LED Grow Light





Introduction: LED Grow Light

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UPDATE: fanless design - https://www.instructables.com/id/an-even-cooler-LED...


I am going to share with you how to make a cheap yet very powerful grow light. this 12Watt - wide spectrum led light will flourish your plants ($7.88 / year). almost every part can be found around the house or at a thrift store - cost is ~$15.


advantages to CFL:

- almost impossible to break

- clean operation, (no toxic fumes or mercury)

- 120 degree light output, unlike 360 degree with CFLs, there is no light loss

- cool to touch. plants can touch these lights and not burn their leaves

- easy customization. size, shape and color.


let.s being..>

Step 1: Frame / Parts

here is a link for the laser cut acrylic sheet. it is the same size as a 120mm case fan.


the metal sheet in between was bought from a local hardware store.


everything is held together with 20x nuts (6-32) and 4x bolts (6-32 x 2"). make sure they are the right size, bring your fan with you to the store and test it.


you will also need;

led driver

high power leds

6x 1W warm white (you can also do 4x warm white 2x cool white - make sure they are 1W)

2x 430nm

4x 660nm

dc adapter (matching with case fan voltage !!)

ac cable

thermal glue



female & male usb connectors

Step 2: Led.s

first we are going to make 2 in series modules of 6 led.s. then we connect these two modules together in parallel. which leaves the voltage same, but doubles the current - matching perfectly with the driver at 700mA.


apply a tiny amount of thermal glue under and lay out your led.s (wait at least 30 minutes to cure)


measure, cut and snip the ends off each wire - get them ready to solder. I use masking tape to stabilize everything, this makes the entire process very easy.


solder the led.s


the led driver doesn't come with an ac cable. solder the AC cable to the driver.


before going any further test your system. connect the driver to the wall, and touch the positive (+) and negative (-). make sure that they all turn on. do not stare at the light !!


carefully disconnect the driver, do not touch the positive (+) and negative (-) together EVER.

Step 3: Usb Connectivity

i want to easily be able to attach/detach the light system. this is why I converted each connection with a usb socket.


connect the male usb sockets to the fan + lights


connect the female usb sockets to the dc adapter + led driver


now you can mount the power adapters to a frame and still be able to remove your light for upgrades/fixes.


for more info on connections: instructables.com/id/usb-power-source-hack/

Step 4: Conclusion

I have been working with high power led.s for over 7 months now. they are superior to CFL grow lights in my opinion. here are a few prototypes.


the new system (12Watts - 4.5x4.5inches) is going to be replacing the current 16Watt system in the plant box (8x6inches). I will be loosing a few led.s but this light is much more stable and sleek, less moving parts, much less space. (will post about this soon!). I am planning on a time-lapse plant grow movie with this new system once box1 is finished. I can't wait to put this thing to a real test.


my new system is very similar to another older design. this auto grow system is power with only 6Watts. (4.5x4.5inches)


here we have another led grow light system (11Watts) with a fan on top again. (4.5x4.5inches)


last we have a system without fans. it is also 11Watts but the sheet size is 9x9inches (3.5mm thick). I have successfully raised 3 lychee trees sharing all the light. the heavy frame acts as a heatsink.


thank you for your interest, remember to subscribe to stay in the loop..!

love & peace




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    awesome instructable man. iv'e bought/found most of the stuff to make it but i wasjust wondering, did you use any resistors in your circuit? i read up on it and apparently you need to.

    1 reply


    unlike regular leds, high power leds are very robust. i have never used resistors with any of my light builds. however, you have to use the correct driver that is designed specifically for this application as listed above - this is very important.!!

    check out this page to find more info; https://www.instructables.com/id/LED-lights-1/

    thank you for your interest and picture your work.

    While it is not uncommon for manufacturers to use series-parallel arrangements with LEDs connected to a single constant-current source, it can be a Bad Idea if you value long-term reliability but rely on matching published nominal voltage specs without actually verifying them in circuit. The forward voltage of ANY LED in reality (not the spec given, which is only "typical") is neither constant during use, nor consistent on production lines from batch to batch, etc.

    It is well that you made sure to have the two series-connected strings of LEDs (of different types, no less) mirror each other with LED type. With luck, their overall voltage drop at operating temperature will be equal enough to evenly divide the 700mA between the two strings. But LEDs from different voltage bins or manufacturers could be mixed in a single order yet treated as identical types by someone building this. It won't take a large difference to result in one string running at less than full output while the other one is being overdriven.

    Also, "thermal" glue is convenient for mounting star LED boards, but it usually compromises efficiency of heat transfer compared to mechanically clamping them to the heatsink with a microscopic layer of thermal grease instead. I cannot find ANY numbers for the thermal conductivity of the silicone-based glue being sold cheaply on eBay to hobbyists, but I would be skeptical of a source that doesn't give that spec. Thermal glue is simply regular glue with fine grains of something like aluminum or silver or just carbon mixed in it, and its thermal conductivity can vary tremendously yet still be called "thermal" simply because it's more heat conductive than the same glue with nothing added. Again, this is something that may not make any apparent difference when you turn it on and it seems to work great. But a year or two later when the maker realizes their wonderful LED light fixture is losing lumens faster than it was supposed to, or some even fail prematurely but it's not obvious why, it's too late for hindsight.

