DIY LED grow lights experiences

guod

guod

Well-Known Member
i´m working on it. no .XLS here. C++ and a database for the leds

the user-interface for the channels

aigl-beta09.jpg
grey line is full output 100W
red line is 25W neutralwhite for better seeing plants(work light)
with boost also good for making pics(35W)equal to 200W Halogen.
it´s all beta, so not for public.

and this will maybe the light...aiglbeta.jpg
 
stardustsailor

stardustsailor

Well-Known Member
Awesome!

......
(Speechless.....) .....


Question :

Since airflow is sideways ...
And gravity/position of the heatsink's fins and of heat source ,do play a crucial role in cooling ...

( ..I'm only asking,in order to learn,from you ....
I'm not pointing to a " weak spot" .. )

Is it possible that this design ,might have uneven temperature " zones " ?
I.e. close to fans ,fins to be really effective (cold) and as distance increases from fans ,fins start to be warmer ?

Or ,the " cage " fin design of this heatsink and the thin fins ,do minimise the possibility of such phenomenon ?

And ....

This "cage" fin design ....
Is it possible for fan air flow ,to cause any " pipe blowing " / " hissing " /"whistling" noises ?
Or no ?
Does depend on air pressure / air-flow in analogy with " pipe/channel" diameter/shape ?
....


Edit/ P.S. ..

I'm thinking ...
This cage fin design ...
(used also in L4A )
Entrapping / encaging the air flow ....
Seems really efficient ..,..
Althought it seems a bit "bulky " ...( but lightweight ? )

And I think also,it needs cleaning oftenly ...
At least if the operational environment is dusty ....
 
guod

guod

Well-Known Member
And gravity/position of the heatsink's fins and of heat source ,do play a crucial role in cooling ...
Click to expand...
this is right for standart heatsink.
here we have a heatsink that is without fans more or less useless, no real air movement between the fins(fin very closed packed), so if there are problems with fans the lamp has to go out.
But if anything work correctly we will see less then 10°K over ambient at 100W

is it possible that this design ,might have uneven temperature " zones " ?
I.e. close to fans ,fins to be really effective (cold) and as distance increases from fans ,fins start to be warmer ?
Click to expand...
yes, but it is negligible this one is to short and the base is really thick(10mm)

Is it possible for fan air flow ,to cause any " pipe blowing " / " hissing " /"whistling" noises ?
Click to expand...
i hope not, it depends of the number of revolutions from the fan and so it´s possible that this system get in resonance.
but both fans will be controled by a microprocessor(PWM) so i think this problem can be solved.
also airflow changed from 2.5m/s to 1m/s acording to power of light, or in other words from 0.08 K/W to 0.14 K/W
quiet in veg, more noise in flower...


And I think also,it needs cleaning oftenly ...
At least if the operational environment is dusty ....
Click to expand...
a filter is must in this design and at startup the fan will be drive at max. for a short moment
 
SupraSPL

SupraSPL

Well-Known Member
Wow you guys have an excellent discussion going on here. Here is my take on this and why I selected Cree XTE 3000K for my lamp.

Warm whites have a lower radiometric efficiency than cool whites because of the increased use of phosphor (Stokes losses). High CRi LEDs suffer even more from stokes losses so they have an even lower radiometric efficiency. Here is an old graph provided by Nichia that demonstrates this:

NichiaLED-CRI-Info.jpg (This chart says "normalized" but the curves are not normalized to each other. For proof I cite the fact that if those curves were normalized it would not be possible to have a 25% luminosity loss.)

I am no CRi expert but consider this, an incandescant bulb has a CRi of 100 even though I would rather judge colors with my 5000K Cree XM-L which is about CRi 70. This is because the incan bulb has a smooth output and the Cree has peaks. High CRi LEDs seek to fill in their gaps in output. Would this SPD be slightly better for growing plants than warm white? Probably yes, but not enough to offset the loss in efficiency IMO.
 
SupraSPL

SupraSPL

Well-Known Member
The problem that creates confusion is that most manufacturers provide very general graphs labeled "relative radiant power". Yes output is relative on each curve, but the curves are not normalized to each other. For example, every Cree chart shows the same amount of blue output on cool and neutral white LEDs making neutral whites appear to have a higher radiometric efficiency which is not the case. The cooler the tint the less phosphor that has been used and the higher the efficiency. The curves would have to be normalized to each other in order to use the data quantitatively.

