LED Quandary

It seems the most popular panels are the 300-450 watt types. These are generally something like 15" x 8" to 15" x 15". The most common lens beam angle is 120.

Here's the problem. The inverse square law doesn't exactly apply here but I wont get into that. On one 300 watt light at 6" distance the output was measured at 82,500 lumens by the manufacturer and 30,300 lumens when 12" away. So if you'e only 6" away you have ~9000 foot candles in a 3x3 space which is phenomenal.

With the common LED lens beam angle of 120 degrees though and the unit only measuring maybe 15" x 15" once you go 6" to any side at 6" distance the lumens are half or ~4,500 foot candles.

This is because with a 120 beam angle once you go 60 degrees to either side the lumens are half and 60-60-60 is a perfect triangle.

With CO2 and correct temperatures plants can use 5000 foot candles or more. We're trying to go with the or more here because hey you're paying for the light and LED PAR is utilized much more efficient than HPS or MH. If we can get 5,000 fc with LED then we're really doing well on lighting.

Since the beam angle is so limited and the distance so close you're limited to 2x2 but not because there isn't enough light but because it's too concentrated in a small space.

What is the solution?

You could make this ~3x3 by hanging it from a disco ball mover and using a rod to hang it 6" off center..

OR...

Ditch the larger panels and order a bunch of UFO's. I see 180 watt UFO's online with 3 year warranties going for $60 and with a 120 degree beam angle and 11" diameter you're so much closer to equal light distribution and it's not that much more money as the cheapest 300 watt panel I've seen is $102 or something.


What do you all think?

cobs

You seem intelligent or y o u just copy and paste the above. Either way a 300watts unit is NOT $100. It's prob closer to 150 watts if your lucky and that's using absolute garbage leds.

those output numbers on likely from the cree cobs, area 51 and AT panels not the cheap Chinese panels.

I didn't copy and paste any of that but I am not nearly as intelligent as I'd like to be.

http://www.aliexpress.com/item/Free-shipping-300w-led-grow-light-full-spectrum-best-led-grow-light-2013-for-growing-mj/941775668.html?tracelog=back_to_detail_a

They say they use Epistar, Bridgelux, and Cree but I haven't confirmed. It is probably something like 150-200 watts because I thought LEDs would only use ~2/3 power to keep from frying themselves.

I'm just confused on the 2x2 flowering recommendation. Ed Rosenthal recommends half the HPS wattage when using LEDs . Quote,

"By tailoring the diodes’ light spectrum to plant requirements, LEDs can be more efficient PAR producers . HPS lamps deliver more total light per watt of input, but LEDs are twice as efficient in PAR light per watt as HPS lamps. That means a 200w LED lamp can be substituted for a 400w HPS lamp, and the 300w LED lamps can be substituted for 600w HPS lamps. The first generations of LED lamps did not emit an intense-enough light to support either active vegetative growth or flowering, but modern fixtures, which use higher-capacity diodes, have solved those early problems."

Rosenthal, Ed (2009-07-01). Marijuana Grower's Handbook (Kindle Locations 2166-2170). Quick Trading Company. Kindle Edition.

So I guess you need to use half the actual or rated watts of LED that you would use with HPS? Except I'm not sure if he's talking standard HPS distance lumens/par or air cooled or water cooled and how that compares to the distances from the canopy you'd be running with LED's hence the quandry.

On a side note he also recommends 5000 fc or more for flowering. The U.S. govt did some research on cannabis sativa and found with temps up to 30 celcius and 750ppm CO2 (they didn't test higher) the plant could handle 1500 micromols/m/s. foot candles translate differently depending on MH or HPS but I can't figure out how that translates to LEDs since the use a targeted spectrum and I'm not sure how much more efficiently it's absorbed. Here's the full text: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3550641/pdf/12298_2008_Article_27.pdf

Well I think I've solved the quandary. Use the larger LED light panels.

I think Ed meant the ACTUAL wattage draw is twice as efficient as HID. Still, you can only grow so much in x amount of space as determined by the genetics of the plant.

So, if you're using a decent yielding strain just try to get your actual LED wattage to = 1/2 the grams per square meter advertised and likely the panel will be so large that you can still keep it very close to the canopy. You're going to pay a butt load more up front but your electricity bill will be half and without all the excess heat and ducting, blowers, and filters that come with it.

LurchLurkin said:

Well I think I've solved the quandary. Use the larger LED light panels.

I think Ed meant the ACTUAL wattage draw is twice as efficient as HID. Still, you can only grow so much in x amount of space as determined by the genetics of the plant.

So, if you're using a decent yielding strain just try to get your actual LED wattage to = 1/2 the grams per square meter advertised and likely the panel will be so large that you can still keep it very close to the canopy. You're going to pay a butt load more up front but your electricity bill will be half and without all the excess heat and ducting, blowers, and filters that come with it.

Click to expand...

I would say actual wattage draw is 10-15% more efficient than HPS for what you linked and 25-40% for the higher end LED setups.

After reading Positivitys DIY thread all over, I would pass on anything with 730nm on all the time. White leds are good and being pushed right now, but mono's of known bins are just as good in some aspects throughout the grow cycle.

