4x6 matrix array help

Other Hardware LEDs and Multiplexing
1

I built this 4x6 matrix/array found here:
http://www.instructables.com/id/Easy-4x6-LED-Matrix-Arduino/

It works fine, but I can't figure out how to do what I want it to do. I want it to do a random twinkling effect, where a random number of LEDs come on at any given time, not just come on but fade in and out. The idea is directly from this:
http://www.nerdkits.com/videos/ledheart/

The instructables project's random code only lets one LED come on at a time, and it comes on then goes off, doesn't fade in and out like I want.

I can't use the code from the heart project because not only is it in C, but it has 1 row and 20 columns as opposed to 4 rows and 6 columns on the instructables project. I just want to do the light effect, don't want the LCD screen on the heart.

I did find this which the person borrowed the code from the heart project to do the twinkling effect, but he doesn't have it set up like an array, he's got individual LEDs going to the arduino pins:
http://generalio.blogspot.com/2009/02/arduino-powered-led-roses.html

My ultimate goal is to do the twinkling effect like in the heart project, add a pot to control the speed (which I have managed to do with the 4x6 array code), and add a button so I can switch between different patterns (which I can probably figure out). I just can't figure out how to do the twinkling and add randomness to it. I'm looking for any help or suggestions, or if there is a better project than the instructables one which will let me do this. Thank you.

2

You can't really fade a matrix driven like this, see this thread:-
http://arduino.cc/forum/index.php/topic,66941.0.html

if there is a better project than the instructables one which will let me do this.

Any project is better than an instructables one, they are almost always very poor projects written by people who don't know what they are doing.
That circuit is appalling and was produced by a complete idiot. That is not the way to do a matrix, nor drive it with transistors. Words fail me on how stupid that circuit is.

3

Is there another way to do this other than using an array? I want to take 24 (actually 23) LEDs and have them fade in then out then off randomly, meaning a random number of LEDs on at a time, and random LEDs that fade in then out then off (no particular pattern). I am using a duemilanove.

If you saw that led heart video, thats what I want to accomplish. That only has 20 LEDs and I need a few more, plus it is programmed in C. I played around with that but could not figure out how to add the extras and the potentiometer to change the speed, so I switched to arduino hoping it would be easier.

4

Use two TLC5940 chips, that gives you good fading control.

http://www.arduino.cc/playground/Learning/TLC5940