LED - Lumens/sq. ft.?

willard3 said:
The other thing to observe here is that Cornell's greenhouse, where they grow for both research and market, uses HID for light source. I will guess they did their research before they purchased..
 
LED is pretty cool and eventually may catch HID for efficiency, it just hasn't happened yet.
 
Read pond area lighting:
 
http://www.cornellcea.com/attachments/Cornell%20CEA%20Lettuce%20Handbook%20.pdf
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That was an interesting read, they also mention PAR vs lux/lumens as well:
Measurements of PAR give an indication of the possible amount of
photosynthesis and growth being performed by the plant.
Foot-candle sensors and lux meters are
inappropriate because they do not directly measure light used for photosynthesis.
 
I was curious why they never mentioned LEDs as a potential alternative for lighting, and looking at the citations and references at the end of the handbook might tell us why. There are no mention of any articles, journals, etc after 1998. How old is this handbook?
Jeff H said:
There are a bunch of resources on the net to modify old power supplies to use as DC power supplies. I have one I did a few years ago but it will only put out about 15 or so amps at 12v. YMMV....IIRC, it doesn't take much more than the right resistor on the 5v leads to make it work but please look it up, it has been several years since I did this
 
 
 
It is interesting that it is usually engineers and designers that get into these technical discussions. My degree is also in engineering, 
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Ha, when my engineering buddies and I get together and have a few beers we have some really lame discussions (to anyone listening that is :) )
 
Jeff H said:
There are a bunch of resources on the net to modify old power supplies to use as DC power supplies. I have one I did a few years ago but it will only put out about 15 or so amps at 12v. YMMV....IIRC, it doesn't take much more than the right resistor on the 5v leads to make it work but please look it up, it has been several years since I did this
 
 
 
 
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1 resistor off the 12V rail should do it. Not sure on how this power supply is, i think its 250W according to the internets, but who knows, there's no markings on it.
Not that important but Im hoping I can run 2 sets of 10x10W LED's for a total of 200W. Even if this one doesnt cut it I can buy a much bigger one for way cheaper then what they want for these LED's drivers.
 
On the plus side, I've got 3 nice cpu fans running for almost half the power, and twice the coverage, as 1 smaller AC fan. :D
 
llbuckshotll said:
1 resistor off the 12V rail should do it. Not sure on how this power supply is, i think its 250W according to the internets, but who knows, there's no markings on it.
Not that important but Im hoping I can run 2 sets of 10x10W LED's for a total of 200W. Even if this one doesnt cut it I can buy a much bigger one for way cheaper then what they want for these LED's drivers.
 
On the plus side, I've got 3 nice cpu fans running for almost half the power, and twice the coverage, as 1 smaller AC fan. :D
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Let us know how it goes, I'd be interested in pics and a grow log.
 
I've debated going all white LED to see if there is a noticeable difference. Don't forget you are going to probably need a heatsink for those LEDs
 
IMG_20131115_151635.jpg
IMG_20131115_173549.jpg
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20 10W LED's.
http://www.ebay.com/itm/141096327397?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649
 
The power supply is drawing about 1.5A and my MH light on the other sides is drawing about 2A (600W digital balast running at 50%)
 
The LED covers about a 6' x 2' area while the MH covers closer to 2' x 2'. Measuring roughly 10K lumens at the plants top.
 
The LED spec's are for 9-12V 950-1050ma for 1100 Lumens. They are actually using closer to 9V and 650 ma currently, so they are turned down. I can tell you these suckers are BRIGHT.
But only time will tell if they can grow as well as the MH

Full gallery
https://plus.google.com/u/0/photos/108210399764936390185/albums/5936549244656283249
 
Keep in mind that most of the DIY LED research and experiments comes from the cannabis grower community.
One of the reasons why marijuana is called "weed" is that marijuana grows like a weed.
But what might work great for a cannabis plant,does not necessairily hold true for a chilli plant.

My little DIY experiments indicate there are some fundamental differences :
For instance if you have a flowering chilli motherplant about to grow fruit, and you take clones from it, these clone will NOT be juvenile / baby plants, which is what marijana clones would be.
They will be adult miniature plants and begin flowering immediately, instead of growing tall first, regardless of the color light they receive.

