Jump to content

experiences led


Recommended Posts

Steven, it is a far more complicated subject granted, but what I am trying to convey is that "white is best" depends entirely upon ones viewpoint, "best for what"?

It is all a matter of balance, and red and blue wavelengths are both used and needed by the plants as a greater percentage of the spectrum than offered by an aparently white light.

White light may offer all the wavelengths needed, but not in the correct (or most economical) ratios.

When we buy a growlight say a CFL, the better (for growing) taylored lights are either warm (redder) or cool (bluer) but neither are ideal.

When custom building a whole lamp using individual wavelength constituents, we can taylor the output much more accurately, and so more economically. It is a bit like buying a printer that uses individual inks.

White light to my mind is Jack of all trades but master of none.

Link to comment
Share on other sites

Plants use most red and blue peaks, but they also use the rest of visible wavelenths, even the green light! As Stephen said, the rest wavelengths are not wasted, but less used than red and blue. However, is not a huge difference but for the green light. (The most reflected and non absorbed light)

You can get a little more efficience set up using a more targeted lights. But if you want to display it in your living room is not the best colour to enjoy. I think the difference in saving costs between using only red/blue light, and white light can be given in big set ups like greenhouses or comercial aplications. But in a small tank, differeces in costs are very small.

Anyway, in spite of using mostly white to display my plants better, I keep using some blue 450nm and red 660nm to boost up the most efficience wavelengths.

I agree with you again, and the facts in your last sentance confirm my statements also, it is more a matter of how far you wish to tune it up.

Link to comment
Share on other sites

Hello Dicon, it's always a pleasure to exchange views on this topic.

I believe that my knowledge of optoelectronics and plant biology are good. As for the white LED's in my opinion are the best and then explain motivation. Therefore, plants absorb the wavelengths that have been classified as PAR (Photosynthetically Active Radiation), the wavelengths PAR have a range of 400 to 700 nanometers.

The following graph shows the individual absorbance values​​, and then represents an average of individual absorbance values​​, this average is the best PAR that a plant can receive.

gallery_8021_665_29437.png

gallery_8021_665_2895.jpg

the blue and red lamps only cover a spectrum very narrow and are dedicated only to the peaks of chlorophyll of type A, the rest of the PAR is not covered.

below the wavelengths of the LEDs used for lamps with LED red and blue

Red led 630 nm

gallery_8021_665_9985.jpg

Blu led 450 nm

gallery_8021_665_25429.jpg

As you can see the bell is very narrow and covers a mini but part of the PAR, now I show you the white LEDs graph that I used, the line blu is cool white led and the line red is warm white led.

gallery_8021_665_23981.jpg

Adding the two tones (cool+warm) you have a spectrum much more comprehensive than just red and blue LEDs. Be careful with the white LED's talk about range, while red and blue LED talk about peak. Now, summing up the range of cool white and warm white LEDs have a spectrum similar to the PAR. This means for me a spectrum valid for the proper growth of plants.

Certainly does not hold precisely the peaks of chlorophyll type A, but I assure you that this mixture are very efficient

Prompt

Edited by Prompt
Link to comment
Share on other sites

Hello,

there are many more wavelengths wich are classified as PA radiation. To my knowledge there are about 89 individuell wavelengths known to science wich are classified as PAR, and i think there will be coming up much more soon.

The PAR ranges down down to a sector of electromagnetic radiation wich scientists believe is on half way to the planck length. That means that one photon carrys a huge ammount of energy, and there also is the border of LED technology.

An official diagramm shows wathlenghts down to the UV-B/C sektor

http://www.google.de...52&tx=264&ty=16

It´s certainly senseful to use a light wich combines several wavelengths, than just put together some monochromatic peaks of Blue/Red/Orange/IR.... LEDs.

But in fact you will never ever reach the full PAR spektrum. Also because not all PA wavelengths are known to science yet. (in my personal opinion)

For example i grow my plants with LED light an they also grow in a EM field. I got some surprising results out of these experiments. So the plants wich grow under a EM fiel dont grow in the direction of wich the light comes, instead the grow in the direction of the field stregth.

I hope you can understand what i try to say. My english isn´t that good yet. I apologize for any misunderstandings :blush:

best regards

Karl H.

