Although most MH produce almost no light at 660 nm, most are not very blue either therefore how is your recommendation theoretically justified? Most typically, MH produce most of their output in the UV, violet, cyan, green and yellow regions of the spectrum, see https://en.wikipedia.org/wiki/File:Metal_Halide_Lamp_Spectrum.jpg . What brand of CMH are you using and what is its Power Spectral Density?

A long time ago, I discovered that adding a 1000 watt incandescent bulb to a 1000 watt MH, more than doubled the growth rate of plants. At the time, I attributed this to the Emerson Enhancement Effect, see https://en.wikipedia.org/wiki/Emerson_effect . But, later, I was unable to produce any growth increase by adding incandescent to Gro-lux fluorescent which peaks at 660 nm, see http://forums.gardenweb.com/discussions/2005610/how-to-easily-supplement-fluorescent-with-incandescent-light?n=47 (I was Struwwelpeter). I am still trying to figure out why.

I think there is a lot of misunderstanding and fairy tales on the internet telling how great LED., HPS, TL CFL etc plant lights are. here is a link, I think, having very interesting information about the subject

http://www.hortilamp.org/plants.htm

I have used the information to make my own LED lights, later I have replaced the warmwhite with 660nm grow LEDs.

http://home.zonnet.nl/rooijen10/Web/Flask-Storage/Images/Storage-07.jpg

The biggest advantage of LED is they are easy dimmable and the light output is a directed in a 100-120 degree angle and not all the way around.

But the easiest way for the not so handy people is go to the shop Buy a 2 or 4 foot double tube fixture and replace the tubes with a combination of warm and a cool white, maybe not as efficient as LED or HPS but it will work.

A last word on the LED grow lights, a lot of those cheap ones are overrated for example I bought a 15 watt growlight and it turns out to be a 4.5 Watt after some "work" I got is at 10 watt, it become to warm running higher.

"here is a link, I think, having very interesting information about the subject

http://www.hortilamp.org/plants.htm"

That information is misleading because photon flux is an obscure unit of measurement that makes practical decision making difficult. It is sort of like having your car's speedometer read out in the square root of furlongs per fortnight when every speed limit sign is in miles per hour. The appropriate unit of measurement is watt flux because it more directly relates a bulb's power consumption and/or lumen output. In particular, the photosynthetic action curve of Figure 2 is misleading because one might falsely conclude that, at equal power efficiencies, an X watt blue LED bulb is better than an X watt red LED bulb. But, at equal photon fluxes, it typically takes 660/430 = 1.53 times as much electrical power to generate 430 nm light as it does 660 nm light. Photosynthetic action spectra based on power flux have been measured for 33 different plant species:

http://www.general-cathexis.com/images/ActionSpectra001.png

http://www.general-cathexis.com/images/ActionSpectra002.png

http://www.general-cathexis.com/images/ActionSpectra003.png

It can be seen that, at equal power flux, blue is typically 70% as active as red light for photosynthesis. Notice that, contrary to common belief, the relative minimum is not in the green region but in the cyan region. Often "blue" LEDs have a substantial cyan output. Good luck finding an LED with a narrow band at 430 nm.

"I bought a 15 watt growlight and it turns out to be a 4.5 Watt after some "work" I got is at 10 watt, it become to warm running higher."

Please, describe this work in detail because I have this "27W" lamp,

http://www.hortilamp.org/LED/PAR38_6R-3B.htm ,

which consumes 4.5 watts when operated at 120 VAC.

Hi Azurinsky,

You know your physics ( Planck) and you are right blue photons have more energy so it takes more to make them,

The DIN graph don't tell how much the plant need of a certain color but how efficient he use it, so most of the grow lamps have a ratio between 1R-1B to 4R-1B. My home made LED light have Blue/white and Red separate adjustable. I only set the power ratio between the two, white is in the blue string.

