Introduction: LED Plant Growth Light

Picture of LED Plant Growth Light

My LED plant growth light has been an effort in my new found hobby; gardening.
I have been extremely intrigued by the whole urban gardening movement, and my
dream is to help bring it indoors. So here is the part of my efforts that involves LED's.

Step 1: Tools & Materials

Picture of Tools & Materials

(A) Soldering Iron
(B) Cutting pliers
(C) Breadboard

(1) LED's, lots of them. (Ive been using these: white, blue, and red ones.)
(2) Resistors ( I have changed resistance as needed.)
(3) Solder
(4) Wire
(5) Circuitboards (Size depends on how many LED's you want use.)
(6) Power supply components
(7) Spray on Insulation (Optional)

Add some patience and imagination, and you'll be one your way to create something
 awesome with your own two hands.

P.S. Don't forget a hammer and some elbow grease to get you out of the tough spots.

Step 2: Breadbording

Picture of Breadbording

It probably does not need to be said, but always remember that your body can be
very conductive with the right accidental conditions. Always respect any electrical
safety guidelines that you've learned. If you don't know any, goandlearnsome.

I always like to check my LED and resistor combinations with my breadboard.
It ensures that not only the LED's and power supply are in working order, it will
also allow to tweak with your resistances before you commit to soldering. My first
LED light uses a total 34 LED's. I chose to use 12 white LED's, broken up into 4
strings of 3 LED's. Each string has a 220 ohm resistor soldered to the anodes
of the LED string. Same goes for the remaining 3 blue, and 3 red LED strings.
However since i used 11 blue and 11 red LED's. Their strings had to be two 4
LED, and one of 3 LED, strings for each color.

Once you've verified your components, you'll be ready to move on to permanently setting
those components on a circuit board of you choice.

Step 3: Chosing Various Paths, and Soldering Them.

Picture of Chosing Various Paths, and Soldering Them.

Now that you've got working components its time to decide how to lay out your
components within the confines of your chosen circuit board. I should also mention
that being able to etch your own PCB design probably saves a lot time and second
guessing. I however lack that skill still, so I decided to use the leads from my LED's
and various other components to make the solder connections.

I setup my power supply first, making sure to keep the components close together
and well aligned to limit any wires crossing that should not cross. But also leaving
enough space for the resistors to fit as well. Make sure that the components are
connected in the right order like when you verified on your breadboard. Once you made
your layout decision, you're ready to solder the power supply into place.

Now your ready to lay out your LED's according to the strings we verified in our
breadboard. Figure out the most efficient way for all the LED's to fit in the circuit board
string by string. Once you've visualized where the leads are going to fit your ready 
to cut the excess leads and solder the components as you see fit. Remember to solder
the anodes to the resistors and the cathodes to your negative  coming from your power
supply. This is the step that requires much patience and imagination.
Once you've got your first string soldered, run power to it and make sure it lights.
This step is probably unnecessary, but it sure saved me a lot of second guessing.
I powered every string after I soldered it, this is how I noticed that I had flipped an
LED so it was not getting power on more than a few occasions.

Keep soldering until you run out of the strings of LED's that you prepared previously.
Once you finish those you pretty much have your finished product.

Don't be afraid to play around with your lay outs prior to soldering them. As you can see
on my both my later light versions I took some very different paths. Use both sides of
the circuit board; that doubles your working area and makes your lead runs much cleaner
and less likely to cross and short circuit your design.

Step 4: Finishing and Enjoying Your New Light.

Picture of Finishing and Enjoying Your New Light.

Well now that you are finished with soldering and you've verified that you haven't crossed
any wires its time to doll up your new light. I decided to use a spray on insulator to add
protection to my bear leads. This will also block light from escaping upwards and therefore
your plants get more photons to feed on. Ive also looked into adding Mylar around my clay
pots to have more photons bouncing around the plant. But be careful to not make the Mylar
tube too tall for you risk reducing the plants air supply.

Or you can even start using your light as is. I guarantee that the results will impress you
and your plants much more than you might expect. I have been growing Jalapeño plants
for a bit over a month and a half in some potting soil with some very impressive results.

Step 5: Update!

Picture of Update!

