Spectrum

[Lean_McSheen]

I've copied and pasted a couple of posts from another forum by a guy who has a mind like a well oiled machine. This is about the light spectrum and how and where the plant uses it. It's a bit technical but well worth a read. The guy is from Greece so his grammar is a little off but you can still understand it.

w|s - White spectrum.
SSL - Solid State Lighting
Tc - Case Temperature (basically the temperature of the LED Chip)
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Red wls of 640-680 nm are mainly absorbed by the PhotoSystem 1 of each single leaf cell ... These red wls provide vast numbers of photons ( >4.5 umoles/sec/ Radiant Watt ) which get absorbed (mainly) by Chlorophyll A .Magnesium atom in the center of the chlorophyll A is "biased" (with protein(s) ) towards absorbing light maximally at 640-680 nm range. (Peak ~662nm ,not on alive cells,but measured at dilluted ChA ) ...

PS1 is considered the "High Energy Photosynthetic " system... For high irradiances .. For clean bright sky, at noon.
(Water/Vapour absorbs -thus 'filters out' mostly at red/FR wls... Under a cloudy sky blue and Green wls dominate (at PAR range ) )

Those wls (640-680 nm ) get highly absorbed by top layers of leaf canopy. Where the younger leafs / shoots are ...Older leaves ,are not able to efficiently absorb and use those wls.

Those wls also can cause Photosaturation of the PS1 in no time ... If exposure is prolonged and or of high irradiances ....

Older leaves have to avoid the exposure .. Younger (and more photosynthetic efficient ) leaves 'protect' thew older/deeper/lower parts of canopy , by absorbing the 'high Power Red wls ..."

Thus they grow like crazy ..

From the other hand ,older leaves have larger photosynthetic area .... Thus they absorb and utilise very efficiently the Green,Yellow ,Amber and Lower red wls ...
( 500-630 nm )

They can photosynthesise for longer period of time ,than from top -young- canopy and almost in as high irradiances, but on different wl range... (photons are also less than 640-680 nm range ,per radiant Watt ..But of higher energy each ... That translates to heat ..Thicker older leaves ? )

The result is that plant(s) 'capture' as many 'energy quanta ' as possible and use them accordingly -depending on 'quanta' 's characteristics (energy / wl / frequency/ numbers ), to satisfy the different needs ,of different 'parts'- subsystems - of a living organism ....

Plants can adapt of course ... To light quality and quantity ... To altitude.. To growing techniques .. To plenty of things ..

Warm White leds (3000K 80 CRI ), do provide a 5-10% of blue wls ( all what's needed,actually ....)

About 15-20 % green wls ( 520-550 nm ) (pretty useful feature when irradiance (quanta flux ) is over ~300 umol/sec, if irradiance is less than ~300umol/sec ,then some Shade Avoidance 'kicks in 'and that's if only illumination used is WW leds ....)

At least 50% of their radiant power is at the range 550-640 nm .... Some 15-20 % of power at 640-700 nm .... And 1-3 % at 700-750 nm....

I trust that at average irradiances and above that ...(300 up to 1500-2000 umol/sec ) All what is needed ...

(And probably could not get better ..Ok .. Maybe some ..Some UVA-UVB ..Maybe ...Some ...)

All what's needed is WW 3000K 80 CRI ....(Or maybe NW 4000 K + WW 2700 K ,both 80 CRI )<= Another great white combo ...

No blue ,no red ,no NW ,No high CRI ... Nothin' ...

Blast 'em with 600-800 umols/ sec / m^2 ,of WW 3000K led light... And just watch the SSL version of HPS ,how it ' helps' mj to grow thick dense crazy buds .

Regarding the red /amber/yellow/green

"Makes up ' ..Maybe wrong expression ..

At low irradiances ( 200-300 umol/sec/Sq.m ) Warm white 3000K ( 80 CRI ) ,if used solely, will grow some bud ...Thing is that at such irradiances ,the green wls percentage will envoke Shade Avoidance Syndrome ... Not necessarily with a negative impact in yield ,but neither with a 'positive' .. But with a certain impact at the morphology/physical appearance of the plant(s) ... (Extended leaf stems ,for example ...Large ,thin (thus 'sensitive' ) leaves ...Etc ..)

At such low irradiances ,green wls are not necessary .. Better that % of power ,to've been at red or amber wls instead of green ..

Blue & red led combinations,still are the most efficient at those flux densities ... Given the fact that they are used as supplementary illumination to greenhouses and with bedding / flooring growing techniques ... And output power spreaded over large surface / area ... Nothin' can beat them ,at this type of horticulture ...Still ... They are used for plants that they do need more than 300umol/sec/m^2 to grow... (peppers and tomatoes are some exceptions ,but then B&R combos are used as supplemental illumination, to natural sunlight ,in nothern countries ...)

If leds are to be used as the solely source of illumination and at high irradiances ...
Then green wls ( 520-550 nm ) are mandatory ...
Yellow wls(550-590 nm ) are also mandatory ..
Amber (590-610 ) wls are mandatory ...
Low reds (610-640 )are mandatory ..
Deep reds (640-700) are mandatory ...

