I always see an rgb led ran with 3 resistors, for example a 20ma led on 5v power uses 150ohm's for red due to it's lower voltage but only 100ohms for green and blue. I am running 6 shift registers off of a microcontroller via spi. I have 16 common anode LED's. all of the anode's on the led's share the same source. my question is could I potentially limit the current going to all the anode's and then only have the red cathode's use an additional resistor?
g on led no resistance- 1-|--------|-16 -vcc b on led no resistance- 2-| |-15 -50 ohm resistor to R on (rgbled) 50 ohm resistor to R on (rgbled)- 3-| 74 |-14 -serial in from MCU or prev. register g on led no resistance- 4-| HC |-13 -NA b on led no resistance- 5-| 595 |-12 -latch to mcu & next register 50 ohm resistor to R on (rgbled)- 6-| |-11 -MCU clock and clock on next register g on led no resistance- 7-| |-10 -Master to 5v high for inactive gnd- 8-|________|-9 -to pin 14 on next register _____________________ |____________________|_R____ 50 ohm resistor to pin 15 |____________________|_+____ shared 5v with 100 ohm's resistance |______RGB LED_______|_G____ pin 1 no resistance |____________________|_B____ pin 2 no resistance |____________________|