led matrix driver

[Dr_Doggy]

i am going to copy this guy :

https://gemlit.com/howto/big_sch.jpg

but I wonder why he uses ULN2003, couldn't he take it out and wire led's to shift register and just invert data(1)?

after I copy him i wanna 30x cube can I apply the same driver technique, I read somewhere that you need a current sync(2)?

also how is a pic able to remember all the code?
30x30x30 x 8(colors) x 24(fps) * 10(second show) = 52MB

even on a 8x8x8 x 8(colors) x 24(fps) * 10(second show) = 1MB

what is a good idea for a cheap memory bank(3)?

 

[audioguru]

The LEDs are multiplexed so that only one display is lighted at a time and they look 2/3rds dimmed because each display is turned off for 2/3rds of the total time. The ULN2003 provides more output current so that the displays are brighter.

 

[simonbramble]

You might also want to try:

https://datasheets.maxim-ic.com/en/ds/MAX7219-MAX7221.pdf

This will vastly simplify the circuit and do the current limiting/driving for you

 

[Dr_Doggy]

yes thank-you, but what about when the layer of matrix is bigger, that will increase the number of max led's that need brightening when all on, but then what if only one is on, it may get too much current(?),

or is it best to stick to 12 leds per ULN2003,?

maybe there is like a digital controlled current reg?
Or maybe I could take out 74LS registers on ULN and use adjustable pulse width to control the current on matrix(?)

I really like that max ic but it just dont beat price margins.

 

[Dr_Doggy]

JUST one last question!!!!!

, I want to replace the shift register so I can use each pin directly, however I worry about meeting the current requirements, so I was thinking that I should put a buffer in there, between the pic and the LED's
this is the one I chose :
https://www.electro-tech-online.com/custompdfs/2011/08/sn74act241.pdf

will it work for me? is there a better one I should choose? (the led's ima drive is 5x5x5 rgb 4000mcd LEDS) so I need to run max 25leds at a time (per layer)

EDIT: ok, one more! can I use the uln2003 at the anode to replace the register?