In fact, a "diet" of coolwhite/blue light caused my chilli clones to NOT shoot up,which is what one would expect. Strangely, all of the clones grew very short, maybe 5 inches tall, and spread out horizontally, almost like vines.

Wattage :

For one experiment I compared
4 Moruga seedlings under ca. 60 watts of blue and cool white LEDs.
4 Moruga seedlings under 2 x 18 watts of neon tubes (4500K and 6400K)

All plants came from the same seed,and had the same grow area.
Despite the low wattage, both setups did work.
The LED plants grew (a little) bigger, but had much darker, thicker leaves.
They were much sturdier, stockierand healthier looking.

Up until the aphids moved in, that is....

Anuwhoo hope this helps.


@ llbuckshotll : That's a vert nice "frame" light you got there.
Are all the 10w Leds the same color ? Alternating cool white and warm white might have better results as you'd cover more spectrum.
 
willard3 said:
I love how everybody that wants to purchase lights to grow chiles becomes an instant expert on lighting.
 
I do lighting design for a living and lighting efficiency is defined as lumens/watt. Any other definition of lighting efficiency is bunk.
 
Anybody who uses Wikipedia as a source doesn't have any respect for science.....Wikipedia is unvetted crap.
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Well, TheImpatientGardener and Jeff are right about lumens not mattering for plants unless we are measuring wave lengths they actually use and subtracting the ones they don't. Lightning design is quite different from growing plants. Another bonus with LEDs is that you can use specific wave length combinations to increase growth by not flowering or combinations for them to flower. It seems you get the most control and efficiency with LEDs.
 
hi IIbuckshotll,
i can see on the picture that you have a luxmeter. Would be pretty interested in knowing how much lumen you really get from led set up at your plants level?
BTW very nice DIY!
 
Greenhorn question here:
I've got an 2x4 ft space to start 28 plants in #1 pots. Currently, I use 4 T8 bulbs/6,500k. If I switched to LED, would my energy costs grow through the ceiling? What sized LED would I need? Thanks
 
Sluggy said:
@ llbuckshotll : That's a vert nice "frame" light you got there.
Are all the 10w Leds the same color ? Alternating cool white and warm white might have better results as you'd cover more spectrum.
Click to expand...
Yep all 6000-6500

pekeumat said:
hi IIbuckshotll,
i can see on the picture that you have a luxmeter. Would be pretty interested in knowing how much lumen you really get from led set up at your plants level?
BTW very nice DIY!
Click to expand...
Theres about 10 inches from plant top to lights and the average is about 10K L for the LED's (Not turned all the way up but drawing a little less then 2 Amps, with 3 cpu fans)
Its closer to 20 inches for the MH light to get the same 10K (600w @50%, drawing 2.6 Amps)
 
Note that the power consumption on Led is less, but the LED light covers a larger space. 20" x 72" as compared to 24" x 24"
 
New updated pics up too.
 
i wonder if you could mount the leds to a metal shelf and use them as light (plants under shelf) as well as warming (plants on shelf). Could make heating mats / heater obsolete in a mini shelf greenhouse.
 
OKGrowin said:
i wonder if you could mount the leds to a metal shelf and use them as light (plants under shelf) as well as warming (plants on shelf). Could make heating mats / heater obsolete in a mini shelf greenhouse.
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Athough each led gets pretty hot as well as the big resistors, just running the 2 fans is enough to cool the resistors. The space on the L-Channel they are mounted to is enough of a heat sink to keep them cool.
 
I guess if they were closer spaced you could develop more heat to use, but high temps on the led's also lead to a shorter life
 
OKGrowin said:
ah yeah i read above room temp you are losing efficiency / lowering life.
 
https://plus.google.com/+OlegMazurov/posts/NAHpMvjHRNh
 
This guy used some 50w with CPU heatsink and pumped water through heatsinks.
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I guess we'll see what happens when my plants get bigger, but it appears for now that the leds dont need to be any closer or higher wattage. Dont get me wrong, liquid cooled is bad ass, but simple cpu fans seem to do the trick just fine for now.
 
I am only running at about 780 mA too. These are rated for 950-1150, so im sure if i cranked them up the heat would follow too
 
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