Edited by Karl H.
Link to comment
Share on other sites

Hello Karl, you're confirming what I'm trying to explain and that is that the wavelengths necessary for optimum growth are not only based on 2 colors.

In my Italian forum we often talk about lighting and that's what I always say:

If Mother Nature has invented the sun with all those wavelengths there is a reason!

Staying in LED theme, I wanted to add that the white LED with the same watt are much more efficient than monochromatic LEDs. I also want to point out that the measurement of the peak of the length of a LED is performed at 25 degrees and has a specific input current. As one of the two parameters also varies the peak wavelength moves to the color scale, the displacement can be tens of nanometers to the right or left of the x axis of the scale. Hardly fail to maintain a monochromatic LED with these conditions, costant current and custant degrees.

lastly, the first lamps grow, with only white LEDs, are already on sale.

for example:

http://www.greenhous...ght/grow-lights

Prompt

Edited by Prompt
Link to comment
Share on other sites

I do grow my Heliamphora under white leds, as I didn't want any other colors in my living room.

If Mother Nature has invented the sun with all those wavelengths there is a reason!

Plants are adapted to the sun. The sun is not adapted to the plants ;).

Edited by Vince81
  • Like 1
Link to comment
Share on other sites

Hello,

Staying in LED theme, I wanted to add that the white LED with the same watt are much more efficient than monochromatic LEDs.

That isn´t true. White LEDs produce their light with the help of a monochromatic light source. A white LED consists of a LED chip wich emits photons of a high energy level, such as blue or UV. These high energy Photons hit the yellow phosphorescent layer wich you can see when you look at a white LED. Thist high energy photon brings an electron in the phosphorescent layer to an excited state. The photon an this excited state looses some energy due to thermal vibrations (because were are well above 0K). Now the electron falls down from the excited state minus the lost energy down to it´s point were it startet. At that moment where it reaches that point the electron emits a photon of less energy as the photon wich hits the electron. So the output of the white LED is less than the output of the blue LED (or any other wavelength with higher energy photons as the light you want to get out of the final LED). This means that monochromatic LED can be much more efficient than white LED´s.

Red and blue LEDs also only have a low lumen output due to the way one lumen is measured. One lumen is a energy of 1,464 mW on the specific wavelengths of 555nm. At this waveleghts the human eye has reached it´s sensitivity amplitude. Now the human eye has a much lower sensitivity to red. This means one lumen of a 555nm light source equals only 0,1 lumen of red light source.(the human eye has about 10% sensitivity to red compared to its maximal sensitivity)

I also want to point out that the measurement of the peak of the length of a LED is performed at 25 degrees and has a specific input current. As one of the two parameters also varies the peak wavelength moves to the color scale, the displacement can be tens of nanometers to the right or left of the x axis of the scale. Hardly fail to maintain a monochromatic LED with these conditions, costant current and custant degrees.

That is not true.

Yout have to run your LED at -50°C to move the peak only 10nm to the left. As i explained before thermal vibrations in the LED causes a photon to lose some energy at it´s excited state. This means that the hotter the LED gets the more it output wavelenths moves to the right, of the visible spectrum. (if you go in right direction of the electromagnetic spektrum the ammount of energy per photon decreases) But you could never move the peak to the left (left=higher energy per photon) when heating up the LED.

Here you can see how the photon energy increases with falling temperatures. The Light of the LED moves from the right side of the visible spectrum to the left side of the visible spectrum. At some point around absolute zero the LED theoretically would emit a light wich has the frequency of the Planck-length. Also the different wich temperature makes to the output spektrum of a LED ist in the positive temperature range very small.

Well the last argumentation wasn´t 100% correct. The colorchange in a non flourescent system such as an monochromatic LED ist due to the bandwith depending on the temperature. This is a bit more complicated but the result is the same

Best regards

Karl H.

Edited by Karl H.
Link to comment
Share on other sites

Hello Karl, congratulations!

You gave a great presentation on the science of the LEDs.

I just wanted to add to your argument that the temperatures are lowered more and more electrons travel better in the conductors, thus theoretically a led led to low temperatures is more efficient and therefore the peak of the wavelength remains fairly constant. As if the LED warms the shift of the peak is more evident.

