Introduction: High Power LED Grow Lights M.k2

Picture of High Power LED Grow Lights M.k2

Having played around with growing plants under LED lights before, I thought I'd have a go at building a larger system using high power LED's.

........ I do apologise if it looks like I'm flogging a dead horse, this will be my last instructable on growing things with LED's.....honest.
I haven't found any commercial units that use high power LED's (then again i haven't really looked, and I like to maintain the illusion I'm being original :) ), so i figure this is probably different enough from my other attempts to be worth posting.

I probably better say that you really shouldn't be attempting this unless you have a sound knowledge of electronics and have experience working with mains electricity. Also there will be high voltage near a damp environment, which is generally not the best of ideas.
It also uses really bright light, and can probably do nasty things to your eyes if you stare at it, then again if you can read this you probably don't spend so much time staring at the sun/bright objects, so hopefully common sense will prevail.

Basically be safe, and don't attempt this unless you are positive you know exactly what you are doing.

Step 1: Parts

Picture of Parts

Here's what you'll be needing:

1x Large Tub.
1x High current 5v/10v supply.
4x 3w high power red LED.
1x 3w high power blue LED.
2x 100K 0.25W resistor.
2x 0.47R 3W resistor.
2x BC549B.
1x Aluminium Box.
1x Mains Lead.
Some wire.

Step 2: Theory

Here's the theory behind this:

Plants are green, therefore they reflect green light, which means they don't use it for photosynthesis or anything else they might do.
If we grow plants under only red and blue lights (they colours being absorbed), then we aren't wasting energy by producing green light. Which means not only is energy and money being saved, but it looks like the plants are having a disco too. Do you really need any other reason to build this!?

This all may or may not be better explained here:

Step 3: LED Current Limiter 1

Picture of LED Current Limiter 1

LED's generally aren't the best behaved of things, they need some way to limit the current through them otherwise they have a habit of dying.
With smaller LED's its possible to just use a resistor in series, but when you begin dealing with higher power LED's too much energy can get dissipated in the resistor, and things get inefficient and hot.

There are a couple of ways to limit the current, and pretty much all of them are discussed in this most excellent instructable:
Its well worth having read through as it contains some great electronics theory and is a goldmine of information.

I'm going to be using the constant current source #1 circuit from the above mentioned instructable.
Below is the circuit diagram, (NOTE: i haven't drawn this myself its taken straight from the above instructable, i figure its ok since its under a Attribution Non-commercial Share Alike license, but let me know if its not cool)

The LED's i'm using are rated for 700mA, so using the equations given we get a value of R3 of around 0.47ohms.

I'll be building 2 of these, one to power 4 red leds in series from a 10v supply, and one to power the single blue from a 5v supply.

Step 4: LED Current Limiter 2

Picture of LED Current Limiter 2

It's time to get out the soldering iron and start making!

Solder up 2 of the current limiters on a piece of breadboard (or etch some PCB's if your feeling fancy) and test them to make sure nothing gets too hot.

note: the zener diode you can see on my breadboard eventually blew up (i don't know why but i have a habit of doing that) so was omitted in the final version.

The second image shows the circuit being tested with 4 of the red LED's in my bedroom at night with all the lights turned off. They really are amazingly bright, they lit up my entire room.

Step 5: Super Extra Bonus Step!!

Picture of Super Extra Bonus Step!!

This is a super extra bonus step for the very few people that got posted a 47ohm resistor instead of a 0.47 ohm resistor like I did, and are resentful at the ridiculous prices of Maplins and the fact it would actually involve going outside to catch the bus to get to Maplins, only to have to explain to the guy behind the counter what a resistor is, then get sold the wrong one anyway, but not realise until you get home. So the above situation repeats itself indefinitely in a ground hog day type escapade.

Enough of this silliness, here's what i did to change the value of a 47ohm resistor to 0.47 ohms.

1.) Slowly crush the ceramic type coating around the resistor with a pair of pliers, don't scrape it otherwise you'll damage the very fine wire.

2.) Once all the outer coating is removed unsolder the fine wire from one side of the metal end caps.

3.) Make a connection straight across the 2 end caps with the wire, and measure its resistance. if its not right make another another connection straight across with another length of the thin wire. this can get pretty fiddly.

4.) Wrap it up in tape

note: This is a very silly idea, the resistor cannot handle 3w's any more, and tends to get pretty hot when used in the circuit, i did this because I was desperate, and include it merely as a point of interest.

