[Dion]

Recently a fellow grower contacted me suggesting an LED FAQ thread, I was honered. so here goes its a faq thread about building led growlights and one where you can get your specific questions answered on the fly.

I wont go into the nitty gritty about what an LED is or how it works just how to use it for growing plants, i will be using the metric system (mm cm and degrees C for temps but will use feet for discussing growspace as this is more common) and will use a lot of pics from manufacturer's design guides as well as those from my own builds and other growers who allow it. I am by no means an expert engineer or an electrician i am just a grower like you who has been building leds for a few years now(both for horticultural applications and general) using engineering tools and data sheets and the advise and experience of a retired electrician. so there will be some questions i dont know the answers to, rather than google it and recycle an answer from elsewhere or give bad info i will just tell u i dont know. that way others with better electrical/engineering brains can help us all learn.

IF YOU ARE LOOKING FOR KITS FOR THE 1-3 square foot range click HERE
i hope to use this thread to guide ppl from wanting to build their own to actually doing it

Topics to be covered include(but are not limited to)

Where to start-defining your needs:

mEChaniCaL DEsiGn:

Chips,connectors, assembly, optics




ELECtriCaL DEsiGn

power source/driver, connections, multiple leds

thErmaL DEsiGn
heatsink type/size , thermal interface materials, fans



also I will include a tutorial for a super simple led assembly

like this one but for cobs

https://www.icmag.com/ic/showthread.php?t=302493

to Build your an led grow-light you will need:


Chip
Driver
Heatsink( option of pc fan and driver for that fan)

Bits/tools: screws, wire, TIM(see mechanical design) drill and/or soldering iron(see mechanical design)

hopefully i can keep editing this post over the next few weeks so keep checking back in as this thread is officially under constructing until then any things you would like to have in this faq please pm me

for questions please post below

[Dion]

Where to start

The first thing to consider is your own needs for the garden. there is no specific formula for calculating how much light you need in watts as different LEDs will give different efficiencies and lumens is arguably not a good indication of light needed as LEDs for plant growth should be considered in PPFD( basically how much useful light is coming off these LEDs) so spectrum will play its part here.Also considerable research is being done into "what light do plants need?"the debate is on-going so lets keep it super simple and avoid in this early introduction any discussion of spectrum, we will focus on LED cobs being labeled by kelvin i.e. 2700k, 3000k, 5000k etc

the general rule of thumb for hps seems to be 50w/sq ft and around 5000L per/sq ft (you will hit these numbers at 100L per watt)

in veg you can get away with very little light, it just means that your plants will veg slowly but if you want hyper productive veging babies lets aim for around half of what we use in flower.

With LED ,on average, for flower we need 35-40W per sq ft or 5000L to match traditional light sources, however if we are considering this more expensive technology we have to kick traditional lights in the arse otherwise whats the point, right? Right
also consider that with an LED all those lumens are shining down on the girls not coming off the light source the wrong way and being redirected and lost by a reflector.

so with that in mind lets get closer to the 6000-7000 Lm per sq foot and try for efficiency to still keep watts under the traditional( consider total watts not just the watts of the lights i.e. cooling the room and also consider we will have these LEDs a lot closer than HPS-further from the light the canopy is the less light it actually gets, regardless of how much the light fixture puts out so with these numbers we will be destroying HPS).

Things to consider when using LED tech:( this might piss people off)

THE LONG LIFE DOESNT JUSTIFY THE COST- in 5 years you will not want to be using the same light you build today, perhaps you will use them in veg or as additional lighting but the newer tech will be better and you will want it

The penetration just wont be as good as HPS
if you wanna grow trees you can't just have a huge LED spotlight to do this, you need multiple smaller lights closer to the tree. I would assume that to light more than 30cm of canopy thickness will result in light bleaching on top and fluff down below

EDIT: to clarify i mean that we cannot consider led a replacement for an hps in its design- its a dif tech and needs to be designed differently- those companies making panels are just doing it wrong so that hps growers will feel comfy making the switch
we need to spread out the multiple light sources not pack them all into 1 place if we pack it al in we need to raise the light to get spread and loose photons doing this so you can grow trees of course you can but you shouldnt expect an led with 500 chips in 20cm2 hung 3 ft above the canopy will get you there

