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I started this journey after after testing several of the low cost grow lights being imported from China. Every one I tested was over hyped, low powered junk. By the time I got tired of fooling with the Chinese junk 3 watt LEDs had come out and I realized that with the right cooling a lot of these could be mounted in a very small space. You can read more about this project on our www.grow-sun.com web site.

Fast foreword 2 years and industry has finally released more affordable LED replacements for screw-in type light bulbs, including LED flood lights. And while in LOWES looking at LED light bulbs one day I wondered if my Grow Sun grow light had been out flanked by technology? I wondered of a lower cost LED based grow light could be put together out of production LED lights? Well, the answer is yes, you can put together your own high intensity LED grow light, and this article shows you how.

We decided to sell a fully assembled version of this grow light fixture. You can find more details HERE.
 
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Step 1: Select the LED flood lights you want to use

Picture of Select the LED flood lights you want to use
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I did a lot of shopping around the big box stores and picked out a LED flood light I liked. It's a SYLVANIA ULTRA LED flood light. The output is rated at 520 lumens at only 8 watts of power and because of the relative small size (2.5" across) I thought I could get 6 mounted to the housing I had in mind.

Step 2: Select the housing

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The housing I had in mind is manufactured by LMB HEEGER in California. It measures 7" X 5" X 2" and I was pretty sure I could mount 6 LED flood lights in the box.

Step 3: Select your light sockets

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The sockets I chose are the ceramic snap-in style & they are designed to mount in the same size hole you would punch in a box to mount 1" conduit. The hole is 1-1/8" diameter.
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I don't think the LED Lights were a good choice. The lumens just don't matter alone. If you want a nice 200 gram steak, you won't be too happy with 2 kg sausage, would you? Like that, light with 3000 K does not have the right wavelengths of light that plants need. With normal fluorescent light tubes, you want to go as high as possible, like 4800K or 6400 K, which I use, or you can mix 2 6400 with 1 4800. But light tubes give off a whole mixture of wavelengths, that is well known. LEDs work completely different and no one knows which wavelengths your lamps have. That is why professional LED Grow Lights use red and blue LEDs in a certain mixture.
Tom Hargrave (author)  Coffeinated1 year ago

I put a tremendous amount of research into lighting and plant growth. I learned that plants are sensitive to all light wavelengths not just blue and red. I also learned by doing my research that the light sensitivity graphs that are scattered all over the net are somewhere between misrepresented data and outright lies. What I discovered through research is the graphs that show high sensitivity to red and blue light and almost no sensitivity to green light misleading. Find the real light sensitivity data and you will see that the bottom 2/3 of any graph that shows only red and blue has been cut-off and that plants are sensitive across the entire range of visible light with red and blue being the most sensitive areas.

Alas, but this is not so. Just 130 years ago a scientist Timiryazev studied this process. Important only the red and the blue part of the spectrum. Green indifferent. Sometimes add a little white. For the aesthetics of the human eye. But plants are indifferent. The white light is wasted much energy.

I successfully grow salad lamp 20W (15W red LED and 5W blue.). This is enough for the area of 40 x 40 cm

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20w "daylight white 5000k" led, as long as pointed correctly, can output absolutely INSANE amounts pf lux at 40cm x 40cm

Thanks! I'd be interested in you doing a write up on this!

Tom Hargrave (author)  RedBinary1 year ago

As in, you want to build one or you want me to loan you one so that you can use the light and report to the rest of us?

I had originally intended this to just be a project to share, but based on the initial interest in these instructions I wonder if we should start selling light kits?

Here's a variation on the graph Costarus posted

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Tom Hargrave (author)  RedBinary1 year ago

I've seen this chart in many variants but what the publishers don't tell, or at least what the original publisher does not tell is the lower part of the chart is cut off and the range is re-scaled. Find the actual data and you'll see that plans sensitivity to green is not close to 0 as the chart leads you to believe, but plants are about 1/2 as sensitive to green as they are to red. The problem is this chart has been posted on the net and has gained traction and is now taken as "the gospel truth" for lack of a better term. I'm sure you've seen the insurance commercial - the one where the lady states "if it's posted on the internet, it must be true?"

