Building LED lights from facts, no theories

[knna]

I came to the conclusion mnay years ago that for indoor growing, single cola plants (many of them) less then 2' was the way to go, 18" or so is ideal.

Fully agree. I grow SOG style, 15-20" tall plants at harvest time. Floros and LEDs (without narrow optics) don go further than that.

I prefer to grow two stacked tables (one over the other) of 15" plants than one with 30" ones. Higher bud to total dry matter ratio with shorter plants, apart of the reduced (almost none) veg time.

Anyway, the arrays im designing now are intended to be used into canopy so im going to try to grow taller plants that produces good buds along all the height.

As for using the cooltube, it was just a matter of necessity....to protect the LED PCBs and T5s from dripping nutrient and water. Plus it is easier to clean a glass 6" tube then 8 individual T5 tubes not to mention the 8- 20" metal PCBs. I clean the glass at least once a day!

It sounds sexy to say I grow in a rotating garden, but it is the most labor intensive system invented by man so far, and it is not a "clean" operation. Only thing worst I can think of is being a dirt farmer. BUT it has had one advantage... more then twice the growing output with the same amount of light input.

Yep, in that sense vertical grows works better, although the problem with them is to get an even nutrient distribution for plants at different heights.

The question I have for you kanna is can you quantify light output in terms of micromoles of photon energy for T5s? I have to admit I didn't know a micromole from a gopher until I read some scientific papers posted by physicnole; but it seemed to make the most sence when talking about plant growth.

Yes, i can do it. You can do it aswell. Ive uploaded the spreadsheet to do it easily. The spreadsheet uploaded on The Garden's Cure already have floros SPD's from phillips digitalized.

54w T5 HO have about 27.5% energy efficiency working at 35ºC, for about 76 uE in PAR (~1.29 uE/watt, already counting ballast losses). It drops to 24% and 66 uE when running at 25ºC.

Losses at reflector are about 25%. So 76*0,75=57 uE avalaible for plants. Close to 1 uE/W.

Clearly uE (micromols of photons per second, abreviated) is the relevant figure when talking about plant's lighting. Any calculation or stimation must be based on it.

I saw you mention that a 250HPS had about 100 micromoles, that would put SmartLamp at 310 claim well within a possible 600w HPS.

I said that if the Procyon uses the top bins for CREE it may emit more than 200 uE so it should compete with a 250W HPS. If it uses normal bins, it likely gets half way to do it.

A good 250w HPS gives about 385 uE. If working with reflector, its about 290 uE avalaible for plants. Pretty close to Smarlamp output, which should outperform slighty it (the other smartlamp model states 265 uE, and that should be on par with the 250w HPS). Slighty improved photons absorbance from the LEDs spectra (near 10% based on NASA experiments) and similar average quantum yield (photosynthesis for photon absorbed).

I like how the SmartLamp preforms; in a grape vine propagation experiment, it covers and grows equal to a 600HPS, but with a high light level loving plant like MJ..."a photon whore" (I love that) it suffers what most "brick design" hi power LEDs suffer from, coverage area. Bring the light close enough to take advantage of its higher output, (and you can because there is no heat) and the area covered is just too small. Raise the light to get a wider footprint and suffer with not enough "umph" for those photon whores.

The critical factor is to give the adecuate light density (uE/m2).

Most HPS grows range from 500 uE/m2 (at 400w/m2, or roughly 35 w/sqft) to 1000 uE/m2 (70 w/sqft). Its clearly more than required, as those high light densities are provided by means of achieving enough photosynthesis on lower areas. Probably 300-400 uE/m2 are enough if growing short plants. And when growing taller plants, adding LED lighting to lower areas directly instead than from top seems the way to use way lower average light densities than those used by HPS grows without losing much yield but increasing strongly productivity (g/W).

I just happened to luck into my first T5/LED hy-bred light. Its results and what I'm hearing from others, seem to confirm that currently it's the way to go. When I first started with LEDs, I was comming from the "I'm going to save at least 50% of my electric bill". I even got hung up with trying to compare grows to a 600w HPS, but frankly now even if I use the same amount of electric power, if the results in both weight and quality are superior, that is what counts. My new hy-bred uses about 640watts of light, so I hope it can compare favoribly to a 600watt HPS. If not I really am going backwards here.

You have choosed a really ambitius target. 600w HPS are the kings about uE emission per watt burned. And they have a very decent spectra for cannabis. Perhaps easy to beat, but for little. Quantum yield for well tuned LED lamps should be slighty higher, but not much more of 10%.

So to beat a unreflectorized 600w HPS is really difficult today. Its way easier to beat a reflectorized one, wich cost a 25% of the light, and easier too if it has a glass barrier, which blocks an aditional 10% of light. You need to give at least 80% of the photons the HPS emits to be able to compete with it.

With current LEDs efficiency, you need to use top bins runned at 350mA max to be able to achieve it.

I think current state of art of LED are still insufficient to compete with 600w on circular gardens. Its possible to beat it by little, but at way higher cost, impossible to take back for electric savings.

Currently i think LEDs are good to give supplementary lighting to low areas of HPS grows and for very small grows. Large wattage HPS are still unbeatable on price/perfomance, IMO.

Today CREE has reported a lab result of 161 lm/W of a white high power LED. Surely it will take about two years to see it commercially avalaible, but at those LEDs efficiencies beat large HPS is going to be much easier.