I'm trying out a grow experiment, since my trusty 400W HPS was in storage and hard to get at. I've always thought LED was the way to go, so I thought I'd splash a little cash on some reckless experimentation and share the results as I go.
I'm just doing a very small cupboard grow, so the aim was to get about 250W HPS equivalent of lighting.
As a starter, I had a 65W 2700K CFL and an 85W 6400K CFL. These were to keep me going until I'd ordered my parts. Parts for this were easy to find. I'm in the UK, and these are all available on the internet easily. I bought:
1 x Bridgelux 9000lm 5600K Array LED (£60)
1 x Bridgelux 7000lm 3500K Array LED (£60)
2 x LED Driver (100W each, 2.8A) (£70 each)
2 x Heatsinks (Big ones!) (£20 each)
So, not a cheap experiment! £300 for the key ingredients.
The heatsinks were designed for these arrays, so once I'd soldered the leads, it was pretty easy to screw the arrays on to the heatsink, making sure to use some good thermal paste. The arrays were tricky to solder with my puny iron, but if you've soldered before it shouldn't be too challenging.
Here they are hanging up. The heatsinks are about 20cm long, and are painted aluminium. Chunky!
There are a few reasons I think LEDs are better than HIDs.
1. Directionality - LEDs put all there lumens in one direction. (These arrays say about 120 degrees angle of output) HID lumen output is measured all around the bulb, some of which you lose in the reflector. With LEDs, this automatically gives them an efficiency advantage as up to 20% of light leaving the bulb going up will be lost. (So a 50,000 bulb actually could be sending only 45,000 lumens down) All the lumens from the LED are heading down, and even without a reflector there's very little coming out sideways.
2. Spectrum - HIDs put out a lot of energy in infra-red (IR) frequencies. These aren't useful for growth, and actually end up burning the plant if they get too close. LEDs of this type use blue LEDs with a phosphur coating to provide the wider spectrum light. There is very little energy wasted in the IR spectrum.
Here's the LED's spectrum:
Both have sharp peaks at 450nm and a wider peak from 550 to about 675nm. Unsurprisingly, the difference is that the red array puts out significantly more in the red end, and the blue puts out more at 450nm. These aren't far off ideal, although slightly more at 400nm in the blue, and more up to 700nm in the red would be better. Still..less UV is probably not a bad thing anyway, and these peaks are well within the plants preferred light frequency range. I know some people get very in depth when talking about PAR, but from what I can see these lights are equal or better than HID systems which we all know work fine despite their patchy spectra...so I'm pretty certain they'll work just fine. Intensity is just as important as colour as long as the light is in the right sort of ballpark.
3. Long-lasting - The lifetime is about a thousand times longer than an HID bulb and is pretty sturdy compared to a glass bulb. Nuff said.
4. No ballast? -Well, the LED drivers are balasts, but they're pretty compact. They also put out low voltage, so they're much safer in a grow room. You could probably still get a shock though given there's almost 3A. I wouldn't like to test it too thoroughly.
Based on the manufacturer estimates, my setup is running at 320W, and is outputting 25,800 Lumens. (81 Lm/W...not bad) As mentioned above, more of this light is going in the right direction, and less of it is being wasted in IR frequencies. This means that I should easily have as much useful light as a 250W HPS system. A 250 HPS would be much cheaper of course (at least to start with), but where's the adventure in that? I also believe that a HPS would be less useful in my small (and short!) grow space than LEDs. I could have done this much cheaper by building the LED driver myself. That would have save a third at least. If I could have salvaged or DIY'd a heatsink I'd have also saved a bit. Ideas on building a cheap 100W current-control LED driver would be welcome.
2 White Ice fem - White Label
All organic. Soil mix: 20% peat, 30% perlite, 50% wormcastings (not a good mix, but I didn't realise just how high quality the wormcastings I'm using were until after I'd first watered. They are very fine, and this has caused major problems with slow development)
From seed. Easy germ, but slow since then, solely due to an initial overwatering of the worm-casting heavy soil which I'm using. Even generous handfulls of perlite in the mix didn't improve drainage enough to help get enough oxygen in there, and the only thing to do really was to keep things warm and dry and be patient while the soil dried...unfortunately I wasn't patient, and tried to re-pot one with predictably disastrous results. The roots were tiny and fragile, as expected in oxygen-poor starter soil, and I ended up breaking off almost half of the tap root. I should know better than this. I though I was past being over-attentive by now. Re-potted it anyway, and all seems ok now. Its just starting to grow a little stronger today. Finally the roots are getting some air!
Lights look good so far. I need to run a fan over them when on otherwise the heatsink hits 60-70C, but a small computer fan at the top of each would do the job perfectly. At the moment I'm just running a desk fan for general ventilation and cooling. The heatsink sits at 40C with the fan on, giving me no problems with heat.
Day: 25C Night: 19C
Humid: 45-50 (on the low side I know, but I'm trying to sort out my damp soil problem)
I'll post pictures comparing the brightness of the CFL vs the LEDs shortly, and let people know how the plants like them when I'm sure. They seem to be doing just fine now, slow start aside.
Here are some comparison shots, taken with identical aperture and exposure:
I know I should use reflectors on the CFL for a fairer comparison, but this setup helps to show why a flat light emitter like an LED makes having a reflector not quite so vital! I also don't have reflectors for the CFLs, which is probably the main reason!
65W Blue and 85W red CFL: (Total 150W)
85W Red and 85W Blue LED: (Total 170W)
Overall I'm pretty happy, and should be able to grow to within 10cm of the lights if I have to without worrying I'm going to char my flowers...
FYI, I'm running all four lights, which looks like:
Last edited by MajorCoco; 03-18-2012 at 01:20 PM.
Sigh. Has anyone seen my "like" button? I'm subbed.
We want lots of pics/updates. Thanks for doing this.
Here's the set-up:
Very basic. You can tell it's been years since I last did this too, as this pair are tiny for 2 weeks (and technically it's 3, since they had a week just under CFLs. Embarrassing progress I know, all because of a bad soil mix)
Anyway, I've got a much lighter soil mix seedling in the back which is 1 week old. As well as the better soil mix it's in a small pot, so I can definitely ensure it isn't over-watered, and see how it compares. I hope it grows faster!!
Here are some close ups:
Cheers everyone. Nodes are looking amazingly tight at the moment, 4 nodes in only 4cm. I'm still suffering from the early overwatering problem, which seems to be causing some early nute issues, so I might have to get on with some foliar feeding.
Thanks for the response..................any updates??