Senior Project LED help

Discussion in 'The Projects Forum' started by DancinNancy, Oct 1, 2008.

  1. DancinNancy

    Thread Starter Member

    Oct 1, 2008
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    Me and my friends are working on a senior project for college. I am fairly new to all of this and was wondering if anyone had any suggestions on what type of microcontroller i should use to light up 126 leds. They have to be lit up sometimes individually and sometimes in certain combinations of 2 to 30 at a time depending on the users input. Help please, thanks
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    No microcontroller can control all those LED's individually. You will be ahead to think about the requirement of the patterns and combinations of LED's and design external hardware to control current. Think of addressable latches and logic level FET's.

    Once you have the control hardware thought out, the microcontroller selection will be pretty easy. Think of the project as an elaborate interface.
     
  3. DancinNancy

    Thread Starter Member

    Oct 1, 2008
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    Do you have any recommendations on how to go about it...the combinations will be chords,scales, or notes and how they are played on a guitar. The leds will be layed out like the frets and strings of a guitar. (ex. user selects the g chord and the leds light up showing which notes are in the g chord)
    [​IMG] [​IMG]
     
  4. S_lannan

    Active Member

    Jun 20, 2007
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    You could save yourself some extreme pain and do it with a graphical LCD. I know graphical LCDs aren't the most straightforward thing to use so i would recommend finding a few demos of how to interface them to microcontrollers.
     
  5. scubasteve_911

    Senior Member

    Dec 27, 2007
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  6. beenthere

    Retired Moderator

    Apr 20, 2004
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    One way to start is to make paper diagrams of the strings and frets, and use markers to draw in each cord (one to a diagram) and the progressions. See if some patterns don't suggest themselves. That may clarify how you want to proceed.
     
  7. SgtWookie

    Expert

    Jul 17, 2007
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    Do a Google search on "Charlieplexing"

    You can control a remarkable number of LEDs via a Charlieplexed display.

    n * n-1, to be exact. So if you had a uC with 30 I/O pins, you could theoretically control 30 x 29 LED's, or 870 of them.

    You need a uC that has the capability of sourcing/sinking 25mA per I/O pin on 12 pins.

    12 x 11 = 132 LEDs.

    This is quite do-able with a low pin count uC - if you use Charlieplexing.
     
  8. hgmjr

    Moderator

    Jan 28, 2005
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  9. DancinNancy

    Thread Starter Member

    Oct 1, 2008
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    I looked into charlieplexing and multiplexing a little and i know with multiplexing i wouldn't be able to make all the right combinations. I also read that in charlieplexing you could light any single led individually but do you know if any combination is possible or are the combinations limited due to the way they are wired in
     
  10. beenthere

    Retired Moderator

    Apr 20, 2004
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    External addressable latches.
     
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