LED Plant Growth Light




About: 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 I love all kinds of technology. But I also have an immense respect ...

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

(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

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.

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.

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!

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. 



    • Tape Contest

      Tape Contest
    • Arduino Contest 2019

      Arduino Contest 2019
    • Trash to Treasure

      Trash to Treasure

    49 Discussions


    7 years ago on Introduction

    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.

    3 replies

    Reply 5 years ago on Introduction

    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.

    The FreakSurferdude

    Reply 6 weeks ago

    He has commented this nonsense in other LED growlight posts. Please don't follow his advice, plants don't care about wattage, they care about photons, i.e. lumens. The only thing that matters in terms of efficiency is the right wavelength output and efficiency of the led in terms of lumens per watt of these wavelenghts.

    SurferdudeThe Freak

    Reply 6 weeks ago

    I built my grow lights using 3W LEDs. There are 342 LEDs arrayed in a 1 meter square grid. I used about 45% 620-630nm, 45% 660nm, and 10% 450nm LEDs. Since 3W LEDs are not really 3W, it actually uses something between 300W and 500W, depending upon what current you drive them at (I use 600mA - 700mA). A grid with fewer LEDs doesn't seem to be as successful. I got the constant current supplies from Aliexpress for $8-$10 ea. While I like building my own stuff, at some point I had to trade cost for time to get these done. Soldering that many LEDs already takes a LOT of time. The aluminum racking acts as a good heat sink. I used heatsink paste to improve the heat dissipation to keep the LEDs cooler.
    3W LEDs seem to be the sweet spot in terms of price per watt. Plus, having them arrayed on a grid to cover a square meter means that the light is penetrating better because it hits the plants at all angles.
    Plants don't care about lumens. Lumens is not the same as photons. You need a PAR meter to get the true brightness of light from a plant's perspective. The scale of lumens is weighted in the green region because it's intended to determine brightness according to the human eye. If you use lumens, a green LED will appear to be brighter than a deep red LED, even when they provide the same quantity of photons. Photons toward the red end of the spectrum are cheaper to produce in terms of electricity, and they are closer to the wavelength that activates chlorophyll directly without intermediate reactions.


    3 years ago

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


    4 years ago on Introduction

    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.


    7 years ago on Introduction

    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.


    7 years ago on Introduction

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

    Just sayin...  ;-)


    8 years ago on Introduction

    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 digikey.com or mouser.com or even superbrightleds.com 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.


    8 years ago on Step 2

    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 !

    8 replies

    Reply 8 years ago on Introduction

    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.


    Reply 8 years ago on Step 2

    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 Instructables.com 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.


    Reply 8 years ago on Step 2

    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!

    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.