DIY LED with COBs - small medium and large grows

[Toaster79]

So the led strips without resistors are more efficient than those with them? Interesting. What's the role of the resistors on 12V application where LEDs are wired parallel?

Lumen/Watt ratio tells you the efficiency of light source and it also tells you the total ammount of emitted light at certain power under certain condition. The ammount of light per surface is usually mesured in lux. Lumens can also be measured but that is done in an integration sphere.

Cree anounced a led with 200lm/w efficiency years ago. Its called MK-R. Ofcourse the numbers are only reached in lab. Not long ago Cree also anounced third generation of their XP-G pushing 193lm/w if we're talking smaller 5-10W chips.

 

[Nomadic]

So the led strips without resistors are more efficient than those with them? Interesting. What's the role of the resistors on 12V application where LEDs are wired parallel?

If you push 12v through a typical led you'll cook it. The resistor is a current limiter/voltage divider. Resistors only create heat...no light...hence the drop in efficiency (lumens per watt).

That's why constant current drivers excel in efficiency.

 

[jdb420]

The lumen per watt only matters in lighting cost and no matter the lumen per watt you are still going to be using less energy than a big grow light even if you have to use 6 different 12v power supplies. The led strips I linked were just ones that I found to link, I would shop around for the brightest and best deal.
The reason I linked this is because tommy trichome is killin it with yield and potency from some very expensive versions of those led strip lights. He will tell you that his lights will grow it better because the strips dont have resistors but until someone does a grow log with regular cheap led strips that dont do well, I will believe that you could get the same results or similar with regular led strips.
https://www.thcfarmer.com/community/threads/introducing-the-sun-cloak-vertical.76703/

It also matters in efficiency, which equals heat in the less efficient lights you speak of. They may make the same lumens, but with more watts consumed. More of those watts consumed will be converted to heat than light. So, that tends to be another advantage of the cobs. Do whatever makes you happy, but do some more research before getting your feet wet. That way you get the best efficiency for the money you spend. And spend less money removing the heat from less efficient lights.

 

[3N1GM4]

I already have a cob, if I can ever get to a place where I can do a side by side cob led strip surrounding a plant and see the yields/environmental conditions/power consumption I will post it on here.

 

[provos]

Hi just got a mars 300w real power 135w got it for veg but don't know how far away from the top of a young 7 days old seedlings should be first led any info would be good

 

[jdb420]

I would say around 24 inches. The newer mars lights say 24 to 36 inches, but they draw around 205 watts. I would start at 30 inches and move it down an inch or two every 2 days. Download a free lumen measuring app on your phone and measure the luxs or lumens at the same height as your seedling. That way you can measure the amount of lumens that are getting to the top of the seedling. Just go slow with it if this is your first grow. Take notes of what works well, and let that be a guide in the future. Every light is different and you have to test your light to know what makes it perform best for your needs. Just know that as the plant develops roots and more foliage, it will want more light. You will learn what it can handle. At first go slow and in time you will know what you can do to improve your growth without setting it back from too much light intensity. These plants love light, but you gotta be careful when they are young. I've seen really weak seedlings and really strong ones. I guess some of that is genetics, and the rest has to do with environment. Make sure your humidity isn't above 40 for the whole grow. Led grows will see much slower growth if you use a normal 50 to 55 rh. The led lights lack the infrared which means less heat and less evaporative water loss. The temp of the leaves should be around 84 to 86, and the temp of your room should be the same. The old mh and hps bulbs must be kept at 74 to 78 to maintain leaf Temps of 84 to 86. Not so with led lights. Yet, another advantage because that is less cooling to provide your garden in the Warner months. Any other questions, feel free to ask. These other farmers could tell you way more than me. I haven't been doing it near as long as most of these guys. But remember that the lower your Temps go, the slower your rate of photosynthesis. Too hot and you start to cook off all the terpenes and flavor in your smoke. So find the sweet spot for your strain, and go for it. Indicas like it cooler and a little less light, and sativas like it a little warmer with a little more light.

 

[Tejashidrow]

Useing this DIY I built a
DIY cob running 2 cxa3070 cobs fan cooled with
2 - 80 watt drivers, 38 volt
I want to upgrade to 36 v cxa3590's Cobs
Can these drivers drive cxa3590???
Thanks

 

[provos]

Thanks jdb420 the info I got with the led did not make sense to me never used one before it's just for veg as I have heard good things about this small light so though I'd give it a try as they are cheap with good customer service and have been around for years now hopefully I will do my own build for flower tent with some cob,s but as you said I will take it slow with it being so young as I don't want to burn the tops and see what this led can and cant do thanks P

 

[jdb420]

