Senior Project LED help

Thread Starter

DancinNancy

Joined Oct 1, 2008
24
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
 

beenthere

Joined Apr 20, 2004
15,819
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.
 

Thread Starter

DancinNancy

Joined Oct 1, 2008
24
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)
 

S_lannan

Joined Jun 20, 2007
246
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.
 

beenthere

Joined Apr 20, 2004
15,819
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.
 

SgtWookie

Joined Jul 17, 2007
22,230
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.
 

Thread Starter

DancinNancy

Joined Oct 1, 2008
24
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
 
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