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White LED experiment

The luxeon tri-stars in 85CRI white are suppose to start shipping in June. A few of us have been talking about these for months, now the time has come. So Ive taken the plunge and preordered a couple to experiment with.

Capture.JPG

Excellent spectral performance IMHO

Still too expensive to build a rack's worth, but cheap enough for some fun experimentation
Finally an LED that no one would know was an LED unless you told them.
Av

---------- Post added at 10:57 PM ---------- Previous post was at 10:38 PM ----------

http://www.luxeonstar.com/ANSI-White-4000K-20mm-Tri-Star-Rebel-255-lm-p/mr-4000-85-20t.htm
 
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How are the lumens compared to some of the Cree (or other current) LEDs?
 
Its hard to compare their data, but the luxeon appears to be about 10% higher.. and these are ANSI rated, whereas Crees are not as far as I can tell. It's a Ford-Chevy thing.... Im sure Cree wont be far behind.

Of course this is only one component, you still need the driver and an auxiliary lens. As are their optical angle is about 120 degree (both luxeon and Cree) which is way too wide for our application

Each tri-star will driven at 700ma (with proper heatsinking) and should be 9 watts +/- with a very small footprint (20mm) and Ive ordered 22 degree axillary lenses so the luminance should be extremely high

Max current is 1000ma, so I could go up if needed

Calculated lumens @700ma will be 450ish each, Luxeon does have a higher lumen model but at cost of much lower CRI (70)

The big advantage of the luxeon is the 85CRI compared to the 70CRI of the equivalent Cree model.
 
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I look forward to seeing your results. I too am ordering a tristar of these to do some experiments, along with some coloured leds.
 
It's a shame that the peak in the green wavelength isn't shifted slightly more to the red end of the spectrum, then they might have made good grow lights.
 
Av8tor1,
What plant are you going to experiment on?
The luxeon LED's are REALLY bright.
 
I like how you customize you own 3 LEDs. Personally I'd like to see what the results would be putting a 6500K, 627nm and 447nm on one of those tri-star base. :poke:
They look funky though, how in the world do you hook one of these up and mount it??
 
It's a shame that the peak in the green wavelength isn't shifted slightly more to the red end of the spectrum, then they might have made good grow lights.

Mobile,

I think they have the potential of doing very well...
Here is the spectra of the lamps Ive used for the last few years with what I think is decent performance
narva5000k85cri.jpg

Narva 5000k 85CRI
(measured with my own spectrometer)
Compared to these the green is shifted quite a bit to the red I think

Zero, ummm dont know yet.... but I did get a dimmable driver module so I can adjust the intensity based upon the plant's need.

Z... yes, Im anxious to follow your results as well.... If you dont mind me asking what driver current and aux optic angle did you decide on?
I went with the externally dimmable 700ma and 22 degree lens as a starting point

Av

---------- Post added at 10:37 AM ---------- Previous post was at 10:19 AM ----------

I like how you customize you own 3 LEDs. Personally I'd like to see what the results would be putting a 6500K, 627nm and 447nm on one of those tri-star base. :poke:
They look funky though, how in the world do you hook one of these up and mount it??

Yann,

You have to mount these to a heat sink, even at 350ma the rule of thumb is one square inch of heat sink per watt (bare minimum)

Thermal runaway and spectral shift is a real issue with heat build up
 
Hello. I'm doing a theoretical 735mA, although the actual value may vary. Mine is not dimmable, other than through pwm. I'm using 27 degree lens.

I'm using the following combinations (where blue is royal blue)

3 blue
2 blue 1 red
1 blue 2 red
3 red
3 ansi white 4000k
3 4100k neutral white (i bought these by accident since I did not know about the ansi whites, so might as well use them too!)

I'm still a bit far from getting everything up and running. I'm still soldering my constant current drivers. I'm planning to experiment on gemmae.

Can I ask how far are you planning to place the lights from your plants? I have not decided on that yet, but in order for the 3 85lm leds to match half of 4 5000lm T5s placed 40cm from my plants in flux (which my pygmies are currently under, half since they are kinda off to one side), I have to do something like 6.3cm from my plants, which I would assume to be too close. Using the current optics I have, the radius of light does not fill a pot.

Edit: also, where did you get your spectrometer? I would like to have one too to play around with. I tried ebay, but I'm getting very expensive lab versions.
 
  • #10
Im not sure how far to place them. I did experiment the the Grow Master LED plant light LGM5 for about a year and it stated to use about a 24" distance.

