Here is some additional info about the dimming circuits that I installed in my SB reef lights
I used the circuit from @Ryan115 from this post reef-pi :: An opensource reef tank controller based on Raspberry Pi.
Here is a picture of my circuit. My perfboard doesn't have any traces on it so all the wiring was point to point on the backside (connections on back of board are in red below). The advantage of using the specific connectors listed below is that you don't have to cut any wires on the SB reef light black box so it is trivial to back to stock (if you have a different black box, I recommend opening your light to find out what type of connectors you will need before ordering!)
Parts list:
2 NPN transistors (I used 2N2222A transistors)
2 LM7810 voltage regulators
2 3-pin JST XH (2.5mm pitch) male connectors
1 2-pin JST SM (2.5mm pitch) male connector
2 1k ohm resistors
2 10k ohm resistors
1 solderable perfboard
A three wire input connector of your choice to connect PWM from the PCA9685 on Reef-pi to the dimming circuit. I used Ethernet cable and JST connectors but other people use headphone cable and jacks
I made a video to help explain more about the circuit, wiring, and functionality
Very nice. Its similar to the recommended kessil circuit, except it uses lm7810 instead of lm2596 to generate 10V DC current. I wonder if you need two of them,
Thank you for sharing, this will be helpful to others