Step 6: Mounting the Leds

Picture of Mounting the Leds

The LED's get exceptionally hot, without some kind of heat sink they'll die on you, and you'll probably need a larger heat sink than you think, I chose to use the metal box I used to enclose the electronics as the heat sink, it's quite a bulky piece of meal, but it gets surprisingly hot, I'd recommend you use some thing larger.

The LED's I got had a star type heat sink attached to them, this makes it a bit easier to mount them, i marked out some fairly random positions and used some small bolts to hold the LED's in place, it would be a good idea to use some thermal paste to improve the heat conduction if you happen to have any lying around.

Step 7: LED Current Limiter 3

Picture of LED Current Limiter 3

You'll probably need a heat sink on the MOSFET of the current limiter circuit. Now here's the catch, you cant have the 2 MOSFET's attached to the same heat sink, as the tabs tend to be at different voltages, and unless you can insulate them, you'd end up with some nasty short circuits and erratic behaviour.

I made 2 aluminium heat sinks attached together with a piece of perspex, which was then mounted inside the box making sure the heat sinks didn't touch any part of the inside of the box.
This set-up got really quite warm after extended use and I would highly recommend using larger heat sinks or some kind of cooling.

Step 8: Putting It Together

Picture of Putting It Together

I chose to drill a couple of holes and use some plugs and sockets too attach the power to the box holding the lights and current limiter stuff.

Holes where then drilled down through the aluminium box and some nuts and bolts used to hold it to the lid of the tub.

I was fortunate enough to be able to pick up my power supply for £2.50 from JPG electronics in chesterfield (they're really good, they have shelves full of random things). It had some useful holes i used to bolt it to the lid with as well.

When choosing your power supply keep in mind the current and voltage requirements, and make sure it wont get too hot under load, and is suitably protected from shorts/current spikes. Remember this will be running for extended periods of time! you don't want anything bursting into flames.

Step 9: Test

Picture of Test

You'll be wanting to make sure nothing gets too hot or blows up. Here's my usual method for testing stuff.
Plug it in, if it doesn't work unplug it straight away and try and find the fault. After a few seconds unplug it and check to make sure nothings getting too hot and have a smell around for burning stuff.
If its ok plug it in for 5 minuets keeping a constant check on it, assuming all goes well leave it on for an hour, checking regularly. If it gets hot you'll be needing a larger heat sink for the LED's or the Mosfets, or beefy-er power supply.
If everything turns out ok its probably fine for use. To be on the safe side make sure your in the house for the first 24hours or so that you have the system running.

The first photo below shows the system running in my room at night with the lights off and the curtains drawn. It literally lights up my entire bedroom.
One odd thing to note is that there is no green light in the room whatsoever, this means beer bottles look black, which is kinda odd.

Step 10: Fin

Picture of Fin

That's pretty much everything. My original intention was to build a totally enclosed grow system using hydroponics, but i wanted to get this done in time for the LED challenge.
I might make another instructable on how i go about doing that, but there's quite a few decent ones around the place anyway.

Here are a few potential improvements i'm going to make in the future:
Fans to blow on the plants and encourage thick stem growth.
C02 producer (yeast, sugar, water).
Larger heat sinks all round.
PWM light control using microcontroller.
Timer to turn lights on and off.

Happy electric gardening!

P.s I know what your all thinking.....I'm growing pot, well I'm not. Honest. I do things like this because it interests me.


TegistG (author)2016-08-16

How much did all this cost you?

AdamA65 (author)2016-01-12

Who is the author of that Signals and Systems book

jugurthahadjar (author)AdamA652016-05-13

It's a book by Alan V. Oppenheim from MIT. You can hit MIT OCW for the very popular course. He also did a more recent one on edx under MITx (if I recall correctly) but you can't access the archived version and have to wait for a new class to be in session. You can also check out Discrete-Time Signal Processing.

HenryCrespo (author)2015-11-28

Even though I profit when people buy LED grow lights from my site, I always advocate people build their own, if they're short on money, but have sufficient free time. Let's face it, top quality LED lights are expensive and lower quality lights are not worth buying. If you make your own (and do it right), you end up with a great light for a fraction of the cost.

shadowrangler (author)2015-10-04

can these lights besourced as strips or do you need to know about soldering etc?

PinkLeaf790 (author)2015-09-14

LED grow lights are absolutely a wonderful thing.And these products helps in indoor and greenhouse use Top LED Grow Lights for growing Plants, food, medicine and More.

JjGardner (author)2015-05-03

It doesn't look as nice as those fancy LED grow lights in the market, but I guess it will do for some small indoor plants. Besides, it's a lot cheaper too. Looking to try this on. Thanks, man!

joker098 (author)2015-04-22

chicobandonado27 (author)2015-04-01

Plants do absorb green light, their green colour is due to chlorophyll beeing the major pigment in plants. Chlorophyll may not absorb, it reflects it, green light but other pigments can.

