Growing Plants With LED Lights




Posted in TechnologyLeds

Introduction: Growing Plants With LED Lights

In this instructable i shall be demonstrating how to grow small plants under the glorious glow of LED lights. Woop!

Step 1: Introduction

First and foremost...Hullo!!
This is my first instructable (long time reader, first time "actually-post-anythinger", i should be revising for exams, hence i have done this instructable!), any comments and criticism is greatly appreciated.

This instructable will demonstrate how to grow small plants under LED lights.
The idea for this came from an odd source, a friend of my step fathers recently had to run away to a different country because he was caught purchasing large quantities of lights from electrical stores for growing some none-too-legal plants indoors.
I don't condone this in any way, by all accounts the man was an idiot. But it got me thinking about ways to grow plants under artificial lights,after a bit of thinking and a lot of googleing this project was born!

A bit of theory:
Plants look green, therefore they reflect green light, so it probably isn't used in photosynthesis or any of the other interesting things plants do.
So hopefully by using red and blue lights (the colours either side of the spectrum from green) we should be able to keep plants happy and use less energy because where not producing green light which would just get reflected.

(apologies in advance, i cant seem to be able to get the image tag thingys to work, i will try and explain images as best i can.)

Step 2: Materials

This instructable assumes you have experience with soldering, and have some basic knowledge of electronic circuits. There are instructables elsewhere that should be able to teach you some of this stuff.

Things you will need:

A Tub (Twiglets not required, but reccommmend on grounds of deliciousness)
A smaller tub to grow things in.
Tissue Paper
Strip Board
High Brightness Red LED's (number depends on size of tub and brightness, try some experimenting)
High Brightness Blue LED's (you'll need fewer of these.)
Misc. Seeds (Experiment with different kinds. cress works well)
220 ohm resistors
A power supply (A bech top variable one is highly recommended, although others will work)

(apologies for the shocking quality of the photos. i'm a poor student and cant afford a decent camera)

Step 3: Construction: Soldering the Leds

There are a couple of ways to do this, in past experiments i have just drilled holes in bean cans/tubs then glued LED's in place and wired them up by soldering wire between each one.
In this incarnation i have chosen to build 3x3 LED "modules", in the image below is a very quickly scrawled diagram of how the LED's are wired on the pieces of strip board.

Once each module has been built they where wired in parallel to the power supply.

.......i wish i was better at explaining this.
basically, as long as you have enough light coming from the LED's and you are comfortable with the way they have been wired, and most importantly nothing explodes or smells funny you should be ok. It's pretty simple really.
Whatever you do, don't forget to include some form of current limiting resistor, if the first year and a half of my electronics degree is anything to go by, they seem rather important.

With the size of my tub i chose to use a 3 3x3 LED modules, giving a total of 27 red LED's, and only one blue LED.

Why only one blue LED??
After a bit of googleing sometime ago i stumbled on a (i think) NASA project to do with growing plants under LED's, and they said you need a lot less blue light than red, and a biologist friend of mine confirmed this....and that is why there is only one blue light.

Step 4: Construction: Erm.....constructing It!!

This step is fairly straight forward.

Take the glue and haphazardly glue the LED's to the lid of your container of choice then plug it into a power supply and hope nothing blows up

(DISCLAIMER: its not my fault if anything blows up.)

when nothing does blow up let out a sigh of relief and relish in the futuristic glow of your new LED grow light system!

(Note on voltages: for the set-up i'm using i found that 7 volts was adequate to light all the LED's and for nothing to get too hot, and for the current consumption to be adequate. YMMV. i strongly suggest using a variable power supply to find the optimum voltage.)

Step 5: Using It

Now for the best bit, actually using it.

1.)Place the tissue paper in the small tub and dampen with water, then sprinkle a few seeds ontop and place inside your LED growing tub.

2.)tun on.


4.)eat delicious plants!

depending on what your growing you may need to transplant the seeds into a better growing medium once they have germinated.

During my first attempts at growing plants under LED lights, i grew cress in a bean can, and used a PIC microcontroller to turn it on and off every 12 hours, this produced failry good results, the cress grew quicker than some placed on my windowsill.
After reading around a bit on the internet (whether you agree with the use of a certain herb which is currently illegal in the uk or not, the people who grow it tend to be very knowledgeable on plant cultivation, and have a wealth of experience in growing plants under artificial lights) i found talk of keeping lights on for 24 hours during vegetative growth stages, then encouraging flowering by switching to 12 hours on and 12 hours off during, i don't know if this applies to all plants, but i shall be experimenting.

I'm still playing around with this so any suggestions/improvements are greatly appreciated, and if anybody decides to do this themselves (i hope you do, its great fun) i would love to hear about your results.

Step 6: Update! Thigns Have Grown.

Below is a photo of a little spinach sprout that has been germinated and grown a few leaves using the LED lights.

