led - Arduino and 5A 12Volt driver

I want to drive a 5 metre strip of 300 5050 SMD LEDs. It comes with a 5A power supply but I don't know what the rating are for these LEDs.

The thing is I want to be able to change the voltage using the Arduino from 1v <> 12volt for dimming effect.

What kind of driver should I build for that? And would anybody have a schematic or something that's already available on eBay or similar :)

I am bit of a newb in the prototyping area-but have good skills; and all I need is some guidance in the correct way.

Thanks!

---

EDIT Thanks for the great answers- I did find this though.

http://cgi.ebay.co.uk/LED-Bulb-Dimmer-Adjustable-Brightness-Controller-DC-12V-/250828609755?pt=UK_Light_Fittings&hash=item3a668cd8db#ht_1869wt_1140

Guess whats going to be taken apart before it even turned on.. Is this a PWN dimmer? or just a simple Voltage adjuster?

Is it possible to control/replace or build on top of the analogue potentiometer using the arduino? Like for if i turn it on it fades to 100% over a period of 1second for example..

Answer

I would wire up a Power N-FET, that could handle up to the full 5A and 12V across it, wire it in series between the LEDs' common-cathode and the GND, and pulse-width-modulate its base using the Arduino to control the brightness. That will give you the illusion of dimming, as brightness is a function of the average current experienced by the LED, and the physiology of the human eye will take care of the rest :).