Brocky53 (author)2015-03-29

It's so clear and helpful. I want to share how to choose led light that I found.Please visit my profile to gather more information:

PeteSummers (author)2014-06-29

Amazing article there man! You really know what you are talking about. This is one of the finest led grow lights that's been made via DIY that I've seen. I'm planning on assembling one myself using your instructions. A couple of question though: how big is your grow room and how many lights do you use? Are they all LEDs?

dannyrob (author)2012-12-04

Really cool man! I wish I have the guts to make this awesome LED grow lights. I have some basic knowledge about electronics stuff but I not really confident about it. I guess I have to read more. Thanks for this idea.

DOPED substrate (author)dannyrob2014-05-20

use the emergency lights you get every where swap L.E.D's for Nm yr choice and use a PC PSU to beef it up perfect for beggining

DOPED substrate (author)2014-05-20

pc power supply can give you alot of power for yr leds

DOPED substrate (author)2014-05-20

HI guys i found that collecting emergency lights from buildings can make the job alot more easy ..up rate the suppply and re solder your desired L.E.D's and hey bang

case and everything

these are low power but are built for you .. thay also have battery back up :)

great for starting yr grow until you need to move on to upgrading power output

fixing a timer is easy too ...

Hope This Help

Akin Yildiz (author)2014-05-05

very nice setup, i love the box and the use of LEDs. i am trying to prove another theory, here it is;

we don't need so much power, it's all about the angles, i have a 7W plant arm with no fan - no heat sink... check it out. you can attach these plant arms to any pot !

can be powered via USB, rechargable battery or solar even !

visit my profile;

james26 (author)2014-01-04

Really nice build. This guy did a build using 165 Watts of CREE LEDs to get a full spectrum LED grow light for his very small grow space.

DIY LED Grow Light - 165 Watt 

- CFLs as an additional boost
- Small stealth grow space
- Passive cooling, no fans which I thought was cool
- Over one gram per Watt which is better than most do with HIDs

I would like to know if anyone could improve on his design, he mentions the CREE XLamp CXA3590. Maybe that would help?

boogiemanspud (author)2012-12-29

Good job. I know what you mean. I grow herbs (basil, cilantro, rosemary, chives), radishes and various vegetables in my basement year round with artificial light and anyone I know asks if I am growing pot. It's so annoying. To me it's just interesting, a good hobby, and a bit mad scientist like. I guess we are just wired differently than most people. But I think that's a good thing. I would be bored to tears if I couldn't experiment and play around with interesting stuff! I'm using CFL bulbs so it's not as energy efficient as LED. I joke that my radishes are probably $15 a pound, but meh, it's a fun hobby. Hopefully LED can cut some energy consumption down. By the way, hydroponic lettuce is next but I need to learn more about nutrients and such.

gegg (author)2011-03-10

Why didn't you just use one power supply?
Couldn't you just use all 5 leds in series with one current source?

snotty (author)gegg2012-11-30

Yup! I do this all the time. One controller and a bunch of LEDs. Put the LEDs in series if you have more voltage and in parallel if you have lower voltage. Then adjust the r3 value accordingly. Beware though: If you have LEDs in parallel on the same driver and one LED disconnects (or dies?), then the remaining LEDs can get overdriven and you could get a cascading failure. I think this is a bigger problem with fewer leds.

Jack Corsair (author)2012-08-24

I am currently trying to grow some plants in my cube at work and have been looking for as much info on leds as possible. have been following you with your attempts. I have had hit and miss success.

I went with something easy but it is turning out to be kinda a crap shoot. im working with moss in small containers. glass bottles and what not.

heh "iamhonestlynotgrowingpot" XD

there are no windows in my part of the building. and I want something that will grow. cant have regular sized house plants because they turn the lights off on the weekends and they die a slow death. but if my LED's are plugged in the maintenance wont unplug it.

so yeah, just wanted to tell you. thank you for your research!

skuitarman (author)2012-05-03

lol plants at a disco.....

ricardovw (author)2012-03-25

The result

123cryderman (author)2012-02-11

Do the LED's work for growing plants? I thought you needed special bulbs for that???

hanlin_y (author)2012-02-09

Would the yield be larger if you add more LED's. I see that most pre-made grow LED's are 90 watts or more for a small but open space but you used 15 watts here. Your container is about 8 sq ft and based on the recommendations for UFO grow lights, it looks like they recommend 45 watts.

skaar (author)2012-01-24

using the same method of switching supplies to reduce the 10 volts to 5 volts, then a strobe for them could make them nearly as bright, but last longer, and produce less heat.

codyg102 (author)2012-01-11

Best affordable heat sink materials are (in order) copper, then aluminum - in case anyone's wondering.

