microprocessor controlled LED spotlight

[beep]

Hi every one,

I'm renovating my bathroom and put up some powerLED spot(down)lights.
I like to have them controlled by a microprocessor so i can use remote controller, nice fadeing etc..
I got good experience with arduino. So that my candidate.
Every spot is setup with 3 * Z-LED P4 - natural white. I really like this LED not to blue(cold) nor yellow(warm).
Each LED have ratings 350mA 3.2V 1.2W and in the setup each spot have 350mA 9.6V 3.36W. I have a heatsink attached so i can go up little more.

I found that ST L200 regulator is more or less made for this.
Its a current and a voltage regulator. 2A, 2.85V-36V
The Current Limit Sense Voltage is 0.45 so 1 ohm will regulate the current to 450mA. and that should be ok.

I like to use voltage regulator part to control the dimming.

What i really need help with, is to use one of the PWM pin from arduino to control L200 voltage. MIN PWM will be 5.5V and MAX PWM will be 9.6V

Vo is calculated as Vo = Vref (1+ (R2/R1)). Vref is ~2,77

Any one have used PWM to control voltage regulator?
Here is the L200 PDF Datasheet **broken link removed**

Many thanks,
::Beppe

 

[beep]

Didn't found any PWM potentiometer which is what a need.
Did found a digital potentiometer controlled by SPI AD5206 and Arduino gladly supports that...

Is this how i should calculate the voltage range.
Vout(max) = 9.8
Vout(min) = 5.5
AS per the Datasheet. Vout = Vref * ((R2 / R1) +1)
Or
Vout = Vref * ((R1 + R2) / R1)

To get Vout(max).
R1 = 1k
R2 = R1 (( Vout / Vref) - 1 ))
R2 = 1000 (( 9.8 / 2.77) -1 )) ~ 2538

To get Vout(min).
R2 = 1000 (( 5.4 / 2.77) -1 )) ~ 986
If R2 = 1000, Vout(min) = 2.77 * ((1000 + 1000) / 1000) = 5.4

To get the span 5.4 - 9.8 V with a 10K pot i have to introduce R3 witch is parallel with P1.
When P1 is 0 ohm only 1K by R2 and Vout is 5.4V

When P1 is 10K it should really be 1538 (2538 - R2) ohms
R3 = 1/1538 - 1/10000 ~ 1/0.00055019
R3 = 1800
Vout(max) 9.77

Am i right here?

Regards,
::Beppe