CREE CXA 3000°K/80CRI spectrum analysis.

Bravo Mr. SDS, excellent thread once again and absolutely the best explanation I have seen so far on the subject! Knna would approve too

One question though regarding the CXA and white leds in general, isn't there a shift in the spectral distribution with varying drive current/voltage/tJ? How much would you estimate the shift being with a CXA 3070 driven at 350mA and 1400mA? I guess we would need spectroradiometer data for that... But curious anyways.

Thank you so much for everything you have written here!

Supra, the digitizing isn't hard at all, I'm just not too sure if I can trust those SDP curves enough to use so much time and effort for a number that can throw 10% in any direction... I sure hope that Santa would bring me a spectroradiometer for christmas

Awesome lesson SDS, I am going to have to read that one a few times !

stardustsailor said:

If I will manage to find some free time ,I will gladly do some calcs for the Vero you've asked .
..

(Do you want the spreadsheet I use ?
I can email to you .- It runs on OpenOffice Suit.-free to download )

Cheers.

Click to expand...

YES Absolutely, I'll IM my email.

So now ...

We know ..

1) λ (nm ) / 119,708 * Φ (Radiant Power in W) = umoles/sec
2) Absorptance Y values (factor ) for PAR range (400-700 nm )
3 ) Relative Quantum Yield Y values for PAR range ...

Our led of 1 Watt Φ at 480 nm ,outputs 4 umols /sec
of which a potential maximum of 2,53 umols /sec is/ can be absorbed and utilised to drive photosynthesis .
(By quanta numbers..Remember ? )

No matter if one plant radiated or one thousand of them ...
The maximum potential photosynthetic quanta flux of that led
is 4 umols/sec * 0.92 absorptance factor *0.69 RQE

For 8 quantas used ,plants "break " one CO2 molecule into Carbon and Oxygen ,as gas ..
Or the plants need ~8 quantas (here the numbers ! ) for evey molecule CO2 to be
processed .as a direct result of photosynthesis .

Make them 10 ...
The quantas ...
To make our lives easier and allow for some " slack " there ...
So ,it takes ten photon's excitation energy ,the whole CO2= C + O2 "separation " thing ..


2,53 umoles per sec / 10 =

0,253 umoles of CO2 processed per second ( ideally or better yet " potentially " )
0,000000253 moles * 22,4 lt = 0.00000568 lt = 0.0056 ml of CO2 processed per second ...
Maximum and ideally ,thus " potentially " .... )

A blue led outputing 1 Watt of 480 nm light ,
has a Photosynthetic Potential of 0,253 umolsCO2/sec per Radiant Watt ..

Various 480 nm blue leds will have the exact same Photosynthetic Potential ,for it's wavelength dependant ....
But they will have different Photosynthetic Potential Efficiencies .
Photosynthetic Potential Efficiency = Photosynthetic Potential / ( If*Vf )



Ok ...

What about white leds ?

Or before that ....
What is the Quanta * RQE* Absorptance per nm ?

That is :
" For 1 Watt or Radiant Power per nanometer ,the number of Quanta * RQE* Absorptance ...."

It 's PAR's Photosynthetic Potential or PAR Quantum Efficiency.



1 Watt radiated at every given nanometer ,will be equal a x number of quanta per sec .
Multiplied with absorptance per wl and RQE per wl ,that graph comes up ....

Photon Flux per wl ,per W x Absorptance x RQE

4 ,for example ,means that at that given wl ( i.e. ~588 ) 1 watt of light ,will produce
4umoles/sec of photosynthetic potential light flux ...

It combines light physics with plant biology ...
What "light" has to give "by nature" (quanta numbers ) and how plants can ultimately use it ..
(absorb and utilise )

The photosynthetic max potential of PAR range ...

SupraSPL said:

According to Mr Flux method, the Vero 4000K curve is 325 LER with 13% blue. At 1.4A (Tj 50C) it would be 37.1% efficient. Of course there a few problems with that measure. It is using the minimum numbers, which Mr Flux pointed out is more beneficial to the CXA than the Vero line, and Tj 50C might not be realistic in some applications at 1.4A.

It would be interesting to see how the SDS method compares. If a bunch of us can learn how to digitize these curves, we can share the burden

Click to expand...

http://www.edn.com/design/analog/4410588/Digitize-graphical-data-easily-and-accurately


"Use the “Curve Point” tool to manually insert points on the curve that are not automatically detected"

Better use this only ,all the way ..
Vey easy,simple and powerful free software ..
If version 5.1 does not work ,up one step in download folder to download an older version .
(I use 4.1 )

Results are amazing and super precise if graph is accurate and in usable state/ form ..

Where is the mountain in the above graph that is used a bit more abundantly..620nm - 680nm?

The photosynthetic potential curve looks more like a high cri led versus 80cri..no?

Or by leaving spectrum out we are improving on that curve

And back to the CXA again .....
For its LPP and PPE ( Light Photosynthetic Potential & Photosynthetic Potential Efficiency )
.......



The blue curve line is PAR PPE ( or Photosynthetic-Active-Radiation-Quantum-Efficiency) .

The orange curve represents the rel.Power y value of CXA 3000K 80 CRI ,turned into umoles pwer wl ,
and then multiplied by Absorptance and RQE ....