Get away from the "light fixture marketers" and turn instead to sources hosted by educators (Universities & such) and you see the real plant light sensitivity curve. It took a few minutes to wade through the HPS, MH and LED marketing sites to get to university hosted sites but right away I found a chart of the actual plant light spectrum sensitivity. It's the second image I uploaded. The image shows a dip around green but the dip is no-where around 0!

Also, the human eye sensitivity to light bell chart in this graph is dead wrong. I added the correct graph that does show our eyes are more sensitive to green but is nothing like what's in the previous chart.

Eye Sensitivity.gifPlant Light Sensitivity.gif

Not to pick nits, but since you infer that I'm gullible and only read marketing drivel: the scaling of the charts are different. Yours aren't really labeled well and contain no citations whatsoever. Regardless, it appears that in your second chart the black line is chlorophyll blue absorption wavelengths with the peaks at A and B just as in the one I've posted , while I have no idea what the green line is. You've also taken issue with "human eye sensitivity peak: perceived white light" in the chart I posted and then posted a chart showing almost identical sensitivity, just scaled differently.

As far as scholarly articles here's one of the several I looked at before posting: http://plantsinaction.science.uq.edu.au/edition1/?...
an excerpt of which is "Upper curves: Diethylether solutions of chlorophyll a (Chl a, solid line) and chlorophyll b (Chlb, dotted line) show distinct absorption peaks in blue and in red regions of the visible spectrum (redrawn from Zscheile and Comar’s (1941) original data)." as well as "Leaves absorb visible light very effectively (>90% for all wavelengths combined; solid curve).Wavelengths corresponding to green light are absorbed less effectively (absorptance drops to c. 0.75). Beyond 700 nm (infrared band) absorptance drops to near zero, and forestalls leaf heating from this source of energy."

Tom Hargrave (author)  RedBinary1 year ago

I did not intend to infer that you are gullible, my comments are for everyone to read & not just you. Unfortunately there is a lot of marketing hype on the net and I'm just stressing, or maybe over stressing that point.

Actually, I was replying to Costarus' comment. I'd like to see more about what he's using for the targeted wavelengths. After my comment I did a little looking around online and this appears to be the current "state of the art".

After my admittedly cursory reading around I am curious how much of the 425-465nm and 640-660nm spectrum is being emitted in the configuration you've used. I understand that your goal is to open up the area to less technical people, but I've found some of the red/blue LED grow lights online for around $20 each.

Tom Hargrave (author)  RedBinary1 year ago

Buy them, use them, please let us know how well they work!

I bet when you get the lights in they will be powered by small power supplies that can't deliver any real power. These are the type lights I mentioned at the beginning of my article.

years ago, I was using exactly the same 1000 watts HPS lights that every other commercial grower is using, most growers were getting 0.5 pound ~ 1.1 pound of harvest per light, I was getting just over 2.0 pound per light, there's a lot more to growing than just lights. If you do it right on the entire process, simple HPS works just fine.

other way around.

ALL white leds emit significantly in the entire visible spectrum, with high blues and reds, and comparatively lowrr green and yellow. meanwhile, fluoros and cfls emit three HUGE NARROW SPIKES in R G B and barely anything else
Lumens can matter alone just fine. HPS or MH grow lights dont have nor need a perfect full spectrum to grow from seed to fruit because of the pure amount of lumens they output. If you're serious about growing, you switch between the two to simulate summer/fall sunlight though (spectrum as mentioned). The point is, lumens CAN cut it. However, I dont know how much you'll really grow with only 3000 of them.

