Remote Power Switch Using USB Port to Control

mitchsc · #1 Oct 29, 2009, 05:37 PM

I would like to do something that may never have been tried, although it seems simple enough. But before I get out the old soldering iron, maybe there is already a device that exists to do it.

I bought a 1.5TB FreeAgent backup drive. I plan to format it and load my Rebit backup software (a very cool program similar to Time Machine for Macs) that does some stuff that the FreeAgent can't do..

Issue: The original FreeAgent software will spin down the drive after 15 minutes of being idle (nice feature). The Rebit software was originally designed for a portable backup drive that is USB powered, so when the PC was turned off, off went the backup drive.

But the FreeAgent Drive uses an AC adapter that allows it to run all the time, 24/7. I know I can just unplug it, but that is not so cool, and I would probably forget.

I was thinking of making, or hopefully buying, a remote device that plugs into a PCs USB port to switch on a relay that would in turn switch on the AC power to the FreeAgent drive. Essentially this would power up and down the backup drive with the PC.

In terms of design, the USB would power a relay that would switch the AC power.

Does anyone know of a device like this that already exists?

Also, would like to know the maximum current a USB port can supply, in case I go the relay route.

Any other ideas would also be appreciated.

Thanks...

mitchsc · Oct 29, 2009, 05:45 PM

Well, here is the idea...

A USB Power Controled Plug Strip. With Isolation.

KeepItSimpleStupid · Oct 29, 2009, 05:59 PM

I believe, not sure, that without negotiation to raise the power level, it would be 5 V at 100 mA. Max for root hubs is 5 V at 1A

mitchsc · Oct 30, 2009, 06:30 AM

Thanks,

Are you saying the Max output for a USB port is 100mA?

I don't know what a root hub is (good up to 1A)?

KeepItSimpleStupid · Oct 30, 2009, 07:48 AM

There is a whole bunch of stuff here: USB.org - Welcome

I just don't have the time to go through it.

USB has two power levels available and I'm not sure if you have to enable the high power output. Meaning, I think, you have to establish communication and then raise the ouput. You'll have to look at the docs.

2 pins are data and 2 pins are +5 power.

Some USB ports don't have the ability to operate at the high power levels. If you look at the device manager you will see entries labeled Root hub.