Hey bobert, I found a calculator on the web that will give an approximate conversion of millicandellas to lumens.
LED LUMEN CALCULATOR
If each of your LED's is identical and produces 3000 millicandellas, and the lights are 180 degrees from the plant, then the plant is receiving about 18.85 lumens per/light using this formula.
At 18.85 lumens per light and 50,000 lumens being the target for optimum growth, then 50K/18.85=2652.5198938992042440318302387268
Or rounded up = 2,653 lights.
With a ratio of 92% red to 8% blue, you would want to have 212 blue lights spaced at one blue after each 12 reds, and you would use 2,441 red lights.
Using the power ratio that you've shown in your first post in the thread, I get 32 cents per/year per/light.
That would be a cost of 850 Dollars a year US.
850/12=71 dollars per/month US per/sq. foot.
This makes me wonder if the lumen calculations are accurate in this formula. That seems like a lot of money per/month for 50K lumens.
Because of what you've said about the distance to the plant being less, I'm wondering if perhaps only say, 10K lumens are needed using LED's. Perhaps even less. If so, then the costs would also drop proportionally.
The common formula for lumens uses a 12 inch distance from the measuring point. With LED's, I'm guessing that 2 to 3 inches may be usable. One sixth of the distance would require only 12,500 lumens per/sq foot. Using the above figures, that would require only a total of 663 lights per/sq foot.
663 lights would only have a cost of 212 US dollars per/year per/sq foot.
I have 20 sq. feet of grow space in my grow room, so it would cost me about 4,240 per/year for these lights? That's 353 dollars a month!
I think that perhaps only one sq ft of lights will provide the needed lumens to as much as 9 sq ft. if so, then only two sq ft of lights would be necessary to light my 20 sq ft.
This would reduce the yearly cost to 424 dollars US or 35 US dollars per/month. I like that number way better.
I'm going to talk to a lighting engineer about this and see if I can find a true conversion. I'll let you know man.
Good luck to you! Lets see some more pics of the girls!!!
bobert said:
Here are some stumbling blocks i have hit with comparing LEDS to say...HPS
LEDs are rated in millicandellas which cannot be directly converted to lumens (there are approximation equations out there).
LEDs are directional, some ambient light can be seen through the back of the board and you can't even look at the front with your eyes open. The light intensity would not be same if it radiated all directions.
LEDs by design give off a huge percentage (i.e. 90%) of their energy as light, whereas a HPS gives most of its energy as heat, and say...10% as light.
If you cut the distance from the light source to the plant by half, you quadruple the light power hitting the plant. From what I understand, HPS needs at least a few safety feet whereas our leds are anywhere from 1"-12" away. So, quick calculation says at 3.5" away a HPS light would give 256 TIMES more light to the plant than at 60" (dang heat). So if we had our current leds at a 60" distance they would have to be 256x more powerful to obtain our current results.
im sure somebody will figure it out someday
