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Micro USB Power cable -- which are the power pins

Discussion in 'Electronic Design' started by [email protected], Mar 10, 2013.

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  1. Guest

    If this is a slightly off topic query,
    I apologize. Could some electronics guru
    please help ? I am not at all familiar
    with the micro USB power cable, and here
    are some questions:

    1. As I understand it, the USB cable
    has a micro USB connector on one end,
    and a regular USB connector on the
    other. The power is fed in via the
    regular USB connector, and the micro
    USB connector plugs into the device
    that uses it. So, where do I connect
    the regular USB connector to, for the
    device at the other end to receive
    power over the USB cable. In my case,
    the receiving device needs a power
    supply that can supply 700 mA
    (max) at 5V. I can easily build a
    power supply to these specifications,
    and so could I just put a matching
    connector at the regular USB connector
    end of the cable, and then power
    the device this way.

    Please let me know your thoughts on
  2. Sylvia Else

    Sylvia Else Guest

    A micro USB power cable is just a micro USB cable that doesn't have the
    data line wires.

    You can still plug it into into a computer (laptop, or otherwise), just
    to access the power.

    You could also plug it into something like this

  3. You may find many devices are not capable of providing 700 mA. Common
    protective devices limit output power to 500 mA.
  4. whit3rd

    whit3rd Guest

    You don't need to find the pinout, unless you want to wire to the plug.
    NO ONE wants to manually wire to a mini-USB plug; just buy a
    prewired cable/plug assembly (or, equivalently, sacrifice a cable
    or an unsatisfactory power adapter).

    Just use your voltmeter on the unsatisfactory adapter's output wires
    to find the right polarity, before you cut the cable off.
  5. hamilton

    hamilton Guest

    I see you ground all the signal lines.

    Do you not need the USB connectivity or ignore just those lines ?

  6. Guest

    The data lines are normally numbered 2 and 3, 4 is ID
    So I'm guessing most of the grounded pins are actually mechanical

    If you don't need usb but just power I think the standard says you
    should short d+ and d- to signal that you want high current

  7. Guest

    some of them probably are:

    But I think most of what a chip like that does is signal to the
    how much power it can expect, so say a tablet can charge at 2A when
    connected to a charger and at 500mA when connected to a computer

    I guess you could use that, so if someone plugs your device into a
    that will only supply 500mA, you can tell him it won't work

  8. Guest

    2.0 is also 500mA, 3.0 that is up to 900mA when running high speed,
    something like 1500mA when it is for charging

  9. Jasen Betts

    Jasen Betts Guest

    these protective devices aren't particularly common in the wild.
  10. josephkk

    josephkk Guest

    No need to guess. The standards are available here:

    Nice price as well.

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