With regard to the lumen in fact you're right, you can not use the lumens for plants. As regards the efficiency meant that overall, in the white LED wavelengths are varied and summing these lengths theoretically the efficiency as well for plants, increases.

In monochromatic LEDs but also in white is used for testing a specific costant current, it is evident that the variation of the current may lead to a shift of the emission peak. I also remember that more power equals more power dissipated into heat.

view: http://streetlightingresearch.org/programs/solidstate/pdf/Gu-SPIE6337-17.pdf

I wanted to thank you for sharing your knowledge

Prompt

Edited by Prompt
Link to comment
Share on other sites

White LEDs have peaks and those peaks often do not closely match those of the chlorophyll absorption bands. If you take for example the graphs above, you can see that the chlorophyll 'a' absorption peak is above 650nm, probably somewhere near 660nm, but the red LED you have chosen to show is 630nm and the white LED graph is starting to significantly fall off at this wavelength too.

To my mind, the ideal combination would be to use LEDs from the two main chlorophyll absorption band peaks and add some white LEDs to help achieve some of the other wavelengths. Red LEDs in 660nm are commonly available and would fit the absorption band shown in the above graphs much better than 630nm for example. But as stated, white LEDs still do not cover the whole spectrum, so even as supplementary, the plants will not be getting all the wavelengths they would from natural light.

What I have not seen though, and the only way of quantifying this scientifically, would be to perform a controlled experiment. Anything less than this would only be theoretical and subject to debate. But theoretically, targeting the wavelengths at the chlorophyll absorption bands would seem be more efficient, rather than the shotgun approach.

Link to comment
Share on other sites

Hi All,

not had enough time to reply before and some of what I wanted to say has been partly covered in latter posts.

I have been putting this together during odd minutes over a couple of days.

Hi Prompt,

I too find this subject very interesting as I know many do, but there is a whole mass of misinformation surrounding the whole subject of grow lights in general, and LED’s in particular.

Firstly I would like to say that I have no formal qualifications in this field so must bow to superior technical knowledge, however I understand general sciences and I am very enquiring and would like to take this opportunity to hopefully discuss some real facts. I will try to ask, I hope, intelligent questions and may even ask the same thing twice but from another direction in order to fully understand and maybe get to the bottom of this subject. In doing so I may challenge some of your own views.

I have read many versions of what is represented by the Absorption and Spectrum graphs. Whilst they all look the same, they are perhaps interpreted differently.

From Prompt post:

The following graph shows the individual absorbance values​​, and then represents an average of individual absorbance values​​, this average is the best PAR that a plant can receive.”

Absorption: Chloro.a absorbs over 60% of light offered to it at about 430nm but absorbs nil at 500nm, it also absorbs about 50% of light offered at about 660nm.

Chloro.b absorbs over 80% @430nm and 25%@640nm

At these wavelengths, Chloro.a photosynthesis within the plant cells is at 90 to 100% ie very efficient.

Chloro.b is at about 80% active.

Roughly 50nm either side of these peak wavelengths, both Absorption and therefore Photosynthesis Rates fall by about 50 to 100%. Ie ZERO.

Carotenoids or “antenna pigments” absorb a wider range of wavelengths and channel energy into photosynthesis action centers, however this is far less efficient than direct chlorophyll photo-action, and is probably more use to a plant in deep shade or undergrowth collecting reflected wavelengths ??

I am aware also of Cryptochrome and Phytochrome that also happen to be activated by blue and red light respectively.

So the primary, most essential colours (I use the word colour as this describes a range of wavelengths and not a specific nm) appear to be reds and blues.

I am not saying ONLY but PRIMARY.

Yes photosynthesis takes place at other wavelengths, however

1. If photosynthesis is 80 to 100% efficient at a specific nm then this is pretty much all that is actually needed to do the job.

2. Providing other wavelengths is by definition wasteful and therefore inefficient. (if you invite a Vegan to lunch, putting meat and two veg on their plate is a waste of meat)

3. If you were to provide a plant with all wavelengths except red and blue, it would die within weeks, but if you only provided it with red and blue light it would survive and grow.

Again I am not saying that this is absolute good advice, I am pointing out that these are the basic principals of targeted wavelengths.

