30Watt LED Driver Transformer driving 10 3Watt RGB Common Cathode LEDs

Thanks in advance to anyone who might help or assist me in this project and to everyone who make this forum possible. I've made some RGB lamps before but I've only used small LEDs directly powered by the arduino board. Now I wish to move up to the High Power Star LEDS.

I searched but couldn't find a schematic for driving 10 3Watt RGB Common Cathode LEDs with a 30Watt 12V 2.5A Driver. Here are the links to the items I have.


i wish to drive 3 channels of 10 leds. Having all the RED hooked to a channel, BLUE to a channel and RED to a channel. I would like to use the PWM modulation on the Arduino to vary the brightness of these three channels to make a large mood lamp.

i found this layout that seems close and i have a few LM317s around but i want to use more LEDs and didn't understand the language.

from controllare LED RGB 350mA 3watt: resistenze o driver? - Generale - Arduino Forum

Any help would be appreciated. And i'm cool with using eight or nine LEDs and/or ordering some other transistors. Thanks!

In that circuit the uln2003 will not handle that amount of current before overheating.
I know its specified as 500ma per channel, but note that it refers to only One Channel in use at any One time, not 2 or 3 etc on togther at those load.

There are Led Drivers made for that job, lots on the market, and if you want to drive a lot more leds together you really need something up to the job.

Meanwell drivers are very popular and you can find out lots more about leds from the Marine fishkeeping groups who make there own led arrays.

12volt supply, 4-pin LEDs, and LM317s. Bad combination.

You will be wasting >10watt in heat in the LM317s to drive a single 3watt RGB LED.

Get 6-pin RGB LEDs on a star base, so you can connect three green LEDs in series, three blue LEDs in series, and three red LEDs in series.
Then the volt drop across three LEDs (three stars) is ~10volt (red = ~7.5volt)
Then you can replace the LM317s for three resistors.
Absolute minimum R for green/blue string = ~2.7ohm/1watt
Absolute minimum R for red string = ~10ohm/2watt.
The ULN will be HOT, and can only handle three strings.
Maybe wise to double-up channels (two inputs together, two outputs together).

If you want to avoid the heat, look for switching CC LED drivers.

P.S. The blue LEDs on these star bases are very sensitive to static discharges.
I lost several of them once (going dim) by just soldering wires to them in a static safe situation.
Unplug the hot iron just before soldering wires to the LEDs.

Thanks for the replys guys. Lots of good info on the Aquarium forum and I'll order some six pin LEDs tonight. I'm sure i'll have more questions in the future but you two got me on the right track for sure. Thanks Again.