/diy/ - Do It Yourself

>>1353709
Run each segment separately, in series, with 20mA pushed through the lot. Putting them in parallel may cause some to be brighter than others and worst case scenario can cause thermal runaway, but this likely won't happen with a collection of the same-model LEDs. If you have 2 sets of 5 with each series set being fed 20mA you should probably have a seperate current driver for each series string, which is pretty easy to do and only requires a transistor if you're running current-mirrors. In the end whatever series X parallel ratio you go for will be a function of what supply voltage you're working with. I think pic-related's equation is only correct for 5V.

>>1343605
Stack more in series man. Instead of dropping 9V across the resistor for the IRs you should put 14 or 15 in series and just drop the remaining 3-1.5V, much more efficient.

If you want to you can search ebay for parallel LED driver circuits, but 20 parallel is fairly large. Another option is just having 22 TO-220 transistors and a couple resistors set up as current mirrors, which would be more stable.