The reality is that a blend of spectrums is probably better for a plant, but to be BEST (most efficient) the spectrum should be heavy on red and blue.

My LED panel consists of about 5.2 : 1 red : blue ratio, specifically 13 x 640nm, 13 x 660nm, 5 x 430-450nm and 4x Cree XR-E warm white (all 3watt)

This, whilst clearly mostly red and blue, also covers many other wavelengths via the XR-E’s .

Karl has covered what I was to say about Lumens.

LED's run at different voltages but constant current and so power sources must be of CC. also the cooling of LED's is as has been mentioned above, actually quite important. The problem with most "available Grow Lights" is that they cram as many chips into as compact a lamp as possible, this leads to overheating and premature fade and life of the chips. Also cramming 100's of watts of chips into as small a space as possible, concentrates the "beam" like a spot light and can easily be blocked off by foliage shading, for better penetration, is is actually better to spread the chips out.

Edited by Dicon
  • Like 1
Link to comment
Share on other sites

What area are the respective arrays intended to cover? I've only noticed reference to large and small terraria.

Fred I use my 70watt panel as a winter supplement in the greenhouse, as such it covers about 1sq M.+ However if using as a sole light source, it is recommended for about 50 x 50cm (1/4)

Link to comment
Share on other sites

In my Italian forum we often talk about lighting and that's what I always say:

If Mother Nature has invented the sun with all those wavelengths there is a reason!

Mammals, insects, plants etc do not use them all, only parts so it is not really relavent

Staying in LED theme, I wanted to add that the white LED with the same watt are much more efficient than monochromatic LEDs.

At producing LUMENS perhaps but targeted wavelengths are not measured in lumens as lumens are perceived by human eyes only and not relavent to plants.

Prompt

Link to comment
Share on other sites

Hello everyone,

White LEDs have peaks and those peaks often do not closely match those of the chlorophyll absorption bands. If you take for example the graphs above, you can see that the chlorophyll 'a' absorption peak is above 650nm, probably somewhere near 660nm, but the red LED you have chosen to show is 630nm and the white LED graph is starting to significantly fall off at this wavelength too.

I talked a lot obaout this with Andreas Wistuba and a friend of mine who ist biomechanics professor. Due to this conversations i think that ist isn´t very importand to reach the amplitude of the abosption graph. I will translate the mail from the professor for the explanation. Well with my english it could take a while :unsure: . But to see why i have got this impression you just have to look on the spectrum of a T5 840 Philips flourescent tube. Many growers will confirm tha the T5 flourescent tube ist very good for grow rate and coloration. Now look at the spectrum:

http://www.narva-bel...ite_RGB.jpg.png

You can see the emission peak in the red light sector is well before 650nm. But nonetheless the Plants grow very good onder this tube.

If you were to provide a plant with all wavelengths except red and blue, it would die

@Dicon,

it isn´t true that a plant would die without red and/or blue. Currently i grow some plants under orange 590nm an UV 365nm. There isn´t any other light source near to the plant and they´re doing very well an get a deep red coloration.

Also it´s sensless to give the plants a huge ammount of blue an red light, because there is not only a absorption maxima to the wavelenghts. There is also a absorption maxima of the ammount of photons wich one plant cell can take and process with. So at some point also red and blue light is just wasted. Unfortunately we dont know where this photon-ammount-maxima is, an we also don´t know if this maxima value ist the same for all wavelengths. (but i think it´s not)

The cooling by the way of the comercial available grwo lights is quiet good. The temperatures of the heatsink doesn´t go over 45°C. So if you now calculate bakwards with the thermal contact resistance you end up with a actual chip temperature of 124,3°C. Thist value ist quiet normal even Cree LED´s work with higher chip temperatures.

Also the plants had million years time to adapt to the sunlight. They perfected their photosynthesis under the given light circumstances, an we can´t simply take a big range of the natural wavelengths away und just fire some high and low energy photons at the plants, just because we think it´s more efficient. All processes in the nature underlie the laws of physiks. And when it comes to efficiency of a system with a input output enregy comparison, the laws of physics are unbeatable good in. ;)

best regard

Karl H.

