The important thing to remember when making more than 1 channel - you cannot tie those GNDs together; they are NOT 0V and are NOT equal to each other. Call one GND_A and one GND_B. Or Bob and Greg. Each FL5150 must be separate. Which then means your microcontroller needs to be totally isolated. Which is where a digital potentiometer becomes very handy.

@ptr727 My design above did work. And it was 2 channel. But it did flicker a little. I'm going to try a digital potentiometer.

The important thing to remember when making more than 1 channel - you cannot tie those GNDs together; they are NOT 0V and are NOT equal to each other. Call one GND_A and one GND_B. Or Bob and Greg. Each FL5150 must be separate. Which then means your microcontroller needs to be totally isolated. Which is where a digital potentiometer becomes very handy.

If anyone else ends up here like I did.

To drive the DIM Control pin without pulling from Vdd, try this.

This will keep the micro isolated. This assumes that you use a dual optoisolator, and that the CTR is the same. To ensure they ARE equally matched, you can buy the more expensive IL300 or LOC110 - built especially for this purpose.

Also do note: if you are going to make a DUAL dimmer, then do NOT connect the 'GND' between dimmer A and dimmer B. They must be separate.