Proper thermal compound will vastly improve heat transfer (if you doubt that one, try running a computer processor without thermal material between the proc and heat sink... smoke will probably soon follow... and not the good kind ;-) ).

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.

codyg102 (author)arnookie2012-01-11

I have to agree with phlange and pansartax. The arbitrary wattage value makes no sense without some supporting documentation. Plants don't know from watts!

What matters is light output, normally expressed in lumens (or lux).

I'm sure that's what you're trying to get at, it's just that most people -including me - mentally equate wattage with the output of conventional lights types (incandescent, florescent, mercury vapour, sodium-halide, etc.) and can't "picture" what a 1-watt LED output looks like. It would probably be helpful to explain it in terms of output for comparison purposes.

arnookie (author)arnookie2011-04-26

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.

pansartax (author)arnookie2011-08-07

Uh.. do you have a source for this? It seems very odd seeing as many 1W LEDs are comprised of 2x0.5W junctions or something similar, and all my 3W LEDs have 3x1W junctions.

I don't see how plants could distinguish light from 100 1W LEDs from light from 10 10W LEDs. The energy contained in each photon is defined as hc/lambda and does not vary with the wattage of the source

You are however correct in saying you need big LEDs. Using small 5mm LEDs, you would need an absurd amount.

phlange (author)pansartax2011-08-28

coincidentally, what is considered the "very high output energy" LED's are of the One Watt gender. You pump a whole Watt into an LED and it will draw an exponential amount of power(in amps...i.e. the actual power of the light).

I concur with this "1-Watt LED grow light rule", but I must insist on a bit of reference, or a source for your view of it.

phlange (author)arnookie2011-08-28

can you please verify your references in this information.
it seems as though you have posted the "1 Watt only" rule in every 'LED Grow Light' thread in
Hoping you could shed some light on where it came from.


Electronics Man (author)arnookie2011-08-12

I have a question, since you think that it is so important to have 1 Watt LEDs at the min. then how many 5mm LEDs would it take to equal 1 Watt? Lets say they are Ultra-Bright red LEDs rated at 8,000mcd

Answers are appreciated

andybuda (author)2011-09-04

can the high power led be used with a led transformer that outputs a constant current.... you can get them for a few quid and just connect directly.. + just found the ribon type leds on ebay check them out 12v and have 18 leds that can be cut in to 6 x 3 and there flexible there £7 iv started using the other one for growing but its a bc conection, cpc....they are 2 for a fiver and work really well there is a lense inside that focuses the beam but that can be removed

derrekito (author)2008-09-07

One thing that needs mentioning is that plants are very picky about what kind of red light they absorb. Often the frequency range is normally outside of commonly found red LEDs. In fact, I have yet been able to find any purchasable in the specified range. according to the image in this comment, most red absorption occurs at ~ 600-625nm. Many LEDs are in the 630-660nm range, so be cautious.

AlexCphoto (author)derrekito2008-09-08

Thanks for this chart,.. iv been looking for something this detailed,.. due to this data iv decided to add in a few (12) 573nm LEDs to increase my Phycocyanin coverage and also add in the gap I was completely missing for Phycoerythrin. with that change I still miss the primary Chlorophyll a peak just a little, but have the secondary Chlorphyll a peak (which is only a bit lower in efficiency) fairly well covered. I certainly would like to hit 425nm but im not finding any ultra bright pink LEDs out there,.. Ill run with this for a bit and see. (LEDS at 1/5 power for photo)

pansartax (author)AlexCphoto2011-08-07

As long as you are'nt planning on growing algae or cyanobacterium you dont have to worry about Phycocyanin or Phycoerythrin, they are'nt present in green plants.

derrekito (author)AlexCphoto2008-09-09

Simply put - the LED tech isn't there yet. With NASA picking up the scientific slack, I hope to see better LED bulbs out sooner than later MARKETED toward farming needs.

larsmunck (author)derrekito2010-05-08
I found some 430's..
A german retailer sells 5mm 430 nm LED's

peak wavelength 430 nm,

viewing angle 16 degrees (±8°),

luminous intensity 150 mcd,

forward voltage 4.0 V

What do you think?

derrekito (author)larsmunck2010-05-09

 After glancing at the specs, I think one would need to get a hold of a batch and do some measurements.  Power dissipation is rated at 105mW without correlating to operating voltage or current.  If max current is 30mA and operating voltage is 4V then power dissipation should be 120mW - but this isn't stated in the document.  Operation at a test current of 20mA yields a radiant power rating of 0.8mW where power dissipation is 20mA*4V=80mW (1% efficiency). This sounds like an awful waste of electricity to me, but I don't know how this compares to typical LEDs or HIDs.

