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Cheap and Cheerful DIY using Citizen cobs

Discussion in 'LED and other Lighting' started by JorgeGonzales, May 17, 2016.


    Dreddd Active Member

    Very interesting, just by eyeballing the spectrum graphs it looks like the gen 6's have more blues & greens in exchanges for some reds, you can clearly see that the cyan valley isnt as deep as in the gen 5 graph, for the 3500k the cyan/480nm bottoms out at 32% for gen 6 vs 22% for gen 5 and in addition the greens are also higher for gen 6, could this be why the par meter shows a higher reading for gen 6? since green and cyan are still part of the PAR spectrum it measures higher since the increase in greens and blue came in exchange for far red that the PAR meter might have not been registering in the first place? where is the PAR meter cut off? 700? 730?
    Joe34, moondance and DankaDank like this.

    CobKits Well-Known Member Rollitup Advertiser

    hard cut at 700. ill shoot these when i can maybe this weekend
    moondance and Dreddd like this.

    DankaDank Well-Known Member

    Most light meters are also less sensitive in measuring the red and blue.
    Joe34 and moondance like this.

    Dreddd Active Member

    That falls in line with my thinking, basically exchanged some far reds that weren't getting measured by the PAR meter for some extra blue/green spectra, makes sense that gen 6 reads higher PAR,

    on that same note, if the spectrum of gen 6 3500k is really more green/blue heavy with less red then gen 5 is gen 6 really more efficient then gen 5? i mean from what i understand it takes more energy to make red light then say blue or green, so if gen 6 had the same spectrum but better lumens per watt i'd say its overall more efficient, but it looks like Citizen instead decided to sacrifice red light for better lumen output, not sure i like that if thats really the case.

    idk, maybe i'm just nitpicking..
    MrTwist1, Joe34 and moondance like this.

    CobKits Well-Known Member Rollitup Advertiser

    im tabling the discussion until i can look at the actual cobs with the spectrometer, will post here and we can pick it up.

    ill shoot gen 5 h5m2, gen 5 h6m2, and gen6 h5m3-f1 with both the spectrometer and par meter and we'll see whats up
    alesh, Joe34, moondance and 2 others like this.

    CobKits Well-Known Member Rollitup Advertiser

    li-cor PAR sensor response:

    moondance and DankaDank like this.

    DankaDank Well-Known Member

    That's actually pretty accurate. Would I be right in saying there is a rough 5 % variance in sensitivity across the spectrum.
    moondance likes this.

    Nutria Active Member

    How far should I keep my cobs?
    I have 4x clu048 1212 @700mA
    Tent is 2x2x4.5ft
    I am worried I am running out of space

    Attached Files:


    Evil-Mobo Well-Known Member

    Start at 36" and then work your way down. When you start to see leaf curling stop or raise the light. If you leave the light too far away it will cause more stretch which is what you fear. Also as always this is all strain dependent. Once you get to know the strain and the lights you won't be fiddling as much with the adjustments. You're off to a good start with the 1212's inside a tent and no reflectors don be afraid to get close to the plants with the lights.

    wietefras Well-Known Member

    @Nutria , You lower the COBs till you get good light uniformity. If you hang them too high you waste light on the walls. If you hang them too low you will see bright and dark spots (ie poor uniformity).

    I'd start at around 15". You have to go really low to actually burn the plants. Well below 10".
    Joe34 and Nutria like this.

    KonopCh Active Member

    Could you post PAR numbers?


    After reading this thread and several others like crazy I still can't figure what model should I buy. I'm really lost in this debate 80cri x 90cri x color temp. The vendor I am going to buy has only these three options:

    CLU048 1212 3500K H6K2 90CRI bellow BBL
    CLU048 1212 3000K M2K1 80 CRI on BBL
    CLU048 1212 4000K M2K1 80 CRI on BBL

    @CobKits , which one should I choose between this three? I'll use only one of them for veg + flower... Looking at the datasheet it feels like the 4000k spectrum is more complente, but it peaks on 600nm with only 80-90% intensity on the 630nm and even less in the 660nm. The 3000k 80 CRI looks perfect on the red end of the spectrum, but has only 50% intensity on the blue side. But if I understood what I read, the McCree curve states that it is better to have more red since it has larger quantum yield compared to blue.

    One can really be lost in all this CRI X K discussion...
    Joe34 likes this.

    Metacanna Well-Known Member

    I was lost in the same dilemma when I had to order my 1212s. From the research I did in this forum, it seems it's not consensual among users, mainly because the differences are not significant, making it hard to say something conclusive.

    Maybe a good approach would be to spread the eggs, buying cobs with different CRI and spectrums. I bought a package of 5x 1212 CRI 80 4000k. If I could choose individually I would prefer to have some with a different CRI and spectrum.

    After all, unless you are building a huge array it might not be worth the hassle.
    Joe34 and MAJOR GANJAH like this.


    I'm building a small 4 cob array. Maybe I can throw in some 3000k 80CRI, but I'm worried that mixed temps in a small kit like mine won't be able to evenly distribute it's spectrum, making one plant be under 4000k while other is under 3000k and so on. But I'll guess it is not really worth the hassle, and if it really makes a difference I can always build a 630-660nm red led panel.
    Moflow likes this.

    Metacanna Well-Known Member

    From my understanding the 3000k have a lower PAR, even if we consider the sweeter spectrum curve, the 3500k might be a safer bet. I got the 4000k since I need the lights to veg and flower.

    Dreddd Active Member

    I too had the exact same problem, but after reading countless threads, charts, spectrum graphs, side by sides and comparing lm/W of basically every single cob out there i've come to the conclusion that while pretty much anything will grow good plants, if you want the best bang for your buck, 3500k 90 CRI is what to aim for, more specifically Citizen cobs for both efficiency and low relative cob cost.
    Last edited: Mar 17, 2017
    Joe34 likes this.

    ilam Member

    Try 16 inches, might even be good to try 12 inches. I've worked with 1212's before and they started burning weak leaves @7-8 inches when i ran them @800-900mA

    Good luck on that harvest, you should make a growlog
    Last edited: Mar 17, 2017
    Moflow likes this.

    Nutria Active Member

    Y I should

    Attached Files:


    Moflow Well-Known Member

    I'm vegging with 3 1212s at 680ma.
    Around 66 watts at wall.
    My light is around 10" to 12" from tops.
    Seems fine
    Joe34 likes this.

    CobKits Well-Known Member Rollitup Advertiser

    1000 mA in the sphere

    3000k 90 cri gen 5 vs gen 6. and just to confuse things i thru the "H6" below BBL 90 cri gen5 version in there
    definitely a slight shift

    gen5 "H5": blue peak 449 nm, red peak 627 nm
    gen6 "H5": blue peak 451 nm, red peak 620 nm

    considering mccree YPF is 100% from 590-625 nm i wouldnt worry about it. the additional 5-7% PPF of gen 6 more than makes up for it

    Last edited: Mar 20, 2017

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