Turning coal into...Ok ..Silver!

stardustsailor

Well-Known Member
I have a couple of dozen of those going and they are not so bad at all. There is an EpiLED chip inside. I did some crude caloric measurements of the radiometric efficiency and it's in the ballpark of 30%. They are slightly better than the 620nm from Satisled.
Is their efficiency all that matters ?
Those leds have other "troubly " characteristics ...

Neither I can trust that are more efficient than the 620-630 nm ones ..
Not the Epiled dies ,at least ....
The AlGaInP semiconductor alloy is far more efficient in light generation than the Zinc Oxide Gallium Phosphide ...
Technically the 660 nm Epileds could not be of superior efficiency than 625-635 nm ..

But this is not the real problem with those ...

Their emission spectrum is way dependable on chip temperature and impurities (of GaAS )..
And really narrow banded ...


(..)AlGaInP is used in manufacture of light-emitting diodes of high-brightness red, orange, green, and yellow color(...)

https://en.wikipedia.org/wiki/Aluminium_gallium_indium_phosphide





(...)Gallium phosphide (GaP) is a polycrystalline compound semiconductor that appears pale orange and has an indirect band gap of 2.26 eV. Single crystal wafers that are not doped have a clear orange color; however wafers that are doped strongly look darker as free-carrier absorption takes place. It does not dissolve in water and is odorless. The dopants used to obtain n-type semiconductors are tellurium or sulfur. For the p-type semiconductor, zinc is used.(...)

(...)Gallium phosphide is used in the manufacture of low-cost red, orange, and green light-emitting diodes (LEDs) with low to medium brightness since the 1960s. It has a relatively short life at higher current and its lifetime is sensitive to temperature. It is used standalone or together with gallium arsenide phosphide.

Pure GaP LEDs emit green light at a wavelength of 555 nm. Nitrogen-doped GaP emits yellow-green (565 nm) light, zinc oxide doped GaP emits red (700 nm).(...)

https://en.wikipedia.org/wiki/Gallium_phosphide





 
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lax123

Well-Known Member
I mean I could put those 660 on a really nice cool heatsink no prob or I drive them lower then 650mA.
What I dont know are their impurities.
Other than that i dont know if its thaaat bad if the 660 is narrow. Maybe I should use 660 vs 630 like 1:4.
Or I trash them if you think they do more bad then they do good.

I have 4x 30W WW, 2x 30W CW, 4x 100W WW, 2x 30W 630nm, 18x 3W 630nm, 18x 660nm, 15 WW, 8 CW, 4 B, 1x XMLU2 WW 12Vf, couple cree CW
And lots of heatsinks, lots of 30W 900mA drivers and 4x 50W 0,65A 73V drivers
My Space is 56cm x 78cm x 200cm

If I use all of them thats a lot of wasted Wattage for that space and since my first grow went well for me (but not efficiency wise haha), all I want to do now is to have fun trying to build the most effcient panel(s) for my space with the (shitty) components I have or even buying some more if neccessary.
Even if it means just to use 150W in that space.

Btw what do you think which Wattage I should aim for for those 0,44m^2 or 4,7 sqft?

(Too bad my lowest driver puts out 600mA, i wish it was 350mA for those 3W leds.
I tested parallel with arrays and there it worked good even without additional restistors, their Vf match very well.
hmm but I guess trying to run two strings of 3W in parallel on 600mA CC could be a pain.
Another Idea of underdriving is to put all 4x 30W WW 2 in series + in parallel on that 50W, 650mA 70V driver on the same heatsink.
Hehe so many possibilites.)
 

MrFlux

Well-Known Member
Somehow I missed an entire page in this thread. But EpiLED is using AlInGaP according to their (ancient) datasheets, see here or here.
 

stardustsailor

Well-Known Member
Somehow I missed an entire page in this thread. But EpiLED is using AlInGaP according to their (ancient) datasheets, see here or here.
Mr Flux ,somebody here is telling lies to us all ....

Either that is the person ( my ' inside informer' ) who told me the details of manufacturing those 660 nm deep reds ..

Or Epiled is a big fat liar...

Epiled BH-C4242D-A1 :
- 42x 42 mil chip
- 650-680 nm peak
-Radiant power : @350mA : 12-40 mW !!!!!