About the blue/uv leds , no problem, look at this Ebay seller

http://www.ebay.com/itm/221810182099?_trksid=p2057872.m2749.l2649&var=520676613104&ssPageName=STRK%3AMEBIDX%3AIT

I try to give later this week a short description of the "hack" I did on the Ebay 15W grow lamp.

http://www.ebay.com/itm/E27-LED-Plant-Grow-Lights-15W-126Leds-Lamp-for-Greenhouse-Hydroponic-Red-Blue-/171959859013?hash=item28099b3745:g:jawAAOSw4HVWE3zb

You need to know which side of the soldering iron to hold :-) to make this work. At the moment I'm busy making a lecture I give this evening at the Orchid society,

Your lamp can be more difficult because there are metal parts mine was mostly plastic.

"About the blue/uv leds , no problem, look at this Ebay seller

http://www.ebay.com/itm/221810182099?_trksid=p2057872.m2749.l2649&var=520676613104&ssPageName=STRK%3AMEBIDX%3AIT"

If they are like these,

http://www.ebay.com/itm/251468113696

they are too inefficient to use for grow lights. Notice the specification, "Luminous Intensity: 25~30mW", which translates to 1% power efficiency. In comparison, you can buy 420 nm peak fluorescent bulbs that are about 20% efficient. Anyway, I ordered these LEDs just to check whether they are as bad as specified. Maybe, this is the one in a billion Chinese sellers who does the opposite of exaggerate. Hope springs eternal!

I think that those LEDs are to far in the UV region, those down to 390-400nm are normally just as efficient as the royal blue ones see this article

http://www.digikey.com/en/articles/techzone/2014/aug/uv-leds-boost-flux-density-and-efficiency-driving-new-applications

It is also difficult without a spectro meter to get a good idea of the output, a lux meter is corrected for the human eye. maybe you can do something with the temperature of the led, all the energy not converted to light will be heat so take such a star heat sink put a resistor on it and give it the same power as the star LED and compere the rise in temperature. the first part will be a kind of linear

Still a lot to try to get our plants nicely through the dark winter days

There is another inexpensive way to compare UV, violet and blue power fluxes. Put a visibly fluorescent phosphor that is equally excited by the wavelengths in question and it will glow with a brightness that is proportional to the power flux. Where to get such a phosphor? Some LED chips are coated with them. I recently received these chips, http://www.ebay.com/itm/High-Power-10W-full-spectrum-380nm-840nm-SMD-LED-Chip-EPISLEDS-for-plant-grow-/371423021249 and determined that they glow red with approximately equal brightness under 420 nm and 460 nm fluorescent light.

Test 30W LED full spectrum

https://www.youtube.com/watch?v=L2Eg94NLXzU

I'm not familiar enough with wavelengths and grow technology to yet make an informed decision, so hoped you guys could help.

I have a 4ft high-output T5 fixture and need to replace the bulbs. I posted a separate thread regarding a price comparison (and thanks for your help there, aruzinsky), but now I think I want to just find which is the best bulb.

I've been told by the manufacturer that 5000k LED bulbs would be suitable for growing basil, cilantro and dill, but I'm skeptical, and would like your input.

Unfortunately the bulbs I've been considering aren't available in 6500k:
http://www.amazon.com/Hyperikon%C2%AE-equivalent-100-277V-Dual-End-UL-Pending/dp/B00YWG5L0C

I like these bulbs because I'd never have to replace them. They appear to provide as much light as the current T5 fluorescent bulbs I'm using. I just don't know if they provide the proper wavelengths, and hoped you could guide me.

If these aren't appropriate, can you recommend a T5 high-output fluorescent would be best for growing herbs?

Don't buy those Hyperikon LED tubes because the description, "Provides an industry-leading 2500 lumens within its 160° wide beam spread making it brighter than a fluorescent T5.", is a big fat lie. The reflector on your fixture should reflect enough light to direct at least 90% of a T5 fluorescent tube's 5000 lumens to within 160°. If not, you should get a fixture with a better reflector.

