Multiple USB Power Supply Issue

[Yanzzz]

Hi,

I was trying to build a DIY circuit which would connected to 2 of my computers with USB cable, but talk to only one of them at each time. I wish this circuit could be powered by either of the computers, as I may not power on both of them all the times.

The issue here is, I suppose I cannot just short the 2 USB Vbus supply together as it would cause short current and damage the computers.

Any idea how I can power the circuit with either of the 2 USB power supply without shorting them together?

Thanks!

 

[betwixt]

What you are doing isn't recommended because it still leaves the other connections intact but the simplest solution is to isolate the power outputs by wiring a Schottky diode in series with each +5V output from the USB socket with the cathode ends joined and used as your new supply output. It will drop the voltage a little but it will prevent the computers trying to 'feed' each other.

Brian.

 

[Yanzzz]

Thanks Brain,

I was looking for something like a USB switch ic which is design for this kind of usage but didn't realize that it could be solved by discrete components.