Lighting Help using COB/QB Combo

[4d-Rock]

Hey all,
I know everyone has a different space and lighting setup so I was hoping that with various peoples input i'll be able to come up with a good plan for the use of my lights.

I have a 3' L x 2' W x 4.5' H tent which I have 2x DIY COB lights, each 55W and 3500K. I also have an HLG 135W QB288 v2 3000K Quantum board.

I know that light height is going to highly depend on many variables but I'm more interested in what people think of what lights to use at each stage. So far I've completed one grow with this setup and am almost a month into my second.

With the first grow I used one COB per plant, and tentatively turned on the qb a few times through veg, but i never let it go very long because I was scared of giving too much light. I did eventually turn it on after they fully started flowering. From there it was all good.

The current grow is similar, using one COB for both during the seedling phase, and one COB each. They are placed as high in the tent as possible as well (~36" from top of 2gallon pot).

I was wondering, am I waiting too long before using the QB? Should I be using it as soon as possible, maybe after the seedling phase is done, to give as much light as possible to grow? Or will this prevent that by giving too much light and not allowing the plant to stretch?

And if it's best to wait to turn on the QB until flowering, at what stage would be appropriate? At tail end of Veg stretch, as preflower sets in, or once fully flowering?

Here's what the setup looks like at the moment. I'll be moving the COB's to the side a bit and turning the QB parallel to the tent when I do turn it on.

Thanks!

 

[Arthur]

I run 9 diy cobs 50w 3500 in a 4x4. I dim for the first 2 weeks, then begin dialing it up. I'm at full by flower. But...the top of my heat syncs is currently at 51" to give me 26" between lights and tops.

Lose the reflectors, they'll make the light too focused.

 

[4d-Rock]

Thanks for the input @Arthur , nice setup! With my lights unfortunately, neither COBs or QB are using dimmable drivers. So it’s 0 or 100 for whatever I use.

After some quick calculations it looks like you are running 28w/sq ft. Dialed down to 50 you would be at ~14w/sq ft (not sure if intensity by dimmer is linear but I’m assuming).
The 2 COBs would give me 18w/sqft , then adding the QB it would bump it up to 40w/sqft. Not sure if 40 is overdoing it. But I’ll take your advice and take off the reflectors.

Knowing the appropriate heights are also going to influence how well things do in there. One of these days I’m going to have to bite the bullet and buy a taller tent...

Interested to hear other people’s opinions so keep it comin’!

 

[Arthur]

That's probably about right wattage wise, until they toss their first set of true leaves they're busy under the soil and don't need a ton of light. Just enough to keep them from getting leggy. But, I want them adjusted to as much might as possible by flower. Until I see stress on the tips, the light gets brighter or lower. Have had a couple strains that were happy 12" away @ full blast, others grumble it's to strong at 30".

 

[Mañ'O'Green]

The QB's spectrum would be better for veg and you can run it 20" from the canopy then as the plants set the fourth node or set of leaves turn on the Cobs which are richer in red. Run all of your lights full speed after that. If you want to get really technical you can calculate DLI (daily light integral) and run your lights just enough hours to meet the needs. I just run 18/6.

 

[Ozzie Greenthumb]

Hell yeah turn it on! Watch your temperature and Humidity. Also buy a cheap analog light meter. It will help! This is in a 2x4x6 tent!

 

[4d-Rock]

That's probably about right wattage wise, until they toss their first set of true leaves they're busy under the soil and don't need a ton of light. Just enough to keep them from getting leggy. But, I want them adjusted to as much might as possible by flower. Until I see stress on the tips, the light gets brighter or lower. Have had a couple strains that were happy 12" away @ full blast, others grumble it's to strong at 30".

Gotcha, so it's all part of that balancing act. So what would your vote be then? Start all 3 lights once the seedling can take it and play with height from there (likely with all three they would need to be right to the top). Or stick with the 2 COBs until a point and turn on the QB (and when)?

The QB's spectrum would be better for veg and you can run it 20" from the canopy then as the plants set the fourth node or set of leaves turn on the Cobs which are richer in red. Run all of your lights full speed after that. If you want to get really technical you can calculate DLI (daily light integral) and run your lights just enough hours to meet the needs. I just run 18/6.

The QB is at 3000K and the COBs are at 3500K, I thought that would mean that the COBs have a higher spike in blue, at least that's what their spectrum graphs show. Although the difference isn't great, maybe by 10% or so. So then you'd say turn them all on after the 4th node -ish, maybe after the recovery of topping or before? I'll take a look into DLI, that's something I've never really looked into, just a bit into Lux, ppfd, etc. I've pretty much been consistently at 20/4 for my grows. When I was using CFLs to start seedlings i'd go 24/0 until they were under the big lights.

Hell yeah turn it on! Watch your temperature and Humidity. Also buy a cheap analog light meter. It will help! This is in a 2x4x6 tent!

Nice setup! How many watts for the lights you are running in there?
Ya, with just the COBs the temperature is around 23C, dips to about 18C during the dark. The QB will increase the temperature 4-5C which should be reasonable, I can increase the exhaust if needed to keep it from climbing too high. Plus winter is starting to set in so its cooler in general in the house. I do have one of those cheap digital light meters that measures lux to a max of 100k. With the COBs on only I'm measuring around 16-18k lux. When I turn on the QB it brings it up to 40k.

Here's my current grow at day 27 with just the COBs. Topped at day 21 and been doing a bit of LST.

 

[Arthur]

Currently running 450w over 4x4. I'd run the first week under 1 cob, maybe bring in the other at the first true leaves, then add in the QB. Or you bring them all in high, and lower slightly daily too, but you'll be wasting power... but sometimes its necessary to get on top of the environmental changes adding the lights bring along.

 

[Mañ'O'Green]

Oh shite, you are right I got that backwards Cobs more blue so run them first. Damn Dabs!

 

[MrMedicinal]

Hell yeah turn it on! Watch your temperature and Humidity. Also buy a cheap analog light meter. It will help! This is in a 2x4x6 tent! View attachment 1126500View attachment 1126501

‘hey there I’m just going to set up my 2x4x6,would you mind telling my what you’re using in your tent?! Lights etc