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Apogee lists some conversion factors for various bulbs (Cree not listed obviously as this site looks a bit old). http://www.apogeeinstruments.com/conversion-ppf-to-lux/ I'm aware I can get ballpark estimates given instruments listed but it'd be nice to be on the money....

Hi all. Forgive me if this is somewhere among vast amount of information on this site, but could someone please let me know how to get the PPF given the lumens for a given Cree color temperature? It's easy to look up the luminous flux from Cree's datasheets, and to get to Lux given the beam...

Forgive me for missing it. Mind providing the link? Much appreciated!

By the way what soil mix is that? Are you adding anything?

Cheers. I like the kit a lot and all the time you've dedicated to this. I really appreciate it. Also Netherfly's build looks absolutely perfect. Still, I don't think you quite answered my question regarding the use of reflectors/lenses and whether it was hurting more than it was helping. Mind...

Love your build man. It's so clean!

Cheers jewbag I gotta check out your setup....

Looks pretty awesome in there. Do you use a chiller for your system? Forgive me if this was answered I just skipped straight to the latest bud porn. Also run Jack's for the whole grow with some Terpinator in flower. Works great.

I think to solve the uniform PPFD problem requires very smart thinking regarding cob placement and work with a light meter. Forgive me if this has been addressed already on thesw forums. Just trying to make sure we get the best bang for our buck...

Here is what I'm talking about. Take the AT600, a popular LED fixture. Here's the PAR footprint at various heights (attached). In my opinion the goal should be to hit about 800 PPFD at every measurement point. Cannabis won't even use anything much beyond 1000-1500 based upon the studies I...

Oh, and this may be a very stupid question, but where does one source the light rail to which one attaches these DIY cob kits?

More on this point. If you take a look at the par tests from Growershouse's blog almost every single LED fixture (cob or otherwise) suffers from covering a 2 x 2 far too well (the PPFD readings often go beyond what plants will even use) and then it falls off a cliff for the other 12 square feet...

Thanks for your input. My thought is the goal should be to have a uniform PPFD reading over a footprint (most common is 4 x 4) at a reasonable height (say, e.g., 24 inches). Has anyone done such a test? You should be able to come up with some estimates of the lux given COB placement and Cree's...

This is a great idea. Thanks for doing this for people... Really awesome work. Also, do you think the reflectors are necessary? In my experience LEDs often focus light on too small a footprint rather than too large of one (especially when comparing to HPS with a good reflector). The 115 degree...

Take a look at the McCree curve. While it is completely true that certain parts of the spectrum lead to faster growth, it is also true that warm white does a very good job of replicating the curve. Most LED companies omit tons of the yellows and greens and your grow room looks like you're on...

Love your build. Mind sharing the details on it? Also, you can probably get a lux meter for about twenty bucks and use some tables with warm white color temperature to convert to PAR roughly. You probably want to have about 800 PPFD ideally spread out uniformly at the canopy. Those reflectors...

Thanks for the replies. Yeah, I was thinking cxb2530, maybe two in series with that driver? I'm worried about what the 55 - 70v means ... seems rather fishy. Also to be honest I have no idea about the efficiency of the driver. It's just a Houyi Chinese LED 16 x 75w = 1200w I got a few years...

Anyone?

Hi all. Thanks ahead of time for your feedback. I have an older led fixture with 16 cobs (some of which have failed) and I want to replace them with Cree CXBs. The drivers aren't a great match for Crees as far as I know... they are 550 mA constant current and voltage says 55 - 70v. What...

Pic of mom in Mother Keeper attached.