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Brain JR LED matrix ghosting problem

Hi everyone

I'm using a brain JR to control a matrix of white leds (41 pieces, type:3.2v, 20mA), but I noticed that if I light one LED, another LED starts to illuminate very dim on another row.
I can replicate the issue on a testboard, connect one led on row 1, column 1 and a second led on row 2, column 1.
if I activate led 1, led 2 starts to glow but very dim.

What can I do to remove the glow from the other leds? I tried adding a resistor on each LED, up to 330ohm, but that's not changing anything except the brightness of the active led.
I'm using the leds in a dark environment so it's very annoying to have active leds when they are not active.

Thank you very much for your help
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Comments

  • Hi Justin

    I'll try to make some pictures later this weekend, but this is how I can replicate this on the experimental board which was supplied with the Brain JR:
    take two leds and connect both cathodes (-) together with a wire on row 1 (12 available), now I use two wires to connect the anodes (+) , one goes in column 1, the other goes in column 2 (4 available).
    I use the brain configurator to send note "1" with velocity "127" to light up the first led, the first led goes on, which is normal, BUT now we see that the second led is glowing. it seems there's some kind of leekage towards the other columns which causes some leds to start lighting up, but very dim. 
  • Here's a picture of the issue. as you can see the first led is on and three others are glowing (red circles, only 2 visible on the picture).
    when I light the second led, three more leds will begin to glow, etc...
    My today tests show that all the other leds connected to the same column (4 available) will glow.

    image
  • Hi Justin


    Allready checked that and even removed the pcb from the housing placing it on a pace of paper to make sure, but no change, even replaced the usb cable :-(
  • The board has the latest firmware (v2.22), I even tried an older version without any effect.

    I'm not using a shield, I use the connector directly on the main pcb. (Brain JR revision 1.03 , 2013)
    The leds used are white ones :3.2v, 20mA.
    I'll try to make a schematic how I connected the leds and upload it here.

  • Here's a schematic of my setup.

    The led in the red square is on, the leds in the blue circle (are glowing).
    image
  • Here's how I wired it:

    image
  • Every row is affected.
    To exclude all wiring issues I tested it on a testboard, only the pcb remained the same all the other parts were different, even the connector, but with the same results.
  • The led used is the following one:

    http://www.conrad.be/ce/nl/product/175290/Seoul-Semiconductor-LW340-A-LED-bedraad-Wit-Rond-3-mm-2600-mcd-44-20-mA-32-V?ref=list

    The testboard is the one supplied with the Livid jr builder kit, picture follows.

  • The red wire goes to the first column (4 available), each blue wire is one row (row 1 and row 2)

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