Epistar ES-SMBRPN42C :
-42 x 42 mil chip
- 650-670 nm peak
-Radiant power >:(350mA :210-250mW !!!!!



http://www.epistar.com.tw/upfiles/files_/ES-SMBRPN42C.pdf


Well...To me they do not seem to be both from AlGaInP alloy ...
Way -way much output power difference ...
One of them uses the old tech ....of ZnO doped GaP.....
Don't you think so ?
 

stardustsailor

Well-Known Member
I mean I could put those 660 on a really nice cool heatsink no prob or I drive them lower then 650mA.
What I dont know are their impurities.
Other than that i dont know if its thaaat bad if the 660 is narrow. Maybe I should use 660 vs 630 like 1:4.
Or I trash them if you think they do more bad then they do good.

I have 4x 30W WW, 2x 30W CW, 4x 100W WW, 2x 30W 630nm, 18x 3W 630nm, 18x 660nm, 15 WW, 8 CW, 4 B, 1x XMLU2 WW 12Vf, couple cree CW
And lots of heatsinks, lots of 30W 900mA drivers and 4x 50W 0,65A 73V drivers
My Space is 56cm x 78cm x 200cm

If I use all of them thats a lot of wasted Wattage for that space and since my first grow went well for me (but not efficiency wise haha), all I want to do now is to have fun trying to build the most effcient panel(s) for my space with the (shitty) components I have or even buying some more if neccessary.
Even if it means just to use 150W in that space.

Btw what do you think which Wattage I should aim for for those 0,44m^2 or 4,7 sqft?

(Too bad my lowest driver puts out 600mA, i wish it was 350mA for those 3W leds.
I tested parallel with arrays and there it worked good even without additional restistors, their Vf match very well.
hmm but I guess trying to run two strings of 3W in parallel on 600mA CC could be a pain.
Another Idea of underdriving is to put all 4x 30W WW 2 in series + in parallel on that 50W, 650mA 70V driver on the same heatsink.
Hehe so many possibilites.)
100-200 Watts (@ plug )would do the job,just fine ,I pressume..
 

MrFlux

Well-Known Member
Epiled BH-C4242D-A1 :
- 42x 42 mil chip
- 650-680 nm peak
-Radiant power : @350mA : 12-40 mW !!!!!
This is an error in the documentation, instead of mW they mean mcd. Anyway these red LEDs from Satisled perform well for the money and it would be a waste to just throw them away.

About COBs and better light spreading: Don't forget about small COBs! For example Cree CXA1304, Bridgelux V8 or Vero 10. Of these three the vero 10 is the most cost effective, even though V8 was supposed to be lower cost. Vero 10 is the same size as the familiar 20mm star, but much brighter. Think of it as a superstar. What you get are 18 Bridgelux 1W chips conveniently packed together in a star format.
 

stardustsailor

Well-Known Member
Dear Mr Flux ..
I would gladly accept that this is a error in the documentation ...
But I have several doubts still...

1)
(...) This specification applies to AlInGaP metal bonding 42 x 42mil red LED chip, BN-R4242E-A3
( 600-650 nm die ..... typ :625 nm )

Luminous intensity(Iv) : 350mA : 1600 - 13100 mcd => 5- 41 lm @ 120° <= those numbers seem to stand as true ...

http://led.linear1.org/lumen.wiz
......
It can not be mcd ( 12-40 millicandelas ? => 0.0 something lumens )

2)
If it lumens (12-40 ) ,then that chip has similar efficiency with Osram Oslon Hyper red bin T2 ..
So ,it can't be lumens either ....

3)
(...) This specification applies to AlInGaP metal bonding 42 x 42mil red LED chip, BH-C4242D-A1
(650-680 nm die )

Radiant intensity(I) :350mA : 12-40 mW

4) Do not give any importance to driving currents on the following document (it refers to small 20mA epoxy leds ).
Read about the semiconductor alloy properties ...


"
Original Visible Red, GaAsP on a GaAs Substrate - These LEDs were the original commercially successful visible type. The working chemistry is gallium arsenide phosphide with an arsenic/phosphorus ratio of around 60-40 by number of atoms, on a gallium arsenide substrate. The spectral output typically peaks around 660 nm in a band that is unusually narrow for red LEDs. The color is a pure red. The efficiency is horribly low, a few hundredths to around a tenth of a lumen per watt. Most LED lamps using this technology have a maximum continuous drive current of 50 mA and need 20 mA to be reasonably bright, optimistically working OK at 10 mA. The efficiency is maximized at higher currents of 20 mA and up. Typical voltage drop is 1.6 to 1.75 volts. These dimly glow at 1.5 volts.