Here's a few more pics of the progress Ive had. As you can see, Ive cleaned up alot of the clutter and moved the lights up the ceiling. Everything is much easier to clean and more accessible. 


psachdeva3 (author)2015-10-05

i wanted to ask does that light really increase plant growth or was it just for fun.

thrudd (author)2014-05-13

This is a very old instructable. For anyone interested on trying something similar but more up to date I suggest to use your Google-Fu with the key words [ led driver ic constant current ] and check out the chip manufacturer suggestions for DIY circuits.You also could just pick up a prebuilt module for a few bucks if you are not so adventurous.

Akin Yildiz (author)2014-04-29

I believe that if we carefully place single 1W high power LEDs at precise angles, we can penetrate the hidden under leaf parts of the plants better. check out my designs..

arnookie (author)2011-04-26

If you are thinking of building a diy grow light please take note of this.
Each and every led needs to be atleast 1watt each. Anything below that will be useless so don't use old leds out of toys or old boards, they simply will have too little Total lumens versus lumens per watt. You need atleast 10mm LEDs with 1watt per LED to supply enough light to the plant anything lower will not work. A good combination is a pannel made from 75% 1watt red high brightness leds, 20% 1watt blue high brightness leds and 5% 1watt amber high brightness leds. somewhere in the region of 660nm for red and 460nm for blue
There is also no effective difference in penetrative power for horticultural purposes between a 1W LED and a 3W LED. So anything over 1watt is just wasted. This means brightness has very little to do with the benefit you will get once you use 1wat leds. Don't confuse this with a pannel made from say 20 LEDs rated a 10watt as to one with 10 LEDs rated at 10watt. As the 20 watt pannel will use the useless 0.5watt leds verses the 10watt pannel that uses 10x10watt 1watt LEDs that are ideal. This has been tested and proven that 1watt single LEDs have great benefit to plants and anything less is just a waste of time and has no benefit at all to plants. The same applies with going brighter than 1watt has no benefit either.
Hope that may help some of you. Especially if you are growing indoors.
Also LEDs are more efficient than any other form of grow lighting available.
The commercially available LED growlights outperform all other growlamps from HID lamps to including high pressure sodium (HPS) and metal halide (MH) lamps.
So prepare to see other grow lamps become obsolete as LED growlight take over.

Surferdude (author)arnookie2014-02-17

Would you please provide your source for the info above? Given approximately the same luminous efficiency (not efficacy), 10W total should give you the same light output regardless of the power rating of the individual LEDs. The high power ones (1W/3W/5W) just seem to be heavily heat-sinked, not some special design. The light density depends upon the power as well as the half-power angle (angle of spread). Why can't you just put the 3W higher up than the 1W to get the same amount of light per sq ft?

I've also seen different info on ratio of red to blue. The research I saw said something like 200:1 of red to blue and cited two different red wavelengths that need to be included for best results.

hanlin_y (author)2012-02-05

I understand that we have to be careful around electricity. When electricity is near water, you should plug it into GFCI outlets. If your indoor garden does not have GFCI outlets, you can get GFCI extension cords. Depending on how hot your LED's run, it is not a bad idea to add a tip over sensor so it turns off when it falls over.

I really want an LED grow light too. I just ordered some 3W royal blue and deep red LED's. To make it simple, you can use flexible clamp lamps for LED's that fit standard fixtures but this method is bulkier and more expense is needed.

jexter (author)2011-09-26

Are you sure you're clear on the concept ? Because I think you may be more at home at www.wherecanibuyoverpricedcrapicould  

Just sayin...  ;-)

CidlyLydia (author)2011-08-15

good, you have a great yield

mr_man (author)2011-01-08

Good Job! If my tone sounds critical, I apologize in advance. I just want to share some information with whomever might read this. This is just free information.

If I build a LED grow-light I will do a few things differently. For anyone considering a similar project, here's what I would recommend:

1. The most common Red LED is made of GaAs and has a wavelength of 625 nm. This isn't bad, but it isn't ideal for plants. A "super-Red" or "deep-red" LED emitting a wavelength of 660 nm is better (FYI the LED material will have "Al' or "P" in addition to the "GaAs") . These are harder to find, and may cost a bit more, but in theory they are worth the trouble to obtain. Order from a site like or or even where they actually list the wavelength and other useful spec's.

