Sorry about my lack of forum etiquitte; I am bit of a newbie.
Based on CrossRoads' design I think I will connect 2 groups of 3 LEDs to 1 transistor collector pin for a total of 6 LEDs controlled by 1 arduino pin. Each group of 3 LEDs will need a resistor, so R = (9V - 3*(1.85V)) / (.01A) = 345 ohms (or the next highest resistance available if 345 isnt common). Is this correct or is there a voltage drop accross the transistor that I need to account for as CrossRoads did for the resistor between the arduino and the transistor?
I would post a circuit diagram but am currently using my phone for today as I do not have internet access on my laptop. The design I described is the same as CrossRoads' but with 6 LEDs instead of five for symmetry and so that the two resistors can be the same resistance. Any answers to my original questions would still be appreciated as well! Also, how long could a 9V power 50+ LEDs? Would I kill the battery within the hour (in which case I will look into buying some rechargeable batteries) or within a full day of lighting all of the LEDs or can the battery life even be guessed given the current draw of the LEDs?