I clicked the link you posted. They have two types of LED, one is red the other blue. However the red is only 635nm, not quite the optimum 670nm. I think the biggest problem with this light, it is not full spectrum. Having only red and blue is like having only bass and treble in music. You want everything between 280 and 700nm. There are full spectrum LEDs out there, but I haven't been able to buy any, they are recently developed and not very efficient electrically.

The plasma arc tube is the simplest way to get continuous and full spectrum.

Electronic ballasts use 10-30% less power, prolong bulb life, operate the bulb more efficiently, and produce a more continuous (high) frequency and spectrum. So I recommend an adjustable 250-400 watt ceramic metal halide with electronic ballast.

Well, that really does depend on your perticular application. NASA had quite a few experiments using just monochrome blue and red LED light to grow vegtables, and they seem to grow fine. Lettuce has been grown in Japan with just monicrome RED with no blue. (IEEE Spectrum Apr, 2005 issue) (Sorry, don't have the links handy right now... do a search on this forum, and you'll find quite a few discussions on this.) For the purpose of just growing your plants, just red (about 80%) and blue (about 20%) is enough, but you have to be careful with the ratio, depending on the plant.

Here's a guy that's been growing stuff with red and blue LED's for a while... greenpinelane.com

On the other hand, if it's flowers you're growing, and you like to look at them (looks awful under this purple light), you'd stay away from monochrome light sources and go with something with a high CRI.

In my case, I prefer to look at my orchids under normal lights and have them on only for viewing, but want to save on electrical costs when I'm not in the room. If this thing really can replace a 400W HID with just 125W, then that would meet my criteria. Your CMH, no matter how good, still burns 400W. It's not saving me any money, since I need to cover the same area (space is limited) with less power.

I went to the September issue of Spectrum:
http://www.spectrum.ieee.org/sep05/inthisissue
and didn't see the article you referenced.
Concerning the NASA article, references please. A friend of mine consults with NASA scientists concerning plant growth lighting, and he is the one who convinced me in favor of full spectrum lighting.

I didn't say plants wouldn't grow well with just red and blue light. Those two are the most important parts of the spectrum. However, plants have evolved for many millions of years under full spectrum sunlight. Often a forest canopy will limit the amount of blue light reaching low-growing plants.

There are many articles in the scientific literature on the functions of other parts of the spectrum. For instance, here's a NASA-related article that talks about the near for far-red:
http://www.sbir.nasa.gov/SBIR/abstracts/92/sbir/phase1/SBIR-92-1-12.05-0300.html

The UV-A and UV-B ranges also have specialized functions in plant growth. That is not to say, you can't do very well with just monochromatic red and blue. The Philips booklet, Artificial Lighting in Horticulture, shows a photo of an experiment of a plant grown under only red light; it stretches with a lot of stem growth; and only blue light results in a short bushy plant with reduced yield.

Just as most plants prefer full-spectrum, so do most animals. That is not to say, humans wouldn't thrive under indoor lights that weren't full-spectrum. The differences maybe subtle, and measuring their effects difficult. However most people are happier under full-spectrum light.

Concerning the power consumption issue: if you dialed the wattage on the digital CMH to 250watts, and save 20% because of the electronic feature, that means you're using only 200 watts. Less power consumption than 4 of the t-5 HO fluorescents, which are 54 watts each, totaling 215 watts.

And only 75 watts more than the 125w LED. Even at 10 cents per kilowatt hour, that means the extra 75 watts is only .75 cents per hour. That will take you a lot of hours to equal the extra cost of the LED light.

Interesting lights, at least the marketing material for them is realistic rather than making the outrageous claims that most LED vendors do. They claim that 14W/square foot works with their LEDs. I think that ccc1 nails it by saying that the comparison to a 400W metal halide assumes an obsolete metal halide, but even assuming the best modern equipment they are claiming to match a metal halide system of twice the power. Whether that claim holds true depends on three things.