MKR MK-R SPD.png
XML2 XM-L2 SPD.jpg
XPG2 XP-G2 SPD.jpg

All of these charts lack normalization between the curves and include the labeling "relative radiant power"

Philips Luxeon data sheet include accurate curves for each color tint but they separate each curve into a separate graph so once again we lose the ability to compare their output quantitatively.
 
SupraSPL

SupraSPL

Well-Known Member
When I estimate the radiometric efficiency of white LEDs I have to guess at the LER. As SB posted earlier we would need the lumens/watt and an accurate SPD graph. Once you have that data you could use software to arrive at the LER. The software would need to calculate the lumens/watt for each wavelength in the curve. The maximum LER possible would be 683 lumens/watt if the light was pure green. KNNA used 280 for cool white and 310-315 for warm white and I use the same number in my spreadsheets but they are just generalizations.

Once you have the LER you can figure out the radiometric efficiency of the lamp at each drive current and junction temp. I estimated the Cree XTE 3000K R3 bin to be 34.5% efficient at 700mA 50c. I estimate a 600w HPS to be 40% efficient but that number drops as the lamps ages. With HPS we get into a gray area because the HPS does include output in the far red range some of which may be used for photosynthesis. The best deep reds (on paper) are the Oslon Hyper 4T (46% @ 700mA 50c) and the 3T (41% @ 700 mA 50c).

Now we have to consider the release of the Cree XM-L2 which may be a game changer for some DIYers. The blues they are using are close to 65% efficient at 700mA. The XM-L2 is currently available in these bins: U2 5700K is 58.5% (700mA 50c), the T6 5000K is 52% (700mA 50c) and the T3 3000K is 39% (700mA 50c). Based on these numbers it may be best to use neutral whites and supplement with as wide a spread as possible of reds and deep reds.

If manufacturers would release data on the radiometric output of each LED and/or accurate SPD curves that would make our job comparing LEDs much easier. Since Cree seems to be the leader in white LED efficiency it seems like this would be a way they could trump their competition.
 
green surfer

green surfer

Well-Known Member

  • The cooler the tint the less phosphor that has been used and the higher the efficiency. The curves would have to be normalized to each other in order to use the data quantitatively.​
Click to expand...

  • If manufacturers would release data on the radiometric output of each LED and/or accurate SPD curves that would make our job comparing LEDs much easier. Since Cree seems to be the leader in white LED efficiency it seems like this would be a way they could trump their competition.​
Click to expand...
Totally agreed with you Sup!

I asked this question of radiometric efficiency to OSRAM, I waited 1 week for the answer, finally they gave me the name of a led specialist who is working for an Osram distributor. I sent a mail to him and he suggested me to make a comparison in his laboratory between an OSLON CRI95 WW and the led of another brand of my choice, I have XTEs so I will send to him an XTE. So we will know soon the accurate radiometric efficiencies of the XTE 7C(2800K to 3000K) R2 bin VS OSLON 2700K CC (i don't still know the exact reference of the OSLON they will measure but I asked for the best 2700K oslon CC bin they have, and they are selling them). I asked for 10-15 samples too for experiments.

I'm almost sure the XTE will beat the OSLON. And we will have the accurate graphs, scaled. It will probably take about 2 weeks but I can't wait to see those graphs and datas.
But yes, the OSLON wiil probably peak at 630nm and give more far red and IR than the XTE, and it is good to take it into account.

Supra, thanks for the infos about the new XML.
 
guod

guod

Well-Known Member
Warm whites have a lower radiometric efficiency than cool whites because of the increased use of phosphor (Stokes losses).
Click to expand...
Stokes losses has nothing to do with increased use of phosphor
http://en.wikipedia.org/wiki/Stokes_shift

The cooler the tint the less phosphor that has been used and the higher the efficiency.
Click to expand...
it´s not the amount of phosphor, you need different phosphors to change the tint
http://www.mt-berlin.com/frames_cryst/descriptions/led_phosphors.htm

if manufacturers would release data on the radiometric output of each LED and/or accurate SPD curves that would make our job comparing LEDs much easier. Since Cree seems to be the leader in white LED efficiency it seems like this would be a way they could trump their competition.
Click to expand...
osram has this data for each led on their site
http://catalog.osram-os.com/applications/applications.do?folderId=2&act=showBookmark&favOid=0000000200034c80025d0023
go for the ASCII or ASAP files
...
LCW_CQDP_6M