Low Current Red, GaP - This was the original high efficiency red LED, which was available as far back as 1976. The chemistry is gallium phosphide doped with zinc oxide. These LEDs are usually impressively efficient (1 to maybe 2 lumens/watt) at low currents of a few mA or less, but are only about 2-3 times as efficient as the original formula red ones at 20 mA. The color varies with current, and is nearly enough pure red at .5-1 mA but more orange at higher currents. If the lamp is not tinted red, the emitted light is usually orange to sometimes slightly yellowish orange at 30 mA. The spectral output is a broad band, nominally peaking at 697 nm and maybe only peaking that far out in the red at really low currents. There is a secondary spectral band in the green peaking around 550-560 nm which is more noticeable at higher currents. Maximum drive current is usually 30 mA, but these LEDs have noticeably nonlinear light output that increases less than proportionately with current above a few mA. Voltage drop is around 1.9 volts.


Super High Brightness Red, GaAlAsP - These things became available in the mid 1980's. Earlier models with opaque substrates were impressive back then with efficiencies of 1-2 lumens/watt. These have since been improved, with transparant substrates and other refinements. Agilent has a similar chemistry which they call "T.S. AlGaAsP". The overall luminous efficacy of the best models is about 9 lumens/watt. The spectrum usually peaks between 650 and 670 nm, but some Agilent models peak slightly shorter. The color is pure red to He-Ne laser red, with a dominant wavelength (wavelength of monochromatic light of matching color) usually in the 640's but anywhere from about 635 to about 650 nm. Efficiency is usually maximized at currents near 20 or 25 mA. Efficiency at low currents of around a mA to a few mA is not impaired as badly as it is in many other types that have efficiency peaking near or over 20 mA. Typical voltage drop at 20 mA is 1.8 to 1.9 volts. Maximum rated drive current is usually 30 mA but sometimes 50 mA. These usually glow dimly at 1.5 volts.


High Efficiency Red, Orange Red, and Orange, GaAsP on GaP substrate - This was the first non-low-current high-efficiency red LED. The working chemistry is gallium arsenide phosphide, with an arsenic/phosphorus ratio around 40-60 on a gallium phosphide substrate. The GaP substrate is transparant to the emitted light and GaAs is not. This is one reason why these LEDs are more efficient than the original formula red ones. The color is normally orange-red with a dominant wavelength around 620 nm. A slight variation of this has a dominant wavelength usually around 610-615 nm and is considered orange. The peak wavelength is usually around 630 nm. Typical drive current is 5 to 20 mA and maximum current is usually 30 mA. Typical voltage drop at 20 mA is around 1.9 volts.


Ultrabright Orange-Red, Orange, Yellow, and Green, InGaAlP - The indium gallium aluminum phosphide LEDs came out in the early 1990's. These are usually either red-orange with a dominant wavelength around 610-617 nm, or yellow or "amber" with a dominant wavelength around 590 nm. Dominant wavelength can be as low as the 550's of nm ("pure green" or "emerald green", yellowish green but less yellow than usual for LEDs) and as high as the low 630's (He-Ne laser red). The most efficient ones are usually orange to orange-red. Overall luminous efficacy for orange and orange-red ones is anywhere from 7 to 28 lumens/watt, with most made after 2000 achieving at least 12 lumens/watt. Yellow ones are mostly a little less efficient, 4 to 15 lumens/watt with most made after 2000 achieving at least 8 lumens/watt. Green ones are less efficient still (mostly 3-4 to about 8 lumens/watt) but more efficient than GaP and GaAlP green LEDs. With the exception of some more-red models, these LEDs have significantly reduced efficiency at low currents of a few mA or less. Typical drive current is 5 to 20 mA. Maximum drive current is usually 30 mA in 3 and 5 mm "bullet" style units. Typical voltage drop at 20 mA is around 1.9 to 2.3 volts depending on the specific variation. "

http://donklipstein.com/ledc.html
 

MrFlux

Well-Known Member
It can not be mcd
Yeah it can't be mcd, I don't know what they could have meant. It's wrong in the lower table too. Take Chinese or Taiwanese documentation as far as you can throw it.

These red and deep red chips from Epileds must be used on a massive scale (in the Cidly panels etc) and are likely growing more weed at this very moment than any other chip.
 

stardustsailor

Well-Known Member
Yeah it can't be mcd, I don't know what they could have meant. It's wrong in the lower table too. Take Chinese or Taiwanese documentation as far as you can throw it.

These red and deep red chips from Epileds must be used on a massive scale (in the Cidly panels etc) and are likely growing more weed at this very moment than any other chip.