One issue with it (and most other individual LED designs IMHO) was the spectral blending... so the distance was needed in part to let the colors combine. In addition the luminance of the LED's will be extremely high due to their small size and power level.

This was another reason for my thoughts on a dimmable driver module and the 22 degree lens... but so much of this is just a best guesstimate at this point

Question.... what did you decide on for thermal transfer.... Paste, glue or tape?
I found a thermal silicone glue that was getting some real good reviews and cheap to boot so I ordered a tube of it. My only experiences with thermal tape have been less then satisfactory in high temp applications.

Thermal glue

Ive got three spectrometers and by far the best is: http://scientificsonline.com/product.asp?pn=3082305&cm_mmc=Mercent-_-Google-_-NULL-_-3082305&mr:trackingCode=D5701735-DB81-DE11-8C0A-000423C27502&mr:referralID=NA

Here is a pic of that LGM5 from a distance of about 4 foot, notice the spectral blending and luminance
lighton.jpg



Av
 
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  • #11
I am also worried about the blending, but I'm thinking if I sacrifice the lm per area, I can place it further for a better blend. The T5s are probably way too bright to do a fair comparison anyway.

I'm using Arctic Silver Thermal Adhesive. It hardens and isn't elastic. It also binds things together for basically forever, so that might be an advantage or disadvantage depending on how you look at it. It's a little bit more expensive, but I heard good reviews about the brand too. I got mine off ebay.

Thanks for the link to the the spectrometer, I'll definitely have to pick one of those up.

Also, nice lights there. Are you going with 5 tristars or will there be more?
 
  • #12
At this point and price level its just trials for me... but IMHO with the wide selection of aux optics it kind of depends on application. For low canopy applications, a less distance to plant, wider lens angle and fewer tristars might be the trick. For taller plants like neps where a deeper canopy penetration is required, a greater distance, tighter lens angle and more tristars might perform most efficiently.


A lot of unknown variables and a lot to learn
 
  • #15
Av8tor1,

What exactly is the benefit of having a higher CRI index? I was under the impression that spectrum and intensity were the only relevant factors for plants. In fact, because photosynthesis is only occurring in part of the visual spectrum, wouldn't theoretically ideal light render colors poorly?
 
  • #16
Ent, so much of the tribal knowledge is based on a single red and blue wavelength. But as the NASA research has shown the spectral needs of plants are not all the same. In addition you have accessory pigments, beneficial organisms and phytopathogens that are all affected by certain wavelengths. But for me its having a energy efficient plant light that is not only a high performer but is also aesthetically pleasing.

I've tried the traditional LED format and found it to be a good "supplement" but unsatisfactory as the primary lighting source.

If i can have all the advantages of LED's and at the same time have a "true" white light then that's the holy grail of plant lighting IMHO

I will have reaced LED Nirvana

People have been trying the Red/Blue based LED's now for a few years... For many they find that in the real world it's just not quite enough for long term plant performance. Basically once you start adding in these additional needed wavelengths you are back to "white"

If I grew only one species and had no concern other then plant mass, then a couple specific wavelengths are more feasible

Of course this is also a personal preference and personal opinion thing, I'm looking for a LED that performs like a T5, LED and HID hybrid, but at a fraction of the energy cost.
 
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  • #17
I don't know for sure if CRI has any affect but I know that my plants grow better under ceramic (HCI), rather than quartz (HQI) metal halide lighting. Both types of MH lamps were the same colour temperature but the HCI has a much better CRI and looked whiter. So far, I have found metal halide to be the best grow light, far superior to fluorecents in my conditions, but the running costs are high. If I could get an LED setup that gives similar results to MH then that would be my Nirvana.
 
  • #18
Sounds like we pretty much have the same philosophy, Av8tor1. I much prefer viewing my plants under "natural" light, even if the alternatives might give marginal improvements in growth.

Your comment about "accessory pigments, beneficial organisms and phytopathogens" is interesting. It reminds me of the reef aquarium hobby being revolutionized when people realized the value of biodiversity (live rock, live sand etc...) Not really an apples/apples comparison, but I wonder if nuances of the bog ecosystem are being overlooked by the CP hobby as a whole.
 
  • #19
tristar.jpg

I dislike using the term lumens, but this should be approx. 450 lumen at 750ma and do it at 85CRI

Imagine the level of light flux density, impressive!

now if they were only 1/20th of the current price LOL
Av
 
  • #20
I bet that you check and double check the driver current and wiring before you power it up :grin:
 
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