COB DIY (sort of) idea

So I see you guys making your own COB LED lights and it just looks like a lot of work.

So I have to ask...has anyone thought of mounting up a bunch of these?

http://www.ebay.com/itm/Ultra-Bright-MR16-GU10-E27-Dimmable-CREE-LED-COB-Spot-down-light-bulb-6W-9W-12W-/301020298272

You can get the Cree Cob LEDs in MR16/6W, non-dimmable, warm white, 10pcs for ~$32

A pack of 15 MR16 holders for ~$4

Put 50 of them together and you have a 300 watt 6 watt chip panel and just blow a very large fan across them. I imagine the fan would be so large that you wouldn't need any other fans in the grow room.

Because of the lack of efficiency, unknown bin of diodes and really, a lot of work, to put it all together, it isn't in most people's interest.

Doesn't mean it can't be done.

I would thinks something like this would be good for supplementation or experimenting with odd angles or something. You would save yourself a lot of hassle by even doing just 1 Cree Cxa Cob module on a Cpu Cooler.

It'd be more work to put together a fixture that had 50 lightbulb sockets. And +1 you really don't know how efficient the components are.

Well yeah I guess my idea isn't much cheaper and a lot more work with unknown results haha.

Except the DIY COBs are also a lot of work and it's $400 for 4 of them to cover ~ a 3x3 area (that's how captainmorgan did it) as I recall. I know he broke the gpw barrier but I also can't remember how many watts they were I think a little less than 300.

At any rate it seems like any use of COBs is fine if you're growing in a little tent but for anything bigger it sounds like too much hassle.

There are folks on here who built 6-cob units and using them in decent sized rooms.

CXA 3070 Z4's with 1400 ma drivers delivering 30 watts a square foot will kill it.

Most average HID growers have traditionally gotten 0.5 grams/watt. To cheaply light a 4x4 table for the highest returns they would use 1 1000 watt HPS. That's 500 grams in 16 sq ft.

To match that same yield for the same space utilizing CXA's at 1.3 grams/watt would require ~384 watts. At 30 watts per square foot this would cover a foot print of ~ 13 sq ft.

Just how many of the COBs would someone need to make though? I'm not clear on the watts per fixture or if the grams/watt included the fans too.

Also, more experienced growers can get much closer to 1.0 gram/watt. Except with COBs you'd either have to go to 60 watts per square foot or double your growing foot print and I don't know if you'd still be getting 1.3 grams/watt at 60 watts per square foot.

it's not that much work. The only hard part is tiny soldering pads on the cobs. Just about everything else is as easy as wago connectors and/or crimping.

Check the "how to power them" thread, as well as SDS's CXA analysis stuff.

I know at least one person yielded over 1 g/w w/ merely 2 3070s... if you dig around you can find the link to that grow (on another forum, IIRC).

To cover a 4x4 I believe you need 9 COBs @ 1.4a (50w) each or 5 @ 2.7a (100w) ea. So between 450 and 500w nominal, drawing more like 500-580w from the wall. In the 30w/sqft range. Spread evenly over the canopy and set nice and close <10" if using 9, a bit more if only 5. I believe that done right, 1.5-2g/w is very possible.

The CXA 3070 Z4's at 1400ma pull about 52 watts but when you add the driver and the cooler fan it's about 63.5 watts at the wall for each COB. I used 3 COBs over each plant to pull 1.3 g/w.

capn, that lines right up. With top bin AB COBs and passive cooling, 1.5-2g/w, should be very possible.

Yikes, then you're looking at $900 to cover a 4x4 table or about $506 per square meter plus all the work to assemble them and still only getting the equivalent of ~0.5g/w for the same space/number of plants albeit using much much much less electricity.

Yes, the initial outlay is large. But you are looking at equivalent yields at half power and significantly reduced heat profile. Plus no more bulbs to buy every 8-12 months. I believe these COBs make sense even in large installations. Cutting direct lighting power in half and seriously reducing the A/C load in multi - 1k grows will result in seriously reduced costs long term. With electric rates going no where but up, ROI is not long at all, and many who simply cannot grow during the warm months, might just be able to keep things moving all year now.

Prices will continue to fall over time and startup costs will come down, but I believe the numbers already fall clearly on the COB side of things today and will only get better.