Late bloomer needs DIY LED light help!

Calling @dbrn32 Lol!

I’ve decided to build a setup for indoor growing this winter. I had planned to just stay an outside grower but, as usual, plans have changed. Lol! So, now I’m faced with finding or building a light. I think I’d like to build one. I’m pretty handy but electronics are a weak spot in my repertoire. I just don’t have much experience at it. I’d like to build a really good LED to save on electricity and so I know how it works and how to repair it if/when it breaks. I’d like a light that will take me all the way through flower and have the capacity to produce dense nugs, if I do my part. I’m still debating whether to get a 5x5 tent or just a 4x4 but I’ll probably go with the larger one. I’d like to build it as affordably as possible but I’m willing to go up to around $1k (complete) if I HAVE to. Can I build a light that’ll work in a 5x5 tent but that would physically fit and work inside a 4x4 tent? It’s possible that, down the road, I could add a second tent and I’d like to know that this light would work in either size. Or, is that a bad idea?

I don’t know enough about the effective difference between COBs, quantum boards and strips so I don’t have a preference. I’ll lean on y’all’s advice on which to pick. I’d like to stay shy of that point of diminishing returns. This is too costly a venture for me to blow $$ unnecessarily chasing an additional few percentage points of output or efficiency. I want a “great” light, not the ultimate one!

I will need a “Grow light for Dummies” instruction to get this done so I’m going to apologize, up front, for my ignorance; and thank everyone in advance for any help/advice they give!

So, how do I get started?


Really, The thing about LEDS now, it seems they’re at a point where you can get a pretty nice light, in either direction you go. COBS, QB’s or strips. It all comes down to preference really, on whether or not you would like to actually build a light. Or have something in a kit ready to go for you. Plug and play sort of thing.
HLG’s Quantum Boards are extremely versatile, and can really be thrown in just about any situation it looks like. So many people have been jumping on them its been fun to watch the sort of thing people are coming up with. Its actually that way with LED’s in general.
You should have no problem having a light that can be 2.2-2.3 umol/j or higher, even spending on the cheap.
Here is a PPFD map of a 4x4 area using the 48 SAM from Timbergrowlights. The PPFD readings are pretty uniform across the board. While this setup will not work for your 5x5, it does show the boards capabilities. You would just need to build a different frame, or use the XL heat sinks. (all PPFD measurements are x1000)

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Well you’re in luck lol, I was just discussing a potential plan for building a light that was versatile enough that you could just add fixtures to from one space to another with @Bogleg.

I’m not sure if that particular setup would be ideal for a 5x5 because it would require 6 drivers, and likely multiple 20 amp circuits to cover inrush current on them. I can assure you that you won’t be the first person to feel a little short on knowledge that built a kick ass light. I’ll be happy to help you get the right components and assist in assembling anyway I can.

As far as cobs, strips, and qb’s they all kinds have their advantages. Qb’s are the least labor intensive, usually the easiest to source, and have the greatest efficiency potential. Cobs usually the most difficult to build and source, but they do give you that heavier single point intensity and leave more potential for future upgrades. The strips usually fall in between the two and perform more like the qb’s. It’s all pretty much the same to me, but I think the strips are really popular because it leaves more of s door open to use some stuff someone who is handy may already have laying around.

$1,000 should be a plenty reasonable budget to work within. But we should nail down the space first. Building a light that will optimize both will be difficult, you’re going between 16 square feet and 25 square feet. To me that means over building for a 4x4 which would be a waste of money, or going to a multiple light setup as mentioned earlier, where you could add more lights. Neither situation is exactly cut and dry. My personal opinion is that you’re better off doing a small space well than the alternative with a bigger space. Of course not everyone agrees with me, and that assumes you could do as good as one in the other. But, for whatever reason the average grower seems to struggle a little when moving indoors to outdoors or the other way around. So take that for whatever you feel it’s worth. I can tell you pretty confidently that there’s not a light I’ve designed that won’t pull well over a pound dry in a 4x4. Obviously abilities and factors will play into how well each individual does, but lights plenty capable.


@Aolelon - Thanks for the reply! Unfortunately, some of the terms you used are foreign to me; so that makes it hard to understand. Could you break down some of those acronyms for me?

@dbrn32 - Great points! Im pretty sure I’m going to go with the 5x5. I wish I could find a 4x6 - that’s what I’d really like. But, since I’ll likelt get a Gorilla tent I’m stuck with square shapes. I’d like to shoot for a goal of 2lbs (or more) so a 5x5 with a light designed by you should have no trouble meeting (or even exceeding) that goal.

I can probably run some new wiring to pu all the grow equipment on their own breakers. The room is near the main panel and I don’t think it’d be too much hassle to run wire and install some new breakers dedicated to the lights and other grow gear. I’d just need to know what size breakers to install and how many of them.

I like the idea of QBs but my concern with them is failure - does the whole board go down if one LED in the board goes out? COBs seem more customizable because they look like they could be swapped out easily and if one went out it’d be easy to replace. However, I don’t know what I’m talking about so that assumption by me is probably wrong. Lol. What about a combination of QBs and COBs? Really, I’m going to go with your suggestions because I don’t know enough to make an informed decision. If there’s a big difference in the effect on my electric bill, with one vs another, with minimal difference for the plants, I’d like to go in favor of saving electricity/$$ How many watts are you guessing I’ll need to pull from the wall for a 5x5?

One quirk about my situation: access to my grow area is tight. The room itself is large but getting in there is a bit of a squeeze. So, I need to build a light that can either be broken down easily or is no more than ~3.5’ wide. I can assemble it in the room but in case we move, I just need to make sure I can get it apart to remove it.

