Turn off power on usb port?

dengamle · Post by **dengamle** » 03 Jul 2007, 18:10

Hi there,

I am using an external USB drive (WD MyBook Essential) for automatic daily backups using cron and rsync. The drive has its own power supply.

The drive automatically detects when the USB port, which it is connected to, has power (i.e. the "host" it is connected to has been powered up) and powers up its drive. Since my Bubba is up all the time, my external drive is also up all the time and therefore consumes more power than actually needed (since backups only take a fraction of the time the drive is up).

I guess I could make my external drive "go to sleep" (and save power) if I was somehow able to turn off power on the USB port from my Bubba. Then I could build into my cron scripts to turn on power on the port and mount the drive a couple of minutes before running the backup scripts, and do the opposite after finishing the backups. Would this be possible at all? Are there any handles for turning the USB port on/off from Bubba?

Hope you might have some info on this, since I'm quite blank on this one

Best regards

Martin.

stewed · Post by **stewed** » 04 Jul 2007, 02:59

The WD MyBook Essential spins down automatically after being idle for 10 minutes. At least it does that when connected to a PC. Doesn't it do that when connected to the Bubba?

dengamle · Post by **dengamle** » 04 Jul 2007, 06:09

Yes, the drive automatically spins down as you point out, but it doesn't *turn off* as it would if I turned off my bubba.

/Martin.

Post by **johannes** » 04 Jul 2007, 13:56

It isn't possible to turn off power on the USB port, the power supply (VBUS in USB terms, +5V) is always on except when an overcurrent event has occured (a semiconductor resettable fuse is used). However, wouldn't it be possible that your drive would "turn off" when you unmount it from Bubba?

Also, I wouldn't count on the drive consuming less power when "turned off" as opposed to being spun down. It's common that the hardware still has active power supply, perhaps just a LED being turned off. But that's just a guess.