Lumens are not the important number when it comes to growing. LUX is the correct identifier. Believe it or not, there is real science behind this. You need to provide plants the correct color ranges for photosynthesis and enough LUX to make it happen. Science says these are in the red and blue range. (see chart above from costarus)

It's hard to admit, but even if your light works for a grow light, there are MUCH better ways to do this.

Metal halide (predominately blue) and
high pressure sodium (predominately red) bulbs have been the standard
for indoor growing for how long? Neither of them give off a perfect
red/blue spectrum, yet you can grow from seed to fruit under either
because of the sheer amount of lumen output. As I pointed out in
another post, people that really want the best results start with metal halide bulbs and finish with high pressure sodium to simulate the change in seasons.

Conversely,
most reviews of red/blue LED's were for the longest time, poor. They
simply didn't provide the lumens even though they were the optimal
spectrum colors. They're definitely better as of late through
technology improvements (IE More juice!). But still, I stand by what
I've said that you'd be better off with true high power LED's like the
Cree cxa3050 (something I'm currently building with myself).

Of course, as long as the right wavelengths are at least there, you can just give off more light and it will eventually be sufficient at some point. But that is of course not the best way. To get back at my steak/sausage example, if I give you 2 kg meat of which 50 gr are the steak you want, of course I can just give you that four times so you have 200 gr steak. No problem.
Metal halide and sodium pressure lamps are just easy to get, and known technique.
If you would try to grow plants with a green laser, even 100000 Lumens would not be okay for your plant, it just would get quite hot. So if my lamps give off just the right spectrum, I can save energy because I don't have to emit the waste, the useless light.
So, with mixed spectrums, lumens can kill it, but that's not the clever way.
Tom Hargrave (author)  Coffeinated1 year ago

As I stated earlier and I will state again. Because one of the goals of this project is to make it build-able by
anyone with local hardware and you aren't going to find a 50w LED spot
light at your local Home Depot, Lowes or Menards store.

Also, the person most likely to build this project is looking at buying or building a "grow light" to grow a few plants indoors or start seedlings for his garden. The folks shopping for HPS or MH grow lights as well as those looking for high wattage red & blue LEDs is probably not going to be interested in building one of these lights.

I'm interested, but not for a grow light. We have a large torchier that we've owned for 20 years now, and has seen everything from a 300w T3 halogen, through a 150w PAR38 reflector, to a twin-circline T8 fluorescent fixture (there worst of the bunch in terms of light quality, thanks to the incomplete spectrum, but the best in terms of heat output). This idea might just work for me.
Tom Hargrave (author)  Tex Arcana1 year ago

The trick will be to adapt a fixture to screw into your floor lamp. Maybe you can build something from a screw in base, a box and 4 sockets, kind of like a 1 to 4 adapter that you screw into your fixture?

In case you didn't figure it out, I did all of those adaptations. so, yes, it'll be something akin to yours. http://i.imgur.com/iyzaw0o.jpg is the fixture, except I pulled everything apart and flipped the base, to act as a reflector as well as allow it to sink into the fixture more. I'll likely use that plate, and see how an array of LEDs will work I'm guessing I need at least 4000-5000 lumens to make enough light, the 500w T3 worked great, but the heat output and power consumption don't make it worth it.
Tom Hargrave (author)  Tex Arcana1 year ago

Interesting, that's a picture of an old Circle-line fixture. I'd like to know know things ultimately work out.

precisely. cost me $5 after my employee discount, the bulbs cost more than the fixture. I'll get pics of the fixture shortly.
Aadieu4 days ago
uhm NO

cheap closeout multisocket strips bathroom strips (those things u see over mirrors a lot) and/or 2:1 Yconnectors and/or 4:1 splitters

