Build Your Own 3120 Lumen LED Grow Light





Introduction: Build Your Own 3120 Lumen LED Grow Light

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 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.

Step 1: Select the LED Flood Lights You Want to Use

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

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

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.

Step 4: Layout a Template

I used MS Word to layout a quick drill template. You can use paint, another drawing program, or hand draw something. regardless you need a template to make the project look sharp at the end.

Step 5: Tape Template to Box & Drill Pilot Holes

Any time I'm going to drill a hole in metal I start with a pilot hole. A pilot hole acts as a guide to larger drill bits and you end up with a much sharper project at the end.

Step 6: Drill Holes in Rear of Panel

I drilled the holes for the power cord, power switch, and grounding point. Because this is a metal box it's extremely important that you use a 3 wire power cord and properly bond the green safety ground to the box.

Step 7: Drill the Main Mounting Holes

Then I drilled the main mounting holes. See how stright they are? It's because I used a template then I started the large holes with pilot holes!

Step 8: Mount the Light Sockets

Once I completed the holes I mounted the light sockets and did a trial fit with the lights.

Hint: Because the aluminum chassis is flexible it's impossible to push the sockets in from the front. You have to put the socket in the hole, place the chassis on a table top face-down, then use a largish screwdriver to push the chassis into the socket.

Step 9: Wire the Chassis

Because this is a light fixture you are supposed to wire with high temperature wire. I used Teflon coated 22 gauge wire. Why so small? Because the entire fixture is only going to draw 48 Watts & that's only 0.4 Amps at 120 VAC. 22 gauge wire is rated at 5 Amps.

Step 10: Connect the Internal Wiring to the Power Switch

Connect the internal wiring to the power switch. I used a 2 pole, 2 throw switch because that's what I had. If you use only a single pole switch make sure it's wired to turn the black wire on & off.

Step 11: Wire in Power

Attach the power cord ground to the chassis. I used a 3/16" aluminum rivet and a backup washer.

Whe connecting power make sure the power cord black wire is routed through the power switch and then on-to the brass colored screws on the back of the light sockets.

Step 12:

Close the housing and test.

The lights on picture was taking under normal office light. Also, note that the lights run cool enough for me to hold them. Try that with a Sodium Vapor Lamp!!!

But does this fixture produce enough light?
For comparison, a typical 2 tube 24" florescent grow light fixture produces about 1300 lumens of light.
This fixture produces 3120 lumens of light and you can fit three of these fixtures in the same space that a 24" flouescent fixture fits in.
In other words, with three of these fixtures you can produce 9360 lumens of light - about 7 times more light than two 24" florescent tubes, and in the same space!
I think this fixture produces enough light!

What about red and blue spectrum light?
At these light levels who cares?

Thanks, Tom Hargrave

Step 13: Select Mounting Brackets

In a rush to get this instructable published I completely forgot about mounting, so I ran down to Home Depot and bought these mending plates for less than $3.00.

Step 14: Mount the Mounting Brackets

Then I marked the locating holes, drilled the holes, riveted in the mending plates in place, and now I have corner brackets that I can use to hang the fixture with chains and S hooks.

Step 15: Test Light Under Shelf

I can also attach the fixture to the bottom of a shelf with screws. Looks like I need to build two more....

Step 16: Select a CFL to Test

After reading some of the great feedback, I went shopping for some alternate bulbs. I found some 1190 Lumen 6500K "daylight" CFL bulbs at Wal-Mart that were not too expensive.

One complaint I have about these lights is they are not a spot light design and the light will transmit from the sides, so in theory if the fixture is above your plants in a open room your plants will not receive as much light from these as they would from a more focused source like a spot light. But if you are going to grow plants in a closed box like I did in this instructable it probably does not matter.

My second complaint is they draw considerably more power - 6 of these will draw 120 Watts where six of the others will only draw 48 watts.

