need help  LED matrix

Forum 2005-2010 (read only) Hardware Interfacing
1

hi everybody I'm an Artist totaly new with arduino,for an artistic project i made a 8x8 led matrix(40cmx40cm) using white 20 mA 3 volt 5mm led's
i wish to connect it to arduino 2009 directly not using shift registers or transistors.
my problem is how to calculate resistors value for cathods or anodes?!
i plan to play just a tetris game demo(non interactive) on this matrix but programing for me is a night mare is there any aplication converting a simple animation 8x8 pixel to arduino language? please help me with your comments a suggestions.tanx from Italy :slight_smile:

2

Hi,

8x8 led matrix = 64 points. even the arduino mega has "only" 54 digital I/O's so you cant use that board without some external logic IC's, sorry...

3

thanks hakoni ,but it seems 8x8 is possible in this schematic Arduino Playground - DirectDriveLEDMatrix
do you have any idea?

4

thanks hakoni ,but it seems 8x8 is possible in this schematic

Indeed. There's a way to do it "Matrix Style", but, still being a pretty big newbie myself, I haven't the slightest clue how it works :P. But that is possible :).

5

If I apply a 9v comon alkaline as arduino power source it make anny effects on output pins current and voltage? or it's an independent value? I mean if the resistors in the matrix being calculated adapting with 5 volts usb power supply stiil can be ok for 9v alkalaine or must be recalculated?! :cry:

6

That is a BAD circuit and it will damage your arduino.

Yes you need to calculate the resistors for a new voltage.
See:-
http://www.thebox.myzen.co.uk/Tutorial/LEDs.html

You do need to use external circuits to drive a matrix as there is not enough power in the output pin of the arduino to power the matrix safely.

7

thank so much MIKE I have already seen your pages but it's kinda too much for me! I'am a fashion designer and completely new with these issues, i need this matrix to lay in a dress and making effects like a low res. screen(every LED as a pixel) therefore lookin for minimizing the circut and power supply to make it wearable,may you suggest any trustable schematic? and is it risky the way I soldered LED's 8cm distance from eachother?

8

and is it risky the way I soldered LED's 8cm distance from eachother?

No that is fine.

may you suggest any trustable schematic?

How about using these chips:-
http://www.arduino.cc/playground/Main/LEDMatrix
They are expensive but fewer components are used and the multiplexing looks after itself.