40-60 watts per sq. ft of the light type you linked

25-35 watts per sq. ft of higher end

Be safe

How much light depends on size of grow space but for the most part multiple panels with same wattage spread evenly across the canopy will be better than one panel unless that panel physical size covers the canopy

BML SPYDR is a vg example of spreading 6 individual light bars over a 3 x 3 area

With the exception of the 2 outside bars, the inner bars equally cover the ~ 4" space between 2 bars

COBs lend themselves to DIY experiments (see Greengenes 707 COB Drone)

Incorporating a slow speed ceiling fan with COBs on each blade
(4 COBs: 3 @ 2700k + 1 @ 5000k) should be a great performer

Of course there would need to be a mechanical connection to prevent wire spooling

The original poster is thinking wayy to deep into this without really knowing the basics of led lighting. Also when they say we use cree diodes yes they might use 1 cree diode for every 25 no name junk. That is how they can get away with saying it's a Cree panel but yes it is made with creediodes but they are lowest bin and only a small ppercentage.

Bottom line is if your spending 100 bucks on a light and not doing it yourself you will be disappointed.

LurchLurkin said:

It seems the most popular panels are the 300-450 watt types. ...Ditch the larger panels and order a bunch of UFO's. I see 180 watt UFO's online with 3 year warranties going for $60 and with a 120 degree beam angle and 11" diameter you're so much closer to equal light distribution and it's not that much more money as the cheapest 300 watt panel I've seen is $102 or something.


What do you all think?

Click to expand...

It's tough to quantify LED performance in general since using older light measurements don't apply as well and different techniques in manufacturing make quantifying LED performance so maddening, even for the folks who do have the smarts for stuff like that. COBs and smaller panels or a larger panel supported by some smaller ones make defining your space easier. You can really only use wattage for the same LEDs IMHO but Abiqua's statements about wattage isn't a bad place to start. Oh and I read that what Ed R wrote about HPS and LEDs a while ago and have found that it is a number someone pulled out of their ass .

Abiqua said:

After reading Positivitys DIY thread all over, I would pass on anything with 730nm on all the time.

Be safe

Click to expand...

Is it 730nm on all the time is wasteful/harmful or is it anything with over 1% of the panels output is wasteful? IMO we can look at Illumitex's F line for a good answer. The largest output of any F line that has 730nm is .3% (F3). That's less than 1%. I would think that most WWs can generate that much 730nm FR. So IDK if it being on all the time is bad, it's how much is on, right?

And thanks for reminding me I need to hit Po's thread again. Peace Abiqua!

Just from observation on 730nm

The "right" amount always on is necessary for proper flowering. Think sds had it at 3%. That equates in my mind to "there" but "barely"....lol. Just a trigger that plants are sensitive too and not a bud building base. So you can use mono 730/ww in a red blue setup or just use a white based spectrum and have the small amount needed. Or get fancy and save the always on electric and flash them at the end for complete and as fast as possible flowering response.

I think the ops original question was directed towards saving money with smaller, more affordable, led lights. And taking advantage of light spread.

You can look at the old prosource ads in youtube and such showing them hanging their lights en masse over a commercial garden (not sure I believe it). Never really caught on that I know of. Bottom line is those lights are too weak to grow high quality mj. They do work but far from ideal.

Now do that with cree cobs....and you have the most efficient garden in the world currently possible...lol.

1w < 3w < 5w < 10w < 20w < 30w.....where's the best individual power number? Dependant on situation..

Individual emitter power and efficiency matters. Cree cobs got that in spades and can't be touched.

Not to mention the amount of plastic saved!! Each small emitter gets a little plastic reflector otherwise is limited to the smallest tightest quarters...or a surround of the plants...

So....
I'd say save your money till the cree cob grow lights become available which they inevitably will

Or buy the DIY cxa parts and stare at them....bet you'll figure it out.

Or do whatever you like....it'll grow. Everyone has different expectations

Ok so I've read a few of the DIY LED threads and I've read some XGS threads and I've read some cheap chinese threads. All in all I'm not really impressed that any one is better than the other. I've seen them all capable of 1gpw or more. My reasoning for this is because where one product proved to be better than another it seemed like other factors also came into play and so there is no definitive answer unless I'm missing a thread or two somewhere.

In order to be getting maximum return you need to be 80-86 degrees with 750-1500ppm CO2 in aeroponics (not starving your roots for water to try and get "hairs") and a good set of nutrients. If you can innoculate your roots with oh whatever that bacteria is which gets into the nodes and get better results then you're not providing enough nitrogen.

I think in order to really get a good set of nutrients you've gotta make your own because most don't contain silica and then if you wanna add triacontanol and it just seems that no one provides a decent set of nutrients without making you buy 10 different bottles.

Caveat Emptor but all factors have to be optimal to obtain maximum return and I've not seen an LED thread do this to compare results. Please show me one if there is.

I dunno...my grows straight up sucked under cheap ufos

Hay to the Maximus. But hay might be enough for some peeps....I know plenty that wouldn't know the difference

To take a weak light with many missing spectrums and expect it to grow something anything close to outdoor quality is lots of smoke and mirrors.

