Power requirements for RGB LEDs?

Shop Forums QnA Power requirements for RGB LEDs?

This topic contains 1 reply, has 2 voices, and was last updated by  flashteker@gmail.com 4 years, 5 months ago.

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  • #883

    Neil
    Participant

    Hi,

    I built a Winkeyless B.87 and B.Pad last week. It turned out great, and I’ve been using it daily.

    The only problem I ran into is that I can’t enable all of the RGB LEDs. If I do, the USB hub will go into brown-out and cause erratic behavior.

    The WS2812 LEDs you use are rated for up to 30 milliamps per channel (e.g. 90 mA worst-case if red, green, and blue are 100%). I recall there being about 20 WS2812’s on the board, which is about 1.8 amps worst-case. This is well over the maximum power allowed by USB specification.

    I have read the documentation, but haven’t seen anything that implies how this is to be handled? Should I be using a custom USB cable, with power being supplied by an external +5V source? Is it just assumed that I’m not supposed to turn the LEDs all the way up? Is there some other way to do this?

    Any help would be appreciated. I don’t mind making a custom cable (I was going to do that anyway, with paracord 550 braided jacket, gold connectors, and heat shrink). But wanted to get the “official” answer from you first before I did this.

    Thanks,

    Neil

    #884

    Hi

    Sorry for your inconvenience.

    First, the maxiumum electric usage of a RGB LED is 60 mA(20 mA per RGB channgel)
    (Ref. http://cdn.sparkfun.com/datasheets/Components/LED/WS2812.pdf)
    So theoretically the maximum usage of 20 RGB LEDs is 1200 mA.
    But RGB Controller limits the maximum usage to 400mA(when including MCU, 500mA) for RGB LED per USB. (So the real full brightness through usb port is 30% of what it could be.)

    If your hub usb doesn’t support that much currenct, there would be a problem.
    So please check your hub capacity.
    And wheh you use an usb-hub, we recommend the one with power adapter.
    (e.g http://www.amazon.com/ORICO-10-Port-12V3A-Power-Adapter/dp/B00CBEVTIA)

    Of course USB 2.0.

    If you find the same problem after changing the hub,
    please let me know.

    Thanks.
    Hojin.Yi

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