Lets create the most effective cob light!

[cocogrower]

There is an awesome thread at rollitup, where mr flux analyzes the spectrums, par values etc on different colored CXA's and Vero's.

http://www.rollitup.org/t/cree-cxa-analysis.743645/

One of the thing i learned, reading it, was that you get a bit fooled by crees diagrams of spectral output from different K's. This is because the diagrams show's the relative output in different wavelenghts, instead of the absolute output. He use a formula to calculate the absolute output, and shows amongst other things that high-CRI lights are less good than they seem to be if you just look at the relative diagrams. I really like to recommend that thread!

 

[cocogrower]

Compare these diagrams to the ones in post #20.

The relative spectra is what matters to how humans perceive colors, so it makes sense that Cree uses that instead of photon flux. But photon flux is what matters to plants and photosyntesis.

And it sure matters to me and anyone else who wanna play with the software BML offers us, when combining colored chip with cree cobs..

4000k in the BML software looks very much like cree 4000k looks like, after Mr flux has applied the phyton script he uses..

 

[cocogrower]

This is what my spectrum will look like if i take 12,6 watts of 4000k and ad 0.9 watt of 630nm, and 0.9 watt of 660nm:

 

[cocogrower]

Hi everybody! Anyone there? I have a question, and more are to come since I'm a total noob when it comes to building cobs..

If I buy a cree chip from aliexpress or alibaba, is there a way to tell if it's the real deal? Package, printing on the chip etc? I've had mostly good experience with Chinese vendors (mostly bicycle parts) but also a few bad ones, so it would feel good to at least know if I'm getting ripped of..

 

[PetFlora]

Apparently some sell knock-offs of brand name COBs

Their ancestors would be so proud- not

 

[cocogrower]

One seller claims to have "all" binning.. And another one says that she at the moment only has one binning in stock, a pretty good 4000k. I'm more worried that I will get the wrong binning than a total fake chip.

 

[exploziv]

I guess if you had a way to check the spectrum you could buy a real one, then check all the china-bought ones by comparing to that. If it's close enaugh, it must be true one, or a very very good copy, which I doubt are good at all. I think you could see the difference with your eyes if you compare a real chip and a bad copy of it.

 

[cocogrower]

Yeah that's an idea.. A bit of a hassle, but probably worth it, at least cheaper than buying a spectrometer.. But have to say that I'm inclined to trust the seller that says she only has one binning in 4000k even though I'm asking for 3000k. Could of course be a strategy to appear very honest, but that also seems a bit far fetched. But as a wise/mad man said "It's easy to get paranoid when everybody's after you"..

 

[3dDream]

cocogrower - Both my 3050 and 3070 were unmarked other than "cree" in the corner. Digikey and mouser are awesome to deal with.

 

[cocogrower]

Yeah, I wouldn't feel worried at all if I bought from them. Maybe I'm stupid-cheap if I buy from aliexpress. Just feel that there is a pretty good chance they sell the real deal. Crees R&D might be in USA, but production have moved away. I know that at least one factory is in china.. But chances are I would keep wonder, and that the certain ness is worth the extra 80-90$ I'd pay for 8 chips. I think it's worth it, but so far haven't found that chip in so small batches.. Thank's for helping me to think about this!

 

[Dr.Nonagon]

I have the cxa2530 in 5k and 3k so if you get some off aliexpress we can compare detailed pics if you want. I purchased mine from digikey, and I feel confident that I got what I ordered.

Fake shit is running rampant in china now. Breast cancer meds getting into the UK, fake food, fake everything. I don't think I could tell the difference between the 2520, 2530, 2540. I would pass on risking buying fake cxa unless I didn't care about it too much. Coco you seem like you want the best shit and spending $80 more is cheaper then buying the whole order again. With digikey you pick the bin and I would recommend the 3k for flowering.

I ordered some cree xte 5w from china and I got random bin but dirt cheap. I can tell the diodes have uniform brightness and correct spectrum 3 and 5k. I got them off flee bay so I bet they are shit bin but they still work great and I ordered more. I was please that the led's were authentic but I really didn't care if they weren't.

Just looking through Google images for fakes. It seems like the cxa's have a pretty popular look. It wouldn't take much to turn it this into counterfeit.

 

[cocogrower]

Good advice Drnonagon! Of course am I not unaware of the problem with fake items... I think the temptation lies not only in saving money, but also in the fact that there with knowledge and some luck is possible to build something really good with not so much money. I did build an awesome racing bike weighing in at 6,7 kg for the quarter of the retail price in my country. But then again, it's more easy to tell if the gear of your bike is working than if your light emits the right amount and kind if photons .. If I do decide to go to the Far East I will gladly accept your kind offer. Nut as you say, it might be an expensive lesson to learn..

At least I have ordered the heat sinks now to put some stress on my self to get going with the project. It's good to be thorough, but only to a certain degree.. Guess that both my plants, and the few that follow my strivings, would appreciate a bit of action to follow all the talk..

 

[cocogrower]

whoa, finally bought 8 chips

http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail&itemSeq=152284285&uq=635390571423516562

They emit 140 l/w at 800 mA if running 25 C. cool.

Hopefully a bit more if driven @ 350mA.

 

[cocogrower]

Now the hard part begins: Finding drivers. AC-DC, DC-DC with a converter, dimmable, constant driver? I really feel that i have a lot of reading to do here..

If anyone has the knowledge and wanna point me in the right direction it would be a huge help, cause i've spent to many sleepless nights already.

I'm looking for efficiency (no one missed that, right, LOL) but affordability is also a concern..

 

[Dr.Nonagon]

Might not be cheap

Mean-Well PCD-16-350A

Mean-Well APC-16-350 non dimming version. $7 there are 12w versions too

 

[cocogrower]

Thank you so much Dr.!
Think the non dimmable version version was what i fist looked at when pondering this setup, didn't know that it actually was recomended by Cree. Good info! And there should be possible to ad a few 3 watts diodes drivern @350 mA, right?

Think that it's 86% efficient, does that mean that there is a "loss" of 14%? 2,24 watt of heat for every 16 watt of electricity in the right currant and voltage?

 

[cocogrower]

These are 97% efficient and can be found cheaply on ebay. http://www.meanwell.com/search/LDD-H/LDD-H-spec.pdf

They do need a 48v power supply though. Naybe thats where most of the efficiency is lost? Will have to find a 200 watt power supply and find out to wire everything together in a safe way... Going with the recommended meanwell drivers seems a lot easier and probably the way i'm gonna do this unless someone vouch for the latest option, and points me in the right directions..

I've found power supplies on ebay with three outlets, maybe you can connect the cobs in series? Also haven't found any info on the efficiency of the power supplies. If there isn't any benefits at all i really can't see why i should make things this complicated..

 

[cocogrower]

http://ac-rc.net/catalog/product_info.php?cPath=23_35&products_id=78

These also look a kind of interesting.. Look a kind of homemade but would let me crank out a bit more juice if i ever build a bigger cabinet, or just find that i wanna fry my plants in the end of the flowering..

So many options....

 

[sammyz2646]

I am all about a dimmable driver, even if its not super high quality.

Freedom to adjust is huge ,IMO especially in the learning phases, which I am still living in---and may retire in, (the learning phase) lol

 

[cocogrower]

Hi Sammy! Might go for 4 dimmable budget drivers and 4 non dimmable meanwells. Don't think i can utilize mor lumens in The "veg-part" of My cabinett. I write "veg" because my goal is to master the 12/12 from seed method with these lights..

I do think someone at another forum has experience with the dimmable budget drivers. Possibly stardustsailor. Will try to dig up that thread to see what he thought of it..