    16 replies

    this is exactly why i kept the project under $15 so if/when it breaks, you wont be frustrated. but i have made many similar ones this way which all gave great results. but i would rather have kept 12leds in series, i must admit. that was the only driver i had available. my other system is 11 x 1W all in series. same manufacturer, same exact models, voltage etc. but i have been researching with all types of different combinations. this i would say is a very stable, cheap and durable beginner led grow light. you can easily add 4 of these in a 9x9 space and have a 48W system for only ~$60. or if you have the finances, you can make a very professional light still with what ebay has to offer.. thank you for your input.

    Quick question about your wiring. Don't you wanna match the voltage of your LEDs in series? Is the difference in voltage between the 2.5V and 3.2V not an issue? Sorry for the newbie question I've never worked with LEDs before so it's new to me :)

    For my project I've got 14 LEDs all at 700mA 3W but with different voltages ranging from 2.8 vdc to 3.4 vdc hence the question :)

    it will work. according to my research it shouldn't matter. they will only draw the needed voltage. its the mA that matters. but i think if you have the space/finances using the same LEDs could be better in the long run.. however i've made many light this way and they all work without problems. even with heavy daily use. check this out, its my new fanless design; https://www.instructables.com/id/an-even-cooler-LED...

    That is true only if there is a single string of LEDs connected to one driver output As soon as you add another string in parallel to it on the same driver, it does matter very much, since current will naturally flow preferentially through the string with a lower voltage drop and the driver has no way of regulating how that is split - it's simply regulating the total current it supplies to everything connected to it. I'm curious if your research is based on manufacturer's recommendations or something else, because if you have found an industry source that states that LEDs with substantially different voltage drops can be connected in parallel to a single driver oputput without inviting problems I would really like to see it.

    It was my plan to go in series so that's perfect :) I've found a LED driver @ 700mA 40W for it. It's 2 watts lower than the 42W total but I don't think it would matter too much. Rather lower wattage than going for a 50W driver, correct?

    why are you gettin 700mA.? are you using 3W LEDs.? if you are using 1W LEDs you can just get a 350mA driver instead and connect everything in series.

    Yes sorry I should have mentioned it :) 3W @ 700mA for all of the LEDs. I'm going with a mixture of warm & cool white, royal blue and deep red. 14 LEDs in total. Would the lower wattage for the driver be a problem? I could only find drivers for 40W or 50W.

    before answering that questions, i need to ask you another one first..

    how are you planning on cooling 14x3W LEDs :) you are going to need heatsink + fans. remember my design above is missing the heatsink. i wouldn't be able to use as many leds if they were 3W. could maybe do 5 at most.. let me know.!nmmm

    I've got 2 heatsinks for new Intel i7s laying around I thought it would be alright for a test and monitor what kind of temp I'd be getting

    you need more surface area than a cpu heatsink. smtg like this instead; http://www.ebay.com/itm/Aluminum-Heatsink-Cooling-...

    this one can handle 8x3W LEDs. look at the size difference.. the back of the leds should contact fully with the heatsink, it cant just be on the fins like with the cpu heatsink..

    I've got some aluminium and copper sheets. I was thinking about stacking them up with spacers as a makeshift heatsink and those two CPU heatsinks with fans on top.

    Take care when applying what you've got on hand to a modified design. The author is right, you'll likely need one of those CPU heatsinks for EACH of your 3W LEDs if you really want to get a good life out of them, or a heatsink with a lot more surface area and a bigger fan for the whole set of LEDs.

    If you plan to monitor temperatures, it's VERY easy to be deceived as to the true temperature of the LED chip inside that little package-the temperature that actually matters. Any amount of material or distance between it and your sensor, or even an oversized temperature sensor, will give you misleadingly low readings. Though you can account for it using simple formulas if the thermal resistance of the parts is known (which must also include the star board the LED is mounted to). The base of any heatsink larger than your device should be somewhat thick to help the heat spread away from your emitters, and fins on the back are even better. Keep in mind that thin sheets will be terribly inefficient at spreading heat in comparison.

    how thick are these sheets, and why the spacers, if anything they should touch each other and create more mass to sink heat. honestly 700mA each x 14 is going to be very hot. check this out, this metal sheet is 3.5mm thick (picture2); https://www.instructables.com/id/The-Plant-Shelf-li... and look how far the lights are seperated.


    3W leds create a lot of heat, this is how much heatsink a single one requires (picture1); http://www.ebay.com/itm/1W-3W-LED-Aluminium-Heatsi...

    this is why i always stick with 1Watts. when there is no proper heatsink.. you need to be careful. from what it sounds like you will be pushing everything to the limit. i'm going to go ahead and say that you need a good heatsink with 3Watt LEDs especially..

    Screenshot 2015-05-02 at 6.53.56 PM.pngFBB3YF9HWH10LK6.LARGE.jpg

    thank you very much for sharing your knowledge. i really appreciate your time.!

    Awesome thanks :) I'll keep you posted.