How does efficiency effect a grow?

I do want to run at about 18inchs but not sure how hard to run the cobs for that hence the reflectors. And I wish I could bring myself to pay out on a par meter just to set my lights, maybe someone should get one and rent it out lol.

Also I can adjust the drivers so ideally would keep the fixture as one also side lighting would be a hard one without making my fixture again but smaller so I can angle boards, straight side lighting to me would have to go quite low then becomes a nightmare to hang

If you are in the Bay Area, PM about renting my Apogee. You can get a cheap lux meter and get equivalent #'s to check against.

nevergoodenuf said:

If you are in the Bay Area, PM about renting my Apogee. You can get a cheap lux meter and get equivalent #'s to check against.

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In the uk but thanks for the offer I have a lux meter but have 3k 90cri cobs and 35k plain boards the the mixed boards so not sure how I’d work it out

astonehead said:

I do want to run at about 18inchs but not sure how hard to run the cobs for that hence the reflectors.

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Well if you run the COBs that high it makes sense to add reflectors since that smaller beam angle works better with a greater distance.

Malocan did a test and at something like 20" he saw an improvement with reflectors of about 5% compared to bare COBs at that height. Although bare COBs are normally run at half the distance and that gave him 18% more light on average still. So normally it's better to run COBs bare, but only when you want to hang them high it's better to add the reflectors.

Make sure you replace them with clean ones though. They seem to get dirty quickly during a grow and then lose reflectivity.

You could try with the lux meter. At least it will give you some idea. But indeed the 3000K 90CRI will be undervalued compared to the 3500K. Dividing the lumen values for the 3500K by 71 to get PPFD and for the 3000K 90 CRI by 62. Should correct some of that error.

wietefras said:

That is simply not true. Boards are basically a replacement for 4 COBs in a small rectangle. Which means you really need to hang boards higher to get properly uniform lighting. HLG advises to hang QB's at 18". That's twice as high as you'd generally hang a COB fixture.

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Really. A spot light is equal to light spread out. You are simply deluded in your own thoughts. An than you refer to HLG a PCB board supplier. BIASED you are.

Lol straight over my head lol. So at 18 running the boards at 50w each what would you suggest to run the cobs at, 18inchs is a good distance for flowering but I can’t really move my light easily so just need the plants to grow up to it.

Iv got the cobs at 25w bare at the moment as suggested by cobkits and the boards at 45-50w each lux at the plants around 36 inch’s away is around 20000 lux and thinking at the 18inchs+ the light would all mix anyway wouldn’t it?

wietefras said:

That is simply not true. Boards are basically a replacement for 4 COBs in a small rectangle.

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4 small cobs (1212s)

probably 1.5-2.5 larger cobs (1.5 being like a 3618/CXM32 and 2.5 being a 50V like cxm22 or 1818 )

with the 1212s i needed twice as many dies to equal a QB (4 x 144 = 576 which is twice the 288 # on the QB)

an 1818 has 324 dies
a 3618 has 648 dies

but obviously as you cram more dies on a chip of finite size you'll lose a little. particularly at higher currents temps where the board has superior dissipation

that would be a good test though - 3618 vs QB straight up

astonehead said:

Lol straight over my head lol. So at 18 running the boards at 50w each what would you suggest to run the cobs at, 18inchs is a good distance for flowering but I can’t really move my light easily so just need the plants to grow up to it.

Iv got the cobs at 25w bare at the moment as suggested by cobkits and the boards at 45-50w each lux at the plants around 36 inch’s away is around 20000 lux and thinking at the 18inchs+ the light would all mix anyway wouldn’t it?

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With current COBs and boards, about 350W is enough per m2. Which makes it around 500W total for a 4x4. I'd aim for that as a total.

Bare leds have a beam angle of around 120 degrees. Which means that when it's up at 18", the light spreads over a 60" circle. So yeah it will mix.

BTW It's nonsense that running these lights softer would somehow hinder "penetration". Penetration is created by the total amount of light you send at the plants. It does not matter how hard each of the individual light points are driven.

CobKits said:

4 small cobs (1212s)

probably 1.5-2.5 larger cobs (1.5 being like a 3618/CXM32 and 2.5 being a 50V like cxm22 or 1818 )

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Sure, but A QB is normally run at something like 100W and if you run the 4 COBs at 100W in total I doubt it would matter much.

Point was more though that the light from bundled lights like that is not distributed that well and that boards need to hang quite high above the plants. Which goes against the common misconception that boards are good for small grows.

In this case the boards are run quite soft and there is a lot of them instead of the usual one per 2x2, so here they could be much closer to the plants.

In fact I'd hang the whole think at 10" max. But if that's not an option then leaving them up high should work too. It just wastes some light on the walls.