The heat is still there

on average LED lights are 20% more efficient than HPS lights that doesnt equal no heat, it equals less heat-meaning they convert energy( electricity) into light better. where as HPS could convert 100w into 20w of light and 80w of heat LEDs will convert 40w into light and 60w into heat BUT the thing is the heat wont be thrown off the light like with HPS it will dissipate off the back so you wont need to cool the space to as low a temp. think of it this way, in a room that is 28c under an hps light it could be 33c so you really have to keep that room cool to not cook your girls( in reality the room is probably more like 25c but we are measuring at the canopy-read under the light) but with LED in a room that is 28c it will only be 29 or 30 under the light. In reality you will have only a little less heat to deal with but it is cheaper because of the way you have to deal with it ie less watts for Aircon/venting because our room can be 28c and still have the same temp under the light. (it is probably important to note that because of this you should run your led rooms a few degrees warmer than you would with hps, this will also cause the girls to drink and eat more.many led growers report needing to use less nutrient with leds. get ur temps up and this should not be the case,it is possible that many sub-par results from led grows were contributed to by this temperature anomaly causing plants to eat and drink less therefore grow less)


Now it may not come as a surprise that i do not recomend LED lights to growers who wish to replace a/multiple 1000w hps sure it will work the technology can do it BUT its just gonna cost too much to do and in 2 years the technology will be so much better you will feel ripped-off basically it isnt cost effective in my opinion-if u have cash to splash thats great do it. personally i think 400w is the cut off-with the exception of someone who wants 600w but just cant deal with the heat(get creative and cool-tube your LEDs or mount them into the roof of the cab so the heat rises off the sink up into a separate chamber and vent that)

However for the personal grower, the micro grower, the PC grower, the guy who wants cheap Veging with no bulb replacements and the mad scientists: LED is your best option

Ok so you still wanna use led? good. lets start with your requirements.

to choose your parts first select your chips then drivers then heatsinks( this will absolutly make your life easier and avoid ending up with the wrong parts)

Chips- I recommend cree Cobs, they are the best and although the price reflects that you get what you pay for, also cree COBs use a ceramic board making thermal management child's play you can buy them from digikey or mouser. I also recomend surexi chips by illumitex they are great and the company has invested enough in R&D to have a nice range of horticultural chips( https://www.illumitex.com/illumitex-l...iculture-leds/ ), these however are no longer in production as they now are just selling prefab lights but you can still buy them on amazon or mouser while stocks last. Others use vero( bridgelux) and you are welcome to try them I never have and never will. Cheap chines cobs off ebay or aliexpress? nah we are chasing efficiency here leave the junk in china.

if you go to cree.com you will find all the dif chips they have https://www.cree.com/LED-Components-and-Modules/Products

we are looking at cobs so the cxa (https://www.cree.com/LED-Components-a...ding-pages/CXA)
or cxb ( https://www.cree.com/LED-Components-a...ing-pages/CXA2 ) series is what we should look into

the highlights are



some nice options here I am using 2 CXA2540s over a 1x1.5ft conopy (just because i got the chips cheap) but the 3070 is what i recommend very efficient and high lumens ofcourse if you want to use any others they will all work BUT the 3590s are hard to find in the 36v variant(more about that later)

and


Both the CXB3070 and 3590 will work well to light 1sq ft of conopy but the 3590s on the market need to be powered at 72v(more about this later) and the drivers for it will be hard to find/ expenisive beyond justification so from this group the CXB3070 is the only choice

it should be noted that the 25xx series offer the best L per $ so using more of these chips would be a good option too- also for veg lights as the 25xx come in 6500k for veg we can run these at low currents and achieve fantastic efficiency

ok so lets say we decide to use the CXA3070( wise choice grasshoper) how many do we need?

lets see what the manufacturer says?

https://pct.cree.com/dt/index.html

brillliant not only can we see what our lights will consume in volts and watts but also what they will produce in lumens

Now you will notice the drop down boxes choose the chip(in this case the CXA3070) and the binning...

da fuq is binning?

"All XLamp LEDs are tested and sorted by color and brightness into a unique bin. each bin contains LEDs from only one color and brightness group and is uniquely identified by a bin code." Bassically the binning tells us the awesomeness of the chip, more awesome=more light=more bud