2015 prices paid:
$3 / 950 lumen LED bulb for COOL WHITE/DAYLIGHT 5000-6500K
$0.25-0.59 / 1200-2400 lumen CFL for SOFT WHITE (cfl deals too nice to go led for 2700-3000K, also cfl soft whites have 65-70 lumens/watt, which while nowhere near led 5000k's ~100, is just a hair worse if it all than the 60-80 lumens/watt out of common cheap soft white leds...plus fixtures and connectors are pricier than bulbs these days, and good CFLs sit in the 23-40w/1200-2400 lumen ranges vs led's 9-11w / 600-950 lumens, making mixing in some cfl good common sense)
$2.50 / Yconnector 2:1 splitters
$5/ closeout 3 bulb strip fixtures, even had a semblance of a reflector albeit bronze coloured

currently running clusters of hanging yconnects, havent installed the 3 socket strips yet. bulbs totalling ~200w, half LED half CFL by wattage, put out measured lows of 10,000k edges to average 30,000- 40,0000k lux AT FOLIAGE for most plants in a black and yellow aero tote. measurements supported by the most robust growth seen at the brightest spot.

no leaf burn. cheaaaaaap. and puts out the kind of foliage surface lux people look for out of MH and HPS (desirable range often stated as 25k-50k - my 30k-40k for most positions foliage fits right in with that), simply cuz led can be run point blank and cfl a mere 2 inches away or so, and thus their lumens actually deliver. while mh lumens dissipate since its temp requires running it from way far off..
ohbejoyful3 months ago

Love this - very easy to follow, and you make it sound very doable.

I would still prefer LEDs over CFLs, since CFLs contain mercury and thus cannot be discarded in the trash. They must be taken to a hazardous waste collection site (Home Depot takes them here in PDX, and there is also a county collection site).

we don't need so much power, it's all about the angles, i have a 7W plant arm with no fan - no heat sink... check it out. you can attach these plant arms to any pot !


can be powered via USB, rechargable battery or solar even !

visit my profile; http://www.instructables.com/member/0bios0/

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djimdy1 year ago

Aside from (or in addition to) Lumens and LUX, could someone add information about CRI ? It would seem that higher CRI would mean more balanced light. So to that end why not build up shop lights with high-CRI, high Lumen T8 bulbs that also use low power?

Tom Hargrave (author)  djimdy1 year ago

The higher the CRI rating the more natural color rendering appears to your eyes, with 100 being the same color rendering to your eyes as natural sunlight. But this does not mean the light is producing the same spectrum as the sun or that a high CRI rating is the best light for your plants. Here is a good article about CRI.

http://lowel.com/edu/color_temperature_and_renderi...

Thanks for the educational link. It doesn't seem to make sense to me, however, that if a light produces the same spectrum as the sun it may not be the best for one's plants unless plants actually prefer higher or lower K lighting (i.e., with either higher or lower visible wavelengths filtered out, respectively). Is that the case?
Tom Hargrave (author)  djimdy1 year ago

Science discovered a long time ago that plants process some light colors better than others. And if you have control of the brightness of different colors why not tune your light source to benefit your plants? Anyways, that's the theory and the reason you see oddly colored grow lights. This project is all about building a grow light from off-the-shelf lights and my theory is if you get the light bright enough the plants will grow well anyways.

Surferdude1 year ago

This paper ( http://www.plantphysiol.org/content/46/1/1.full.pdf ) gives you the actual data in addition to the graph (on page 4). Although it's only for one type of plant (bean), it has a pretty good discussion and the concept is what's important. Note that it's based upon photons, not lumens. The curve measures how many photons are required to produce CO2 at each wavelength, not just what seems to be absorbed. Since this reaction and the production of ATP form the basis of the energy flow into the plant, it's what's really important. The long wavelength red is about 1/3 more efficient than green, so you're right that the curve doesn't drop to 10% as in the absorption spectrum, but the definition of lumens is so heavily weighted to the green that it makes the miscalculation even worse (as argued by Coffeinated, above).