λ / 119,708 * y Rel.PWR * Absorptance * RQE

That curve it combines what is given ('quanta" emitted by the device ), with what plants can ultimately use ...

The blue curve ,finally describes the best potential rel.specta for photosynthesis ...

The CXA 3070 Z4 3000K 80 CRI ,at 2000mA ,Tc =45 C
With a rad efficiency of 32,97% and a junction operating at ~87C
has a LPPE of 0,1207 umols/sec CO2 / electrical Watt ....
..... x 22.4 lit =
~0,003 ml oF CO2 per sec ....

That is 9,733 liters of CO2 per Hour ...

Per Watt ...
x 78 electrical Watts = ~760 lts of CO2 per Hour ...
760/22.4 =~34 moles of CO2 * 12 gram/mole for C = 407 grams of C processed per hour .

That is the max photosynthetic potential of that CXA chip ...
It can support photosynthetic yields / rates ,up to 400 grams of Carbon per hour .
(at least in an super ideal world .... )

Top notch work as always SS, I think a lot of us are running the CXA 3070 Z4 3000k 80 CRI at 1.4 amps,any thoughts?

LOL ..You need the numbers for 1400mA ?
No problem ..Wait a bit ...

Cheers.

CXA3070 Z4 @ 1400mA -3000°K /80CRI

From single COB's data .
( Pcs #. = 1 )






Tc=45°C






Tc=55C


\






Tc=65°C







Cheers.

My favorite thread yet. So much fun. Really clearing up and furthering my understandings. Thank you for sharing your work. So well put together too, easy to read and follow.

Weird ....
For the relative spectrum supplied at Cree's datasheet...
The CXA 3000K 80 CRI has an "estimated" LER of 344,89 ,according to spreadsheet's calculations ...

used the 2-digit
CIE "physiologically-relevant" luminous efficiency functions consistent with the Stockman & Sharpe cone fundamentals,as reference....



http://www.cvrl.org/lumindex.htm

Click to expand...

And some info for the Vero29 4000K CRI 80 ....

If we assume that Tc = 50C .....
Then from digitized values from this graph ...






At 1400mA If Vero29 will have a Vf of ~38,2 VDC






1.4* 38,2 = 53,48 Watts (electrical Power )

.....................................................................

Max Lumens value of Vero29 4000K is 10260 lm .(typical ,used as reference )
Digitising this graph ...

At 1400mA vero29 4000K has the 68,85% of the 10260 lumens ....

So ,10260 * 0.6885 = 7064.01 lm

7064.01 lm / 53,48 Watts = 132.0869 lm/W ..

132.0869 / 325 = 0,4064 ( => 40,64% efficiency )

0,4064* 53,48 Watts= 21,7354 Watts of light power ...

53,48 Watts - 21,7354 Watts = 31,7445 Watts of heat ....

Tj =Tc + (Q* Rθj_c ) =>
Tj = 50 + ( 31,7445 * 0,25 )= ~58 C (57,9361 )

Continuing further and digitising this graph now ....








Value obtained is ~95% ....

Thus 7064.01 lm * 0.95 = 6710.8095 lm

Estimated Radiometric Efficiency is 125,5 lm / W / 325 = 0.3861
( 38,61% )

Not bad, and I can find Vero's family on Ebay in europe

And some CXA color ratio "corrections " ...
FR added ...

( for a single piece CXA3070 @ 1400mA /Tc= 55 C / Z4 ) )

Green line : Intact Leaf's Absorptance. ( 1=100% , 0 =0% )
(Averaged values ,obtained from a wide range of plant species ,leaf size, age ,LAI and position )

Red line : Photosynthesis Action Spectra. Aka Relative Quantum Yield (RQE ) .( 1=100% , 0 =0% )
(Averaged over a wide range of plant pecies.Indoor/Chamber grown )

Yellow line : The above two factors ,combined (multiplied between ).. ( 1=100% , 0 =0% ) .
Photosynthetic Efficiency of plants per nm .


Highest values at 621-626 nm ,with a combined Absorptance-RQE factor of 88%:

(Look at first column for the wavelength and at the last- violet/blue- column for the values combined ...
Absorptance values per nm is the first from left violet column and RQE values are the next one -also violet colored )

That looks very impressive SDS, I'm glad that you'll be doing the analysis from now on

For reference these are my numbers for the CXA 3000K:
As you can see I've dabbled with the McCree relative quantum efficiency (RQE) too; However it doesn't seem relevant at all. It was measured with monochromatic low intensity light, but everything changes when you use 1) white light 2) high intensity light. PPF (in umol) tells a much better story, together with...

Blue light. I used only the range of blue that has the most morphological effect. The 420-480nm range is based on this action spectrum:

(source)

Finally, you can see a "Lux to photons" number of 67.3. With this number everyone with a lux meter is now also the proud owner of a PAR meter. Simply divide the number of lux by 67.3 to get the PAR (in umol/m2/s). For example, 50,000 lux would correspond to 740 umol. Well at least in theory, and only for the CXA 3000K spectrum.

And the CXA Relative Power Spectra vs the plant's photosynthetic efficiency spectra..
The latter normalised to 100% . A Normalised 100% equals to 88% Absolute Factor .