Creating an LED Matrix

I feel like this is a simple thing to do but I'm pretty new at this and sort of jumping head first into it.

I want to create an LED matrix. I know there are pre-built matrices you can pick up but I feel these are bulky and I want bigger grid than the 8x8 ones i see for sale. I've picked over the "tutorials" using max72xx and I don't know if I understand it. Is that the best/easiest way to go?

If anyone has any samples or advise it would be appreciated.

ornj,

If you want a 1 or 2 color matrix, then I would say the MAX72xx and one of the supporting libs may be the easiest way to go.

Driving the matrix directly would use a lot of pins and resistors. Going beyond 8x8 like that would be even more difficult.

If you go larger than 8x8 you may need more than 1 chip for a single color.

If you make your own matrix go with common cathode if you want to use the MAX.

A shift register (595?) is another way to go. Someone with experance with that may want to comment.

Keeping it simple, the LEDs are all 1 color. Just want more than an 8x8 if possible.

Most people would assume that you will go with a multiplexed display, that means using processor cycles to keep the display alive. The up side is that you use less hardware. However by using latched buffers you might consider driving a lot of LEDs directly. This uses more hardware but has the advantage that you can go on expanding the number until you run out of patience and never have to worry about the refresh rate because once they are on that’s it until you turn them off.
8 by 8 is relatively simple because it deals with a byte at a time but you could stack 8 X 8 tiles next to each other to give you a bigger display. The biggest I have done (by multiplexing) is 4 display of 5 X 7, that’s 120 that was using a PIC but there is no reason why you can’t do it with an Arduino.

Multiplexing seems like it may be the way to go for me. Still trying to avoid the tiles but I feel confident I can work something up with loose LEDs.

Mike,
With the MAX7219 & MAX7221 the multiplexing is handled by the chip, so the uP is not involved with it.
http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1339

hmm, I have a couple MAX7221s in my bin. not sure how to use them. sort of learning as i go.

Hi Bro,
Yes indeed it is, it’s a sort of half way house between the two techniques. The other thing about multiplexing is that as the LED is not on all the time it is not as bright. So you compensate for that by making the current higher. You can get to a state where the current will burn out the LED if the multiplexing ever stopped. Then it is better to use a chip dedicated to multiplexing as Bro said.