I would say around 24 inches. The newer mars lights say 24 to 36 inches, but they draw around 205 watts. I would start at 30 inches and move it down an inch or two every 2 days. Download a free lumen measuring app on your phone and measure the luxs or lumens at the same height as your seedling. That way you can measure the amount of lumens that are getting to the top of the seedling. Just go slow with it if this is your first grow. Take notes of what works well, and let that be a guide in the future. Every light is different and you have to test your light to know what makes it perform best for your needs. Just know that as the plant develops roots and more foliage, it will want more light. You will learn what it can handle. At first go slow and in time you will know what you can do to improve your growth without setting it back from too much light intensity. These plants love light, but you gotta be careful when they are young. I've seen really weak seedlings and really strong ones. I guess some of that is genetics, and the rest has to do with environment. Make sure your humidity isn't above 40 for the whole grow. Led grows will see much slower growth if you use a normal 50 to 55 rh. The led lights lack the infrared which means less heat and less evaporative water loss. The temp of the leaves should be around 84 to 86, and the temp of your room should be the same. The old mh and hps bulbs must be kept at 74 to 78 to maintain leaf Temps of 84 to 86. Not so with led lights. Yet, another advantage because that is less cooling to provide your garden in the Warner months. Any other questions, feel free to ask. These other farmers could tell you way more than me. I haven't been doing it near as long as most of these guys. But remember that the lower your Temps go, the slower your rate of photosynthesis. Too hot and you start to cook off all the terpenes and flavor in your smoke. So find the sweet spot for your strain, and go for it. Indicas like it cooler and a little less light, and sativas like it a little warmer with a little more light.

Also consider doing a scrog. This will get the maximum amount of light to all your buds. This way you yield the most you can of the square footage of your garden. You take a 3 dimensional plant and turn it in to a 2 dimensional grid and this way your plant gets an equal amount of light to the entire plant. Build your screen for your scrog to the dimensions of your light's coverage. Select strains that are good for scrog and take notes of each strain you grow in case you want to grow it again. Also read from the grow journals here and on other sites. I run hpa, and read for over a year before ever growing anything. On my first grow, I yielded just over 225 g's off of one auto that was supposed to yield about 50 g's a plant, 100 g's a plant outdoors. My pump failed within the first 3 days. It was brand new and under warranty. But that didn't help me for the week I was waiting on a replacement. Used a bucket and a makeshift dwc setup till my new pump arrived. Now I have redundancy in every step in my setup in case of an equipment failure. Just know that an ounce of prevention is worth a pound of cure. And in plants, staying on top of them is the key to getting a great yield instead of just average. Being meticulous pays off. So, keep your garden clean and don't do anything that would compromise the health of your garden. Not sure what to do ? Read and read some more before you go making a radical change. And from what I have seen, these plants love consistency. They can handle change, but gradually, not all at once. So, ask the pros and they will help. Then share back to the community when you learn something new that works for you. I have learned a lot from these master growers. Thanks again to all of the people who take the time help others. This is why the genetics and quality is what it is today. Great job and keep on growing !

 

[Warmhands]

Theoretically yes. You need to look into datasheets and see at what temp your COB is running. The resistance is temperature dependent and so is the efficiency.

Have you looked into trying commercial high bay lights. Like Cree commercial high Bay ligjts . They are like $360 at Beelighting I thinking getting one and try it they are 12 Cree cxb leds.

 

[provos]

Hi warmhands yeah I'm looking at the cree cob 3590? I'm in the UK and trying to find it over here bit hard to get the cree they are all U S website, I can get the rest here but any links on the cree cob would be great this one is for a flower tent and 4x4 table how meny cob's would I need for it I'm new to led's but very interested in the watts per foot and gram a watt ? Cheers P

 

[Warmhands]

I sorry... I have no idea. That's why I am here:D Try looking up Philips horticultural lights. I think they sell them in the UK.
Think of putting them around your plants.

Best of luck.

 

[provos]

Yeah i think i have seen them today funny i will send you his email if you want

 

[HughJassBud]

Hello All!!

First off I would just like to thank you all for your contributions over the years. Over the past few days or so I have become hyper focused on LED technology as I became aware of the CXB3590 and COB's in general. I had often considered LED but discounted it for the same reasons stated before in this thread such as the lack of penetration. However, after reading through what feels like thousands of post from guys like Supra, RealStyles, and so many others; poring over all the technical spec sheets I could find on everything; generally obsessing on the subject, I am convinced of the merits of COB growing and want to participate.

I have some questions that are no doubt answered elsewhere, but I haven't found it yet.

Most important is the luminous efficacy/watt. By my understanding this would be the best way of theoretically determining heat output in terms of btu/watt or btu/lumen or whatever else you can equate to each other. Maybe you guys can point me in the right direction or give me a better idea of how to determine this. I just assumed the theory was that x% of watts produced light then (100-x)% of watts must be heat. As I write this I am sure the answer is somewhere easy and I've missed it, but backspace seems like a hassle.