Mandatory ,if we 're still referring to the highest photosynthetic activity possible, under i.e. 700umol/sec/m^2, for 12 continuous hours, at same power (irradiance ) levels ...

You can still supply 700 umol/sec/m^2(or more ) of red & blue wls ... And ,of course saturate or even fry the plants ... (it won't even take half of the 12 hour exposure duration,for photosaturation to 'kick in ' )

( Do not expect high yields at this exact situation described... Test it ...Get the best blue & red leds ,available on the market ... And try to grow with 700umol/sec/m^2 of blue and red ... Try it .. I dare you ...And then compare it with plants grown under same quanta flux density of white light ,coming from a CXA 3000K ... )

..Anyway ...Warm white led light ,probably can grow plants ,in the best possible manner , achieved by solid state light ..

It takes the right leds/arrays (efficient ) and plenty of power ,to make it work ...

And here it gets 'complicated' ....

In my fixture ,to give you an example ,4x CXA3070 3000K Z4 are driven up to ~2A ...
For an average -stable-operating Tc =45C ,the leds efficiency is ~33% ... (Slightly better radiometric efficiency than a HPS 400W ) .. The leds have a total electrical power of 312.3 Watts.
To keep Tc=45C ,the fixture has active cooling .. So total (@Plug ) power of fixture is about 340W (fans at lowest setting ,CXAs @2 A )(with fan psu,cc led drivers,MCU,LCD display,Voltage reg along with fans ..)

Output irradiance is about 103 Watts .. 15-17 Watts lower that the output of a 400W hps ...
But with same or even more quanta flux (umols/sec ) ,than the 400W HPS .. (Due to more output in red wls ,of the CXA 3000K than in HPS )

So 4x CXA 3070 driven @2A ,one can assume that is the SSL replacement of a 400W HPS .. (with slightly better el efficiency,way longer service life,slightly lower output power in W ,better spectrum and better heat management of a 400W HPS..) And all that in a pretty reasonable price tag ...
.....

Now .... What about if ... If instead I had used 16x CXA, but driven at 500mA ?

For the same Tc temperature ..
Efficiency of arrays would have been 46% !!!
The el.power (total ) would have been 272 Watt.
Output light power (total) would have been ~125 Watt !
Given the -slightly- better spectrum ....

At this case ,I've surpassed by far the growing efficiency of a 400W HPS ... Fan Power for keeping the TC at 45 C ,is also lower ..(more arrays ,lower driving current ) Thing is ...I would have needed 16x CXA arrays ,16x CC drivers ..more heatsink mateial .. More space ,thus multiple panels or even larger case ..And so on ... And ,of course ,I would 've needed another ..'cash budget' ..Way bigger/larger ....

Anyway ... No matter what or how ...The CXA3070 array is truly a 'breakthrough' in led horticulture ... (At last ...)

It can be used either hard driven -and few parts needed - to grow like a HPS does ..( With Very closely 'alike' characteristics ..Spectrum,efficiency,el.power ,irradiance ,etc )

Or it can surpass ,in every characteristic the average 400-600-1000 W hps .. If used as 'many and soft driven ' and not as ' few but hard driven ' Truly utilising less energy ,to grow more efficiently,better & higher yielding plants ,than the HIDs ... And-of course- still ,price/total cost is the greatest 'discouraging' / limiting factor ,at such case ..

Secret with CXA3070 array is ...are ..two of them ... -Good cooling ...-High irradiances ...

You won't believe in your own eyes ,what this array can do, if these two ..' conditions' are fulfilled ..(solely by itself..Without any other type of leds added )

Edited January 27, 2015 by distracted

[Lean_McSheen]

When referring to efficiency such as 'For an average -stable-operating Tc =45C ,the leds efficiency is ~33% ...' this means that 33% of the electricity running through the LED is turned into light, the rest is turned into heat etc. So the more efficient a light is, the less heat it puts out in relation to its power. A good thing for those worried about heat.

Edited January 27, 2015 by Lean_McSheen

[Guest zypheruk]

Interesting read for sure and seems to tally up with what others are saying about these cree 3070 cobs, things can only get better and cheaper.

Thanks for posting this, I was going to order some deep reds when ordering the next couple of 3070's but can live without them.

Cheers

[Badders]

Can't see a value for umol/s on the datahseet, do you know where he got the values from? (this is sds from RIU? seems like a top bloke)

bridgelux appear more efficient when driving hard >1500mA ? i think i compared the datasheets a while ago..
Anywho my mate got a vero 29 the other day, much more DIY friendly for mounting.

[Lean_McSheen]

Can't see a value for umol/s on the datahseet, do you know where he got the values from? (this is sds from RIU? seems like a top bloke)

bridgelux appear more efficient when driving hard >1500mA ? i think i compared the datasheets a while ago..

Anywho my mate got a vero 29 the other day, much more DIY friendly for mounting.

I'm not sure where he got them from, these guys usually have the equipment to test these things themselves or know someone who can. Yes this is two SDS posts from RIU that i bundled into one.

