Noob here with QB288 build questions

[Hogie]

Hey everbody, Hoagie here looking for some advice. Ive been driving myself crazy the last few weeks thinking about building a light fixture for my future grow.

A bit about the setup: Will be growing 2 plants in a 2'x4'x7' GGT (8sqft). Im hoping to train each plant to fill 4sqft probably by scrogging or maybe mainlining with some fimming and LST. Anyway, the point is im shooting for a nice even canopy and want to hit my ladies with a nice even flow of light.

So my plan is to build a rig with 4 QB288 V2s on Slate 2s with two hlg-240h-2100b drivers. Was planning on wiring two sets of 2 boards in series attached to each driver. Each driver with its own pot, wired into a box with switchs. (the idea being if i ever do seperate strains i could dim or increase light to either side of room depending on plants needs).

Question #1 If i figured this right, i should be running at around 400W, 4A at the wall? Ive heard people say that qbs only need about 30 - 35 watts/sqft to flower instead of the normal 50W/sqft. So would a 400W setup be insanely overkill for a 2x4 space? I know im planning on dimming, but if im way overpowered then i may be able to tone it down a hair.

Question #2 After watching the review vid for the hlg slate three triple and the ppfd comparisons between the slate 3 triple with two boards and the slate 2 with two boards, i noticed that the slate 2 was really hot in the center 1x1 while the slate 3 was a bit more spread out. Im thinking of doing a bit of both by spreading the boards out but evenly across the room so that they are evenly spaced from eachother and the reflective walls to get the perfect spread of ppfd across the entire space. Again, am i crazy? It would be so much cheaper to just do 2 qb288 v2 singles for the space which is what the are specd at for flower. I just dont like how the ppfd chart shows the light dropping considerably around the edges of the light. Im hoping to achieve 700 to 900 ppfd across the entire tent at 18 inchs.

Hoping that someone who knows better will either agree with me or tell me im being totally rediculous so that i can move on and get this build under way!

Thanks in advance

[unkle_psycho]

There's a fluence guide to high lighting, somewhere in the general section I think. They say you really need co2 to benefit from very high light intensities. I guess its very strain dependent though. I'd love to see side by sides with different light intensities...

I'm running 300w for 2x4, with bridgelux vestas. They are about 10cm from canopy and there has been no signs of damage. But the vestas are 90cri, so lower lm/w and perhaps less damaging since the light is more like the sun.

I'm planning on building a 2x4 box and flower a single scrog plant with 75w connected to 12 strips, half as a top light, and half as sidelight. That should give some kind of an idea on 'how low you can go', with about 8w per foot.

[Hogie]

Thanks for the redponse unkle_psycho! Just searched the forums again for that fluence guide with no luck. I did find some interesting posts though. Looks like someone is doing something similar. Low power boards across the entire grow space.

Co2 isn't totally out of the question for me but I'd prefer not to have the added expense. I just want good, usable, even light across my entire canopy with hopefully a bit of penetration.

With the drivers I was planning on using each board maxed out would be pushing 100w. Hoping for an average ppfd of about 800 at max output at 24 inchs. But I'm not really planning on running at max. Was thinking more like 50% to 75% for better efficiency. So shooting for a ppfd of 400 for veg to about 600 or 700 for flower.

Really only considering doing this because I have a problem with always going too big. Plus hlg has bare kits with 2 boards and 2 slates for $189us per kit, Drivers at $69ea. Wire, wagos, cord, switchs, and aluminum channel would like another $50 - $75. So for about $600 I could make a light that would kill in a 2x4 but could also could probably be split up into two rooms.

Again, really just looking for someone to either root me on or talk me down.

Thanks again

[QuantumMechanic]

I'll root you on. I run a 2x4x6 cabinet and recently built a fixture that's just a little excessive. Here's a link to my thread on GrowKind.com.


https://forum.growkind.com/threads/my-l ... ost-581543

[Hogie]

Man, that looks awesome! Nice clean setup. I'm a sucker for organization. Never understood how people could have wires and chords dangling all over.

Would you mind telling me a bit more about your growth troubles from low temps? My grow will be in a heated garage or a spare bedroom (haven't decided yet) but the ambient room temp will only be about 70f. Were you able to get the lights to grow or did you have to reconfigure your setup?

Cheers

[QuantumMechanic]

Thank you, Hogie.

I knew that the LED would generate less heat, but didn't fully appreciate that the garden would need to run at a higher temp than an HPS garden. With the LED, the cabinet is 72-73F. I need 80-82F to make plants grow.

My problem is that I used a Panasonic bathroom fan that is "single speed only." (Panasonic says "no electronic speed controls".) And I can't cleanly replace the fan with something else, as the cabinet is built tight around it.

Currently, the cabinet has the HPS still in it, and yet another grow. I'm looking into something electronic (and lots more sophisticated than the usual fan speed control) to run the fan. Apparently this electronic gizmo is compatible with my fan. For the curious, It's an Invertek single-phase output variable frequency drive. It hasn't arrived yet, so I don't know for sure that this will be answer. It does look promising though. If it works, I'll look into a temperature controller that can tell it what speed to run the fan. Not quite Rube Goldberg, but getting there...

Moral of the story: Get a fan that you can attach to a temperature-regulating speed controller without a lot of drama and expense.

[unkle_psycho]

I had a similar freak out moment this spring, when I switched to led. Still planning to build a box with good heating, thick walls and sealed to generate the heat without wasting electricity.

btw, i looked through the whole forum and could not find the fluence guide either. Sorry.

[atreum]

Here's the Fluence guide mentioned earlier: http://fluence.science/wp-content/uploa ... .27.16.pdf

[unkle_psycho]

I'm not sure, but I think they propose values for a 4x4 space [edit: 6 inches to canopy, 4x4 space], with the spydrx for non-co2 setups and the spydrxplus for CO2 enriched. The normal model uses 330w and the plus uses 660w. Perhaps I'm wrong about the space, but that would be 20w/ square foot without co2, and 40w/ square foot with CO2.

It seems to me most people running 30w per foot without CO2 keep their light pretty far from the canopy.

When switching from a single light source to multiple bulbs, it might make more sense to focus on the distance to the bulb, rather then efficiency figures. Halving the distance to a single bulb increases light intensity 4x, so while there are benefits in efficiency, the real potential seems to be in spreading the light so you can get it up close. (multiple bulbs have a different math, and loose less with distance, but thats irrelevant for this point).

So switching from a 400w HID with a distance to canopy of 50cm, to 100w leds evenly at 25cm from the canopy should give a pretty equal light intensity. Measuring buds at the side of the grow space should have an even greater benefit, since they would have been even further from the HID bulb then 50cm.

So now I'm looking to replace a 730w LG sulfur plasma, and I noticed that for many buds the distance to the bulb is over 1m. getting the new led bulbs to 25cm should increase light by 4x4=16 fold. I would prefer to halve that once more and get the leds to about 10-15cm.