LED resistors?

In an array of 4 identical LEDs, where one will be constantly lit, and the other 3 will light only one at time (model railroad signal) Do I only need a resistor on the common cathode bus, or will I need 2 ?

Simply put, can a single resistor handle 1 OR 2 LEDs, and switching between them ?

Thanks, and Thanks for a great beginners class!

randofo8 months ago

You could theoretically give them all the same resistor if they are in parallel, but I've been lead to believe it is best form to give each LED it's own identical resistor.

For what you are doing (few LEDs / low power), it seems like either should be fine.