Advice & Critiques on my COB Build

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Digger Leveler
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Advice & Critiques on my COB Build

Post by Digger Leveler » Tue Jan 09, 2018 10:36 pm

Fellow hominids,
I'm looking to do a first ever COB build. This will be for a tent that is 18x30x36"H. 3.75sqft footprint. Tiny, but what exists.

I have chosen a layout that- I believe -will allow me to use the same fixture on what I hope to buy in the future: a 24x30x72"H tent (5sqft).

Here is my COB layout:
3- Vero29se 80CRI C-class (69V) 3500k COBs
1- Mean Well HLG-240H-C1050B driver
3- 140mm Pin Heatsinks (75watt max)
1- Dimmer (Cased Potentiometer with Knob)
Thermal pads, wire, connectors, clamps, lenses, etc...
Alluminum L channel for the frame.

This fixture will pull an apx. 207watts without dimming (69watts/COB)(apx. 182lm/watt).

My assumption is this will be overkill without dimming (I am new to this so lots of assumptions). But with dimming, the efficiency and efficacy factors will be incredible (+190lm/watt?).

My understanding is that 1000umol/s per sq meter is very good as a rule of thumb. That would be apx. 93umol/s per sqft. 50% of that when not flowering. Therefore, I'll need 348.7umol/s for my small tent.

It looks like one can achieve 2.33umol/s per watt using the same COB running at a higher and less efficient currant (Timber fixtures at close to 1.7ma). So I imagine, what I am driving these at will do better.

I calculate that dimming to 150w flower/75watts veg, will put me over 1000umol/s per sq meter (140w/70w with the high efficacy?).

Without dimming it should create 482umol/s. And if I get the 5sqft tent down the line, that will require 465umol/s, so all the better. I can then make a two-COB fixture for the small tent and still be ok on coverage.

I am hoping this setup gives me flexibility and savings in the long run. Growing photon-hungry bonsai tomatoes" at the moment.


Looking for advice and critiques, as I have just recently started delving into this mess of online info- naked and blind.

What do the other bipeds think?

Jibblerjoe
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Re: Advice & Critiques on my COB Build

Post by Jibblerjoe » Wed Jan 10, 2018 1:45 am

Im running 3 vero29 36volt driven 2100ma in a 2x4x5, I can't turn it up past 75percent with out burning leaves.

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LEDG
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Re: Advice & Critiques on my COB Build

Post by LEDG » Thu Jan 11, 2018 5:22 am

Greetings, fellow homo sapien. Sounds like a great plan. I've given up on estimating PPFD because there are so many variables - distance from light to plants being the toughest to factor.

I can say that I've run 4x CXB3590 at 200W total in a 2x2 with good results - you'll likely have to dim but it's better to have to dim than to be stuck needing more light than you have.

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bvolt
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Re: Advice & Critiques on my COB Build

Post by bvolt » Thu Jan 11, 2018 7:06 am

I can’t think of a reason to use Vero Cs in that limited space.

If you had a huge space and were mounting up high - trying to grow trees, they’d be perfect: they’re powerful and put out a ton of light, but from a single emitter. :shock: :o

More emitters, driven at lower current actually produces better (imo) overlapping and complete photon saturation...
You might wanna double-check anything you've read here...

Digger Leveler
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Re: Advice & Critiques on my COB Build

Post by Digger Leveler » Tue Jan 16, 2018 8:48 pm

Thanks all,

I appreciate the insight from LEDG stating that trying to estimate PPFD is often too complicated. I think there should be PAR based data sheets available (including height distances) for each type of COB. Since PAR is the measurement we are all supposed to be looking at, it would make sense that such info is more available. Buying a PAR meter isn't for most people.


In response to BVOLT, my point in going with the higher voltage Vero29 C's is that I get more photons per COB even while running them at a lower current- more so with dimming. The point was efficiency/efficacy. Lastly, I plan on using that 3-COB fixture in a larger space in the near future, while building a 2-COB Vero29 C for this smaller one.
Do you think that the efficiency/efficacy gain from my build is ultimately negligible? Because the upfront cost for a Vero C vs. a Vero B or D is basically the same, and 3 COBs for 3.75sqft seems like it will be ample canopy coverage.

Thanks

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