I have a cheap, small 7 port usb hub from ebay. The auction stated it was externally powered, but it will try to draw power from the USB port if there's no external power.
This is problem for me because I have a USB hard drive plugged into the hub. When it only has power from the USB port, the hard drive will start to spin up, stop, start to spin up, stop, etc.. I don't think this is good for the hard drive.
So, I tried just cutting the power lines coming from the laptop so it uses only external power. This way, the hub is not detected by either my carputer or my laptop.
I also tried wiring the USB power lines to a 5v power source, so the hub still sees 5v from the USB port. That doesn't work either.
Is there a reason this isn't working? And is there something other than a relay that will allow me to cut power to the hub when I go into standby?
You might want to try using devcon (http://msdn2.microsoft.com/en-us/library/ms792824.aspx) to disable the hub before you go into standby, which may (depending on the hub) turn off all the attached devices. I use something similar for my touchscreen.
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