[AccessD] FW: External Hard Drive

There is a max power usage of 500mA per port.

Some hub's have overtension security build and shut of ports when more
then 500mA is used, some do not have that build in security.
I also noticed that sometimes a device generates a small peak, typicaly
when starting/connecting the device cold where USB hub badly respons to
it and shuts it off.

The reason why you have a double connector on the disk is that the
manufactor knows the power usage is to much for one connector. The
indidual small differences between hub could case the effect you
experiance.

You also need to connect the power supply of you hub, a lot of people
ignore to do that. If you do not do that the whole hub get power from
one usb port with total maxmimum of 500mA. When connecting the power
supply of the hub, each hub port get's it own 500mA...

Erwin


 

-----Original Message-----
From: accessd-bounces at databaseadvisors.com
[mailto:accessd-bounces at databaseadvisors.com] On Behalf Of Dan Waters
Sent: Wednesday, March 28, 2007 6:35 PM
To: 'Access Developers discussion and problem solving'
Subject: [AccessD] FW: External Hard Drive

Insufficient power was the problem!

This case actually has a cable with two usb plugs.  I didn't need to
plub in the secondary one before, but using it now solves the problem.

Thanks!
Dan

-----Original Message-----
From: Dan Waters [mailto:dwaters at usinternet.com]
Sent: Wednesday, March 28, 2007 9:37 AM
To: 'Discussion of Hardware and Software issues'
Subject: External Hard Drive

I have an external HD that I use with Ghost 9.0 as a backup device.  The
disk is a 60 Gb laptop disk in a Nexstar case.  This is USB powered, and
is fairly nice.

All went well until I changed from a 4 port D-link hub to a 7 port
D-link hub.  Now, when my laptop powers up automatically at 5 AM to run
the backup program, the laptop can't find the external HD (it did
before).  Once I unplug and reattach the USB cables to the HD, the
laptop will then recognize the external HD, and I can start the backup
program.

Also, once the HD is recognized, I can tell from the flashing light that
the laptop is constantly trying to write to the HD, although it doesn't
write anything and there are no programs running that should cause this.
And, when I was previously connected through the 4 port hub, the light
was a solid green.

I wouldn't think that a change in USB hubs would actually trigger this.
But what could cause this problem?

Thanks!
Dan

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