I'm still fairly new to electronics, but what about if you connected all the grounds of the leds (before connecting to main ground), then placing a resistor from all the grounds of the leds to the ground of the supply (of course calculating the value needed for all the leds)?
But then again, I'm assuming that same value could be too little for just driving one led at a time?
I would experiment, but I <3 my LEDs! Cheesy Questions save me money, generally.
Any help understanding the concept, and how hard it would fail would be appreciated.
Again, the problem with using a single resistor is, unless there is going to be a set amount of LEDs on at any given time, the resistance you will need varies.
For example, lets say you have a 2v, 20mA LED, and youre driving it with 5v. If you have one LED on, you need a 150ohm resistor. however, if you turn two LEDs on, and run them in parallel, with one resistor, you now need a 75ohm resistor. Turn three on and you need 50 ohms. Its possible to use a single resistor, but you will notice a difference in brightness as you light up more or less LEDs