If you add up the red, green, and blue in the chart you show for cone sensitivities in the retina, you end up with a curve that has an even more pronounced peak (because of the overlap with the red and blue sensitivity curves). That doesn't really matter though, because the lumens you're talking about are a measurement standard, not the actual response of your retina. That curve does have a peak in green, so light from bulbs intended for use as general purpose lighting get more "credit" for photons that have a wavelength that is not as useful to plants, as demonstrated by the photosynthetic action spectrum described in the paper.

shadewolf1 year ago

Forgive my ignorance about light meters, because I haven't tested it yet. If I was to make 2 of these units and put a light meter under both of them lit up, does that mean I'll get 6240 lumens right beneath them or will it still be 3120. Ie, adding extra 520 lumen bulbs pumps up the lumens on the meter when tested? Are the bulbs additive in brightness, or will they each show just 520 lumens of light when tested at say 4 inches away under the centre of each light?

Tom Hargrave (author)  shadewolf1 year ago

Total light produced will double and the brightness definitely will increase but measured lumens will depend on where you measure. Unlike sunlight where the light is pretty much a parallel beam because of our distance from the sun, lumens will decrease as you move away from any bulb.This is because with any light source but the sun, light spreads as you move further away from the source. Professionals who grow under artificial light understand this and they measure their light levels at the leaf level.

"This is because with any light source but the sun, light spreads as you move further away from the source"

That's not true Tom. The Inverse Square Law applies to all electromagnetic waves, of which the Sun is one.

The illustration below is the correct one.

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Tom is right on this one. The inverse square law requires that you measure from the source, not from some arbitrary point. In this case, the difference in intensity (L) at point b, 1 foot farther from the sun than point a, is something like L(b) = (93,000,000^2)/(93,000,000.0002^2)*L(a). For a lamp it's very different. In that case you're maybe 2 feet away, so one foot farther away the intensity would be L(b) = (2^2)/(3^2)*L(a)

Dude, you missed what I was saying. Tom EXCLUDED the sun from the inverse square law. I simply said that it applies to ALL em waves, and the sun is a source of em waves. Your calculation should reflect cutting the distance in HALF, not by one foot. Its erroneous and misleading. If you want to compare apples to apples, add another SUN in your calculation, one that is TWICE the distance from the earth/measurement point... and guess what, we're back to the ISL.

My reply had two points. The first is that although light from the sun does indeed obey the inverse square law (ISL), the sun is so far away that any distance around your house (with respect to sunlight) is so small that it's unlikely you can measure the effect: the rays are effectively parallel. People sometimes mistakenly start measuring from the wrong place when using the ISL. You have to measure from the source. So, for the sun, that's a point 93 million miles away. The .0002 at the end in my example is one foot farther away. So if you move 1 foot farther away from the sun, the light flux is 99.9999999995699% of the original value.

The second is that, by not using a factor of two as you suggest, I'm showing the general way of calculating the effect of the inverse square law. It doesn't only work when you double the distance. The general relation is a power law. So if you have a lamp that's 2 feet from a plant, and you move that lamp one foot father away (now three feet from the plant), the energy flux on the leaves is now 4/9 of the original value. If you moved it to 4 feet from the plant (double the original distance), it would be the more familiar 4/16 or 1/4.

Tom Hargrave (author)  dougstrickland1 year ago

I agree that the inverse square law applies as much to sunlight as to any other radiation source. But for the purpose of growing plants the law has no measurable impact on light. We are 149,597,887,500 meters from the sun and the distance between a plant and a grow light is maybe 1 to 0.2 meters? Apply 149,597,887,500 and 149,597,887,501 into your formula and you will see that the brightness difference is so small that 1 meter further away from the sun does not matter. BUT 1 meter further away from a grow light has a huge impact on light brightness. Depending on your bulb & reflector design 1 meter away could be 1/4 of the original light brightness or less.

Tom Hargrave (author)  dougstrickland1 year ago

I agree that sunlight from the sun is spreading out just like sunlight from a lamp is spreading out. But because of our distance from the sun and the short distance between where someone would hang a grow light and the plant leaves sunlight light could be considered parallel.

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