Having sprouted a few plants using this system i have transplanted them over to some compost on my windowsill as I didn't think my bench top supply would be too happy running 24/7.

I've picked up some odds and ends today now my student loan has come through, so hopefully within the next few weeks I'll have a larger system set up with 3w LED's and some nice microcontroller control, and quite possibly an instructable documenting it all.



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    Can I use strong White LED's?

    The LED grow light market is expected to rise to more
    than $1.9 Billion by 2020, growing at a Compound Annual Growth Rate
    (CAGR) of 26.93% between 2015 and 2020.

    All you pro's sure cleared that up!


    poor student? With those tools you don't look so poor :D(jk)

    thanks for the awesome guide!

    How are the results so far? From the images I noticed that you could also get rid of 2 of your 4 blue leds to make it a bit more energy efficient. And I think the first one may need more Red leds. to keep a plant of that size going.

    Hi there! Awesome project but grainy pictures. I am a student too, so I can totally understand (Check out my instructables they've got the worst photos :P). Anyway not straying away from topic, I am doing a similar project with LEDs.

    I don't know much about electronics (Mechanical Engg) so please bear with me. Last week I went to the electronics market and some guy there told me to use a 47k ohm resistor in series with one LED and hook it up to a 220V AC supply (from the wall). I did that and it works!!! But unfortunately it works only for 3 LEDs max (in series).

    Now I want to use the AC power supply to light up about 40 LEDs and I don't want to use a transformer (Again, not possible on student budget :D :P). Can you give me a minimalist circuit diagram and if possible parts list to get this done.

    Please can you tell me what values of resistors I am supposed to use so that I can light up all the 40 LEDs brightly.

    Thank you for your instructable and thanks in advance for all replies

    4 replies

    Bhai yeh wala bhi try karke dekh. They have them on higher wattage too.

    But this is all for just the experiment, if you are planning to actually grow bigger quantities of harvest, I recommend that you grow for LED grow light panels or bulbs, which are easily available online and are much more cheap and energy efficient. Just hooking up a blue and red led is good for the project but market available products have a very finely tuned frequencies of the red and blue on the light spectrum. For a specific crop you would need a specific light frequency for optimal growth. And do not forget to turn of your lights for at least 4 hours, the plants do need to sleep too.

    Rajath you could go for Led strips, they are cheap enough. Depending on the size for your grow bed and the type of plant you want to grow you need to measure out the length of the strips, like if you plan to grow a bed the size that Hitch has used, I don't think you would need any more than 1 a meter of red led strip and probably 1-2 blue single leds. Just hook them to 12 v power supply. You could also use a potentiometer to control the intensities of the lights.

    The typical LEDs have a forward voltage of about 2V, so with 220V you should be able to light quite a few of them :)

    However, a transformer will actually cost less than the LEDs (you could use a 5V USB phone charger as your power source), and eliminate a lot of headaches...

    @Hitch: Nice one bro! Just in case you have some more cash to spare, do check for an arduino comtrolled automatic light switches and watering system for your potted plant.

    Growing planets under artificial lights is very informative and new for me, thanks for your conrtibution

    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.

    Just to clear a point up. If you make a 100watt pannel with 100x1watt leds you will benefit. But if you use 200 0.5watt leds to make a 100watt pannel it will not benefit the plant at all. The same applies if you use say for eg 10x10watt leds to make a 100watt pannel then you are only really getting 10watts overall because the extra 9watt per LED is just wasted as the plant will not benefit. SO using 100x1watt LEDs will benefit the plants by 100watts. 10x10watt LEDs would not because 9Watt of each led is just wasted giving the plant just 10watt of usefull light. Sorry but thats just the way plants absorb light.

    4 replies

    you sir have just tought me alot about leds and growing thank you

    Just so you know some of his claims are incorrect. The 'sweet spot' 1W thing is not even close to being true. It's all about lumens, a big 10W LED will do much better than a single 1W LED (given de 10W has a higher lumen output). What might be true though is that 10 times a 1W LED bulb is better than a single 10W since it's probably more efficiënt.

    it has absolutely nothing with lumens.... lumens is a measurement of brightness... plants respond to spectrum... which leds outperform ... the fact that i can get the same spectrum as the sun in an LED light as i would a light that is 1000 watts is amazing..

    True, they should have the right spectrum. Completely agree on that. But you can get the right spectrum with small about 3 5mm LED's, why not just do that then? Power would be about 0.14W, done you can grow a tree in the basement. See the problem here?
    For your information, the sun has an irradiance output of 1000 W/m^2 where I live (AM1.5 standard). Photosynthetic efficiency is between 0.1 and 8 percent ( of which 47 percent is due to the wrong wavelength. So uptake of energy is between 1W and 80W of energy. Note that this is not the energy of LED's you would use, since they convert about 75% to heat.

    In conclusion yes they do respond to spectrum, this is important. But they also need the right amount of that light, i.e. enough lumens.