I would be interested in its operating characteristics at the LEDs max current rating of 150mA at a 1/10 duty cycle and frequency of  10kHz.


larsmunck (author)derrekito2010-05-10

Wow! It's wonderfull, I didn't understand anything but it was a cool read. Im a total LED noob, but hope to order some good value for money/efficency, when setting up a growlight for my thai basil + cilliplants.

aspalmer (author)derrekito2010-07-22

Warm White seems to match that distribution pretty well It's mixed with 2 peaks, at 450nm and 600nm.

zeroemission (author)derrekito2010-06-26

it would look like simple red & blue LEDs aren't sufficient then. if anyone here can do reflow soldering, then the most economical & possibly superior way to build grow lights is by mixing spectrums using luxeon rebel lights. i was researching this last night and found they have a red/orange bulb no one seems to be using whose wavelength is 617nm (LXML-PH01-0050) which looks like it's output is right in the phycocyanin peak on this graph and more practical than 425nm+ red bulbs where the dropoff starts. not only that, but i saw that a red/orange 3w luxeon star puts out just 190 lumens and costs $8.44 while a pair of rebels would put out 200 lumens and cost only $5.48! figuring out how to solder them would be a real pain though. having just learned about reflow soldering last night, i imagine someone could just etch a circuit to solder onto. if it could be done, the smaller rebels offer the most lumen bang for the buck. one could even mix 617 red/orange with 426nm reds. surprisingly, in all of my research claiming that LEDs just don't offer the same light penetration as house heating sodium & halide lights, there's a simple solution... train your plants horizontally. then you can place your bulbs within mere inches of your plants as they aren't going to get burned. i'd like to start growing exotic veggies & spices for curries, but live in a town where you just can't get them at all. i'd like to not only grow them cheaper & eat fresher, but i'd also like not to heat my apartment up even more on hot summer days. i think if you combined LED tech with training techniques, you can greatly improve light coverage. if everyone has success using LEDs for sprrouting, then horizontally trained plants should provide similar results. put the lights as close to the plants as possible... problem solved.

derrekito (author)zeroemission2010-06-26

Just a heads up: It may not be useful to base a grow light system's performance on the SI unit Lumen. It may be luminous flux, but it is based on the perceived light by the human eye. The visible spectrum is between 450-750 nm. This leaves out the absorption frequencies for beta-carotene and chlorophyll a. It might be better to depend on radiant flux provided that there isn't too much electromagnetic energy being emitted below 250 nm or above 700 nm - otherwise your power/efficiency ratings will be offset by wasted energy you wouldn't want to consider. Ideally we would like to have a rating that could tell us something about the amount of energy generated that could (in theory) be used by a photosynthetic plant. Additionally such a prospect may be futile as I doubt all photosynthetic plants absorb precisely the same amount of light per frequency - thus the absorption rating would need to be plant specific.

zeroemission (author)derrekito2010-07-01

i'd want to grow a lot of different plants, particularly onions i think as it seems every recipe i'm trying needs onions. i can't find curry leaves, fenugreek, black mustard, green coriander & a few other common curry spices anywhere here. i'd also like to try a few different medium hot peppers like pasilla & poblano as well as more common spices. i tried this delicious spicy basil once called cinnamon basil i wanted to buy at a market but was told it wouldn't grow indoors on a window sill. if i had my way, i'd just have my own plot of land and grow all of my needed veggies. i miss old school acidic tomatos that have that cherry tomato flavor and can't stand those flavorless hothouse ones. i was taking it that the chart was a display of all of the wavelengths plants use for photosynthesis and not a chart for some specific plant, i hate apartment living i tell ya.

borisgrishakov (author)2011-08-07

oy, so interesting!)))

LividMonkey (author)2008-10-28

Question: Would UV LEDs be helpful in this setup? I was thinking that plants like UV light so it would be beneficial to add some. What do you think?

}{itch (author)LividMonkey2008-10-28

from what i've read plants use UV-b light during flowering, but i don't think there are any LED's that produce light in the UV-b spectrum (UV-n is the light that can give you skin cancer and other nasty stuff), but i think it is possible to get either "lizard tank" or "aquarium" strip lights that give out UV-b, so that might be something to look into.

ovven (author)}{itch2011-01-07

both UV a and b are damaging to plants, though not sure in what quantities. UV b damages the pigment.

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