In a nutshell:
I want to build a dimmable two channel LED fixture using PWM to alternate the pulses of the individual channels in addition to dimming them. I would also like to have the PWM signal dimming created as a response to a 0 to 10 output of a Neptune Apex aquarium controller. That is where the Arduino may be a good match for the project. I added background and detail to describe why I want this functionality for those that are curios but I hope that it is not necessary to read.
Please help me in this planning phase.
Background and detail:
I want to build a custom LED fixture for a one sided, horizontal, dump style Algal Turf Scrubber. I will need to cover a 45 inch by 6 inch area and be very close to the algae tray. I believe that I need about 60 watts of LED light for my screen.
What I can find out from charts, papers and current best practices, the following is my idea of a dream fixture.
After playing with the layout on computer aided design, I think that I could employ 7 lamps using custom ordered 10watt COB chipsets, each with two channels that are strung together. An output ratio of 8 to 1, red to hyper-violet, that is 660nm (red) and 420nm (hyper-violet) respectively, yields the best algal growth in scrubbers. These lamps would have standard reflectors. Added center pyramid shaped pre-reflectors can redirect the light that is just under the chip which could be too intense and create hot spots.
Additionally, the variability of PWM dimming can be a very valuable feature in both quick starting the scrubber and for obtaining maximum growth output. In short high frequency flashing along with its accompanying dark periods, allows algal cells to process more total light than if it were constant. Being able to separate the timing of the flashes of the different colors, one after the other, allows even better processing of more total light.
If I had two tunable channels, I could use a low amount of light during the startup phase and increase the output as the screen becomes more mature. At that point, I could farther tune the ratio of light spectrum to find the best blend to maximize the harvesting.
The dimming feature could be used to bring the LED’s online in such a way that the photosynthesis in the algae compensates for that of the corals in the display tank at night. This would help minimize, if not regulate pH swings in the water column.
Finally, I want to control the fixture with a Neptune Apex Aquarium controller. Its output for this type of lighting is 0 to 10 volts so I think that I will need something like an Arduino mini-controller to read the analog output and create the PWM signal accordingly.
Now, this may sound like a lot of feature overkill for a simple algae scrubber but if I can implement this, it would be a prototypical project that might inform my reef tank lighting system build with more channels and focusing where intensity, spectral balance and quality is more critical. While the spectral blend is quite different for corals, the flashing is reported to be even more important for them to reduce the likelihood of bleaching.
All that being said, how can I do what is in the first two lines of the nutshell?