2. Use high-brightness LEDs that can handle at least 700mA to 1 Amp of current or more, because they put out a lot more light for the money.

A note on heat... Make sure the thermal pad on the LED is *soldered* to a copper heat spreader that you have first tinned with solder. For a surface-mount part, you will have to use a hot-plate or frying pan, or hot-air gun, or oven to reflow the solder. The Cree website has pdf documents on how to do this. It is often easier to just buy high-brightness LEDs that come pre-mounted on a hexagonal "star"-shaped circuit board with mounting holes and everything. These typically have an aluminum core, which makes an excellent heat spreader, so then you only have to put heat-sink compound on the back of it and screw it down to a heat-sink, or you can just epoxy the whole thing down semi-permanently.

2. Use a higher voltage power supply, like 12 or better yet 24 volts. This allows you to put more LEDs in series. Since so you can always guarantee that all LEDs in the string are carrying the same current, less resistors are needed. The whole thing will be more efficient, and produce less heat, and keep your electric bill down.

4. The voltage regulator probably isn't necessary, even if your power supply is "unregulated". You can probably get away with using smaller resistors if you just add up the voltages of all the LEDs in a given string, and adjust the number of LEDs per string to get as close as possible to the power supply voltage. To do this it helps to mix and match LED colors in the string, just make sure that you don't exceed the LED's current rating. Ohm's law says that the resistor value in ohms that you should use is:
R = (Vs - V_LED) / I_LED

Where Vs is the power supply voltage,
V_LED is the sum of the LED voltages in the string, and
I_LED is the current in amps that the LEDs are rated for

If V_LED is just slightly less than Vs then you will only need a very low value resistor, like 1 ohm or less, assuming a 1 amp string. You shouldn't need to drop more than a volt or so across the resistor. If you're dropping over 2 volts, why not just add another LED instead?

Just calculate the proper resistor value for each string, and after you've built the circuit, measure the current through each string with an ammeter to make sure the current does not exceed the LED's spec.

I hope this helps. When I get organized enough to build a light-source and take photos, I'll try to put together an 'ible.

5Volt (author)2010-09-07

I suspect that all those capacitor in series with the supplies (both at the "in" and the "out" of the regulator) will prevent the circuit to work : you probably want to mount them in parallel, from the pins to ground.
The diode also seems to be reversed.
Three white LEDs can be powered from 9V directly witha few Ohm resistor in series (220 seems a lot). The same for blue LEDs.
Also, same type LEDs seems to receive different current...
I suspect your schematic needs some clean up !

JardineroUrbano (author)5Volt2010-09-07

Thanks for the comments, I was just attempting to make a schematic from the way that this certain power supply I'm using is being bread-boarded. I'm by no means an expert, just an overtly curious tinkerer. But you are correct the caps do need to be parallel to the pins an ground on the regulator. I just wasn't sure how to draw that. Ill try to get those and the diode fixed on my schematic when I get a chance.

I think you did a great job with this Instructable. What matters is that you got it to work and made the effort to do an Instructable. Reading schematics is hard, creating your own is even harder.
Your first schematic wouldn't have caused any harm but wouldn't have worked. Unfortunately, the second one would probably work but isn't quite correct. I am a little surprised that Adafruit didn't have a schematic with the kit.

I've included a schematic I clipped out of a Freeduino that shows how the capacitors should be drawn. For the two capacitors on the left, each one is tied to the input and to ground. The same goes with the two on the right.

Incidentally, the larger capacitors are used to filter out low frequency noise and the smaller capacitors filter out higher frequency noise. With a 9 volt battery, there is basically no noise at all so those caps aren't necessary. On the output side, there's only LEDs so again the caps aren't doing much.

By the way, if your 7805 gets pretty hot you can add a heatsink. That's what the little hole is for. You can bolt on a heatsink from Radio Shack or make your own from a piece of metal

Keep up the good work.


Thank you very much! Your example schematic makes so much more sense; Its much clearer to understand. As for Adafruit not having a schematic of the power supply, its not quite true. I know there was one at one point, which was included on a very handy walk-through of how to build the power supply. I however have not been able to find it again. I have to go check the internet way back machine to see if I can find it there. I'll update the instructable if I ever manage to find the web page again.

