My son's fish-lava light LEDs burned out. Here is the simplified version of the circuit (some components removed for clarity):
I've spent the last few days researching LED circuits. I realize that the circuit is not an ideal configuration and I see the reason it burned out. Since I'm working with a fixed board, I was looking for a formula to calculate the resistance for the resistor on the left (between the sets of LEDs).
I found a similar question was asked a few months ago but the answer there is "don't do that". Unfortunately, that's what I'd like to do only because it seems easier to replace a few 30c LEDs and resistors each time it burns out than to create a new board. In addition, I'd really like to understand the theory even though the practical application isn't desirable.
How does one go about calculating the resistance for a single resistor protecting LEDs in a mixed series/parallel configuration?