The first factor is whether the LEDs produce as much light as other light sources. This is fairly easy to quantify and they don't. The LEDs used in the Procyon lamps produce roughly half as much light as modern metal halide or fluorescents. This is measured as a photonic flux since lumens are not an accurate measure at the red and blue wavelengths used. Measured in lumens, the LEDs would appear much worse. Also bear in mind the lumen maintenance of LEDs does not level off at around 95% like good modern fluorescents. The light output continues to decline steadily until at some point it just gives up. A very approximate rule of thumb for high output LEDs is that you'll get a drop to something near half output at 50,000 hours (the spec sheet for these says 70%), after that they will continue to decline in brightness and some will fail. By 100,000 hours, many of them will be dead, but much depends on exactly what voltage you are driving them at and how warm you let them get.

The second factor is how much light reaches the plants from the different light sources. LEDs perform well here, they are naturally very directional and a very high proportion of the light emitted falls on a corresponding area right below the lights. Note that they are not very flexible when it comes to varying the lit area because you don't get a whole lot more spread by raising the LED array. Theoretically, HID or fluorescent lighting can put 80%-90% of the emitted light onto a specified area below the lamp, but in practice most systems I see are losing at least half their light.

Last is the tricky one. How well do the different spectrums of each light source work to produce good plant growth. Everybody tells you that their spectrum is the best. Experiments indicate that while there aren't massive differences between the various conventional light sources, LEDs operating at about 80%-90% 680nm and 10%-20% 420nm (or near those wavelengths) can produce significantly better (possibly 2-3 times better but that is perhaps a best case) growth than conventional light sources at the same levels. Unfortunately the Procyon LEDs don't operate at those wavelengths, in fact the red is near 635nm, actually 620nm-635nm according to the spec sheet I have. This is no better than a GroLux fluorescent, slightly worse in fact, and I see no reason to expect significant benefits from the spectrum.

Overall, looks like a nice little system but hard to see how will perform much better than a top notch conventional system and the price makes it prohibitive if you only get a small improvement. If their claim of 100W LEDs being equivalent to 200W or so of metal halide, the comparison is close. I wouldn't worry too much about LED replacement because after 5 years or so when it starts to lose performance, these little puppies will be in the 99c bin ;)

LED is senitive to over-current and over-voltage, I am curious as to what kind of driver electronics is being used.

One of the weak link in this fixture is the single fan to cool the LEDs. If the fan fails, the LEDs will have only a few seconds before they are fried.

CREE LEDs require lenses to focus and distribute light, I am not sure what characteristics this fixture's light spread looks like.

dcarch

Check the greenpipelane link. There are lux measurements over a grid pattern under one of these lights. Hard site to navigate though!

I like the fruiting results I'm getting with these lights as far as tomatoes so far. I get lots of them which is what counts for tomatoes anyway. As far as NASA studies and plant biologists, you can find articles on anything you want to see, so much difference out there.

These units do not run hot. The comment about the fan going out and the LEDs burning up is nonsense...the heatsink is 85F tops without the fan running. I have high-powers I play with mounted on sheet aluminum with no fans and they are fine as long as current is controlled.

These lights will support a 3x3 foot area easily with good results.

As far as the LEDs wearing out over time. This is dependent on the current driving them and the heat they are exposed to. The specs on lumen maintenance assume max current and max heat. I would expect to get many years out of these at the power they are driven. Both the UFO and Procyon are not driven to max current.

Summary - they are working for me. The Florida Petite and Florida Basket tomatoes I grow under the Hidhut UFO, Procyon Proto-type look just as good and friut as many tomatoes as the ones I grew outdoors this year. The Procyon 100 release version I'm just starting a test now as the seedlings are just germinating.

With more time of course, I'll be trying different varieties of veggies. I've grown good peppers under combos of traffic lights and blue bulbs. I'm looking forward to seeing what the high powers will do for these.

oh...and sorry about the site navigation....it's an old server and the site is free!

Steve at greenpinelane.com

ledaero

I have followed your LED work once in a while. Very interesting and informative. Good work.

I find your use of the language interesting: I apologize that my comments belong in the " non-sense" category.

