Dimming an 18v led strip

How would I use my Arduino Uno to dim an 18 volt led strip?

Thanks, JTwhizzkid

Does the strip have built-in current limiting resistors like a 12V strip?

If so, use an N-channel power MOSFET with a logic-level gate, such as IRL520 or Stp36nf06l. Connect the MOSFET's source to ground, the drain to the -ve of the led strip and the gate to a pwm arduino pin with a ~200R resistor. A 10K from the Arduino pin to ground will prevent the strip flickering and the MOSFET overheating while the Arduino is booting.

Paul

I like AOI514 and AOI510 from Digikey.com for that. Lower Rds, will run cooler, and lower cost.
http://www.digikey.com/product-search/en?keywords=aoi510

Here's 32 on a board I offer with 32 of them for driving lots of high current strips.

https://www.google.nl/search?q=arduino+mosfet&safe=off

But where did you get a 18V led strip? It's fairly uncommon...