i have four rgb led and thıs leds turn on together. Now i want use 3 pins of arduino instead of 12. is it work?
If you want all four RGBs to show the same colour, you can just connect their individual pins - i.e. connect all four "red" pins to one Arduino pin, all four "green" pins to another, all four "blue" pins to another, and all four ground pins to the ground. (Assuming they're common-cathode LEDs here.)
If you want them to show different colors, I suppose what you need is an analog multiplexer.
yeah i want the four rgb led show the same colour. Thank you for your attention and also i think so like this.
I should probably add that each Arduino pin can only supply limited power - driving three LEDs from one pin should still be fine but you can't just scale this to, say, 100 LEDs.
yeah i know four led's amper is big this is not good for arduino. Thank you
Four LEDs is just fine, but limit the current draw for an Arduino pin to less than 30 mA. 7 mA per LED - with a suitable resistor for each - would generally show just fine.