I can not disagree with that "These red and deep red chips from Epileds must be used on a massive scale and are likely growing more weed at this very moment than any other chip " ....
 

stardustsailor

Well-Known Member
120-400mW is more realistic
Dear Guod ...
It also crossed my mind ...
That they forgot the zeros ..
But then I thought ...
" I can't be soooo stupid and bought myself the Oslons ..."

oslon LH.JPG...

So ,the thought of "forgotten zeros " quickly vanished ....
There's no way those Epileds can reach ~48% efficiency ...
Even if they were having an InGaAlP sem/or alloy ...

Still I insist ....

Stay away from those 650-670 from Eastern led market...
Except if it is an Epistar chip inside ...And the price is ~ 1$ per led or less...
Any other option really,ain't worth the money ..
My opinion ...

Unfortunately ( or not ),in that 8mm volume emitter ' led format ',
there aren't many worthy choices for the deep red range ...
Only few ones ....
 

stardustsailor

Well-Known Member
The most famous LED manufacturers in the world

1- CREE (USA)
2- NICHIA (Japan),

3- OSRAM (Europe)
4- Philips - Lumileds (Europe)
5- Toyoda Gosei (Japan)



Many disagreements on patents and commercial relationships.


shema_interconnection.jpg


Other famous LED manufacturers :

- HP
- TOSHIBA ( Japon )
- SDK ( Japon )
- Smileds ( USA )
- Genelite ( Japon )
- Citizen Electronics


LED Manufaturers in TAIWAN

First level

- Epistar
- Opto Tech
- Tynteck
- Huga
- Arima
- FOREPI
- Genesis Photonics
- Tekcore
- Chimei

Second level
- Formosa Épitaxie
- Ledtech Electronics
- Unity Opto Technology
- Para Electronics lumière
- Everlight Electronics
- Luminous LED Electronics
- Kingbright
- Lingsen Precision Industries
- Ligitek Electronics
- Lite-On Technology
- Harvatek


Chip manufacturers in South Korea
- Seoul Semiconductor
- Epivalley





Chip manufacturers in China

There are over 60 manufacturers of LED chips in China, for the moment.

Here is a top 10 manufacturers of LED chips


1. SANAN, Xiamen sanan Optoelectronics Co., Ltd, Xiamen
2. Silan, Hangzhou Silan Azure Co., Ltd, Hangzhou
3. Inspur, Shandong Inspur Huaguang Optoelectronics Co., Ltd, Jinan
4. Lumei, Dalian Lumei Optoelectronics Corp, Dalian
5. Changelight, Xiamen Changelight Co., Ltd, Xiamen
6. Epilight, Epilight technnology Co., Ltd.Shanghai
7. HC SemiTek, Wuhan HC SemiTek Co., Ltd, Wuhan
8. Aqualite, Aqualite Co., Ltd, Wuhan
9. APT, Electronique APT, Guangzhou
10. Neo-Neon, Neo-Neon Holding SA, Jiangmen

Brief presentation of some manufacturers of LED chips:

1) Nichia (Japan)
It is THE most famous manufacturer of LED chips in the world. Founded in 1956, it created the first blue LED in 1993 and the first pure green LED in 1995. They have many subcontractors worldwide. He has filed numerous patents on LED.

2) OSRAM (Germany)
It is the second largest manufacturer of LED chips, with headquarters in Germany, development and production, however in Malaysia. They mini LED OSLON Square, only about 3mm 3mm. Very little heat exchange between components, the quality of the chips is more stable and more efficient, its lifetime is long.

3) CREE (USA)
It is the most famous manufacturer of LED chips. CREE LED is the brightest LED in the LED world, but it is among the most reliable and stable in the world, with very little loss of optical performance, service life is long.

4) Toyoda Gosei (Japan)
He produces automotive components and LEDs. They created the white LED with in partnership with Toshiba.

5) Toshiba (Japan)
It is the most famous LED supplier for the automotive industry.

6) AGILENT
Their products are used in the automotive industry, billboards, etc.. Their LEDs are very stable and efficient.

7) LUMILEDS
Its production is geared towards high-power LED chips, including the most famous of its patented products: Luxeon range.
If its headquarters in the USA, it also makes the Netherlands, Japan and Malaysia.
Following a joint venture between Agilent and Philips, Philips has finally acquired in 2005.



http://www.dilligot.com/world-factory-led,us,8,44.cfm
 

stardustsailor

Well-Known Member
Now I'm confused ..
Osram uses InGaAlP for its LH deep reds?

