LED CRI suggestions for veg flower, or does it matter?

skoomd said:

Well what size in MM fans are we talking? 120mm can be pretty quiet at 5v, but 80mm fans are too loud for me even at 5v. Cheap fans are of course louder than more expensive ones too. And the more cobs you have running, the louder it gets.

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CPU coolers. You do not hear them. At all. Stop making stuff up.

It would depend what the COB is running at. But an active heatsink has faaaaar less surface area than a passive sink capable of the same cooling load. I have heard from quite a few people that they had a fan go out running a COB at 75-100w+ and the COB burned out before they noticed. Whether that be hours, days, or even weeks who knows. But it has definitely happened to people before. And they often swap to passive afterwards

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If people overdrive their COBS then yes that could happen. Bigger Citizen COBs would be able to take 100W, but they can deal with very high temperatures too.

So this is anecdotal evidence at best, where people probably did something else wrong to begin with.

Anyway, a U channel would work on COBs just as well. Just give it a fat base to distribute the light.

wietefras said:

CPU coolers. You do not hear them. At all. Stop making stuff up.

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Ive been building PCs since 2008, there are definitely cpu fans on the loud side. Especially if you need to cool 100w, which most high powered CPUs run at and will need full 9 or 12 v (whatever it's rated for) to do that. I have a pretty silent 120mm cpu cooler in my computer right now, while it's silent usually it gets very audible under load.

I dont know for sure, I dont have any cobs to test their thermals with different RPM speeds of the fans. I've seen some videos of people's COB setups, and it seemed too loud for my taste. Just IMO though.


I'm anal about noise, my tents sit in my bedroom so I try to go as quiet as I can.

wietefras said:

Anyway, a U channel would work on COBs just as well. Just give it a fat base to distribute the light.

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That is good to know. Thank you.

This are two passive 45" heatsinks made from 2 u-channels, the small channel is glued in the bigger one to increase the surface area and thickness of the bottom plate. The big one is 25x 35x 25mm( |__|) and the small one is 20x 20x 20mm. Works well with thermal tape!
Each has four Bridgelux V18c/3k/CRI90 COB's running @500mA so 70ish watts per heatsink. Temps stay below 45°C with 28°C ambient, even after 12h!

Good shit!

This is the first ive heard people using U frame for COBs. Gives me some ideas....

Yeah, drive them low and they need much less cooling effort. My old CXA2540 3,5k/V4 bin from my old veg light have been recycled and now run with only 175mA/5.6ish watts between some new F-strips. More pics are posted in users-unite thread. The heatsink is build in the same way just with a bigger sheet and a few more u-channels. Highest Tcase was 48°C with 145w and 29°C ambient temps.

https://www.rollitup.org/t/led-users-unite.240615/page-468#post-14162712

has anyone figured out the lumen requirement at the canopy in veg and in flower? (i know it's not the spec i should use, but i only have a cheap meter that doesn't red in par) i'm having trouble dialing in a room for my friend, and as it's a diy light there are no instructions, haha. i really need a good meter, but the funds just don't allow it at the moment. i think i was too close, as the node spacing was too short. then too far because it was stretchy. got a new driver and this thing gets BRIGHT. 4x 3000k 90 cri 1212's on a 185w watt mean well B-type driver. dims down to ~25w with the fans on, and ~230w iirc with the dim leads left open. + i have 3x23w 4000k led strips in there as well.(never are they all on, just hung the 3 on a 8" wide floor board. space is 8 square feet (2x4'), and i have more light than i need, maybe so even in flower (~300w total) do you have any suggestions on what i should run the cob light on in watts for veg/flower, and if/when i should use any or all of the 23w 4' 4000k strips, and also how high (from canopy). i keep the cob light and the strips all at the same height for spread/convenience. i see so many contradictory suggestions for light height, from anywhere between 3 feet above plants, all the way down to inches and this makes it hard for someone without an adequate light meter to dial in a sweet spot for power/distance. any suggestions would be welcomed and appreciated, i didn't want to make a new thread for these questions. thanks in advance!!

Post #23 by @Randomblame. https://www.rollitup.org/t/slow-yellowish-growth-under-vero-29-3000k-3500k.962065/page-2

Start at post #13 by @Photon Flinger. https://www.rollitup.org/t/cannabis-daily-light-integral.921153/

skoomd said:

What about emerson effect?

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Everyone likes to bring up the Emerson Effect - few seem to realize that Emerson himself noted that it fades to nothing with white light levels above 400 umols.... How many of us are shooting for PPFD levels below 400?

1212ham said:

Post #23 by @Randomblame. https://www.rollitup.org/t/slow-yellowish-growth-under-vero-29-3000k-3500k.962065/page-2

Start at post #13 by @Photon Flinger. https://www.rollitup.org/t/cannabis-daily-light-integral.921153/

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sweet, thanks. you rock!

1212ham said:

Post #23 by @Randomblame. https://www.rollitup.org/t/slow-yellowish-growth-under-vero-29-3000k-3500k.962065/page-2

Start at post #13 by @Photon Flinger. https://www.rollitup.org/t/cannabis-daily-light-integral.921153/

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I prefer 90 over 80 CRI but mix both. The 90 just makes the plants look better visually. That's in 3000k. I want to try 1750k but it is only available in 80

Committed to Vero SE lines for ease of connectors and manufacturer support. Very easy to swap or just add to current setups. Large mounting surface and very good thermal transfer let's you stick them on simple metal sheets.

