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LED power

I'm currently building a new midi controller using 16 illuminated arcade buttons and a brain version 1 from an old controller. I'm not interested in LED feedback, I just want the buttons to be lit as long as the controller is powered by usb. Is there a way to grab some power from somewhere on the board? On my old controller I used a separate power source to light them as they were 12v LEDs and there's only room for 14 LEDs on the matrix but I'd rather just have everything powered by usb. The LEDs I'm using now are 5v so I'm guessing the board can power them.


  • The easiest way is to use the built in LED Inputs on the Brain.

    Then light all LEDs, and then 'Save' using Brain Configure.
    They will then turn on whenever your controller turns on.
  • Does that mean I'll have to use an LED matrix?

  • Brain v1 does only have room for 14 LEDs without Matrixing.

    With Matrixing you can support up to 48.
    So in this case, yes, you would need to Matrix.

    There is a 5V Output pin on the Brain, but it only gives you just over 100mA, so if you use it, tune the current limiting resistors for your leds accordingly.

  • On the wiki it says that I need to add a resistor at the beginning of each column in the matrix to control voltage to the matrix. What value do these need to be? Would they be the same as the current limiting resistors attached to the cathodes of the LED's?

  • When matrix, this value can be between 40 and 100-ohms depending upon your LED.

    Yes, these resistors are current limiters, so
    If you have current limiting resistors on the other side already, you don't need any on the column side.

  • I've managed to wire up my 16 LEDS via a matrix but something somewhere is wrong as I can't seem to get them on. Is there any way in brain configure to have them all turned on as soon as the controller is plugged in?

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