How come I remember it-the semiconductor alloy- being Aluminium gallium arsenide ( GaAlAs ) ,for the 660 nm ?
[h=2]Osram red LED smashes the 200 lm/W barrier[/h] Oct 11, 2011 The firm says the results of this project can be extended to all the wavelengths in the aluminium indium gallium phosphide (AlInGaP) range to boost efficiency.
A red high-power LED has set a new efficiency record in an Osram Opto Semiconductors R&D lab with an electro-optical efficiency of 61%.

The 1 mm[SUP]2[/SUP] chip housed on a laboratory package emits at a wavelength of 609 nm (&#955;-dom) and has achieved a record value of 201 lm/W at an operating current of 40 mA. At a typical operating current of 350 mA its luminous efficacy is still an impressive 168 lm/W, which means that even at this high wattage more than half of the electrical energy is converted into light.LED colour mixing systems such as the Osram Brilliant Mix concept are the latest trend, particularly for general illumination applications. These systems enable any kind of white light to be produced, from Warm White through Neutral White to Daylight White. The overall performance of the system is as good as the individual components will allow.

Osram&#8217;s says its new red high-power LED promises a further improvement in the quality of light with lower power consumption, especially in Warm White. This will benefit not only colour mixing concepts but also all applications that use high-efficiency red LEDs &#8211; in the general illumination, projection and automotive sectors.

Higher efficiency means more light from the same amount of electricity, which in turn means lower power consumption for a particular application. Because fewer chips are needed to produce the same brightness level, designers will have greater freedom. The light sources can be made smaller while still producing the same brightness.

Martin Behringer from the LED development team at Osram Opto said, &#8220;The results of this project can be extended to all the wavelengths in InGaAlP chip technology so we anticipate a boost in efficiency in these light colours &#8211; even at 660 nm which is the wavelength needed for plant lighting for example. Probably we will be introducing the results of this development project across the entire wavelength spectrum into production in about a year&#8217;s time.&#8221;

The enormous increase in output was achieved by a chip with the latest generation of the company&#8217;s own thin-film technology.

http://www.compoundsemiconductor.net/csc/news-details.php?cat=news&id=19734099&key=osram&type=n

[h=2]LED performance and thermal stability boosted by Osram[/h] Nov 01, 2011 The Oslon SSL LEDs in red, orange and yellow employ a new indium gallium aluminium phosphide chip technology.
The latest Oslon SSL LEDs from Osram Opto Semiconductors provide up to 20 percent more output than their predecessors and offer improved thermal stability, particularly in Hyperred (660 nm).Energy-efficient applications such as commercial horticulture are therefore much more efficient. Behind this boost in performance lie the latest developments in InGaAlP chip technology.

Powerful, efficient long-life light sources are enormously important for lighting systems that are in operation for many hours day and night, such as those used in commercial horticulture, architainment and stage lighting. The latest chip developments make the new generation of Oslon SSL LEDs even more attractive as light sources that precisely meet these requirements. They offer high efficiency and good thermal stability, combined with a low thermal resistance of 7 K/W.

Depending on the wavelength (590 nm - 660 nm) the new LEDs achieve per increases of 10 to 20 percent. The flagship is the Hyperred version (660 nm) that hits this 20 percent mark. With a brightness of 400 mW at an operating current of 400 mA the LED is much brighter than the predecessor model. It converts 46 percent of the current into light. At an operating current of 350 mA it achieves an impressive 355 mW, which corresponds to a conversion rate of 49 percent. What&#8217;s more, the LED has a long life: At an operating current of 700 mA and at a temperature of 80°C it will last more than 100,000 hours (L70/B50).

In practical applications this means that fewer LEDs are needed to achieve a particular brightness level, or the same number of LEDs can be used to produce a higher brightness level. Martin Wittmann, Marketing Manager at Osram Opto Semiconductors explains, &#8220;Our customers benefit from the large increase in brightness because it leads to much shorter payback times. In commercial horticulture, for example, lighting systems with these LEDs can result in huge energy savings and low electricity costs.&#8221;

With their compact package size of just 3 mm x 3 mm and choice of beam angles (80° and 150°), the Oslon SSL LEDs are particularly good for clustering so high brightness can be achieved on a small footprint. When combined with LEDs in the Deepblue colour (450 nm), they create a light colour that is tailor made for the requirements of commercial horticulture.


http://www.compoundsemiconductor.net/csc/news-details.php?cat=news&id=19734176&key=osram&type=n


So stoned am I ?
 

stardustsailor

Well-Known Member
Ok...