Step 17: CFLs in Fixture

And here is what the lights look like on and off in my fixture.

Step 18: CFL Verses LED Light - Side by Side Comparison

I did a side by side comparison by first mixing three and three. You can see that my camera "sees" some color difference but not much, probably because the sensor is swamped with light.

Then I re-arranged the bulbs - I put thee of one type down one side of my fixture and three of the other type in the other side of my fixture. I separated the two sides with a heavy piece of cardboard and turned the light on in a darkened room. You'll notice the color difference right away - that's the difference between a 3000K and a 6500K light source. But you'll also notice that the brightness appears about the same even though the LED light is rated at about half the lumens. This is because the LED bulb is a spot light design and all of the light is pointed down. The CFL bulb is a non-spot design and the light is spreading everywhere.

We decided to sell a fully assembled version of this grow light fixture. You can find more details HERE.

Thanks, Tom



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    I read your full instructions AND all the comments with some interest. I have a PhD in physics and a new interest in grow lights. Specifically , I want to provide some extra light to a terrarium in a north facing spot in my house that receives only a small amount of indirect sunlight.

    An important point here, often overlooked or sidelined, is that these lights produce a light that is more pleasing to the (human) eye. Whenever mentioned it has been a case of 'but the human eye is different to a plant's needs', but I am interested in simultaneously pleasing both my plants and my eyes! Sure, it must be true that by concentrating power output to the specific wavelengths that are used in the various photosynthetic processes must result both in better plant growth and lower operational cost, but such lights have the drawback of making the room look like aliens are visiting! That might be fine in a basement or cupboard for certain types of horticulture, but it is not going to cut it in my dining room!

    The discussion here about LUX vs. Lumens is very true (i especially enjoyed the tangent about rays of sunlight being almost parallel by the distance of the Earth - something I assumed in so many problems I solved at uni!), but being a physicist, the photosynthetic response curves were completely new to me. Now I assume that the various elements of photosynthesis evolved long before the current variety of plants and these peaks in absorption (as indicated on the graph posted by 'Redbinary') are the same across the diversity of plant species? i.e. Algae, moss, flowers and vegetables all have very similar peak absorptions in the red and blue that are often quoted here and elsewhere.

    From what I understand about photonics (e.g. from the photoelectric effect) is that so long as some of the photons are in the energy range needed for absorption (chlorophyll A & B absorption peaks), then the light will have some effect on the plants. Increasing the intensity of photons at these wavelengths will increase the effectiveness of the grow light but with the drawback that the emitted light becomes less aesthetically pleasing. However, if the intensity of the whole spectrum were boosted by the same amount, the intensity of PAR photons increase, yet the overall light remains white(ish) but gets brighter.

    What is potentially of worth here then, is that it MAY be possible to deliver enough red and blue wavelength (PAR) photons to benefit the plant but where the other wavelengths, far from being useless, result in a light which isn't painful to look at! Given the low cost of LED lighting, I'd pay a bit extra for the light and room to look nice, especially since I have very limited space and only one 18 inch square terrarium to illuminate - my considerations for a nice room with healthy plants are very different to those of a commercial grower who wants maximum yield at minimum cost and it seems that many of the detractors on this post are in the latter category. Such disagreements are like comparing apples to oranges.

    So, rather than saying this light is for reading or other tasks (as suggested in one comment), so long as these LED lights provide some photons at the wavelengths of interest, you could say it is a 'supplemental to natural light' grow light. Only experimentation will tell you whether or not the number of white LED fixtures necessary to noticeably boost growth would result in a set up so bright that your room looks like a floodlit stadium!

    With the last comment being some months ago and it now being the height of summer, I hope that you have been able to test out these lights and that you may be able to let us know whether your set up provided a high enough intensity of photons at the key wavelengths to have an effect on your plants.