I'm glad I could help. Many people have trouble going from schematics to wiring components and vice versa. I've worked in the electronics/computer field for 25 years so it's pretty easy for me.
I'm planning on making some Instructables on basic electronics for the Arduino, I hope I can get them done.

It's easy to find your web page. Just go to and type in
LED Plant Growth Light
in the search box.


Oh... LOL I actually meant I'll update my instructable if I ever manage to find the Lady Ada/Adafruit instructions i used to build my power supplies. I can understand why you would think I meant otherwise, sometimes my command of the English language isn't quite what it should be. Thanks very much for the help either way though.

You can't just draw up a schematic that's wrong and say "I wasn't sure how to draw that." Someone could spend a lot of time and effort mocking up that schematic. If it doesn't accurately represent the circuit you're intending it to, then please REMOVE IT, before someone wastes a lot of effort actually USING it. What good is it if it's not right, anyway? Just for show? Come on! Either fix it, remove it, or at the very least add a disclaimer saying that it's WRONG and shouldn't be followed!

I just put it up as a request, I meant no Ill will or intention. But if you follow the original bread-boarding instructions from the Adafruit website; It should have prevented anyone from that problem. 

That's fine, but the whole point of creating an instructable is that people will be following YOU and your instructions, not instructions on another site. If your instructions are wrong, including the schematics you post, then you are leading people into making a mistake. Faulty schematics are not a help to anyone. I'm sure you understand that.

Well, why don't YOU show us how to draw the proper schematic?

I don't have to, because I didn't write the instructable. That said, it's an easy fix, and if I had the time I WOULD fix it. The capacitors are supposed to be in parallel, not series. The point is, he's aware that the schematic is wrong, so he should either fix it, or remove it, before it causes a problem for someone who relies on it to build the circuit. Can't you see why this is a problem? In fact, when dealing with electrical circuits, a mistaken schematic could cause a serious safety hazard. In this case the voltage/current is low, so the worst-case scenario is that someone's time and effort is wasted, but still... have time to peck out a longish reply here.......

I type fast.

Hahaha. Great thread.


Hey there, my updated schematic is on step 2.

But here it is again, just in case.

JardineroUrbano (author)2010-09-05

Any questions or comments are appreciated. Also be on the look out for more Instructables coming soon. They will all show the progress I'm making to accomplish my indoor gardening system. Stay tuned! ;-)

Good instructable...and i admire your equanimity in handling the criticism

Beta_Orionis (author)2010-09-09

Are you familiar with wire-wrapping? It's a very clean solution to soldering across generic pc boards and much easier to fix later (swap out dead LEDs etc.)

Wow that is neat! I was not aware of this technique, thank you very much for bringing it to my attention. It will come in very handy for me.

No problem! Enjoy. :)

Owlbear (author)2010-09-06

my question is... how do you get enough UV from LEDs? most plant lights are specifically meant o deliver more UV than normal lighting.

Exitao (author)Owlbear2010-09-11

I was wondering about the need for UV myself.

They do make "UV" LEDs, BTW... I have a tiny LED flashlight intended for checking currency.

ml4d3n (author)2010-09-09

Hi friend, I am very curious about this tehnique, and want to know if this is used only overnight, and does the plant need some time in the dark?? And also, why did you use this color combination? Is it the best for the pant or you just like it?

JardineroUrbano (author)ml4d3n2010-09-10

I leave my lights on during the day, generally from anywhere between 7 am to 10 pm. They do spend some time at night in the dark too. And as for the color combination, its just what I ended up picking from my research. Both blue and red are the the most efficient wavelength for plants. And the white is to attempt to provide a more complete spectrum. (comparatively to the sun's spectrum.)

jimmiek (author)2010-09-10

I don't see the schematic all the 'electronics experts' are complaining about. The reason I ask about this is that I'm an electronics iggnoramus, so I'd like to do this thing right ;) I've been wanting to find a good schematic for doing LEDs for my aquaponics system. I guess you have to go PRO to get the schematic, huh? I'm too poor and too cheap to go PRO!

JardineroUrbano (author)jimmiek2010-09-10

Hey there, my updated schematic is on step 2.
But here it is again, just in case.

