Help w/ 12v LED

i have some common Cathode RGB LED strands that I want to power with my Arduino. I need to convert the 5v of the PWM PINS to some 9-12v source for the strands. I'm pretty sure that they draw 20 mA but I cannot say for sure. I have powered them with everything from 9v to 16v with my Wall Wart with no trouble. So I assume that as long as I can use the Wall Wart with some kind of Transistor combination that the varying mA's will be no issue. I have a mosfet P Channel and feel like they might be the answer. TIP120's have been used to no avail.

I am using my Arduino with MIDI control through Ableton Live's MAXUINO patch. So I will post a link to my Instructable using simple LED's that function off of the 5v PWM PINs on my Arduino. I want to do the same with 9-12v Common Cathode RGB LED strands.

Any advice how I could gain the same control over LED's that require more power? It works just fine with the small LED's... Now i need the same control over LED strands that use 9-12v...



Have a look in Playground - left side on top gray panel.

See this thread for how to wire up your FET