Arduino Uno LED Cube (Help needed)

So I'm going to be making an LED cube (5x5x5) and I was wondering if it's at all possible to have it ran directly by the Uno without any 74HC238 3-8 line decoders (what I've seen a lot of through research). Can this be done?

Thanks for any help/advice you can provide!

Sure. Use 4 daisychained TPIC6B595 shift registers to sink current from 25 common cathode columns, use 5 Arduino pins to pull Gate low on Logic Level, Low Rds, P-channel MOSFETs to provide current to common anode layers. Or use balance of final shift register pins to pull the gates low.

Thanks for the reply.

So is it a must to have the shift registers, or can it be done solely by using more pins from the arduino?

Hi drypulse,

An Uno does not have enough pins for a 5x5x5 cube. 30 pins would be needed. A Mega would have enough pins, but even then there is the problem of current. To make the cube a little bright, at least some transistors would be needed. Even then, it would not be very bright. This is why extra chips can help. They increase the number of available pins, and the total current that can be supplied to the cube.

Paul

Well, if you had a '1284P based board with 32 IO pins, and you buffered the IO so that the current limit of the ports and the Vcc pins was not exceeded (because 25 LEDs on at 20mA each is 500mA and exceeds the 200mA limit of a Vcc pin), then you could do it without shift registers. Or a '2560 based board, which would have the same problem of too much current thru a port unless you were careful to spread them out. Either way, you need to control a driver to switch the 500mA current for each layer.

ok, thanks for all the info. I'll grad some extra stuff then and get this thing made.