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Thread: USB communication with battery power

  1. #1
    Senior Member
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    Dec 2013
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    USB communication with battery power

    Hi all,

    I'd like to know if I can power the Teensy with a battery, cut the VUSB trace so that the teensy can only be powered through the battery, and still communicate with a computer over USB?

    I'm assuming this is the case because the following page states USB operation will work as low as 3.4v.
    https://www.pjrc.com/teensy/external_power.html

    Can I the also cut the USB GND connection?

    My aim is to make a device that can communicate over usb but not use the bus power. This is because there are open +/- contacts on the device and CE/FCC guidelines wouldn't allow a product to have that whilst connect to a computer as it might damage it or cause a spark.

    Side note: If anyone is particularly knowledgable on CE/FCC guidelines where open contacts on a PCB are concerned, I would really appreciate some guidance as it's been holding an otherwise complete product back for several months.

    Thanks very much

  2. #2
    Senior Member+ Theremingenieur's Avatar
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    Feb 2014
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    Colmar, France
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    As far as I know, the USB GND connection must not be cut because it serves as a reference potential for the 2 data lines. Out of that, common ground reduces the risk of electric discharge.

  3. #3
    Junior Member
    Join Date
    May 2016
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    Yes, you can do that. Alternatively, I cut the red wire out of my USB cable since I seem to install the Teensy first without remembering to cut the VUSB trace.

  4. #4
    Senior Member
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    Dec 2013
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    Great, thanks both

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