All you gotta do is look at the cmh thread to see how well a fuller spectrum works. Clear as day....

I guess when I'm talking about cheap chinese I'm talking specifically about LGLED and probably apollo. I did see the thread where the XGS had a higher THC content than the HPS though.

I've spoke to the owner of the LGLED company about their spectrum and the only one they have in it that doesn't make sense to me is the 730nm because according to Mr. LEDistwiceasefficientasHID (Ed Rosenthal) 660-680nm prevents flowering while 730 encourages it in the ABSENCE of 660-680.

He does this when talking about sexing plants by leaving blue lights on during the dark period so that they continue to grow and show sex and says he has experimented with it in a limited capacity. The downside is that blue LED's cost more electricity to run than red. Ed says that the plants can absorb both just the same except I'm not really convinced because looking at a mass spectrometry chart for photosynthesis it definitely looks more active in the blue range.

So me wonders if photosynthesis is x% more active in the blue range and that equals the power consumption difference you continue to grow flowers throughout the entire grow by not utilizing any 660-680 and replacing it with 430 [off the top of my head 660-680 is like where chlorophyll a peaks at in the red range but it peaks much higher in the blue at 430] and also using 730 if you would overall grow bigger flowers since they'd be growing during veg too.

That's just a lot of stuff I stop putting a lot of thought into. Nice even spectrum across the board favoring warm. Just like every other lighting tech. Simple..uv is nice too. Only catch is high irradiance brings the goods....and nothing does it as efficiently and easy as a white cree cob.

Positivity said:

All you gotta do is look at the cmh thread to see how well a fuller spectrum works. Clear as day....

Click to expand...

Link? Sounds like a good read My acronyms are failing me..

cheap Chinese leds will work. They will use more watts to cover same area as high end leds. Chinese leds will fail within a year. They use low quality parts and drive their leds to hard causing them to fry. Those Chinese companies don't hold up their warranties.. high end leds will last 10 times longer. Use far less power. One 270 watt Apollo will cover the same area as one 155 watt area 51 led. High end leds like area 51 and apache have life time limited warranties with great customer service. Imo best lighting for flower is induction, CMH, and / or cob leds. For veg, all led. I'm a firm believer in full spectrum and high cri over par (umole/s)

I've seen in a Cree thread here that 30-35 watts per sq. ft is max for LED and then over at 420 magazine I've seen the same recommendation on LGLED lights by a guy running a 1600 watt (780 draw) mars ii.

Has anyone tested this either? I know the U.S. govt capped it at 1500PPF but that was only with 750ppm CO2 and I doubt any of you have PPF meters LOL.

Edit: I found this and now plan to look at grow journals from the different watts per sq ft.
http://www.compareledgrowlights.com/

LurchLurkin said:

I've seen in a Cree thread here that 30-35 watts per sq. ft is max for LED and then over at 420 magazine I've seen the same recommendation on LGLED lights by a guy running a 1600 watt (780 draw) mars ii.

Has anyone tested this either? I know the U.S. govt capped it at 1500PPF but that was only with 750ppm CO2 and I doubt any of you have PPF meters LOL.

Edit: I found this and now plan to look at grow journals from the different watts per sq ft.
http://www.compareledgrowlights.com/

Click to expand...

those forums have sponsors that push those lights. Best led info on the web is found in the led section of this one forum call roll it up.

Hyroot, I know, I was on aliexpress talking with Anna Lee last night the owner of the business. I'm not sold on them either as I don't know how they picked their spectrums or which chips they're using exactly. They list like three brands on the site but told me personally they use epistar and bridgelux(if I remember) but there are cree and something else I think available but there's a minimum order quantity and I didn't ask how many. It would be nice to get the p/n off their chips and see if they are any good.

There's a photosynthesis absorption spectrum above which shows how well plants absorb what light and they claim to cover all the peaks plus a 730nm. Why they choose 730 I don't know but there's only a couple of them even per large panel but I think 730 should be shot after lights out. They will do a custom spectrum and I asked what about switching the 730's out to UVB but they only have UVA in stock so there'd be another minimum order quantity.

I think they were going to do a test with some jon705 guy by copying the XGS spectrum but he never reported back. I'm just not sold on white because it contains green and green isn't used by plants.

I've heard they're basically a copy of black dog and some dude who wouldn't/hasn't posted any pictures said he'd opened both cases and the only difference was black dog used a different sealed power supply.

They can't legally grow pot and are looking for feedback albeit I don't know that it's entirely intelligent to really rely on a bunch of stoners for feedback but it seems to have boosted their sales as they've just moved into a larger factory and have averaged over 30k units a month.

An example of the intelligence displayed: Everyone wants 5watt LEDs but they run so much hotter and have to be spaced farther apart than 3 watt. Sure they get more penetration but due to the penetration issues with LEDs in general I personally feel they're really only suited for SOG or SCROG. Albeit ANY indoor grow should be utilizing SOG or SCROG to maximize efficiency anyways unless you don't care about efficiency and would rather let them just do their own thing to save you tending time.