit still does not work when connected to front USB ports,
or via an extention cable. So obviously the losses are too much here.

Plugging the device into a powered HUB with the supplied cable, also was not
successful with the original cable.

It doesn't seem to be directly related to current, but more the voltage drop
caused by the current.


To overcome this problem, I think I will buy a USB-A Plug and a suitable DC
Plug for the unit, and using some better cable, make my own extra power
cable for the unit, this could be used in conjunction with the first to
share the load between two USB ports.
Any reason why this would not work ?
* The unit does not 'switch' between BUS/host powered, but just combines
everything.