algebraist
Well-Known Member
I have a 2ft x 4ft tent and I'm thinking of building 4 lights: Two 2x2 veg lights and two 2x2 flower lights. I was looking at COBs, but I like the LED strips for their evenly spread out coverage and their thermal properties -- no heat sinks needed. I'm aware of two options, the Bridgelux EB series and the Samsung H-series strips (and I've browsed through the "Bridgelux EB Series" and "DIY with Quantum Boards" threads, but they're huge and it's very hard to sift the useful information out of the noise). I have about a million questions, but I'll start with these:
1) How do I decide how many strips I need to fully illuminate my space? I'm planning to have my lights on a dimmer; I'd like them to be able to produce a bit more light than I could possibly use, and I'll dim them to what seems right. I've read that you can get these as close as 6 inches to the plants; let's say I'm going to run them 12 inches above the plants. On growweedeasy.com I found a chart that claims that for vegetative growth plants should get 40,000 - 70,000 lux, and for flowering they should get 60,000 - 85,000 lux. Would you shoot for a veg light that produces 70,000 lux from a foot above the plants and a flowering light that produces 85,000 lux a foot above? I found a lux to lumens calculator online that suggests that for 85,000 lux over 4 square feet I need 31,587 lumens, but the calculator didn't ask for a distance, and that has to matter. I found another that did include distance (as well as a view angle); that one came up with 14,532 lumens at 1 foot and 90 degrees, but then came up with 1690 lumens at 1 foot and 30 degrees, which makes no sense to me. So I am pretty confused on this basic question.
2) Can I compare "typical" efficacy ratings? Looking at the 3500K units for comparison, Samsung lists their model H562D as having a typical efficacy of 182 lm/W, at 480 mA, 22.5 V (10.8 W). The corresponding Bridgelux model has a typical efficacy of 156 lm/W, at 700 mA, 22.1 V (15.5 W). Ignoring price of the modules for now, does that simply mean the Samsung is the better choice? I'd expect the companies to be giving specs for something near their "sweet spots" -- in other words, if I run the Bridgelux at 300 mA or 400 mA instead of 700 mA, then I wouldn't expect the efficacy to go up appreciably -- in fact I'd expect it to go down (otherwise why wouldn't they list it that way?) -- but what do I know (almost nothing).
and one more, for now:
3) How important is color temperature and CRI? The Bridgelux strips go from 3000K to 5700K, and the Samsung from 3000K to 5000K. Since I am planning to have separate veg and flower lights, I can go to extremes for each, and if I went with COBs I think I can find 2700K lights for flower and 6500K lights for veg. Is that enough of a reason to reconsider going with COBs? Also, these strips are all 80 CRI; COBs are available at 90 CRI. How much does that matter? And finally, the Bridgelux data sheet includes a graph of the spectrum; the Samsung does not (but I can probably find one for the LM561C chip, which is what it uses). Should I be looking carefully at those before making my decision, or can I just rely on the color temperature numbers?
Thanks very much for any help you can give.
1) How do I decide how many strips I need to fully illuminate my space? I'm planning to have my lights on a dimmer; I'd like them to be able to produce a bit more light than I could possibly use, and I'll dim them to what seems right. I've read that you can get these as close as 6 inches to the plants; let's say I'm going to run them 12 inches above the plants. On growweedeasy.com I found a chart that claims that for vegetative growth plants should get 40,000 - 70,000 lux, and for flowering they should get 60,000 - 85,000 lux. Would you shoot for a veg light that produces 70,000 lux from a foot above the plants and a flowering light that produces 85,000 lux a foot above? I found a lux to lumens calculator online that suggests that for 85,000 lux over 4 square feet I need 31,587 lumens, but the calculator didn't ask for a distance, and that has to matter. I found another that did include distance (as well as a view angle); that one came up with 14,532 lumens at 1 foot and 90 degrees, but then came up with 1690 lumens at 1 foot and 30 degrees, which makes no sense to me. So I am pretty confused on this basic question.
2) Can I compare "typical" efficacy ratings? Looking at the 3500K units for comparison, Samsung lists their model H562D as having a typical efficacy of 182 lm/W, at 480 mA, 22.5 V (10.8 W). The corresponding Bridgelux model has a typical efficacy of 156 lm/W, at 700 mA, 22.1 V (15.5 W). Ignoring price of the modules for now, does that simply mean the Samsung is the better choice? I'd expect the companies to be giving specs for something near their "sweet spots" -- in other words, if I run the Bridgelux at 300 mA or 400 mA instead of 700 mA, then I wouldn't expect the efficacy to go up appreciably -- in fact I'd expect it to go down (otherwise why wouldn't they list it that way?) -- but what do I know (almost nothing).
and one more, for now:
3) How important is color temperature and CRI? The Bridgelux strips go from 3000K to 5700K, and the Samsung from 3000K to 5000K. Since I am planning to have separate veg and flower lights, I can go to extremes for each, and if I went with COBs I think I can find 2700K lights for flower and 6500K lights for veg. Is that enough of a reason to reconsider going with COBs? Also, these strips are all 80 CRI; COBs are available at 90 CRI. How much does that matter? And finally, the Bridgelux data sheet includes a graph of the spectrum; the Samsung does not (but I can probably find one for the LM561C chip, which is what it uses). Should I be looking carefully at those before making my decision, or can I just rely on the color temperature numbers?
Thanks very much for any help you can give.
