this is the same post I wrote in the italian section and I hope to gain more helpful answers....
Are there other good chips, as max7219, to drive led matrices? Because the max(and the other sub-version) are much expensive(ca 10? and I need 24 of them...) and I cannot find them anywhere...
What I would to build is a 3D RGB LED matrix so I guessed to use 3 max for each row or column (one ic for each colour and for this reason 24 chips)...
I found out some other cheaper and weaker ic but, in fact, were too much weak to manage 512*3 leds....
You cant easily multiplex RGB leds as they all share a cathode.
Your best bet is the 595 I think. Its simple enough and cheap enough to make the extra complexity worth while.
The best way to do a 3d RGB box with them is to have one 595 per 8x8 grid sinking the cathode current and three (one per colour) sourcing current.
For a 8x8x8 box thats 32 595's for a grand total of $13.44 USD at Futurlec.
Depending on your application, thats a lot of LEDs to multiplex.
You may want to use two ATmega chips, one dedicated to multiplexing.
You cant easily multiplex RGB leds as they all share a cathode.
Your best bet is the 595 I think. Its simple enough and cheap enough to make the extra complexity worth while.
The best way to do a 3d RGB box with them is to have one 595 per 8x8 grid sinking the cathode current and three (one per colour) sourcing current.
For a 8x8x8 box thats 32 595's for a grand total of $13.44 USD at Futurlec.
Depending on your application, thats a lot of LEDs to multiplex.
You may want to use two ATmega chips, one dedicated to multiplexing.
ok
thanks!
but...in tehory I need 48 ICs, beacuse I can use two of them for a single 2d matrix, so there are 16 for the entire 8x8x8 matrix for the 3 different colors (823)...right?
I still think the 7219 might be a good option. It's about 3.77 EUR (from 25 pieces up) at a site I found: www.tme.eu
And you need next to nothing for the 7219, easier to fit, just one resistor needed, etc.
(This is not an advertisement, I bought twice from them and it's fast and mostly cheap
It only takes 4 chips. Each output can drive 15-120ma, since it can put out 16v you can drive LEDs needing higher voltage. I highly recommend designing and making a PC board for this. It's a hell of a lot of wires.
This is not a matrix as each LED can be full on depending on the current setting.
I wish they'd supply this with a header I could hook the LEDs to. I'll have to see about doing that myself.
I think you can do dimming if you use something like a digital pot or transistor circuit on the current set pin and control it from the microcontroller but I'm not sure.