Choosing the correct binning can make or break this project so I advise to never buy chips from an unreputable seller and always know what binning you are getting- as we are chasing efficiency this is key so listen up

as described above binning will be shown in the model number

e.g. CXA3070-0000-000N00Z230F this is a z2 binning

better binning is... well better lol you should down load the spec sheet of the chip you are considering to see the dif binnings available and choose the best one the seller has(highest luminous flux)

another thing to note here is the CRI( colour referencing index) generally growers like the 80CRI for high luminous efficiency. the binning will also tell you the CRI as specific bins have specific CRI

the data sheet will display CRI like this

looks like the 93CRI is awesome to me

however actual PPFD will show it like this



so although you will loose a bit of actual light using the 93CRI ( binning flux will reflect this) you can win a little on the spectrum this choice is yours, most go for the 80CRI which I would probably advise, especially if the budget allows for some suplimntating chips to be added such as UV and IR. also you will notice that the luminous flux increases the colder the light gets-hence the popularity of the 3000k over 2700k (also they have proven to be good from veg through to flower) while others will even use a 4000k if the binning is good- 2x5000k and 2x2700k? sure whatever you want chief i advise 3000k you do as you like

EDIT: now that cree has released the 3500K in BB bin that is the way to go for the cxb3070 however with the release of the old 240(meanwell driver) especially the 1750mA the 3590 is actually cheaper to use(if u calculate total sytem costs)


EDIT#2 Cree is lagging on new bins and models(q4 2016), currently both VERO GEN 7 and Citizen are beating the 'big daddy' CXB3590 and both cost about half the mulla

also I now recommend 3500/4000K

[Dion]

mechanical desighn

For a flowering garden i don't recommend using bitty 3-5w chips(actually they will end up being more like 2w once we power them) unless you are juicing up the UV/IR spectrum/ specific wavelengths for some kinda experiments as they r just too much work to fit enough in for the intensity we crave
Back to deciding how many chips to get

https://pct.cree.com/dt/index.html

Now you will notice the drop down boxes choose the chip(in this case the CXA3070) and the binning

seen as we are savy buyers we got the CXA3070 Ab Bins( "Very Naice" Borat) so we select that option and wait for the friggin thing to load next we change the current range to "very course"( top right) and wait agian

ok now scroll down and check it out we hit 7000L at 1400mA ( 1 amp/1A = 1000 milliamp/ 1000mA this is the current)

so 135.9 Lumens per watt ? 52.4 total watts? 42% efficient? ill take it!


(also notice that the voltage at this current is 37.42 we will need that info when choosing a driver.)

so looks like 1 chip per sq foot( ie 2x2 space= 4 chips) will be fine for us- you could always run this baby harder and get more lumens out of her but then you would sacrifice efficiency or run her lower and use more chips (costly) or you could not use as many chips to save cash( like 2 chips over a 2x2 at 2800mA=almost 6000L/sq ft) and run them harder but will loose efficiency and also get a non-uniform lit canopy which is such an advantage with LEDs

so now we have chosen the chips(CXA3070 AB bin 3000k 80CRI) and we have decided to use 1 per sq ft( aprox 50w/ 7000L/sq ft) lets get the other bits we need for the mechanical/physical design of this sunshine system

optics/lenses

I dont use them you dont need them we dont buy them
if you want to protect your fried egg sure go ahead but you will loose light to the lens( 3-7% depending on the quality)- reflectors can be used they attach to the chip holder but same story really- who needs em? feel free to disagree but i can only speak from my experience


TIM ( thermal interface material aka whatcha gonna stick it on with?)


because we are using such high powered chips we have to transfer the heat away from the diodes as fast as possible traditionally grease does this the best but seen as Cree cobs use a ceramic plate the thermal pads arnt too far behind if you are not a particularly DIY type or dont have the tools to drill and tap the pads will be your best choice

"What's the difference between Thermal Adhesive, Thermal Grease, and Thermal Pads?
Thermal adhesive is a two part epoxy that will adhere your LEDs to the heatsink surface. This is meant to be a permanent adhesive and would be used if you do not have a drilled/tapped heatsinks or a heatsink with T-slots for screws. The advantage to using thermal adhesive is you do not require a drilled/tapped heatsink, and it's relative low cost if using a lot of LEDs. The disadvantage would be if you ever needed to remove the LEDs it's more difficult than thermal grease. If you do need to remove LEDs with thermal adhesive get a tool with a flat edge (ie. flat head screwdriver or box cutter) and get the surface underneath the LED board. The adhesive is brittle so it will 'pop' off.

Thermal grease is not an adhesive so it can only be used if you are holding the LED(s) down with screws. Thermal grease is great in how easily an LED can be removed if it ever needs to be replaced or upgraded.

Thermal pads are like double sided tape. There is a film on both sides that need to be removed, which exposes a sticky surface to attach the LEDs on one side and the heatsink on the other. If using thermal pads you would typically not require screws. If using a small number of LEDs these are a very fast and cost effective way of sticking your LEDs to the heatsink, and is a lot less messy than thermal adhesive.