Edited by Karl H.
Link to comment
Share on other sites

Staying in LED theme, I wanted to add that the white LED with the same watt are much more efficient than monochromatic LEDs.

At producing LUMENS perhaps but targeted wavelengths are not measured in lumens as lumens are perceived by human eyes only and not relavent to plants.

White light LEDs are made by down-converting blue light using phosphors, so how could this possibly be more efficient than the monochromatic blue LED?

Link to comment
Share on other sites

Hello everyone,

I talked a lot obaout this with Andreas Wistuba and a friend of mine who ist biomechanics professor. Due to this conversations i think that ist isn´t very importand to reach the amplitude of the abosption graph. I will translate the mail from the professor for the explanation. Well with my english it could take a while :unsure: . But to see why i have got this impression you just have to look on the spectrum of a T5 840 Philips flourescent tube. Many growers will confirm tha the T5 flourescent tube ist very good for grow rate and coloration. Now look at the spectrum:

http://www.narva-bel...ite_RGB.jpg.png

You can see the emission peak in the red light sector is well before 650nm. But nonetheless the Plants grow very good onder this tube.

@Dicon,

it isn´t true that a plant would die without red and/or blue. Currently i grow some plants under orange 590nm an UV 365nm. There isn´t any other light source near to the plant and they´re doing very well an get a deep red coloration.

Also it´s sensless to give the plants a huge ammount of blue an red light, because there is not only a absorption maxima to the wavelenghts. There is also a absorption maxima of the ammount of photons wich one plant cell can take and process with. So at some point also red and blue light is just wasted. Unfortunately we dont know where this photon-ammount-maxima is, an we also don´t know if this maxima value ist the same for all wavelengths. (but i think it´s not)

The cooling by the way of the comercial available grwo lights is quiet good. The temperatures of the heatsink doesn´t go over 45°C. So if you now calculate bakwards with the thermal contact resistance you end up with a actual chip temperature of 124,3°C. Thist value ist quiet normal even Cree LED´s work with higher chip temperatures.

Also the plants had million years time to adapt to the sunlight. They perfected their photosynthesis under the given light circumstances, an we can´t simply take a big range of the natural wavelengths away und just fire some high and low energy photons at the plants, just because we think it´s more efficient. All processes in the nature underlie the laws of physiks. And when it comes to efficiency of a system with a input output enregy comparison, the laws of physics are unbeatable good in. ;)

best regard

Karl H.

Most of this is speculation and circumstantial. In addition, I would expect a plant to take on good colouration if exposed to UV light but would not consider it to be indicative of good growth conditions.

Link to comment
Share on other sites

Hello,

well good grow conditions also can be seen relative. The plants however grow just as good as unter a T5 tube.

Most of this is speculation and circumstantial

We just know to little about the photosynthesis process to target only a few wavelenths. That´s what even the prof said. In Nature every process is entangled with another, so we cant say that a specific light ist good for a plant, when we even dont know what funktion all wavelenghts in the spectrum of the sun have.

best regards

Karl H.

Link to comment
Share on other sites

We just know to little about the photosynthesis process to target only a few wavelenths. That´s what even the prof said. In Nature every process is entangled with another, so we cant say that a specific light ist good for a plant, when we even dont know what funktion all wavelenghts in the spectrum of the sun have.

This is true, but we do know that plants use red and blue at specific wavelengths, due to chlorophyll absorption. Also, white lights are tailored towards the human eye and do not give an even distribution across the whole visible spectrum, so may also be missing the wavelengths required by plants and will almost certainly be producing wavelengths that are of little use.

For efficiency, surely it would be best to pick the wavelengths that we know plants can use efficiently then add some white in the hope that it might contain some of the other unknowns?

Link to comment
Share on other sites

Hello,

For efficiency, surely it would be best to pick the wavelengths that we know plants can use efficiently then add some white in the hope that it might contain some of the other unknowns?

Yes that would be tha best way. Maybe there are wavlenghts wich trigger processes wich are very important for photosynthesis. So it could be possibile that due to the missing trigger wavelength the efficiency of the alleged good system is lost. Maybe the fact that wavlenghts are mssing shows up just after a long time? Wen dont know about that, so why for example run the risc of loosing the plant due to long term damage caused by missing wavelenghts, when we simply can add the missing wavelengths, by mixing in some white light? That was just an example, there could be far more negative effects, but as is said before, we dont know about them yet.

best regards

Karl H.