The fixture comes with a fan; I will assume that the fan is important to the operation of the fixture. Although this type of brushless fans are ball bearing fans and rated (vertically, and statistically) at about 50,000 hours, they are still mechanical items. For the high price of the fixture, I would have put in two fans just to be safe. These fans are very inexpensive and some of them come with built-in thermostatic electronics to save electricity.

In mine experiments with high power LEDs, I have burned out many by over heating (some accidental, some on purpose). The Procyon 100 uses 56 CREE LEDs. Looking at the design, thats not a lot of heat sink for 56 LEDs.

Of course it sounds like you have actually disconnected the fan and have found that the temperature did not go above 85 degrees F. ThatÂs below normal room temperature in the summertime! Very interesting!

Keep up the good work.

dcarch

The Heatsink of the prototype is about 12"x4"x1.5" pretty thick, finned and weighs a few pounds. I haven't taken the case off the the retail version, but it looks the same.

The prototype has 48 leds and has no outer case. I can put my fingers on the metal right next to the LEDS and keep them there, it's warm, but not hot. I did actually disconnect the fan on the proto by accident when I was hanging it and ran it for a little while before I noticed it. (please keep in mind that wires are not exposed on the final as opposed to the proto) This was when I stuck the thermometer on top. I do have six inch fans for circulation in the chamber. What I would do if the fan burnt out is point a small fan at the light until it could be replaced I guess.

According to Cree specs, max operating temp is 85C (185F)although their thermal/photo output charts go beyond 125C with the corresponding drop. However, even though I may not be accurately measuring junction temp, I think I'm close at 87F, so the light is operating cool enough to allow the LEDs to perform optimally.

As far as direction, there is no lens, so they are the factory 100 degrees. This is why I'm getting better light penetration down into the bottom of the canopy. The 5MMs I was using before were about 25 degrees each. I'm getting a lot more usable light reflection and bouncing around inside my grow chambers with the high powers. I use white titanium paint on walls.

I'm also noticing with these high powers that the light needs to be higher up above the plant canopy and not sitting right on top like the 5MM 'bulb' types. I don't get heat scorch too close, but growth slows down.

The ratios of Red to Blue are very important. Not enough blue vs red in early stages doesn't work. I think the next good step to add is dimming capability to control these ratios as the plants grow.

When stating how many watts of HID an LED light can replace, trying to figure watts, lumens, etc, focused on the chlorophyll curves, etc, is an exercise in futility with a million differing opinions. The bottom line is coverage area, plant growth, bloom performance and then of course harvest. I'm in New England in November, eating great red tomatoes grown under LEDs right now that I just picked . Three nice fruiting tomato plants under the 82 watt UFO light. I can't wait to see what the 125W Procyon will do.

To get better coverage with narrow beam LEDs, I basically sand-paper the lenses to frost them.

I use spray-on addhesive to glue kitchen aluminum foil on cardboards for my reflective surfaces. I think it's more efficient. I get more reflected light where I want that way.

I use LM317 variable regulators to dim my LEDs.

dcarch

Dcarch,

If you are willing, why don't you post some of your photos and designs to my site at greenpinelane.com in my forum? We're always looking for ideas to add to our knowledge.

As you know, I test lights sent to me (i.e the ones we are discussing now) and have hacked some other stuff together over the last year or so, but I'd like to see more homemade rig ideas evolve. I'm working on gathering some parts up to build something over the winter. There is a 'Build Your Own' category under my LED Lighting forum and if you have some electronics and led array ideas that work we would most appreciate it if you want to share some ideas. Thanks

ledaero,
Thanks for the invitation. I am not going to work on LEDs for a little while (until price come down a little).

I am busy building for the coming seed starting/growing season:
1. 400w HPS/MH light with electronic ballast.
2. 250W HPS/MH light with electronic ballast.
3. 100w HPS/MH light with electronic ballast.
4. 65w x 2 power compact light with electronic ballast.

I may post how-to pictures here.

dcarch

When stating how many watts of HID an LED light can replace, trying to figure watts, lumens, etc, focused on the chlorophyll curves, etc, is an exercise in futility with a million differing opinions.

