Wednesday, June 26, 2013

How many LEDs is too many?

The heat sink layout
With the tank underway (or at least under deposit), it's time to start assembling all the hardware I'll need to set it up as soon as it arrives. Since there is no light fixture on the market that will do everything I'd like, I'll have to build my own custom fixtures, if I want to:
  • Have sufficient photosynthetically usable radiation (PUR) to grow corals/clams anywhere in the 40" tall tank
  • Include multiple channels of control to fine-tune the light color for optimal coral growth, attractive coral and fish appearance, color-accurate photography and color-changing sunrise/sunset simulation
  • Provide illumination from different angles to further simulate time of day (e.g., from one side of the tank in the morning, from all angles during the day, and from the other side of the tank in the evening)
  • Dim all the way down to 0% for appropriate levels of moonlight illumination
  • Include an independently-addressable red channel for night viewing
  • Include powerful illumination in the violet and indigo wavelengths for optimal fluorescence
With that in mind, I've mocked up some fixtures that should do all of this and more.

The plan calls for two 48" fixtures suspended lengthwise over the center of the 72" tank, with the fixture closer to the front being tilted towards the back of the tank, and two 24" fixtures suspended perpendicular to the tank on opposing ends, tilted in towards the center. The fixtures will each include 8 channels of LEDs, with the following colors / LED emitters:
The emitter layout(s)
  1. 5000k Neutral white (Luxeon Rebel ES)
  2. 2700k Warm white (Luxeon Rebel ES)
  3. 400-405nm Violet (Exotic "Hyper Violet")
  4. 415-420nm Indigo (SemiLED "True Violet")
  5. 440-450nm Royal Blue (Luxeon Rebel ES & Luxeon M)
  6. 470-480nm Cool Blue (Luxeon Rebel ES)
  7. 495-505nm Cyan (Luxeon Rebel ES)
  8. 660-670nm Deep Red (Luxeon Rebel ES)
Each of these eight channels will be separately addressable on the left fixture, the center pair of fixtures, and the right fixture, for a total of 24 channels. The good folks at Reef Angel are working up a pair of custom dimming expansions with 16 pulse width modulation (PWM) channels each to handle this number of channels.

All told, there will be 308 three-watt emitters and 28 twelve-watt emitters suspended over the tank. All of the Luxeon Rebel ES emitters will be distributed across a variety of custom 3-up "Tristar" metal-core printed circuit boards (MCPCBs) available from Steve's LEDs, and all of the channels will be distributed over the tank as evenly as possible, either in tight clusters or evenly-spaced rows (as illustrated above). The twelve-watt Luxeon M emitters on the royal blue channel will include LEDiL Minnie 63° secondary optics. Whether the three-watt Exotic and SemiLED violet and indigo emitters will include secondary optics is still up in the air, as is whether or not I'll be able to find optics that work with Steve's LEDs' custom Tristar MCPCBs.

Three Mean Well SE-600-48 power supplies and forty-two Mean Well LDD constant-current drivers (as soon as PowerGate LLC gets them back in stock) will power these emitters, and two 48" and two 24" MakersLED heat sinks will dissipate their heat.

The power distribution
If all the emitters were run at their full power, there would be 1200 watts of LED light pouring into the tank, with the following distribution:
  • 252.0W 5000K
  • 115.5W 2700K
  • 70.6W Violet
  • 100.8W Indigo
  • 404.6W Royal Blue
  • 138.6W Cool Blue
  • 81.2W Cyan
  • 39.2W Deep Red
Of course, I'll need to learn how to solder, first. And then how to program a Reef Angel controller to drive all 24 of these channels to simulate sunrise, sunset, and the lunar cycle.