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Charlieplexing using the Arduino Uno?

Discussion in 'Microcontrollers, Programming and IoT' started by AndreeU17, Nov 25, 2014.

  1. AndreeU17

    AndreeU17

    42
    1
    Apr 23, 2014
    Hello everyone, I was given a project by my work (intership), the project consisted of me creating an Array of LEDs that portrayed a title (in this case, school Title), that will blink in a sequence at a very fast pace. So my school name is pretty long (21 characters), so i design or actually sketch a simply drawing of how the LED will represent the title, i manage to get it to 205 LEDs (big project).

    Anyways, originally i wanted to use the Arduino Uno since i found it a lot easier since i can do all the coding (C) and simply uploaded. However, i realize that the Uno does not have enough output to present the LED's HIGH's and LOW's. I read about charlieplexing and was intrigued. However, the formula given (n^2 - n) made me realize that i will not be able to get no were near 205 LEDs with a single arduino. So what do you guys think? what perspective can you guys give me or hints! I'm a student so my knowledge isn't extremely amazing but i do know my basic well, etc. Also would it be best of if i just use the Atmel AVR chip that the Arduino Uno use instead of using the Arduino Uno?
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,186
    2,692
    Jan 21, 2010
    Look at multiplexing rather than charlieplexing and also look at 75HC595's.

    Given that this is a test, I won't be providing a lot more information.
     
  3. BobK

    BobK

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    1,654
    Jan 5, 2010
    Can you refine your description, because it does not sound to me like you need to control the LEDs individually.

    Bob
     
  4. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,266
    Nov 28, 2011
    I assumed he wants to build a scrolling message display with a grid of LEDs. But reading it again, I really don't know what he means.
     
  5. Frenoy Osburn

    Frenoy Osburn

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    24
    Nov 20, 2014
    I do realize you mentioned that you need to blink the title, but is scrolling the name an option?

    It would also help us to know how many characters the title consists of. That would enable us to look at how many rows/columns of LEDs we would need.
     
  6. BobK

    BobK

    7,624
    1,654
    Jan 5, 2010
    The OP said 21 characters, and he laid out the design and came up with 205 LEDs. This says to me that he is making up the lines of each character with LEDs.

    He said he wanted it to blink in sequence, whatever that means, perhaps on letter at a time blinking off?

    Need more info.

    Bob
     
  7. Frenoy Osburn

    Frenoy Osburn

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    24
    Nov 20, 2014
    Oh sorry. My bad.

    How about digital decoders which would reduce the number of pins needed to drive the LEDs?
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,186
    2,692
    Jan 21, 2010
    Did you do what was suggested in post #2?

     
  9. Frenoy Osburn

    Frenoy Osburn

    64
    24
    Nov 20, 2014
    Well the 75HC595 is a shift register. It may seem a bit complex to understand for someone who is just starting out. A decoder or demux is usually easier to understand and code for. Consider the 74HC154 which is a 4:16 demux. You could control 16LEDs with just 4 lines. You do get much bigger demuxs too.
     
  10. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,186
    2,692
    Jan 21, 2010
    The key word is "seem". If you google it you'll find more information and examples than you can poke a stick at.

    You can control 1000 leds from 3 pins if you want to. It's also easily expandable in a way that decoders and demultiplexers aren't.
     
  11. Frenoy Osburn

    Frenoy Osburn

    64
    24
    Nov 20, 2014
    Ok I withdraw my suggestions. Let the OP decide what seems best. I would have considered demultiplexers before moving to shift registers.
     
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