New high powered LEDs

[Al B. Fuct]

godonacid, I did look at that thread. He had an awful lot of trouble keeping the things working! They quit on him several times, leaving the grow without light for a couple of weeks at a stretch, per his description. As it was, it looked like the results you get from plain ol 20W CFLs. His HPS grow would have yielded several times as much bud- and he didn't isolate the LED grow from the HPS light- the HPS grew half of the output from his LED plants.

 

Now... HOW MUCH do those LEDs cost?

 

LEDs may indeed be the way of the future... but that future is a long way off. You sure can't grow any appreciable quantity of weed with the things as they are now.

[Gibs]

Luminous intensity from multiple sources acts more like voltages in parallel. If you put two 1.5V batteries in parallel, you get 1.5V. Same with luminous intensity. If you put two 1500 lumen lamps next to one another, you have 1500 lumens. Neither lamp gets brighter. Intensity is analogous to voltage in that it is a measure of the 'push' or energy level behind the photon. Lumens are not a measure of the quantity of photons, rather the total energy pushing them which the human eye perceives as brightness.

Simple as this- lumen figures from multiple light sources added together are meaningless. The amount of luminous intensity is no higher than the brightest light source.

Naw, that's not how physics works.

 

This idea of "energy pushing the photons" is pseudoscience. Photons do have the ability to exist at different energy states, but these energy states are measured by frequency, and inversely, wavelength (not by 'brightness'). So photon energy levels manifest as the colour of the light. The shorter the wavelength, the higher the energy of the photon.

 

I see that you have your beliefs, and i'm actually pretty impressed that you bothered to set up the experiment! But i can only conclude that your procedure was off. Luminous flux (measured in lumens) is the quantity of light (i.e. quantity of photons) per unit time. Luminous intensity is the angular density of luminous flux. So the theory would say that your premise and conclusion are both false.

 

The point made by sellers of LED grow lights is that they'd like to sell you a very expensive LED grow light.

 

The point they omit is that the spectral output of LEDs is narrow because that's the compromise necessary due to the limits of semiconductor technology at the moment- not because they've tailored their LEDs' spectral output to a plant's needs. LED makers narrow the spectral bandwidth to increase the maximum luminous output. The broader the bandwidth, the more current must be run through the substrate-

That doesn't sound right for two reasons:

1. White LEDs are full spectrum. I don't see any evidence of this narrow limit of spectral output.

2. White LEDs of a given type (e.g. cree xr-e bin xxxx) will have a significantly higher luminous intensity than a LED of the same type emitting only a narrow bandwidth, e.g. blue. Take the luxeon rebels for example - the cool white version puts out about 180 lumens at 700mA while the blue puts out about 48 lumens at the same current. You'll see those kind of numbers with any of the high powered LEDs on the market.

 

Yes, all annual plants evolved in temperate latitudes respond to bluish and reddish portions of sunlight but do so (in concert with photoperiod) mainly as a means of telling what time of the year it is and how long it will be until winter. Early in the growing season, when the sun is higher in the sky, the average sunlight spectrum is stronger in the bluish region. As the summer season wears on and days shorten, with the sun peaking lower in the sky, sunlight is filtered through a greater thickness of atmosphere, which passes more red and filters out more blue.

This part is correct (if the word i bolded is omitted)...

 

That doesn't mean that plants only need blue and/or red light. It means they will respond to a broad spectrum of light with peaks at certain frequencies (wavelengths) by growing in a particular habit.

But this part doesn't follow. Yes, you are technically correct that plants respond to a broad spectrum of light, however virtually all light outside of the red & blue ranges is reflected. For reference, here is the absorption spectra for clorophyll:

 

http://www.biologie.uni-hamburg.de/b-online/ge24/03.jpg

 

Cannabis plants need high intensity light to produce weight and density in the buds. Knowing as we do that 'lumens don't add,' and knowing that a really good LED makes 150 lumens (albeit in a narrow, single colour spectrum), and knowing that 1500-1700 lumen CFLs produce thin, weedy buds... why on earth would you buy a large number of LEDs which only make 1/10 the intensity of CFLs?

 

A larger quantity of photons from a number of low intensity sources will not replace the high intensity required by cannabis plants. If you have one hundred 150 lumen LEDs, you will succeed in putting 150 lumens on 100 spots. You will not get high intensity light that will give you dense, heavy buds.

I disagree with all that except the first line, as per what i've written above.

 

Note that i don't expect you to take my word for anything i've written - i encourage you to research and verify this stuff for yourself. I'm not an expert and it's more than possible i've fucked up my theory or misremembered it. Never trust some dude on the internet to give you the proper facts!

Edited July 16, 2007 by Gibs

[Pam]

~Wow~ I'm no rocket scientist but below I've copied a part of what made me think this might be a way to cut the electric bill! Now as for price... I remember what my sun system HPS (ballast in hood 400w) cost, and I have to say that was over $250.00 USD and one 12" red LED (stop light) was $50.00 USD... And it will last 10 years. I have NO plan to attempt using LED alone, I am adding CFL floods in as well. I may have figured the warmth problem. The dehumidifier is pumping out nice warm air and I had planned to hook it up anyway. It's got my veg box up to 81F (i've got to get a conversion chart...) I promise that should I see stringy sparse growth I will immediatly switch to the HPS. BUT if these LED lights do indeed work like they do in space, and it will just take a bit of tweaking to get the right mix... well, if the boy ever finishes the door to the box, you'll see pix.

