I have 12 RGB LEDs that I need to control as per the following parameters:
-The bulb is on or off
-Brightness control of each color group (meaning I don't need control over each color of each bulb)
I know this is not very difficult to do using LED Driver chips such as the TLC5940 or TLC5971, but I thought of an alternate approach in order to save on cost and hardware.
As shown in the schematic below, I have 3 PWMs (one for each color), that would allow for brightness control of each color group. There are also 12 digital signals (S1...S12) that can switch an RGB LED bulb on/off (note how S1 goes to RED_1, GREEN_1, and BLUE_1).
So all the MOSFETS are essentially used as switches, and the brightness can effectively be adjusted by an "analog" or variable source.
Would this reduce the hardware required (cost) and make the programming simpler? Are there any limitations or design considerations I should be aware of?