hi guys,
i need some advice on what i need to-do to get this project working better.
basically i followed an instructable.com design to make a 3 x 3 x 3 led cube and drive it with 12 pins from the arduino.
here is a link to the instructable on the page how to connect it together.
now i know what the problem is, but i cannot seem to find a solution to it, im using the software from this instructable to drive the cube as well and it works really well, lighting singular led's or one random led's in quick sucsession works fine, there nice and bright, however multiplexing a lot of them to form patterns causes them to become very dim, so dim in fact that in normal day light its pretty much impossible to see them.
I know its the fact that the arduino is providing power for the led's and singularly it gives enough power to light an led brightly, however when it has to light multiple leds the current is split so they light a lot dimmer, my problem is i cannot figure out how to get the arduino to provide enough current to light them bright.
i tried connecting a transistor(NPN) up to one of the "columns", the collector at 5v from the arduino itself not a digitalpin, the emitter to the led column and to ground via a resistor and the base to the pin of the arduino via a resistor , now in this config the leds light no brigher than normal, is this due to the 5v rail of the arduino being shared with the output pins ?? if so if i provide 5 volts from a separate source will it get brighter (i don't have one to hand at present)
if i connect the led column to the collector side of the transistor it does light brighter but due to the way the cube is being multiplexed this also has the undesired side effect of lighting leds at the wrong time (i.e. when its scanning the three layers of leds.
any advice would really be appreciated as its the only thing stopping me from making a final build of the cube with its own arduino chip and case.
thanks
kris
OK i played around some more and figured out what i was doing wrong 
my first problem was my resistor and transistor choice was limiting more current than i expected it to be, ive removed the resistors from the nine input lines and only left the three on the transistors bases and now its lighting a LOT brighter, whilst i know its not ideal to have no resistance on the arduino pins with such low ampage its fine for now, when i box it off with a fixed powersupply i will do some resistor tinkering to protect the arduino chip.