I read Hoppy's guide to LEDs a few times today, and I've almost got my head around it! Seriously though, that's some good work
Anyway, this might be a bit backwards, but I'm trying to ascertain whether or not, theoretically, my BiOrb Intellegent LED light fitting is going to work for me, or whether I might need to go a DIY route with my BiOrb Life 16 (16" x 24" x 12"). The Intelligent Light boasts 3 "High Output" LEDs at 6500K. That's about as much information as I could find. They run off a 12V power transformer, if that helps...
It's going to be a low tech, low light (15 to 30 PAR) planted tank, with Java Moss and Jave Fern, that kind of thing.
Firstly, I'm looking at the spread of the light intensity portion to see how many rows of LED's I theoretically need. My calcs suggest that at an "H" of 21", 1 led (or a tightly packed group) is enough to light an 18" circle - more than enough to cover the base of this tank. The iLight has 3 LEDs, in the centre of the tank, so that's fine.
I'm now trying to solve for the "lumens per LED" to see if they will likely give the right intensity. Using the spreadsheet, H is 21", LED spacing is 2" and I've used 1.5 rows. Not sure if that is correct, but the LEDs are spaced in a triangle, 2 x 1" apart and 1 at the apex, 1.5" from the others. Solving for PAR = 25, we get 72 Lumens per LED.
So, theoretically, the BiOrb LEDs need between 43 and 85 Lumens each to work for me. Have I got that right? Or are my assumptions all wrong? I feel like the Intellegent Light should work, given that many of the LEDs I've looked at are rated around 100 Lumens at 350mA using 1W of power. Am I really wide of the mark here? I feel like I may have made some sense!