Question about MOSFET with LED

I can’t think of a way to do this so here I am.

I want to power (4) LEDs from (1) driver but would like to independently control the dimming or at least the on/off.

"independently control the dimming or at least the on/off" Of the individual 4? Or of the group?

individualy.

To control individually you will need an individual control line for each LED, you don't need a transistor unless the LED's require more current (>40ma) than the Arduino can supply to each pin. If they do, then you would need three transistors to control three LED's.

There are IC's where a single chip (TLC5940?) that could give you this functionality for up to 8 LEDS at the cost of the four spi pins...

Each led is 5w and the driver I had in mind has no dim port. (PWM to DIM). How would you wire 3 transistors from one driver and be able to have one on, one off and one dimming?

mcreefer: Each led is 5w and the driver I had in mind has no dim port. (PWM to DIM). How would you wire 3 transistors from one driver and be able to have one on, one off and one dimming?

Use the driver as the + and then connect each led in parallel with a transistor in series for each led to connect to ground. The transistor gates are controlled by the Arduino. Depending upon the driver this might work Basically this design assumes the driver is a constant current source...

They are constant current. I would need to find an expansion for more PWM pins. The total amount would be (20) leds and (4) drivers so (5) leds to each driver. So I would need atleast 20 PWM pins right? Any ideas on how to tackle that issue?

Be aware that some constant current drivers that are spec’d at a certain LED wattage (example) will not like having their outputs shut off or otherwise interrupted.

You should provide a link to the driver you have in mind.

I plan on using meanwells. http://www.trcelectronics.com/Meanwell/power-supply-led.shtml But have not picked one out yet.