Picture of 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!
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Step 1: Introduction

Picture of 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.)
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rajath1 year ago

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

BogdanS1 rajath1 month ago

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...

BogdanS11 month ago

As the image comment states, you will want to put separate resistors for each series of LEDs (one resistor per 2 LEDs, in this case). The reason is detailed here:

Short version: it helps prevent the LEDs from burning up :P

arnookie3 years ago
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.
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.

You are very welcome. Hope it helps and hope your plants grow beautifully. :O)
SavoJr arnookie2 years ago
Sorry, i have to disagree on this:

"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."

That claim is just ridiculous.

plants dont care how many watts the light bulb is.. the plant cares about the SPECTRUM the bulb is producing.. and 1W red LED produce 5500k just like novemeber skies... and 1W blue LED give off the summer days of 2700k so i can get that and spend no money on energy costs hardly..? thats the point.

i recently bought some 10 mm LED's, and ive been staring at the back of the package trying to find out how many watts they are... I don't know very much about electronics or anything, so how do i find out how many watts they are?

Watts = Volts x Amperage (as an electrician, I'm oversimplifying a bit there, but its close enough), convert milliAmps or milliVolts up to Amps and Volts by dividing by 1000. For example I have a high intensity white LED which runs at 3.5V with 25 mA current draw. Using the above equation, this LED is 3.5 x 0.025, which equals 0.0875 W, not even half a watt.


This information is very interesting. Can you suggest a reference for the power ratings that the LEDs should have? I don't mean to seem as if I'm challenging you. I just want to learn more about this.

I was thinking of trying to build grow lights myself, but it doen't seem worth the trouble after looking at the grow lights available on

Yes it would probably be cheaper to buy the grow light ready built. Especially if you are wanting quite a large one. The cost of led bulbs 1 watt and over is still very high, although if you can find Leds cheap then just make sure each led is individually above 1watt. The only benefit of going above 1watt is if you want the lights further away from the plants. Be very carefull regarding pre built grow lights as they are often not made with 1watt Leds. So always check with the seller before buying.
Hope that helps you.
Akin Yildiz11 months ago

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, How Could the plant know whether the light is coming from from 10 -10W or 100-1W LEDs ? Total lumens is what counts,but there is a limit to how much light the plant can absorb. I agree that the small LEDs are too inefficient to work well,but above .5- 1W it's all the same. ( I work in the electronic lighting industry & have a small farm.)
RoninVj2 years ago
About how long did it take for your seeds to sprout?
(removed by author or community request)
Dude, do you have a computer that just types your thoughts or something?
flourescents put out more light in general, but a large amount of light in spectrums that arent used in photosynthesis. So by using red and blue leds in the 660 and 450 spectrums creates just the right lights for what they need. So LEDs = less light Flourescents = less usable light, w 4 w.
xtank57 years ago
You could make money selling (totally legal) food plants to other students. Seeming as how the grow faster you could make a new crop faster and if you make enough of these and started growing a certain intervals you could in theory have a fresh crop every week and then all your classmates and dorm buddies would be begging you to give them a discount for bing your friends on all your carrots, and chili peppers, and maybe even tomatoes. Yummy tomatoes. :) And since the plants are grown indoors the could be grown organically without pesticides or fertilizers (maybe). I reallly like it! If I could I would give you a +10! Keep up the good work.
aydonis xtank53 years ago
My niece and I have done this. I purchased some organically grown Roma tomatoes more than two years ago. I got the idea to scoop out and save the seeds. I was pleased to find out that these seeds are highly fertile. Every single one has germinated, and they're over two years old and still germinating just fine. I'm getting my last batch off now. The last three springs (including this one I'm working on now) I have been able to give my niece enough baby plants (germinating and growing through youngest stages in my condo windows) for my niece to make a little money for summer. She takes them door to door and sells for $3 / plant. Last year she made 50 -60 dollars, not a bad profit for something that cost me about $5 for the tomatoes and another $10 for topsoil. Tomatoes are also incredibly easy to grow... they don't mind too much water, so I can drown them before I leave on business trips and don't have to worry about them running out of water while I'm away. I've come back to find them wilted and near death before... one healthy dose of water and within a day they were healthy again... except two little guys that dried up and died =(
if one were to do that, gibberilic(no idea how to spell) acid and some Miracle Fruit seeds would be a good could sell miracle berries for a pretty penny