Here go.

How Light Colour Influences Plant Growth

Blue light: plants react to the intensity of blue light. Lessening the blue light will cause poor growth – the strength of the radiation in any other part of the spectrum is not as important as the intensity of the blue, which shapes height and quality.

Red (660 nm) and infrared (730 nm) (also known as IR or far red) light: Intensifying the total of IR in relation with 660 nm red makes plants grow tall and thin. On the other hand if red is increased while IR diminished, plants will be short but thick. Plant reactions are not linear with the red/far red ratio and they can also vary in their response to red and far red light.

Ultraviolet light (UV): While overexposure is dangerous, small amounts of UV light can be beneficial for the flora. In many cases UV light is a very important cause for colours, taste and aroma. But UV-C and UV-B are believed to stop plant spread and this is why they have to be removed from the light under which plants are developed in green houses by UV stabilisers or glass. Removal of the UV up to 400nm is might be effective also in case of virus carrier insects (as insects see partly in UV).

Direct light from the Sun distributes the useful wavelengths only on special times of the day and in small quantum enough for a harmonious growth in some parts of the Earth, yet not enough on others.

Crop production systems are dealing with such problems and find ways to replace natural light with artificial light. The idea of growing plants under artificial illuminators is not new at all. Long time ago NASA started to grow plants in space, and the results were astonishing. Nowadays we know that by using the correct wavelength plants develop harmonious and healthy, sure if they have all the other conditions ensured. Yet getting light of the correct wavelength is not an easy task, especially if one takes into account the costs and efficiency of such light sources.

 

LED Lighting Technologies to Substitute Natural Light

To substitute natural light is quite difficult also if you consider how hard it is to obtain light near the visible part of the spectrum with traditional luminaries. Light emitting diodes are here to change that difficulty.

SSL (solid state lighting) is the youngest lighting technology and by now is believed to be more efficient than incandescence and fluorescence due to the fact that SSLs produce light at or near the visible part of the spectrum and as a result the emitted light can be used straight or with minor conversion. One of the most important advantages is that SSL technology has eliminated damaging components from the light sources (remember: light emitting diodes contain no ultraviolet unless they are produced as UV LEDs).

NASA is already using SSL in its space farming systems. The reasons are quite simple: incandescent or fluorescent lamps are not efficient enough for such purposes, because they consume a lot of electrical power, generate heat and contain electrodes that burn out (maintenance costs are high). This is why NASA’s plant physiologists started to work with light emitting diodes (blue and red) to grow salad plants such as lettuce and radishes. The researchers found our that blue and red light is essential for plant growth and, in general, a percentage of 8% blue LEDs and 92% red LEDs, both with the same frequency and relative intensity per LED, are enough for a harmonious evolution. Blue has a smaller influence than red however a percentage between 1% and 20% of blue light can be selected, depending on the plants and their growth requirements. The NASA scientists have tried to create the most cost and energy efficient light sources possible, and this is why they have eliminated from the fixtures other colours normally found in white light. "What we've found basically is that we are able to limit the amount of colour we give to the plants and still have them grow as well as with white light." said the research scientist Greg Goins of Dynamac Corp. LEDs are not the only ones efficient for growing plants: sulphur microwave lamps are the most efficient light sources known to man, that can generate as much light as the noonday sun, perfect for illuminating large-scale systems such as greenhouses. For smaller applications, such as indoor gardens, LEDs seem to be the right choice.

 

 

It is so far clear that in order to produce efficient LED grow light systems a lot of investigation is necessary. It is not enough to mount some blue and red LEDs on a PCB and say: “that’s it we’ve got the plant growing LED system". NASA created only a mechanism that delivers the minimum amount of light needed for some plants. For greenhouses on Earth other questions need to be answered: how much blue, how much red? What about the other colours, what about UV and IR? Should the light pulse? Should it be dimmed in the morning and evening to imitate natural conditions (sunrise and sunset?). Do plants need light at night? And the list remains opened.

 

I love you guys! P.S. I have a ton of links to all kinds of led sites, plus the cheapest.. email me and I'll send whatever anyone wants. GG

Edited July 16, 2007 by Granny

[Pam]

While cruising ebay I found a UK seller that has quite a bit to say in the listing, well maybe it looks like alot because the dip has it in a huge font... Still I found it interesting in that he has a few comments that the US sellers have chosen to ignore.

I wouldn't buy his lights, it's just his ad that's interesting.

~~~~~~~~~~~~~~~~~~~~~~

 

http://cgi.ebay.com/LED-Grow-lights-powerf...VQQcmdZViewItem

" target="_blank">

http://cgi.ebay.com/LED-Grow-lights-powerf...VQQcmdZViewItem

[Pam]

Ok I'll try again...

 

 

http://cgi.ebay.com/LED-Grow-lights-powerf...VQQcmdZViewItem

 

I guess it's too big.

Ah poot.~~~~~~~~~~~~~~~~This one works!

Edited July 16, 2007 by Granny

[Pam]

Well, I chickened out using the LED's to flower after looking at that HPS-v-LED site. BUT! I am using the red and the blue for veg and they are doing great. I think the addition of the red to the CFL floods is making a big difference.

I plan to move one of the big reds into the flower box to add to the 400w HPS and angle it up from below to see if it makes a difference there

I'll try for more pix soon.