    Hello, I too am like you I am learning about this process. What I have learned regarding the human spectrum and plant spectrum is regarding the PAR (Photosynthetically active radiation). Which is about the chlorophylls and carotenoid response to light waves, specifically measured in nm. I have found lots of research that indicates that the light plants need is hardly ever pleasing to people. If I understand it correctly our vision is much more blue and plants are non-flowering plants are red and green with a smattering of blue. Now to make even more confusing you have to worry about light heat temp and light irradiance. The heat part is hopefully obvious but you dont want to bake your plants. Get it bake. hehehe. Anyway, irradiance is the strength of each light wave group from the distance of the emitter, that says how much of each wave band will be however strong at a specific distance. My research indicates that lumen and watt are more relevant for human sight and less effective for grow lights. I could definitely be wrong but I have read all the research put out by Cornell and they clearly say " (Don’t use these units for referring to greenhouse lighting):"

    Sadly it is next to impossible to carry around a spectrometer to measure light bulbs at Home Depot, and they go out of their way to not break down the light bands even for grow lights.

    Hope this helps.

    You made a great project and I'm going to buy the stuff to do this today.

    I've been reading the comments, and wow man. Chill out and maybe try the project before spouting all kinds of hate about full spectrum lights and raving about how useless all the wavelengths other than red and blue are. Apparently you're all scientists, so do some science. Maybe don't blindly follow online charts and papers, and perhaps do your own experiments? You know, science? Test your hypotheses.

    If full spectrum LEDs work for the author, and they work for me, then the project is a success (Scientific Method, and all that...). If not, then I guess I'll have 6 more LED bulbs to make my place that much more efficient.

    some plants need different spectrums for different stages like our 4 seasons when the sun closer and futher we are getting different spectrums as the 4 seasons so unless you want to waste time and money on house plants that dont produce and give back your normal house lighting is fine maybe open the blinds but brightness on single spectrum house/flood light isnt whats going to make a healthy plant and that set up would be too bright for normal house plants now on the smokeable kind of plants you would want high uv's with lots of blue white and purple specs for vegi stage and for flowering whites orange reds and about 3 weeks til harvest time you would also introduce med to high uv to increase potencey and thats opitional so check the specs and research the plants to see witch type of specs they like and at what lumination and for how long

    man before any of yall go out and a bunch of flood lights from the hardware store do your research first those lights are only giving off one spectrum maybe 2 and some plants need sertian spectrums to be heathy or even to bloom flower or produce fruit yeah if you want to spend money

    How exactly is this a grow light? It's 6 normal "Living room" LEDs as far as I see, you're basically wasting most energy on the green spectrum plants don't even need. If I just assume that each of the lamps above is $10 (which they for sure, if not much more), make your project at least $60 for the lamps PLUS the entire DIY work. Sorry, but then even a cheap 300W+ China LED grow light which can cost as little as $70 (6 Spectrum with 3W or 5W LEDs) seems a much better choice to me than your DIY project there. And might ironically even be cheaper ultimately.

    Yes, it's a project based on normal living room LED lights but that was the plan all along - to build a grow light from material you can buy from LOWES. This is a "grow light" because of the high concentration of light from one source. You won't find a off the shelf light that produces as much light in such a small space.

    Very creative i found only 2-3 sources over the net who suggest using simple LED bulb as a grow light.

    are flood light and spot light are different ?

    What are the different names for the LED flood light

    What should one what out for before buying ?

    Can you suggest more alternative buy (on the LED bulb ) with amazon uk / us ?

    the product you made is sufficient for how many plants ?

    We are in the middle of a LED light revolution, with light technology evolving so fast that even models introduces three months ago seem obsolete. My best advice is to limit your selection to floodlight style LED bulbs, then buy whatever produces the most lumens per watt, then set up as many lights as you can afford.

    "How many plants" depends on what you are growing. The light I made grew two tomato plants just fine with some help from an outside window. The same type plants in the same window grew too tall too fast, so I know the lights made a difference. We don't grow pot here, it's still illegal in Alabama.