Nate Ocean (author)jimmiek2010-09-10

Yeah, this is becoming a chronic problem with Instructables...most of them are "crippled" with the constant "nags" to upgrade to PRO.

What a shame, it used to be a nice web site. Some of the stuff lately is just incompetent junk.

adamlight (author)2010-09-09

I had looked in to this a while back. From what i remember, you should have more red LEDs than blue. A ratio of around 3 or 4 red to 1 blue is good for most plants. Different plants will need different mixes of light. I never read anything about mixing in other colors or white. Also, 10-25 watts per square foot was recommended to really get things growing. You do need more light to grow fruit and veggies.

kea (author)2010-09-09

For some reason White LEDS have a shorter life than other colours.
I would use self adhesive LED light strips ,these have the resistors built in.
Wire them in parrell.
Also different coloured LEDS have different voltage drops.
Cheers Kiwi John M

macrumpton (author)2010-09-09

I was wondering if just getting a couple of strings of LED Xmas lights might be a readymade alternative to this.

I have seen strings of 100 LEDs of various single colors as well as mixed colors on ebay for $6.50 including shipping like these:

To make the LEDs point in the same direction a piece of thin plywood or even cardboard with holes big enough to stick the LED sockets through would seem to be ideal. The cardboard option would let you easily make a curved panel with the LEDs pointing inward toward the plant for light from all directions.

Saprobic (author)2010-09-09

I have been growing plants with some LED arrays I made for a while now and don't let the theory confound the practice. Although by the textbook you will only need red and blue each plant is different and they do use the whole spectrum for various queues. You will find that with a heavy blue load you will get good vegetative growth and poor flowering. More red will increase flowering yet in both of these cases most plants will produce poor fruit. I started to get some better results by adding in some amber (The intent was to stimulate beta caroten production). I was going to add some white next to see if some other secondary metabolite production or growth queues might change.
Also I found I have much better success once I enclosed the growth chamber and covering all interior surfaces in reflective or white background.
Keep up the good work.

tubesman (author)2010-09-08

I hope your White LED's are there so your plants look pretty. They are not worth much for photosynthesis. Plants only use Red and Blue.

fegundez1 (author)2010-09-06

Why use white? Your plants will make the most of red, blue, and some orange lighting. Most important is air! It would seem obvious but this part is what has killed more seedlings than any other thing, at least in my experience. I have been using LED for seedling and small plant/ clone light for a few years now and I have found that long days and air,air say it again air! is what keeps it good of course, you also need to monitor the water as with a breeze going on there will be a little evaporation. I use a pc fan in an area like the one you have there and it works fine. I have cloned a lot of rare plants for my mom who is out to save the world from plant extinction and this is a great way to do it. Good luck with your gardening.

Thanks for the tips, always good to have plenty of air circulation around your plants, they can eat up the co2 they need to photosynthesize way quicker than you think. As for the the white LED's, well I have read many people's claims that plants only need a few certain wavelengths. And while I cant completely deny some of those claims; I believe that trying to get a fuller spectrum, as in the sun's spectrum, would give me better results. I even have plans of adding a few IR and UV LED's in some of my next designs. BTW, keep saving those rare plants! We need more people to think that way. Plants have so much to teach us, and humanity is just throwing that knowledge away....

don't use ir lights they can actually cause damage to the plants. I have some led charts i will send you, keep growing

OverSaltedFry (author)2010-09-06

Well first things first picture 4 in step 3 immediately reminded me of a light bright which really brought me back! That aside, i like the idea and the fact that it's a fairly cheap light to make however a schematic would be nice. I think you should also do a controlled experiment to see just how well your light is working, maybe set it up in a closet and compare in a few weeks.

You are in luck my friend, I was actually working on a schematic. I had just decided to post this instructable ASAP due to the LED contest. ;-p
I have updated step 2 to include the schematic. Though Ill warn you, I'm still a bit of an amateur.

P.S. I did think of using a closet, but honestly I was afraid of forgetting the poor plant in there for way too long. :-o

About This Instructable




Bio: Hey there! I'm an industrious technological hippie. It may sound like an oxymoron, but really its not. I am an overtly curious tinkerer, so ... More »
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