LED Growing - The Numbers

Okay, so I did some research for the sake of doing research. After all, what's a good geek for other then research (and some good ol' geeky lovin')?

A dude over on the UK420 forums did a grow using blue and red LEDs for light. The LEDs he was using were 5000mcd (microcandella) reds and 4000mcd blues. He had 90 reds and 30 blues, for a total of 120,000mcd in the blue spectrum and 450,000mcd in the red spectrum. That's approx. 570,000mcd total.

Candella can't be converted precisely into lumens, but there is a formula that will give you an estimated value. (lumens/12.57)*1000=microcandellas or conversely (microcandellas/1000)*12.57=lumens so (570,000/1000)*12.57=7,164.9 lumens. So, this guy at the UK420 forums had about 7,000 lumens in his growbox. His plant grew pretty slowly, but still grew under this light, although there just wasn't enough light for it to be really productive.

I went searching for some *high-intensity* LED's and that led me to SuperBrightLEDs.com where I found some 5500mcd blues and 12,000mcd reds. (Model #'s RL5-B5515 and RL5-R12008 respectively.) So, I did some math and I figured that if I bought 112 blues and 112 reds, at a total cost of $151.20, I'd wind up with 616,000mcd of blue light, and 1,344,000mcd of red light. That gives me a total light of 1,960,000 microcandellas, or (ooo... I love this part!) 24,637 lumens!

A couple of things to consider.... a LED has two ratings, one "peak" rating and one "mean" rating. The peak rating is how much light the LED throws when it is FIRST turned on the very first time ever, the mean rating is how much it throws after it's "broken in," as all solid state devices have a theoretical break-in period. The nice thing about solid-state devices is that after this break-in period, they don't change much, if at all, unless they're jarred sharply or something, so theoretically, these LEDs could put off these "mean" ratings forever, although an LED is rated to last 17 years. Note that in my calculations, I used the mean ratings, not the peak.

Okay, so, where was I? Oh, yes. So all these LEDs cost $151.20, which is comperable to a 250W HPS and ballast. Here's the thing, a 250W HPS uses 250Watts of Electricity ... These LEDs use 27.44 Watts. So, it's easy to see that the electricity savings is phenomenol. Also, a 250W HPS has a rated life of 24,000 hours or 2.7 years (of course, the light output reduces dramatically after about 6 months) but LEDs have a rated life of 17 years and can, in theory, last forever with no reduction in light output, after the break-in period. LEDs also produce almost NO heat at all (much less then a computer, monitor, or a 40 watt lightbulb) so detection with IR is impossible.

It seems to me that for a micro-grower (somoene growing just one or two plants for themself) that LEDs are the way to go.

I plan on doing some hard-core real-life expirimenting when I find a place of my own.

Note: See Attached: my hand-written notes

 

From what I read over the UK420 forums, HPS's put off a lot of wasted light, in that, there's a whole bunch of light spectrum that the plant doesn't even use for the process of photosynthesis. According to the guy over there, the plants only use the red and blue spectrum, which would make sense since plants are green.

Okay, think of it this way... the colors that we see is the light that is reflected from the object we are seeing, hence all the other colors are absorbed. When we see a green plant, it's green because it reflects the green light and absorbs all the other light. If there is any green-colored light in your grow room, therefore, it is being wasted. Now... light spectrum... Anyone remember Roy G. Biv? The colros of the rainbow, Red Orange Yellow Green Blue Indigo Violet. White light ALWAYS creates a spectrum like that, in that order because of the way the wavelengths of light work. Anyway... if a plant is green, it reflects green light and therefore has no use for it.. We are giving the plant ONLY the light that it will use.

Now, about that light.... to break it down a bit, with those number of LEDs of that intensity that I mentioned in my previous post... You have 616,000 mcd of blue light and 1,344,000 mcd of red light. In lumens thats.... *counts on fingers* 7,743.12 lumens of blue light and 16,894.08 lumens of red light.

Thank you! I'm not really all that knowledgeable yet, but I hope to be some day. Hrm... maybe I should major in botany....

Oh, and as I said, when I get a place of my own, I'll have lots of expirimental data to post. Hopefully a good portion of that expirimental data will be smokeable.

 

Huhhhuhh.... duh!! Why didn't I think of that?? Oh, note that you have to register at UK420 forums to read the bottom two links.

LED Array

Vegatative Growth under LEDs

Budding under LEDs

Well, the red LEDs from my calculations are powered with 2.0V DC current and the blues are powered with 3.5V DC current. The easiest way to power these would be to go to a place like RadioShack and get one of those "power bricks" that plugs into the wall and converts 120VAC to 3.5VDC, then chop the end of the cord off and wire in the blue LEDs on that (MAKING SURE TO WATCH FOR POLARITY). Finding something to convert to 2.0VDC might be a little harder, but the friendly folks at RadioShack might have something for you. (Sorry, I used to work at RadioShack... I was the (read: only) guy that actually knew something about electronics...) If you were to use LEDs that were 5VDC or 12VDC, then you could just power them off the red (5V) and yellow (12V) wires off of a comptuer power supply. The 2V red LED's are really the only monkeywrench in this.... unless someone knows where you could get a cheap, simple transformer to give you 2VDC. *shrug*

 

I've never heard of giving LEDs a surge of electricity. It won't make them any brighter to overpower them, it'll just make them run hotter. Not to mention the only way to kill an LED is to overpower it and burn it out... I wouldn't run the risk.