I was red wrong ...
Sometimes ,things get confused ,floating all together ,in nowhere...
Inside the chaos of my mind ...

red wrong.JPG
 

lax123

Well-Known Member
But not wrong about 660 epileds orrr? sry i read most of the text but I just came home from work and feel a bit brainexhausted :-)
Because MrFlux is usally 99% right about the things he says, too. I think :)

And whats with this new Area51 coolwhite + red?
 

stardustsailor

Well-Known Member
But not wrong about 660 epileds orrr? sry i read most of the text but I just came home from work and feel a bit brainexhausted :-)
Because MrFlux is usally 99% right about the things he says, too. I think :)

And whats with this new Area51 coolwhite + red?
No ,I'm positive about those 660 nm Epileds chips..

new Area51 coolwhite + red....


New A51.jpg
 

stardustsailor

Well-Known Member
Well that is another 'old' Red+White 'school' ....
The first generation of Evo led lights were Cool White +Red ...
some researches have been done for NASA ,regarding Coll White +Red leds And plant Growth ...

Quite interesting ...

I've noted some things,there...


Spectral effects of light-emitting diodes on plant growth and development: The importance of green and blue light



American Geophysical Union, Fall Meeting 2011, abstract #B31E-0371
Light-emitting diodes (LEDs) are an emerging technology for plant growth lighting. Due to their narrow spectral output, colored LEDs provide many options for studying the spectral effects of light on plants. Early on, efficient red LEDs were the primary focus of photobiological research; however, subsequent studies have shown that normal plant growth and development cannot be achieved under red light without blue light supplementation. More recent studies have shown that red and blue (RB) LEDs supplemented with green light increase plant dry mass. This is because green light transmits more effectively through the leaf canopy than red and blue light, thus illuminating lower plant leaves and increasing whole-plant photosynthesis. Red, green and blue (RGB) light can be provided by either a conventional white light source (such as fluorescent lights), a combination of RGB LEDs, or from recently developed white LEDs. White LEDs exceed the efficiency of fluorescent lights and have a comparable broad spectrum. As such, they have the potential to replace fluorescent lighting for growth-chamber-based crop production both on Earth and in space. Here we report the results of studies on the effects of three white LED types (warm, neutral and cool) on plant growth and development compared to combinations of RB and RGB LEDs. Plants were grown under two constant light intensities (200 and 500 &#956;mol m-2 s-1). Temperature, environmental conditions and root-zone environment were uniformly maintained across treatments. Phytochrome photoequilbria and red/far-red ratios were similar among treatments and were comparable to conventional fluorescent lights. Blue light had a significant effect on both plant growth (dry mass gain) and development (dry mass partitioning). An increase in the absolute amount (&#956;mol m-2 s-1) of blue light from 0-80 &#956;mol m-2 s-1 resulted in a decrease in stem elongation, independent of the light intensity. However, an increase in the relative amount (%) of blue light caused a decrease in specific leaf area (leaf area per unit leaf mass). As the relative amount of blue light increased, chlorophyll concentration per unit leaf area increased, but chlorophyll concentration per unit leaf mass remained constant. The relative amount of blue light increased total dry mass in some species while it remained constant in others. An increase in the fraction of green light increased dry mass in radish. Overall, white LEDs provided a more uniform spectral distribution, reduced stem elongation and leaf area, and maintained or increased dry mass as compared to RB and RGB LEDs. Cool white LEDs are more electrically efficient than the other two white LEDs and have sufficient blue light for normal plant growth and development at both high and low light intensities. Compared to sunlight, cool white LEDs are perhaps deficient in red light and may therefore benefit from supplementation with red LEDs. Future studies will be conducted to test this hypothesis. These results have significant implication for LADA growth chambers which are currently used for vegetable production on the International Space Station.






Fulltext Article : http://cpl.usu.edu/files/publications/publication/pub__4124704.pdf
 

lax123

Well-Known Member
Maybe A51 just found that study and thought lets roll.

How do those generic chinese arrays work?
Its different from a "real" cob right?
Is it the same type of ledchips as in other 1W chips just clustered or is it something different and how about their reds and cold whites -same arguments for those as u already mentioned?
How does it work with those chips, in a 100W array there are 10 strings of 10 diodes in parallel, do they select chips by Vf and match them? -they seem equally bright lid up.
 
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