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11x42 LED Matrix with Arduino UNO

Discussion in 'Microcontrollers, Programming and IoT' started by leonardw94, Oct 18, 2015.

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  1. leonardw94


    Oct 18, 2015
    Hey Forum,
    I'm planning to build an 11x42 LED Matrix for my Daft Punk Helmet .

    I decided to split into 2 sub-matrizes, 11x21 each.
    Therefore I will need 11+21 = 32 bits to control each sub-matrix with multiplexing.
    I thought of controlling the matrix with a 32-bit shift register.

    The shift registers will be driven an Arduino UNO that also provides the 5V current.

    The rows will be the cathodes, the columns will be the anodes.
    I want to scan it row by row, so that every row is on 1/11 of the time.

    Now, here's my problem: The number of leds that are lit in one row varies between 0 and 21 obviously. That means the resistance needed varies a lot, too.
    How do make this work and assure all the LED have the same brightness (and don't fry, obviously)?

    I've read about some things people used for their matrix, but I don't know which one really solves the problem:

    -MAX7219 LED driver
    -Current Driver/ Current Sink
    -Darlington Arrays

    Also, how do I deal with the odd numbers (11 and 21)? Most of the drivers come in 8 / 16 / 32 bit only.

    Thanks for helping! [​IMG]
  2. Colin Mitchell

    Colin Mitchell

    Aug 31, 2014
    One of the drive lines has only one LED on at a time or no LED. That's the line you put the resistor.
    9% of the time is not going to give very much brightness and you will need sinking transistors.
    You are much better off the have a run of 5 and a run of 6
  3. leonardw94


    Oct 18, 2015
    Thanks for your answer.
    Is there anything special about sinking transistors? I mean PNP,NPN or something like that?

    Also I read that it is possible to power the LEDs with a higher current that would usually make them burn out, but when powered only 1/100 sec, they can take it. Is that true?
  4. leonardw94


    Oct 18, 2015
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