These three types of thermal material should not be combined, so it's an either/or choice between them."

from rapidled.com

in order of how well they transfer heat from the chip to the heatsink

1) grease ( remember we r just filling this microscopic space between the chip and sink so less is more)
2) pads
3) adhesive (especially remember we r just filling this microscopic space between the chip and sink so less is more)


YOU SHOUDL NEVER USE SCREWS ALONE OR EVEN WITH WASHERS FOR COBS- ONLY USE SCREWS IF YOU HAVE A CHIP HOLDER OTHERWISE JUST USE PADS/ADHESIVE






Connectors


some have electrical connections- personally i think they r awesome
some dont-get the solder ready

https://www.youtube.com/watch?v=U2jtqJHLhN8

https://www.youtube.com/watch?v=UfdNYvYwjfE

ok so we are gonna need to connect these chips to the heatsinks eventually and we have a few options but to keep things simple ill list the ones you should consider

easy/ no drill/no soldering(recommended by dion for biggeners)- get a chip holder that has electrical connection as well. use a pad( its like double sided tape) for ur TIM and slip the wires into the holder

medium/ no drill -use thermal pads and solder the wires for electrical connection

beast mode(what dion does because its cheaper/better heat transfer) use a chip holder without electrical connection( or one with pfft), grease for the TIM and solder the wires(or dont solder with elect connectors on the holder)

don't screw them on too tight- just as tight as your wrist can without lifting your shoulder/elbow will be fine(does that make sense?) if you apply too much muscle you can damage the chips-the pdf for your chip will tell you how tight exactly(if you have a torque setting on your drill)

Screws/drilling/tapping the heatsink

you may not have all the tools available to do this so its worth noting here depending on your design we can take short cuts
of course u can always use pads and solder but if you do decide to go with a chip holder but dont have a tapping tool ( thing that makes thread in the hole for the screw to go into) you have some options

you could just drill all the way through the heat sink and use bolts with a nut on the end( i double nut in this case)
you could just screw in the screw without tapping as aluminium is pretty soft( ghetto at your own risk)


EDIT: so now my preferred method is to drill and use roof metal screws(self tapping) without tapping holes they will glide into that aluminium heatsink like ur sisters...um oh yeah never mind

[Dion]

ELECtriCaL DEsiGn
PLEASE READ BEFORE ASKING ABOUT DRIVERS
lucky for us this is the easy part

LEDs run on dc power so to drive them we need an Ac to dc power supply it also needs to be Constant Current( CC ) as leds are very sensitive to the current too much current and you will cook your chips

these power supplies are called driver( specifically constant current LED drivers)

to figure out what driver to use is super simple

all we need is the chips electrical data specs( voltage, current)

take ur total watts and amps and match

eg we want to run 37 of our 12v chips so (37x12)=444v

they run at 1-3 A so for efficiency lets run them at 1.5A

we need a driver that is 1.5A Constant Current ( CC ) pushing at least 444v so 400-500v is good etc( drivers will list thier min/max as long as you arnt under the min or over the max u are golden


realistically lets say you wanna run 3 3070s on one driver

we go here https://pct.cree.com/dt/index.html

and find they run well at 1.5A( 1500mA) and they pull 37.74 v at that current so

37.74v x 3=113.22v

we need a driver with 113.22 within its max/ min range ie 100-120v @ 1500mA

for just 1 cob we would need 37.74V within it's max min range @ 1500mA

with the cree tool we used earlier its easy to see what our current/voltage requirements are so we use this to find the right driver. at this point in our search we will ignore watts they don't tell the whole story when I look through pages and pages of drivers from sites i search for current and then make sure volts match

ok so we have the CXA3070 we chose earlier- it pulls 37.42 volts at our desired current(1.4A/ 1400mA) but remember we can be flexible in that current just we will loose L/w

I personally invest my money in the chips and to keep costs low buy drivers from china( the same factory as that brand name one comes from i assume- mine have been working for over about 2 years now- tested when first got them specs all matched the manufacturer's claims)

for this build i recommend this driver it will run 1 cob- i like to run each cob on a separate driver so i can move things around as needed( like when i move house and the garden changes shape or i decide to throw one of the lights in to the veg to speed things up a bit) and also it has the advantage of being able to see exactly what needs replacing if your light stops working( eg 1 light goes off so change the driver-still off=chip is broken/change the driver-works=driver was broken)

looking for drivers can be a pain so remember your max/min current requirements(perhaps you find a driver that is 1480mA instead of 1400mA is that ok? look back at the spec sheet

here is one thats good for powering cobs

https://www.aliexpress.com/item/Water...265565611.html


For whatever reason this seller is updating stock so atm the product is not available
Input:
122.4 volts ( will work on 240 as well)
.48 amps ( aprox .25 @ 240v)
59 watts
Power Factor .99-1.0

