Multiple USB Power Supply Issue

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Yanzzz

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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!
 

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.
 
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    Yanzzz

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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.
 

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