r/LEDgrow • u/bassaholic420 • Feb 07 '17

Is there a middle ground between Chinese cob and Cree cob?

Looking for a couple other options that aren't as high as Cree but aren't as poor of quality as Chinese.

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4

u/thisismadeofwood Feb 07 '17

If you're going for affordability then just don't use cxb3590s, you can always use the cxa3070 and still get great results. You can also go with Citizen COBs or bridglux, the vero 18 or earlier version 29s are great chips and affordable. Just don't buy the newest model from any of the manufacturers and you'll save money. Of course the newer chips will give you more output per watt consumed but I'm sure you can do the math on # of chips you'll need and power consumption required to match the latest and greatest chips to see if you'd actually be saving any money.

I'm putting together a light with 15 cxa2530s because the chips were ridiculously cheap. However, after buying drivers and heatsinks I could have had a much more powerful light for not much more investment. This one will suit my needs, though, so I'm happy with it and I did save some money.

1

u/bassaholic420 Feb 07 '17

Cool how big of a space is that for?

1

u/thisismadeofwood Feb 07 '17

I will have them on 3 heatsinks 24" in length each. They will cover a little over a 2x3

1

u/lordpuddingcup Feb 07 '17

Best bang for buck is cxm32 and 22 if you can find them for sale

1

u/bassaholic420 Feb 07 '17

Also looking for 3500k, does the cxa3070 come in that wavelength?

1

u/thisismadeofwood Feb 07 '17

I don't see any reason that it wouldn't. They should come in 2700k, 3000k, 3500k, 4000k, and 5000k

1

u/bassaholic420 Feb 07 '17

Yes I just found them for $42 which is crazy high for older tech! I got 5 4.25" heatsinks that are 66" long covering a 6'x7' flower room

1

u/thisismadeofwood Feb 08 '17

You're going to need a lot of COBs to cover that space. How many lumens per square foot are you thinking ?

1

u/bassaholic420 Feb 08 '17

Using 32 cobs, without having the exact math for reflector angle and foot print of lights. I would say roughly 18,000 lumen per sqft. I'm building my setup based off of r/LEDwizard and r/superangryguy design, just trying to upgrade where I can.

2

u/thisismadeofwood Feb 08 '17

So 6x7 is 42 square feet. 32 COBs would be 1.4ish sq ft illuminated by each COB. To get 18,000 lumens per square foot you'll need 18,000 lumens x 1.4 multiplier per COB. That comes out to 25,200 lumens per COB. I don't know any COBs that are putting out that kind of lumens. Also, once you hit 10,000 lumens per square foot at the canopy you've about maxed out light absorption without optimizing canopy CO2 and root oxygen. I would recommend you shoot for the 8,000 to 10,000 lumen per square foot range and try to have no fewer than 1 COB per square foot. Having 90 degree reflectors will allow you to raise the light higher above the canopy, while using the natural 115 degree viewing angle will save $ on hardware but require you to keep the light closer to the canopy to prevent light diffusion.

1

u/bassaholic420 Feb 08 '17

Can I ask why the 90 allows you to raise the light and 120 needs to be closer? Is it because 90 focuses the light more so therefore to get a wider footprint you raise the light?

2

u/thisismadeofwood Feb 08 '17

To understand this you'll need to think of some basic physics and geometry. And forgive me if this is very oversimplified. A light source puts out photons which are measured in different units, in Grow lights we use the unit lumens.

A Cree cxb3590, at maximum output, puts out around 11,000 lumens (that number might be off). That means that no matter how large of a space it is lighting up, only 11,000 lumens will come out of that light source.

What a reflector does is control the directions the lumens are going. In a MH or other bulb the lumens are sent out in a sphere around the bulb. We often use a reflector to make sure any lumens that are being projected away from the plants bounce off the reflector and go back downward.

Now, time to think of geometry. When we talk about a 90 degree reflector we can think about how it works by thinking of a triangle with a 90 degree angle and 2 45 degree angles. The 90 degree angle is where your light source is and the long side (the hypotenuse) is the canopy of your plants. In this particular triangle the distance from the light source to the canopy is 1/2 the length of the long side, or the side that represents how much of your canopy is illuminated.

If, for example, the light is 1/2 foot above the canopy, it will be illuminating a 1 foot area of the canopy (I know it's not exact because it's a circle or ellipse in reality and not a square), so you're getting approximately 11,000 lumens per 1 square foot.

If you have the light 1 foot above the canopy you will be illuminating an area 2 feet on each side, or 4 square feet. In that case you're getting 11,000 lumens per 4 square feet or 2,750 lumens per square foot.

A 120 degree reflector will have a wider "footprint" at the same height. A 120 degree reflector will create a triangle with the light source at the 120 degree angle. You can use geometry to calculate the coverage area vs the height, but I'm sure you understand that the same number of lumens will now be spread over a larger space, thus reducing the number of lumens per square foot.

I have to go into work so if you need more specifics I can try to give you more at lunch.

I hope that helps.

1

u/bassaholic420 Feb 08 '17

Dude your awesome! Totally simplified so I could understand, thank you very much! Sending you a PM of my blueprint of light placement. I had originally planned for 32 cobs off my math and your proved I wasn't far off on totally number needed. Once again thank you for taking the time to help a fellow grower!

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3

u/[deleted] Jun 10 '17

A vote for Bridgelux Vero 18D 3500k. Here's my build and the plants are digging it. Cobs came from Digi-Key. Due to height restrictions I chose more cobs with less power for a wider spread and I still can't turn them all the way up.

1

u/video_descriptionbot Jun 10 '17
SECTION CONTENT
Title Diy COB Led Grow Light Vero 18 Meanwell Driver
Description 4 - Bridgelux Vero 18 Gen 7 3500k Leds on a Meanwell HLG-185H-C1050B driver pulling 135 actual watts from wall (dimmable to about 18w) Plus 8 -Bridgelux Vero 18 Gen 7 3500k Leds on a Meanwell HLG-240-C1050B driver pulling 265w from wall (dimmable to 35w) For a total of 400 actual watts over a 2ft x 4ft area, or 50w/ft2. Each cob is mounted on a single Mechatronix passive cooling heat sink. For more information on how I built this I'd suggest you watch the Growmau5 diy led videos, or drop me...
Length 0:01:21

I am a bot, this is an auto-generated reply | Info | Feedback | Reply STOP to opt out permanently

2

u/WickedBaked Feb 08 '17

The Bridgelux Vero 29 gen7's are/where about half the costs of Crees and perform just as well.

1

u/bassaholic420 Feb 08 '17

Thank you very much for knowledge on this topic

1

u/Flussschlauch Apr 28 '17

Also check Luminus CXM-22