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USB power for tablet and a USB hub

Discussion in 'General Electronics Discussion' started by john2k, Dec 9, 2015.

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  1. john2k


    Jun 13, 2012
    I have the following USB configuration which takes +12v from the car which goes through a converter to reduce to 5V.

    It seems to work fine without any problems. But my only concern the part where the same power from the converter goes as an external power source to the USB hub. So technically there is a loop. Is this OK or can it cause issues?

  2. Martaine2005


    May 12, 2015
    Hi john2k,
    I am not sure I really understand your description.
    The hub, ext power and the converter require 12V?. The hub has it's own 12v to 5v conerter?
    The tablet takes 12v and 5v usb?

    Your red and black are 12V?
    I think you have no worries about a loop of 12V. As long as the items that require 12V get 12V, they don't mind radial or ring..
    If I understand you correctly..

  3. AnalogKid


    Jun 10, 2015
    Red is +5, black is GND. There is no 12V being distributed in the drawing. Grey and green are the USB signal pair.

    Inside a car the cable distances are so short that I don't see a problem here.

  4. john2k


    Jun 13, 2012
    Hi Martin,

    The 12v to 5v converter is the only device that receives the 12V supply. From this converter, the red and black which are +5 and GND are going to the Tablet to charge it only, at the same time from the same converter it is powering the optional external power input for the USB hub which is also 5V. This makes sure the USB hub doesnt drop-out. From the tablet the +5v and GND come back to the USB hub providing the peripherals with power. The green and grey are data cables.
  5. john2k


    Jun 13, 2012
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