I have recently started building my first 5*5*5 LED cube and so far, I have finished soldering the LEDs. Now I am trying to connect it to my Arduino Mega but after I read about using transistors to connect it, I am worried that connecting directly to its pins might harm the arudino. I realized that currents flowing out from the layers add up so given my LEDs take 20 mA each, it will for sure exceed the individual pin's 40 mA limit. Therefore, I would be really grateful if anyone could help me connecting it together. I have 25 anode columns powered thru resistors from my arudino but without any transistors.(I read this should be okay). This works even though the 5 LEDs in each column should consume 5*20 mA, the entire column shines, maybe less but this works. Is this OK?
On the other hand, it seems almost certain that I cannot connect the 5 cathode wires, one from each layer, directly to arudino pins and define them as GND bcs the current sum is just too much. I bought some UNL 2803 to fix this, am I right about this? Also, could anyone help me connecting the transistor array as I am not really sure. Collector to the layers, emitter to arudino?
Is this all I need to be able to start programming?
Thanks so much! Mike