Re: 420 Consumer Reports Competition - GrowLEDHydro 300w LED vs. 400w HID
Lurker- thanks for the referral to this journal. More of information like this and less of some of the other stuff and we all might learn what really works with these LED's and what doesn't. Good for everybody.
Since I am terrible with figuring out how to use these journals, I quoted the whole message and cut out the parts which I can address later. I would really like to express to all those out there the significance of thermal management for the LED device itself, and the importance that consumers of this technology should pay to your advice on this subject. Aside from the quality of the light emitted (wavelength/ amplitude), the thermal management system of the core LED fixture design should be the primary merit point for these horticultural lights when making a purchasing decision (that is assuming the mfr knows what they are doing in the first place, uses quality components, has taken into consideration the environment these devices are intended to operate in, etc.- all the normal stuff you would expect when making a purchase of this magnitude- these things aint cheap).
These things are basically a bunch of computer chips stuck on a board that produce light instead of processing 0's and 1's. Take a $1000 laptop, stick it in a small box, and then subject it to tons of heat and humidity. How long do you think it'll last like that? Exactly. Cooling is paramount.
Here's the thing, folks (and folk-ettes!). Regardless of what the chips are actually rated at, those 1w boards everyone uses are not designed to dissipate all that extra heat from running it at 500ma instead of 350ma (43% more!).
Heat destroys LEDs. Forget 70% remaining after 7 years, you'll be lucky to get 50%, driving a panel like this.
This is worse for red LEDs than blues and whites, also. So much for targeting specific PAR wavelengths and driving efficient photosynthesis. Too bad flowering lights use a majority of red...
It's just that people need to know what they're buying, and go into any purchase with eyes open. Which is what being an informed consumer is all about - and the reason we're doing these tests. The proof is always in the pudding.
There's still a lot of crap out in the market now...manufacturers using low-bin LEDs in their units that are 30-60%+ less efficient even within the same product family--! ...than a good, high-bin, quality LED:
YES YES YES EXACTLY YES YES YES. Heat kills semiconductors of any stripe- and LED's are the worst of the lot. All the things you mention- decreased radiant output, dramatically shortened life, wavelength drift- all true, so very true. And as for the manufactures of LED dies- Philips Semi, Cree, Bridgelux, Seoul Semi, Nichia, etc, etc- all playing the same game with watt ratings. You can see the header at the top of the Philips data sheet- the data as shown assumes a pad temperature of
25C- now, you run 700mA thru a 1mm^2 LED die and this pad is going to be 'smoking a$$ mother effing hot' (that is an engineering term, don't be offended). You would need some kind of impractical, out of this world cryo cooling unit to keep the pad at 25C. Guess what happens when the pad gets this hot- all of the things you mention in your post!!!
The basic 1mm^2, LED die is a 350mA/ 1W device- regardless of the 'specsmanship' ocurring in these manufacturers' data sheets.
A well designed cooling system is an absolute if you really want the die to output consistantly for a long period of time- these guys are not going to get there with a slab of aluminum and some fans- certainly not overdriving the dies at 2x or 3x the real 350mA rating.
You have brought attention to a FACT that all consumers of this technology should be aware of. LED's are the future as this technology represents the most controllable light source ever invented by man- but the way we are getting there now, in this market, seems to be two steps back and one step forward.
The red dies (AlInGaP) are much worse in all performance aspects than the blue dies (InGaN)- lots of reasons for this- which I would love to talk about in length, but maybe another time.
And yes- consumers need to know what they are buying.
That is fair. The sketchy data sheets I have seen so far on LED fixtures have not convinced me to make a purchase- simply not enough information to make an informed decision. Some of them don't even post the actual spectral output of the light- what else, if nothing else, are we as customers paying for??? I pay for photons- that is a simple statement and it gets more complicated after that, but even the HID guys will give you this data. The emperical evidence provided by these test grows is our only hope- and the only thing that is a bit scary about this is that there are so many other variables involved in the outcome of a grow...
Thanks for your post in this forum- I could not and would not disagree with a single word in it.
looking good!