Output
1.481 amps
37.98 volts
56.263 watts

i have bought from this store before and they are good quality also the seller is an engineer so he can help you adjust the current or find the right driver for your needs( this is totally up to you just throwing out a cheap option which i use-meanwell is supposed to be the best)

running multiple chips off one driver?
refer to the work above

want dimming with that?
then you need a driver with adjustable current just make sure the volts are suited to the chip(s) you plan to run and that the max current( at 100%) doesn't exceed the recommendations of the manufacturer. i have not found reasonably priced dimmable drivers so i would just switch the drivers for lower current drivers if the need came up( i.e. its cheaper to have a few drivers with dif currents on hand than a dimmable one)

A lot of ppl ask questions like "what driver can I run this chip with?" the answer is whatever driver you want
you must choose your chip- from its specs decide how hard you wana push it( current) then find a driver with the volts needed at the desired current then based on the total watts choose how you will cool it

i am happy to help but i did type this up to avoid confusion

[Dion]

thErmaL DEsiGn


basically we want a heat sink, the biggest mother heat sink you can get your hands on. copper is best but too expensive for us so we use aluminium
dumpster diving may produce cheap options( look for PCs and speakers) check sites like craigslist or broken PCs you can gut
ebay seems to have deals as will lots of other online sites like heatsinks usa( i hear good things and the prices are fair)

many people use pc coolers like this https://www.newegg.com/Product/Produc...82E16835186070

notice it has a pc fan on it?

i prefer a passive design ie no fan-its not as noisy and less can go wrong( imagine that fan breaks and cooks your expensive cob)

so for individual heatsinks i use smth like this
EDIT: since writing this i have changed my possition(after cooking 2 cobs lol)- passive cooling is great but use the pc fan for cobs(especially noobs)- its so so so much cheaper and possibly better cooling

EDIT 2: I've now switched back to passive, so many good options available in small quantities now days, pin heatsinks, stars ect


what size sink do I need?

2 things to consider in a heatsink
how much heat can it hold?- size/material will effect this
how quickly can it get rid of that heat? surface area/material will effect this
heat sinks can be complicated to figure out and i dont wanna get too nerdy here so if the seller lists the watts the heat sink can dissipate that makes life easier keep your total watts below that number and you will be fine(ie 42w fixture=50w heatsink/ 73w fixture= 100w heatsink)

if using the pc fan style sink look at the manufacturers recommended heat sinks for your chip and match accordingly(assuming you are like me and dont plan to pay those prices)

"a rough estimate of approximately 5-10 in2* of heat sink surface area per watt of heat can be used for a first-order
estimate of heat sink size."

Cree
*32.25800 square centimeters-64.51600 square centimetres acording to google

that seesms like a lot but that is for passive cooling(no fans) and this is surface area they are talking about so keep a look out for heatsinks with surated fins like this



not smooth like this



more surface area= quicker and better cooling



i forgot to mention keeping these chips cool is in your best interest as the cooler you keep them the more light they reward you with- this is reflected in the cree info(you can change the tj and see for yourself) note the voltage will also drop as it gets hotter

here is a tool to calculate if ur heatsink is good enough
u need to know the specs on the heat sink and the TIM (c/w) to get an accurate reading
https://www.daycounter.com/Calculator...lculator.phtml

[luvdemshrooms]

Originally Posted by Dion

Where to start

PeRhaPs by DITCHing the anNOying use of cAPS.

[unregistered190]

Gonna sub as I am interested in DIY. Thanks Dion

[Dion]

Originally Posted by luvdemshrooms

PeRhaPs by DITCHing the anNOying use of cAPS.

thanks for your feedback, i was planning on doing that but it annoying you is such a bonus i dont think i will

lol jokes dude

any things i skimmed over too quickly or missed would be apreciated

i am dyslexic and the 'm'key on my keayboard is broken so i have to copy and paste it each time i use it hence the wierdness of my writing

ill keep working on that though

[Koondense]

Great thread Dion!

[Snook]

yes, I too thank you but right now it feels like learning about all growing variable values from scratch.... PPMs/nutrients, Ph, fans/cfms and all that other stuff.

bins, garbage cans, right? kidding.