However, it is critical for people to know how much LED light is required. Something as simple as knowing that tomatoes and peppers will fruit well at 15W/square foot is in itself a comparison, since the levels of HID (or fluorescent) light required to get those results are widely known.

ledaero,

When high power LEDs first came out, I had the idea of building a very sophisticated LED fixture. I bought a whole lot of Semiconductor thermoelectric Peltier junction coolers to be part of the system.
Never had the time to go thru with the building of the fixture. I did use one and built a small refrigerator next to my work space for soda, beer and water. :-)

dcarch

A good LED grow light doesn't create heat and won't require the built-in cooling fan. That said- even a good LED array won't directly replace an HID if you are gardening indoors without sunlight. You should run a hybrid system. The LEDs provide light and the HPS provides heat. You run a low watt array (look for 5mm HBLEDs)for the full photoperiod and either just run the HPS one out of every 3-4 hours or run 40% of the HPS you would usually run in conjunction with the LEDs.
Cheers.

Why would you use a HPS to provide heat? Heat is a problem inside. Fluorescents do everything I need them to. I wouldn't waste my $ on either HID or LED.

I agree with the flourescents over HID/HPS... way to much heat from the big lamps... and wasted light. I get best results from running a mix of LED and Flourescents. I have my LED lights running down the middle and a flouresent tube on the side. Plants will grow LED Red/Blue mix only... done it. They seem to do better with just a bit of flouresent to fill out the light spectrum. I run a fan not for cooling but it circulates the CO2 and dries the soil top which prevents mold. My grow box is lined with cheapy mirrors to put as much of the light to the plants as possible.

LEDs need adjustable height! They are cool enough to touch the plants so I keep them an inch above the plant tops. All about getting the light to the plant. I'm a tightwad so wasting even light goes against my blood... "waste not want not".

Mostly I grow exotic hot peppers. Much of my outdoor garden gets sprouted in the grow box... Michigan didn't even get warm plantable weather until June this year... farmers are crying. While late in the outdoor garden I have peppers already and tomatoes any day now.

This past winter i conducted some independent horticulture trials for a new company. Due to non-disclosure contracts i cant go in to to much detail but i can say that they have something that is going to change the game for indoor gardening. I will say that i was very impressed with their product. Sorry for being so vague but untill their website launches (last i heard it should be within the next few weeks) i cant say much. email me or check back soon and i will post a link to their site. i really think you all would be quite impressed with their new take on an old idea.

anyway, I am going to share a few pics. If your knowledgeable, then hey, you know the answers to the questions you have are something I do not have. However basic info is, this is a landscape pond light, outa China, I am really pleased with it, am trying it to grow a passiflora incarnata, the algerian ivy, an orchid a few hours a day. The glass is amazing on it, looks laser led, so looking inside is not something I am going to do. 10v 12w, hooked up to an led transformer.

pic two

pic three

pic four, the light shows green that close, but it is blue

pic four. New light also, but, I don't know if it'll grow. Anyway, fun project.

apparently the green was showing in the last photo on a different thread. anyway, inside the bulb, the reflection of the r b and g. I would be happy if it helped my orchid grow. I guess the only way to know is to get a light meter.. hard water on bulb.

here one more. I know this thread was for more by the book buy a correct light for plants growers, so if you don't know if cheaper alternatives exist like christmas led lights for example because you by the book it, you might not be looking to save a buck for ornamental growing, excuse my posts, because by the book might give you a yield you need to depend on, my posts are not meant for you to deviate from that. This shows circuiting of the light so since it isn't on the box, not much is perhaps someone can say led or led laser, by looking at it.

100W LED can't replace a 400W HPS or MH lamp, the factor four in power difference has not been bridged by technology yet. But LEDs are closing in on them.

Comparing lumen doesn't make sense because plants have a different light response than the human eye. Also the color temperatures like 6500K are confusing because you can generate the same color temperature for the human eye with an infinite number of combinations of different colors - each combination with different plant responses!

There are a few websites on horticulture lamps, most of them are commercial sites. Be careful with the Chinese specifications (on ebay/Alibaba) because they tend to over-specify the lamp power. There's a lot of information on
www.hortilamp.org
(even a lamp comparison page for different lamp types) but the number of lamp reviews is limited.