}{itch (author)  xtank57 years ago
god knows i could be doing with some more cash right now :) the only problem is with this system on a large scale is it would cost quite alot to set-up, the LED's come in at around 20pence each so to make an array large enough to grow large plants could become rather costly. Also there's the energy consumption to think about (also the environmental cost of producing the energy, when the suns freely available to grow stuff anyway's), regardless i think thats a wicked idea, and organic is always good :) Soon as the next student loan comes through i may investigate building a larger system, maybe with hydrophonics. Thanks for the kind words!
xtank5 }{itch7 years ago
Search ebay for the leds. I found a 50 pack for about 6 dollars Canadian and the are in Hong Kong, so the shipping might be a little high but who cares? At 13 cents or less than 10 pence apiece I quite frankly don't give a darn.
xtank5 xtank57 years ago
I just checked Ebay and i found 50 5mm leds for $4 us at $6 flat rate shipping to Canada. Thats $10 or about 5 Pounds Sterling. That is dirt cheap for me.
}{itch (author)  xtank57 years ago
yeah, that's pretty incredible. you'll need to make sure they are of the super bright variety (dimmers ones will probably work, but you'll need more). i'm tempted to have a look on ebay myself now. i've begun the construction of a larger system and i think the best option for large scale would probably be to use 3W luxeon star LED's (you get a bit more bang for ya buck), the only problem is you have to build some kind of constant current source (there's an instructable on it somewhere). but 50 LED's are gonna kick out enough light i should imagine ;)
I used this Maxim app note to build a constant-current supply for a Luxeon Rebel Star. Just replace the 10kohm resistor with a 7kohm resistor for 700mA.
astrong04 years ago
What the hell is a twiglet? are they sold in the U.S.?
twiglets are like straight pretzel bits that are dipped in a yeast spread like marmite
bountycrops4 years ago
Great article! Thanks for sharing this wonderful information.
dwosullivan4 years ago
 Might it be that these ones grew better than those on your windowsill as there were warmer due to all the electrics and being in an enclosed space? 
While i'm sure some plants / drugs might be better grown under artificial light i dare say cress can survive without external power supplies!

Interesting as an experiment though!

andybuda5 years ago
just found a very good and cheep alternative to led.. prolite do a helix design energy efficient bulb in red yellow blue colors sold through cpc at less then £8 there 30 watt... es fitting
el greeno5 years ago
Do plants use any of the infra-red or ultra-violet spectrums at all? If so it may be worthwhile putting one or two of these in as well.
i know of a certain "none-too-legal plant" that uses THC to protect itself from Ultra-violet light, so suppose your growin this plant chances are you will get more THC if you have a nice lil bunch of Ultra-violet LED's(if there are ultra-violet LEDs)
As for adding extra CO2 to the container. There are several methods you could use and most have already been mentioned. However, one was overlooked. Buy a bag of Dry Ice at your local supermarket. It comes in little pellets about the size of a large highlighter cap. Store them in a small cooler in your freezer. The dry ice will usually keep for a couple of weeks like this. Take out a pellet every day or two and drop it in the container. Just be careful not to drop the pellet onto the plants or their roots as it will freeze them. This will raise the CO2 levels in your container out the roof, but don't worry, the plants will love it. This is also the cheapest of all the methods mentioned.
could you tell me more about your dry ice experience? I am in the midwest, Kansas City, Mo. I haven't seen dry ice in the grocery stores here (yet, I have never looked)\ Sounds like a great idea.
In Michigan, they sell it at Walmart. Upfront by the bagged ice.
I use dry ice occasionally in the biomedical lab where I work so I know a little about it, but I have never used it with live plants. Dry ice is nothing but pure CO2 in a solid form so when it melts you end up with only CO2 gas. Dropping a few pellets into an enclosure will raise the CO2 level to somewhere between 40 and 90%. Since CO2 is heavier than air you will need a deep container like an old aquarium. A lid will keep the CO2 in the enclosure so the plants can use it. Here is a link to find a retail source near you.

Dry Ice Sources

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