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  1. #1
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    Connect two USB hosts parallel with a slave

    Hi,
    I want to design a pcb which will connect with a tablet (slave) either an Arduino PCB (host) and either with a PC (host). At the below image i took a senario where of a trouble shouting all devices will connect together (for instance because all relays are damge). My question is if and the three VDD of three devices (below picture) will connect parallel (two USB host devices parallel connected with a slave device-tablet) this will cause a damage to the devices or just there will not be a valid connection between them?

    •   Alt28th February 2016, 22:32

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    Re: Connect two USB hosts parallel with a slave

    Do you plan for external power adapters going to your devices? This is safe only if you can verify that the power supplies have internal isolation from mains. If not, then there could be unknown connections to mains AC, which could result in abnormal current flow between the devices, possibly causing a short circuit.



    •   Alt29th February 2016, 02:17

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    Re: Connect two USB hosts parallel with a slave

    The one supply is from computer (usb output) and the other is from arduino where arduino is powered from a switching supply 230/12Volt with an internal transformer (magnetic isolation). With these power specifications I will have a short circuit between all powers?



    •   Alt29th February 2016, 05:46

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  4. #4
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    Re: Connect two USB hosts parallel with a slave

    Since you have isolation, then it should be okay to connect those devices. Come to think of it, I have USB drives which run from a power adapter, and I plug them into my computers without thinking about whether it has isolation.



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