C version is the best for performance but pricier than the B or D versions. It is common to see low quality cob light vendors use the B or D versions mounted on active heat sinks and driven over 100w each to save money and ride off the Bridgelux Vero name. Avoid those scam artists and build your own. For the price of those units, you can get twice the number of C version cobs, drivers, parts all for half the price. 1 cob/ft2 is heavenly and can last forever.

FYI, CPU coolers they are designed to absorb short intense bursts of heat and are overkill for a continuous heat source like an LED. It is a relic of the past, time to move on.

IMO it seems impossible to make a 1750°k spectrum with CRI90, the light is just too pink for that.
But that's simply not necessary, because it contains more red, deep red and far red and red already peaks around 645nm. But you could take CRI97's if you don't like living on mars which provides more green but has the red peak almost in the same nm region...

I hate those spd charts. They suck for old eyes. But they do provide enough information after you figure out which line is for what. I have some drivers with enough voltage range to run a 29 and 18 in series so I might pop on some 18s in 1750k (80 CRI) and 2700k (97 CRI) along side some 29s in 3000k 80/90. 3000k 90 CRI has r9 of 50 whereas 80 is 0 so going to 97 CRI bumps that r9 up to 98.

Lol, I know exactly what you mean, dude. For me it needs to be three times zoomed to keep the lines apart.
Getting old is shit..!

R9 from CRI80 is around 20 but they use 0 for the sake of simplicity. But CRI/Ra is "also" tailored to the human eye and everything else is purely coincidental. The 1750's just do not have enough green to get a better CRI. But their r9 should also be higher as 80 if not even higher as 90.

A 1750/CRI80 + 2700/CRI97 mix would give a nice flowering boost for sure with lots of far-red vs. 3k/CRI80.
I'm using 3000k/CRI80 f-strips for vegging because CRI80 it gives me a more even canopy. I bump up the V18c/CRI90's only when changing to 12/12h to get a tad more stretch and increase the DLI.
If necessary, I can use my additional 730nm diodes(mainly installed for end-of-day threadment) to get more stretch, but this is a balance act, because it can quickly be too much and cause unwanted SAS(shade-avoidance-syndrom).
With CRI90+ alone I have not observed any SAS yet.

Below is a spheere test for LM301b in 4000°k/CRI80 and it has an r9 of 18, 3000°k will be a tad better.

Yeah I got the CRI for other purposes than for what we need part but it does have some elements that influence the reds we are after. But on another point which I think is important, the higher CRI are visually better to look at for our eyes. 80 CRI seems a bit harsh, more blending of colors, not the pop you get with 90+ CRI.

Still less irritating on the eyes than blurple. Seedlings and clones love them though so they are staying in mix.

Yepp, under CRI80, they look more yellow than they are. With CRI90 and above you do not have to turn the light off for inspection purposes which is a good benefit. I've modded an old torch and changed the coolwhite XPE against a XPG2 4k/CRI90 diode especially for this reason.

nfhiggs said:

Everyone likes to bring up the Emerson Effect - few seem to realize that Emerson himself noted that it fades to nothing with white light levels above 400 umols.... How many of us are shooting for PPFD levels below 400?

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what does that mean?

in laymans terms,

Im tryin to hit Emerson with 3500K90cri and 730nm, with added 4000K80cri.

probably not enough 730, as its just Growmau puck, huh? 3.5x3.5 area

I personally think Emerson effect is magic if we hit it right, no?

"LED CRI suggestions for veg flower, or does it matter?"

>>no..and please add 3000-5000 kelvin to that too..
the rest has to do with what you grow where you grow how you grow..
from what i am seeing most of the "fundamental truths"[low kelvin flowers better]
difference is navel gazing..and techy
3000k 3500 k 5000k flowering vegging..
nah the rest is up to you imho

OLD MOTHER SATIVA said:

"LED CRI suggestions for veg flower, or does it matter?"

>>no..and please add 3000-5000 kelvin to that too..
the rest has to do with what you grow where you grow how you grow..
from what i am seeing most of the "fundamental truths"[low kelvin flowers better]
difference is navel gazing..and techy
3000k 3500 k 5000k flowering vegging..
nah the rest is up to you imho

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I don't have any first-hand experience with LEDs outside of 3000k and 3500k, but it seems to me that the plants just want enough light (and an appropriate environment) more than they want any particular spectrum. I imagine spectrum-tuning could be of some value to someone that has already dialed in and maximized every other aspect of their grow, but I think most would be better served by just getting on with things under whatever spectrum they already use.

But I could be wrong.

Humple said:

I think most would be better served by just getting on with things under whatever spectrum they already use.

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Exactly. Bugbee and others have done many tests and there really isn't much difference between different SPD's.

In 2014 people here started adding mono leds to the COBs to "improve" the spectrum. It died out quickly, because it quickly turned out to be easier/cheaper/more effective to simply add more COBs instead. So people returned to just COBs. Then new people enter the forum and they go hunting for the pot-o-gold at the end of the SPD rainbow. At some point they run tired of it too. New people come on the forum etc etc etc rinse and repeat.

It's just one of those things that people, especially those new to growing under "white" leds, think will make a massive difference, but it just doesn't.

There is no wrong answer other than what you find works best for your grow style.