The difference between best and worst fluorescent, LED and HID lighting for growing plants is small, maybe, less than 50%, so, except for initial cost, it doesn't practically matter much which you choose. My obsession with fine points is intellectually motivated with an emphasis on practicality. If you decide to join that party (I expect that you won't.), I would recommend that you perform controlled experiments comparing different kinds of T5 fluorescent tubes. You can put 4 tubes of one kind and 4 tubes of another kind on opposite sides or your 8 tube fixture with an aluminized mylar partition in between and see which kind grows plants faster. Then repeat comparing the current best with a new kind. For such experiments, I recommend that you include:

http://htgsupply.com/Product-AgroMax-4ft-T5-Pure-Bloom-Bulbs

http://htgsupply.com/Product-AgroMax-4ft-T5-Pure-Par-Bulbs

Of course, report your results in this forum.

Thanks very much. I don't really have the time or resources to experiment in such a way now, but I'm very interested in growing plants in the best way possible.

For herbs, I suppose the Veg bulbs would be best. However, they're out of stock! Should I now just go with the generic ones on Amazon?
http://www.amazon.com/gp/product/B005OLL5IG
http://www.amazon.com/25-Case-Output-Phosphors-Plusrite/dp/B00CNI6YQ6/

Hi Azurinsky,

Just a little note which steps needed to hack a led lamp.

First run the lamp for about 15 minits and check the temp of the lamp, for example the room is 23 Deg, and the lamp is 38 than the temp rise of your lamp will be about 15deg/5.4 or ~ 3deg/watt when you dubble the wattage the temp rise will nearly dubble too, if that is a reasonable value you can try to take the lamp apart to reach the electronics. Be carefull sometimes the main side capasitor (350-400V) has charge left so discharge it before continuing.

Normally there will be an IC which controls the current if that is the case look with a magnifier for a little smd resistor marked something like 1R2 or 5R2 etc, sometimes there or two parallel, you have to add a resistor to lower the value and the current will increase

Run the lamp for some time to check if everything is OK if so put it together again and you have you higher output lamp, I think 10 to 15 watt will be the max you can get out without forced cooling and maybe not even that

When you don't know what you are doing DON'T DO IT !!

DISCLAIMER: Trying this kind of hacks is totally for your own risk !!

FWIW I just started growing/harvesting various Lettuce, Spinach, Basil and Cilantro under 6500K LED's and can tell you they thrive and are delicious! Grow about 2-3 times faster, are much greener, and even seem to taste better than when I grew same seeds outdoors over the summer.

Can you tell me which LEDs you purchased? Sounds awesome!

I bought 40 Cree XT-E's 6500K on heatsink stars which are 5w each for a 2x4' grow area. Thermal glued them to a sheet of 1/8" aluminum also 2x4' and soldered together to get proper voltage and current for power supply. If you want to flower/fruit things like tomatoes and peppers you are supposed to use light more in the red spectrum. Building out my LED fruiting section now which will also be 2x4'

DIY LED Grow Panel 20W for plants https://www.youtube.com/watch?v=hsvBlHpmNwk

If you have trouble finding your particular lamp or fixture on the usual sites, try farmtek.com--They keep huge amounts of inventory to accommodate commercial farming ops

Hi Scorpio_Bafh,

Thank you. I decided to make my own LED spotlights for plants and I may use your information to tweak the drivers. My objective is to do it more cheaply per watt than can be bought from sellers who lie about the wattages. Of course, the other advantages are that a DIY spotlight is user serviceable and the power consumption is whatever you want. The hardest part is familiarizing myself with the available lens collimators. I just completed a spotlight that uses a 10 watt chip and a massive glass lens collimator which is the most expensive part. It seems to work relatively well. Next, I will build some spotlights using 3 watt chips and cheap plastic lens collimators. When I am done, I will post photos and instructions because few people seem to do cheap DIY LED spotlights.

For a few years I have been growing lettuce under T8 shop lights. The bulbs are Philips F32T8/TL741/Alto II. 30 bulb pack, says color Temp is 4100K. I have been satisfied with results but thought I would try a LED shop light. Below is label. It's from HD http://www.homedepot.com/p/Commercial-Electric-4-ft-LED-Linkable-White-Shop-Light-54103161/205331022 and cost $40.

