# LED Growing - The Numbers

Discussion in 'Indoor Marijuana Growing' started by Pot Geek, Sep 10, 2004.

1. #21

I'm sure if we get enough like minded people, we can combine what we know and figure it out... I'm in the same boat froggy. I want to give it a shot, but there is alot more I need to learn first.

But I want to experiment on it first in a cloning chamber.

2. #22
Last edited by a moderator: Nov 11, 2009
lumens are only a rating used for the brightness of the light as seen by people, us not plants. To enable pot to flower under led lights you need a white light in with them or you could use a hybred system. Whatever you do do not put led lights close to your plants as it will damage them.The intensity of the led s is very strong close to the light and spreads out like a funnel as you get further away. That is if you get the led s I am talking about that come set up to grow with.

3. #23
to elaborate on the last post, candles and lumens are NOT interchangeable units, not only that, they are measured by the peaks of certain spectrums, namely those that humans can see.

Even moreso, your math is somehow wrong, in another post of mine I figured the %eff of HPS, CFL, and LED (seach if you'd like), and HPS was about 70-80% efficient at turning power to pure light, meaning any wattage of LED's you have under that value will NEVER produce as much light as the HPS will.

Of course the light output is measured as the area under the lumen curve, so you would be right if you were to say "but you can have x amount more lumens in red". Myself, and many other have their reservations that ONLY red/blue can grow a plant properly though -- many more frequencies of light are likely needed to grow perfectly. Much in the same way you can feed a person pure protein carb's and fat's in 1 form and expect them to develop right.

Anyway, LED's are a lot more eff, over 90% I think. So you can potentially get (9/7)*wattage the efficiency of a HPS, with a lot less heat. But its going to take a hell of a lot more than 30 watts to ever grow weed properly.

4. #24
Let's not forget the inverse square law.

Lumens are measured at one foot from the bulb. So if you can put your plant at 6 inches, you'll get 4 times the lumens. If you can put your plant 3 inches away, it will get 16 times the lumens.

In my understanding of LEDs, there is a problem with putting the plant too close. At less than a foot or so, the red and blue colors aren't mixing (you get red and blue spotting), so you can get weird artifacts in the grow.

This is the beauty of CFLs. They put out so little heat that you can put the plants real close to the bulb (like an inch or two) and effectively get many times more lumens than the bulb's lumen rating. And no red and blue spots, because the spectrum is broad and mixed.

5. #25
No, your thinking of making LED applications more efficient for home appliances, theyre switched on and off at a rate of 50hz (every 20ms), so that they conserve energy, and still look like theyre on permently, becuase of an optical illusion called " pesistance of vision".

This thread is full of specualtion, and "chinese whisper" style Information, i'm going to flood it with some facts in about 5 minutes once i can pull up my old posts for you all.

6. #26
There's a common misconception that Lumens only refers to white light
This is false, and is usually propaganda spread by LED haters, trying to "disprove" things using basic definitions, hopefully the following clears things up.

All light is measured by Radiant Flux (power) and radiant intensity (the concentration, eg bulb spreads light out, small viewing angle LED concentrates the light intensity)

Lumens refers to the eyeballs sensitivity to the color green, and Luminous Flux is calculated by using the Radiant flux value, multiplied by 1 when the light source is green, and then this multiplier lowers the further you move away from the 555nm wavelength, either up or down the spectrum.

If the light source isn't exactly green, but made up of different colors, then calculus is used to find the multiplier, it is the integrate of Wavelengths in the bandwidth the Light source is producing.

That means every light that isn't a green 555nm Led, has had its Lm/w rating calculated by this process, whether its a LED, HID, or a Standard Light bulb.

7. #27
PAR is very important for growing, Its sort of like lumens, but for plants.
It is weighted like Lumens, but the 1x Multiplier is at 700nm, and then rapidly drops as you move up the spectrum, going down the spectrum the multiplier doesn't roll off to 0 until 400nm

This scale is "weighted" in bias of the bandwidth of wavelengths that plants use to grow, unlike the Lumen system which is Weighted to bias 555nm wavelength.

This is so that growers know they're getting all the light they need to cover these Wavelengths:

(Originally Posted by Strictly Haze)
chlorophyll a 430nm, 662nm dual peak
chlorophyll b 453nm, 642nm dual peak
phycoerythrin 590nm, single peak
phycocyanin 625nm, single peak
Beta-carotene 450nm, 480-485nm dual peak

Note that PAR doesn't Value Short wave infrared (>700nm), or UV wavelengths (<395nm); these are outside of the 400-700nm PAR range, even tho many LED grow panels specifically advertise they include an Infrared and UV led to "optimize growing"

8. #28
dusty5330, you should necro some threads from 1994 aswell, im sure the people that posted info back then would be really interested in the updates of technology aswell

9. #29

wow didnt even catch that, haha