Link to comment
Share on other sites

Well there's plenty theory out there and the argument seems to fall into varied camps on what is important. Can we hear more about PRACTICAL trials now?

I'm using red / blue lights in the cellar so it's the only light source, except for when I go down there with the standard cfl lights on.

I have 4 trays of 21" x 21" (51cm x 51cm) using about 15W each so 60W for 1m². at present lighting is on for 10 hours / day.

Temperatures are from 6C to 12C.

Two trays have the commercial 225 led panels and I think they are just OK, I'll be supplementing that light soon with 4 x 3W blue leds.

The other two trays are lit with arrays I made up . They compromise 5 x 3W 120° (60 led) bulbs held lower down to the plants..

I have plans to add a further circuit to each array and have that on a seperate timer so light intensity can be increased for the miiddle hours of the 'day'. Here I am considering using 4 x 2W 120° (38 led) bulbs which can be red/blue or white or any other colour / combination. the 3W bulbs could also be utilised if it is considered more light is required but I doubt that would be necessary.Hours will also be extended on all lights as the season progresses.

Even at these low power usages I have Utricularia bisquamata "Betty's Bay. Utricularia livida and Pinguicula Tina in flower.

Please note This set up is mainly to provide frost free conditions for the plants however It is proving to be quite interesting.

Edit Perhaps I should also add that my home made arrays are a much cheaper way of supplying the light cheaper than even the 225 led panels which were under £20 each. If a bulb does prove faulty ( which has not happened yet) the whole array isn't lost as with the panels, it's just a matter of replacing a bulb ( £3.50)

Edited by FredG
Link to comment
Share on other sites

As an observer and not by scientist, I see that many times our theoretical discourses remain.

In nature, plants have adapted to different types of light, full sun, shade, or mixed light, which is why my argument is based on giving the plant the largest range of shades possible. As mentioned by Karl still do not know for sure all about the life of plants, and a spectrum of light designed not necessarily be better than another. The white LEDs as well as the plants grow very well (this is not theory, but practical), are also visually more natural to the human eye.

Many of the fluorescent lamp we use 6500k or 4000k are not specialized in the peaks of chlorophyll but the plants grow well, even in a scentiphic test on the germination of seeds of Nepenthes is referred to as the yellow light is the one that did germinate seeds . while blue light germination was low.

http://www.tuengr.com/V02/083-091.pdf

Prompt

Link to comment
Share on other sites

With regard to the lumen in fact you're right, you can not use the lumens for plants. As regards the efficiency meant that overall, in the white LED wavelengths are varied and summing these lengths theoretically the efficiency as well for plants, increases.Suming the wavelengths is not a benefit surely?as it is firstly a dilution of the best or desired wavelength that is being added back together, (sounds ok) but as the "off target" wavelengths are of Zero use to the chlorophyll they lose any benefit and cannot be added back so are a drop in efficiency. In monochromatic LEDs but also in white is used for testing a specific costant current, it is evident that the variation of the current may lead to a shift of the emission peak. I also remember that more power equals more power dissipated into heat.As each emitter requires a different voltage, running at constant current is essential, this means that in a properly constructed lamp, th use of say 100 x 3watt chips run correctly (to ensure long life) consumes somewhat les than 300watts.view: http://streetlightin...SPIE6337-17.pdfI wanted to thank you for sharing your knowledgePrompt
Edited by Dicon
Link to comment
Share on other sites

For efficiency, surely it would be best to pick the wavelengths that we know plants can use efficiently then add some white in the hope that it might contain some of the other unknowns?

This is as I have described my current LED panel

Link to comment
Share on other sites

Well there's plenty theory out there and the argument seems to fall into varied camps on what is important. Can we hear more about PRACTICAL trials now?

From a practical point of view, I have a 7W GU10 4200K lamp and nothing I have tried growing under it does any good.

Interestingly, Philips have entered into the grow light arena and their lamps are based on various combinations of deep red, far red, blue and white. As far as I can see, they only use white in combination with one of the other wavelengths.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...