I did compare it to my current T8's and found it did not grow the lettuce as fast or as well. But it uses 35 watts vs the 64 (32 x 2) watts in the T8 fixture.

Reading your info and the label in the picture I'm now thinking the LED has less blue light than the T8 . Is that correct and is that the reason the grow is not as good?

Can you recommend a better "out of the box" 4 ft LED light for lettuce?

Thanks

Hi fred o connor.

A rule if the thumb is more blue for leaves and more red for fruit and blooming so for good lettuce I think you need more blue. The problem is you cannot compare 4000K TL with 4000K LED, for our eyes it look maybe the same but you have to look to the spectral emission of each light source to know the distribution of the colors.

"I did compare it to my current T8's and found it did not grow the lettuce as fast or as well. But it uses 35 watts vs the 64 (32 x 2) watts in the T8 fixture."

Your fluorescent fixture uses close to 70 watts due to ballast losses.

"Reading your info and the label in the picture I'm now thinking the LED has less blue light than the T8 . Is that correct and is that the reason the grow is not as good?"

It is just less light within the PAR.

"Can you recommend a better "out of the box" 4 ft LED light for lettuce?"

You can buy another of those LED shoplights and operate two side by side over the same grow area. Then, at equal power consumption (70 watts), I suspect that you will get better results than with your fluorescent. But, personally, I wouldn't spend $40 for a shoplight. (period!)

I have no experience growing lettuce but look at the YouTube video posted above, by Alexander Magarovsky, of lettuce growing under a DIY 30W LED lamp. If that favorably impresses you, there are "out of box" flood lights that use the same kind of LEDs for sale on Ebay:

http://www.ebay.com/sch/i.html?_odkw=led+380-840nm&_sop=15&_osacat=0&_ipg=200&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.H0.Xled+floodlight+380-840nm.TRS0&_nkw=led+floodlight+380-840nm&_sacat=0

Or, you can buy 5-10 10W warm/cool white LED flood lamps for under $5 each and mount them on a 4 ft. board:

http://www.ebay.com/sch/i.html?_sop=15&_ipg=200&_from=R40&_sacat=0&_nkw=led%20floodlight&rt=nc&LH_BIN=1&_trksid=p2045573.m1684

Possibly, depending on whether the LED chips inside these floodlights are screw mounted and not glued, and the electrical characteristics of the chips are the same, you can upgrade the LED chips inside these floodlights for about $2.80/lamp:

http://www.ebay.com/itm/High-Power-10W-full-spectrum-380nm-840nm-SMD-LED-Chip-EPISLEDS-for-plant-grow-/371423021249

Incidentally, blue 10W chips cost about $1 each. Possibly, you can intermingle blue with warm white spotlights.

Very interesting!! Maybe I can assemble something.

Thank you!!

I ordered some of those $4.40 10W LED floodlights. Within 2 weeks, I should be able to post here whether the LED chips inside can easily be changed.

Here's what I bought for $8. I realize it's "full spectrum" and not just for vegetative. I will let you know how it works but I guess it will be awhile.

http://www.ebay.com/itm/231767167266?_trksid=p2057872.m2749.l2649&var=531026964159&ssPageName=STRK%3AMEBIDX%3AIT

KorallenZucht FIJI PURPLE

Boom myth of only led being able to be tuned is busted.

Fred O Conner, please, don't kill the messenger. I warned others about that scam, here:

http://forums.gardenweb.com/discussions/3018913/failed-led-strip-lighting-experiment?n=1

I know it won't help for online purchases, but if you're able to check out grow lights in person (such as at a hydroponics store) I would recommend bringing a spectroscope to confirm what the manufacturers are claiming about their spectra.

There is another thread I posted to with some spectrum examples (see the updated chart in the post just above this linked one): [Artificial Light Spectrum[(https://www.houzz.com/discussions/artificial-light-spectrum-dsvw-vd~3482922).