Next question, and again maybe I just need to look around longer. Has anyone done a side-by-side with hps vs COB?
I have been growing with 5200 watts of HPS (2 x 600w + 4 x 1000w) for several years now. I have experimented with running more 600's on movers vs 1000's and other things. Its always the same battle, how many lumens can I make while still maintaining a reasonable temperature while getting the penetration for taller plants. So, I want to replace some 1000w HPS lamps with LED. As much as I would love to drop $4k+ on this endeavor and swap them all at once, its not in the cards at the moment. However, I think I can scratch up the dough to make at least one light to compete with a 1k watt HPS.

Finally, the BIG question is what seems fair for a side by side? Do I assume 140k lumens from a 1k watt HPS and try to match this with the same lumen output from COB's or just run 20-CXB3590's on like 4 of those HLG-240H type drivers to make roughly 160k lumens but ~1k watts. I think it would take about 16-CXB3590's to make 140k-ish lumens. I'm basing all of this on the spec sheet available for these COB's and the assumption that I can source 16-20 3000k or 3500k CXB3590's with a bin of CD or better and run 5 of them in series at about 700mA, 72v. I may need to adjust my driver configuration.....but it seems like that should work. Otherwise 5 of the 185H types would be fine like I've seen Realstyles do with 4 Cobs in series. I want to enclose all of these in a Raptor hood so I can vent it inline with my others or vent it separately at ambient room temp if that's reasonable.

Perhaps this would be better in a thread of its own, I certainly don't mean to Hi-Jack.

-HJB

My first post here, but long time reader. Thanks again everyone for all your help over the years!

 

[Toaster79]

@HughJassBud

These are the numbers you're workimg with and is where you'll find all the answers:

And you seem to be one of the few that's actually thinking in the right direction about venting those COBs out of the grow space.

 

[HughJassBud]

Awww yes, I have looked at these over and over. I guess I should have been able to surmise as much.

 

[HughJassBud]

From those with more experience, how does this heat really compare to HID sources? How quickly will one of these lights heat up a space by comparison? What temps do they run at in steady state operation with ~50% load? I have seen where RealStyles runs them basically naked on a heat sink with success. I assume he is in the dessert part of California so he's probably dealing with similar heat issues to me.

Kind of a side thought, but has anyone tried using CPU water cooling type approach to cooling these? It would add an additional benefit over HID in terms of not needing to filter vent air, for those of us who are trying to be discrete. Also, I assume the cooler temps would extend the COB life and if you're creative you could plumb your heat exchange out to somewhere that the temp isn't an issue.

 

[Toaster79]

Right, let's brake those number down.

3590 nominal power is 90W and is where it reaches 100% luminous flux. Now if it produces 11000lm @90W @85°C Tj (3500K, CD bin) that makes about 122lm/W. Now at 700mA it produces 60% of luminos flux bit the voltage is at 68V @85°C which makes 47.6W and 6600lm so you get 138.6lm/W.

Now for the heat produced you need to know thermal resistance of your COB, thermal compoumd and heatsink to determine the raise of tje temperature in the core of your COB which will determine the efficiency and the raise of tje ambient temperature at give power.

 

[Toaster79]

From those with more experience, how does this heat really compare to HID sources? How quickly will one of these lights heat up a space by comparison? What temps do they run at in steady state operation with ~50% load? I have seen where RealStyles runs them basically naked on a heat sink with success. I assume he is in the dessert part of California so he's probably dealing with similar heat issues to me.

Kind of a side thought, but has anyone tried using CPU water cooling type approach to cooling these? It would add an additional benefit over HID in terms of not needing to filter vent air, for those of us who are trying to be discrete. Also, I assume the cooler temps would extend the COB life and if you're creative you could plumb your heat exchange out to somewhere that the temp isn't an issue.

I'm running 315W worth of COBs in an 1x1m tent and get the temperature to raise 10°C above ambient temperature if the tent stays closed and my exhaust on high. Even at the highest efficacy like 50% you still have half of the power provided to ypur lights turned into heat which you'll have to get rid of.

Water cooling is an option but so is an enclosure with intake of cold air from outside the room being exhausted again outside the room so no smell management is needed.

 

[HughJassBud]

Now for the heat produced you need to know thermal resistance of your COB, thermal compoumd and heatsink to determine the raise of tje temperature in the core of your COB which will determine the efficiency and the raise of tje ambient temperature at give power.

Ok, this is what I was really getting at. I supposed you can assume some of those values and calculate others, but the only real way to know will be implement some design and test it or use Comsol to do some finite analysis.......which is probably overkill.