The Vero range are more efficient if you are ramping up the power compared to the CXA range. The only issue is the more power you put through them the more heat you get too. Preference will depend on your setup. For me, i grow in a smallish enclosed space where heat can build up quick, so for me CXAs driven very soft would be proffered over the Veros powered hard. I'm looking to build a new setup running CXAs at 17watts each, this will give me 51%ish efficiency. My current lighting setup is about 36% efficient so i will be getting extra light and less heat out of them (i will need more LEDs though which is pricey). As for the Vero Mounting, It's just cheaper as you can but the mounts for CXAs, but tbh kapton tape works alright for me. If i was to use mounts i would need a pillar drill (preferable to handheld) and tapping tools, both cost money and time. But power to you if you have the patience for that! i know i don't .

[Badders]

Hey Lean;

I'm running 2 x 3070's @ 1.4A each in a small box, 0.5 x 0.5 x 1m. Working pretty nice, temps are steady at around 22.

Drilled and tapped 2 x m3 holes for the vero with a cordless drill no prob, took about 20 mins.

I've never used kapton tape, or seen it, but I did have some m3 bits laying about, if supra etc say kapton is good enough I'll go with that.

What driver(s)are you lining up for the, 17w is what 400mA or so?

I got a few fasttech drivers in the post the other day,

gonna run the 2 cxa's from those and the vero from my 1.4a driver.

B.

Edited February 22, 2015 by distracted

[Lean_McSheen]

Hey Lean;

I'm running 2 x 3070's @ 1.4A each in a small box, 0.5 x 0.5 x 1m. Working pretty nice, temps are steady at around 22.

Drilled and tapped 2 x m3 holes for the vero with a cordless drill no prob, took about 20 mins.

I've never used kapton tape, or seen it, but I did have some m3 bits laying about, if supra etc say kapton is good enough I'll go with that.

What driver(s)are you lining up for the, 17w is what 400mA or so?

I got a few fasttech drivers in the post the other day,

gonna run the 2 cxa's from those and the vero from my 1.4a driver.

B.

Well at 52w each you are at a pretty much perfect 37w/sqf. See, if i were to use a cordless drill i know i would mess it up. Kapton tape is a heat resistant if i remember right, it looks like an orange/brown tinted sellotape. Supra says it's good enough but SDS is of another opinion, personally it has worked fine for me so far and is less time consuming. it doesn't look at pretty or professional though.

Well with the new CXB range out it's put a bit of a spanner in the works. I'm not sure if i will be going with the CXB3070 or the CXB3590. The CXA3070 would actually cost me more, the CXB3590 would cost less but have less spread. I'm looking at running SOG so spread will be quite important. I will be working with only 90cm total height too so i'm not sure i would have the distance for the 3590. Which ever COB i go with i'll be using the meanwell HLG120h-500b, that will power 8 3070 or 5 3590 so i'll need 2 either way. I worked it out last night that the 3590 setup i would use is cheaper, more efficient and puts out about 4,000 lumens more than the 3070 setup. But the 3070 is spread out better and uses about 70ish watts less. If i evened the watts out i would need 20 3070 cobs, that would put out about 10,000 lumens more than the 3590 setup. it's a hard decision but i think i'd be better off going the 16x 3070 route so the light is evened out more over the canopy and doesn't need as much clearance.

:oldtoker:

Edited February 22, 2015 by distracted

[Badders]

O nice, just looked at the datasheet comparing cxa3070 to cxb3070 they don't appear an awful lot different; the lumen output on the bining tables is very similar and the spectral graphs follow suit aswell, have they changed much?

Sounds like going down the 3070 route would suit your requirements better..
What are you planning to use for cooling them? I only ask because alpine 11 plus's dont appear on the over clockers website anymore, the cheapest I can find them know is £12 inc. pnp!!

[Lean_McSheen]

O nice, just looked at the datasheet comparing cxa3070 to cxb3070 they don't appear an awful lot different; the lumen output on the bining tables is very similar and the spectral graphs follow suit aswell, have they changed much?

Sounds like going down the 3070 route would suit your requirements better..

What are you planning to use for cooling them? I only ask because alpine 11 plus's dont appear on the over clockers website anymore, the cheapest I can find them know is £12 inc. pnp!!

The cxb is slightly more efficient and the cxb3070ab is actually cheaper than the cxa3070ab.

Well i've been looking at passive cooling because i will be powering them so gently. So i've been looking into heatsink companies which have a heatsink i could use. I have found one that is local to me, i e-mailed them on thursday but i've had no response as of yet. I have a feeling it will be a costly thing though, i'll be needing 4 x 1 meter lengths for 16 3070 cobs.

[Badders]

Oh okay, Are they due out on dk or ali ( I tried getting some cree's from ali and I couldn't buy from the china vendor, bit odd....) theres rumour on riu that vero 2's may be out soon, makes sense if cree are also releasing.

Let us know how you go on with passive, its certainly something I'd be interested in, my mate got 2 700mA fast tech drivers tohter day, the plan is to run 2 x 700mA 3070's and 1 vero 29 @ 1.4A

peace dude,