...
422.0000 0.2321
424.0000 0.2982
426.0000 0.3858
428.0000 0.4952
430.0000 0.6210
432.0000 0.7509
434.0000 0.8682
436.0000 0.9553
438.0000 1.0000
440.0000 0.9988
442.0000 0.9577
444.0000 0.8874
446.0000 0.8020
...
...
609.0000 0.9256
612.0000 0.9426
615.0000 0.9582
618.0000 0.9722
621.0000 0.9838
624.0000 0.9929
627.0000 0.9983
630.0000 1.0000
633.0000 0.9967
636.0000 0.9893
639.0000 0.9769
642.0000 0.9607
645.0000 0.9400
...
735.0000 0.1343
...
a spreadsheet which does all the calculation. loaded with Ledengin Leds.
http://www.sevengens.com/sitebuildercontent/sitebuilderfiles/ledengin_spectrum_tool_20110906.xls

there is one error in this spreadsheet
table cw5500 cell D102 is linked to table All_spectra_101212 cell O11 thats wrong change this to cell O13.
same for table ww2900: D102 O13 > O11.
 
SupraSPL

SupraSPL

Well-Known Member
I am not a scientist or expert just a regular guy trying to make sense from the information I have in front of me. I find evidence contrary to your statements which I linked below but I am open to learning :)

I think we can agree that there are energy losses when you convert blue photons to longer wavelengths. As you can see from the graphs, cool white LEDs emit more of the original blue photons than warm white, therefore they have a higher radiometric efficiency. For warm whites and high CRI, the layers can be thicker, have more or different phosphors but the end result is the same, lower radiometric efficiency.

--------------------------------------------------------------

"There are two losses associated with any downconversion approach. One is the Stokes loss associated with the fact that higher-energy photons are converted to lower-energy photons and the other is simply the fact that the quantum efficiency for downconversion is typically less than 100%." Luminescence Cees Rhonda 2008

"Details differ, but generally cool white leds have less phosphor in the way so they are more power efficient at the expense of CRI. Warm white LEDs have more phosphor, so more loss and less efficiency, but a higher CRI because there is less blue spike and more broad hump." "Colour rendering from LED lighting" Steve Bush 2011
 
green surfer

green surfer

Well-Known Member
we will look at the laboratory results, the XTEs will be shipped to Germany on monday, it won't take long to have both graphs and radiometric efficiencies, we will see.
All things will be easier to digest.
 
SupraSPL

SupraSPL

Well-Known Member
guod said:
osram has this data for each led on their site
http://catalog.osram-os.com/applications/applications.do?folderId=2&act=showBookmark&favOid=0000000200034c80025d0023
go for the ASCII or ASAP files
Click to expand...
That is wonderful it will be interesting to see how the LER of high CRI compares to warm white. Maybe I can translate the spreadsheet into google docs.

What we really need to compare efficiency is the radiometric output in watts (as they provide for deep blue and deep red). The LER is just a means to arrive at that end. That will be more than half the battle. Then at some point we will have to figure out how to compromise between efficiency and SPD. That will be the tricky part and with less reward.
 
SupraSPL

SupraSPL

Well-Known Member
Awesome GS can't wait to see the results! It will make my spreadsheets more accurate, I just use a standard 310 LER for warm whites, flying blind.
 
K

K5Doom

Member
If I was to build a led array today, what LEDs should I get? Looking to light about 4 plants in a 60cmx55cmx80cm area.
 
S

SnotBoogie

Well-Known Member
K5Doom said:
Duh. No but seriously, Luxeon/Cree/Osram? Which ratio? Can I use the same lamp for both veg+flower or I would need to build 2 separate?
Click to expand...
I'm sorry man. I was just being a douche coz your question was so vague. I suggest you check these threads:


https://www.rollitup.org/led-other-lighting/633304-if-you-new-led-want.html




https://www.rollitup.org/led-other-lighting/642213-diy-initial-thoughts.html


Personally i ascribe to the "veg with your flower panel" philosophy. :)
 
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