I ordered the LEDs from
here - they say they're 3 volt, and I just figured that they're 20 mA LEDs... I don't know anything else about them.
I don't have any transistors on hand, since I really haven't done much in electronics past simple hook ups like this using a couple resistors and a switch. I think I might have come up with a new solution though...
After wiring up an LED with a 220 ohm resistor and powering it with 5 volts, it seemed ok but very bright... I'm not sure if it was supposed to be that bright, but I only left it on for a second. This is a test LED anyway
Then I put a 560 ohm resistor before it, and that gives me a nice brightness for when the LEDs are dim.
Since my LCD has more than one 5-volt output, I am now thinking of putting that 560 ohm resistor between one of the outputs and the LEDs, and having another resistor between the second output and the LEDs. This way, I can have just 1 of the outputs on for dim LEDs, both for bright LEDs, and neither for complete off (which I really wasn't planning on, but it would be an additional feature I could use). So now all I'd need is to figure out that second resistor's resistance.
I seem to just be guessing now. I think I need to go back and read up on basic electronics some more... every time I try that formula to figure out the resistance, it doesn't turn out the way I would think it should. Thanks for the help anyway.