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Thread: How many rgb LEDs from USB power with tlc5940?

  1. #1

    How many rgb LEDs from USB power with tlc5940?

    Hi, this is a rubbish question I know because I have no data on the LEDs. They are amazing little RGB LEDs. I am driving them with tlc5940 and I am wondering how many I can have. Ideally will be 42 but max 12 at any one time. The rest of my project has very low current draw, around 30mA. Thanks for any advice.

  2. #2
    Senior Member
    Join Date
    Jun 2013
    Torrance CA
    I didn't see a specific current draw from your link but in general you can assume about 20mA per individual LED, or 60mA per package.

    If you're talking about USB power from a device like a computer you're limited to 500mA. Some ports on some computers can do more, and very old computers with USB 1.0 ports are only guaranteed to 100mA, but 500mA is safe. This works out to about 7 LEDs. You could drive 12 RGB LEDs if you limit them to about 55% maximum brightness.

    If you're talking about USB power from the wall, the most I've ever seen is a 12 Watt adapter (12/5 = 2.4A) but the spec says 2.1A is the maximum. This would be enough for about 34 LEDs.

  3. #3
    Thank-you very much. Perfect.

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