Another good tool is a light meter to confirm the light output as well. One that does DLI (PAR) is preferred, but a lux meter can be used for comparison purposes (generally).

I suppose after purchasing and assembling a new LED setup, measurements would be kind of late... but at least you can plan for modifications/upgrades based on numbers (immediate) rather than just plant response (several weeks).

ewwmayo, good post but I have a question. Since your spectroscope doesn't have a numbered grid, how do you know that your photographs, http://st.hzcdn.com/simgs/1a623fdd063a4b6a_9-1063/home-design.jpg, are aligned? All unfiltered fluorescent bulbs emit the same lines from mercury plasma and some of those lines are out of alignment in your comparisons, e.g., the 4th and 5th spectra are out of alignment at the 436 nm line. See

http://www.neon-lighting.com/articles/spect-mercury-clear.gif

I use this toy spectroscope with a numbered grid (read my review):

http://www.amazon.com/gp/product/B00FGARIAO?psc=1&redirect=true&ref_=od_aui_detailpages00

I have tested several LED chips sold by Chinese Ebay stores and the advertised spectral peaks were accurate. On the other hand, this LED lamp was falsely advertised (see my review):

http://www.amazon.com/dp/B00MN79L94/ref=pe_385040_128020140_TE_3p_dp_1

Dear, new DIY Grow Box + LED Light

https://www.youtube.com/watch?v=IIhXVhRcTog

ewwmayo, Thanks for your education. I do have an inexpensive light meter and may look into getting a spectroscope.

Alexander, very well built grow box!

Aruzinksy - Thanks for the links and I agree a spectroscope with a scale is better. My graphs were only roughly aligned and the goal was just to show the differences in general (but of course being very precise is more helpful).

"I ordered some of those $4.40 10W LED floodlights. Within 2 weeks, I should be able to post here whether the LED chips inside can easily be changed."

fred o connor, I now have two models, HK-LD300 and Plighting CLEF120V10DL and neither will allow you to change the LED chip without also changing the drivers because the installed drivers are 25-38V and the grow light LED chips are 9-11V. But, for what it's worth, HK-LD300 has much better quality than CLEF120V10DL which, unlike HK-LD300, has unmarked drivers with plastic cases and actually uses 4.5 watts of power. Also, HK-LD300 has a larger aluminum body with larger cooling fins.

It would be easier and cheaper for you to mount 10W LEDs on a 48" x 2.5" x 1/8" aluminum bar, with 60mm cooling fans, like I did with the blue LEDs shown here:

http://www.general-cathexis.com/images/LED1.jpg

http://www.general-cathexis.com/images/LED2.jpg

http://www.general-cathexis.com/images/LED3.jpg

If interested, I will give you more details.

Aruzinsky,

WOW, very nice!! Thanks for sharing. But more involved than I want to get at this time. (Also not sure I could learn how to do it. I've bookmarked this thread and may come back to it to figure out more of the details.

What do you plan to grow?

Thanks again,

I bought 2X 48" led shop lights,4500 lumens,40 watts,240 led's(white) for $37.00 a piece. Are these lights any good for plants just to keep them alive during the winter months?. These lights have alunium bodies made by Lights of America.

"What do you plan to grow?"

That light setup is for starting seedlings, mostly tomato, in April for planting outdoors in May. Meanwhile, I am making LED spotlights for houseplants on my windowsill.

"I bought 2X 48" led shop lights,4500 lumens,40 watts,240 led's(white) for $37.00 a piece."

At 113 lumens/watt, that sounds like a much better deal than the one Fred bought. I expect that two will suit a wide variety of purposes. Do you have easy access to the interior?

I do not know,i just hang one of them up and i got a very bright light.It look well made. The frame is made of alumnium.I was at Sam's Club today and they have a new suply, $35.64 each.

Btw aruzinsky i sure like your posts on led's,it make want to make a few my self. With my limited knowledge i am afraid to jump into it.I usely work from scematics and with safety issues i worried a bit. Thanks Bob.