12V RGB LEDs don't turn off

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Hello community.

I have a problem with my TLC5940 Breakout board.

I connection the TLC board to the Arduino Uno as followed

  • VPRG -> GND

    XERR → Empty

    XLAT → Pin 9

    BLANK → Pin 10 and parallel a 10k Pullup to 5V

    SIN → Pin 11

    SCLK → Pin 13

    VCC → 5V from Arduino

    GND → GND


    • The Arduino is powered by an USB connector.

    Afterwards I put an ordinary LED onto my breadboard and connected the anode to the 5V and the cathode to one of the outputs of the breakout board, just to get familiar with the functionallity. Everything worked fine. Turn on and off the led and dimming as well.

    Then I tried to control one of my 12V RGB LED spots. So I connected the 12V from the power supply to the anode of the LED. The RGB wires I connected to the outputs of the TLC5940. I connected the GND of the 12V power supply to the GND of the Arduino.

    The Problem is now, that the LED Spot doesn’t turn off, even if the output is set to 0. There are still 2mA.

    Does the different power sources cause this problem.

    I hope someone can give me a hint, how to solve that problem.

    Best Regards

    NightHawk