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Well, a single diode going out won’t generally shut down a whole board. Probably more like a string of diodes, unless the trace shorts then the driver would go into protect mode. To change out a single cob is indeed pretty easy. Upgrading can be a little more difficult depending on what you’re going for. They don’t all use the same bolt pattern. But if you get something like a pin sink from rapid led, they are pre drilled and tapped for most of the major players and sizes. Coincidentally, price isn’t bad and you can get s discount for being s first time buyer.

The numbers @Aolelon mentioned were par measurements and photon efficacy. It’s making reference to your actual light levels and how much radiometric energy you’re getting per watt. Much better than just using watts, as that’s simply energy consumption. For now think of it like this. An led thats 2.2 umol per joule is 10% more light per watt than a light that’s 2.0 umol per joule. So you could reach the same photosynthetic photon flux density with 10% less power. Each time you grab a 10% increase your light gets significantly more expensive though. We usually do this by dropping operating current, which means more leds.

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Just realized I didn’t answer all your questions, sorry!

A hybrid light utilizing something like cobs and qb’s or strips is a possibility. Which also reminds me that the chilled logic boards may be an option too. It’s kinda like a qb, but gets mounted on a pin sink like a cob.

Typical 5x5 setup would usually be in the neighborhood of 800-1000 watts. Could be a little more or less though. Once you decide on a platform, you kinda thumb eyeball based on which drivers match up to the leds well. I don’t like to instruct people to use parallel wiring with leds, so that kind of closes a few doors as far as what I would recommend.

Dont want to disuade you from an LED build but you did mention your neophyte electrical knowledge. I went with this fixture and its pretty awesome and under your tenative budget of 1K.

Hope this helps.

@DTOM420 my 2 cents… My light through rapid with 10% first time discount was about $820. I did have to build my own light frame but then you can build it to fit either space if you like. And you could run more efficient( cheaper) turning it down in the 4x4. It is a cob build and you will be very happy with it.

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So, what’s the most efficient, longest lasting, best veg/flower spectrum, and cost effective light?
Eb strips, quantum board or cob?
I like the height of quantum boards/eb strips.

I feel like doing another lighting project :+1:

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Well, there’s so many variables in that question it would be hard to give an answer that doesn’t have holes in it. I’m pretty sure the lm301b and nichia 757’s are still the most efficient diodes available. So that would point towards the 288 v2 and some mildly available strips as they’re available in a ready to wire package. But depending on operating current of any of them, it’s entirely possible to have a softly driven cob more electrically efficient than a board or strip driven stiffly.

Same kind of stuff could be said about the light spectrum. With all the technology available, I still don’t think we’re at a point where we can say what is the best light spectrum. Limiting the conversation to white phosphor coated diodes, the higher cri options would be more in line with the McCree action spectrum. Nichia has a 5000k 97 cri that has nearly replicated the par region of sunlight, if you’re a “sunlight is king” kind of guy. But I’ve yet to see conclusive data that there’s any major difference in quality or quantity among any of the color temps or cri that we commonly use for seed to harvest type of growing. In fact, it appears that if you’re in that neighborhood, light spectrum takes a backseat to intensity on almost every account.

Because one color temp and cri rating can show variance from manufacturer to manufacturer in spd performance makes it even more difficult. But anything from 3000k-4000k in 90cri would be difficult to say is not good. Some of those colder temps in 97cri too. But people have been pulling nice quality yields with 3000k and 3500k 80cri for years. So I would hardly say you absolutely need to go to any of those higher cri options.

Personally, I like something like 3000k-3500k 90cri for seed to harvest.


Ha. I didn’t think there’d be an easy answer.
I’m really enjoying scrog grows, so a rectangular light pattern is probably best for me.

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If arrow is still running 30% off for new customers it would be a good time to at least get leds and drivers. Not sure if you’ve ordered from there for first build? I had to create a new email address and ship to my parents house. Worked though, and I saved about $140 on a few drivers and gang of strips.


@dbrn32 I’m still hoeing back and forth on what size grow to do. Lemme ask you a question about a couple scenarios. I have a lot more room one way than another and that’s why, if I had my choice, I’d get a rectangular tent. Now, after mulling over the great points you and others made, I’m considering whether I might not be better starting with a 4x4 tent with the intention of (down the road) putting in another 4x4 tent next to it. That way, I’d be able to have a veg room and a flower room, ultimately. I guess my question is: Is this sort of setup much more efficient (production-wise) than a single tent? Of course I realize my overall footage is a lot bigger (and ultimately more expensive) but my turnover would/could be 2x as fast with plants almost constantly in flower. AND it’d be a better setup for breeding my own seeds for outdoor growing - my main focus.

I’m thinking his would also reduce my cost for getting started and allow me to make sure this indoor thing is going to work for me. Obviously there are lots of ways to look at all this but I’m curious what your thoughts are on a strategy like this?

BTW- I’ve never bought anything from Arrow so I should be able to get a pretty good discount on this first build.


Starting up a 4x4 will absolutely be more affordable than 5x5. The cost of lighting alone will be close to half if you want to do it well. If you grow to two spaces, you’ll be able to harvest a full tent something like 5-6 times per year once you get setup properly. There are some multi space tents that would allow you to veg and flower in the same tent, that could be a good option for you. And for whatever reason, I feel like hlg has a 4x6 tent set up like that if you’re interested. How to best use them could vary, but there are multiple ways to go about it.


Ok, that seems like a no-brainer, then. If I can build a terrific light for about half of a 5x5 I can probably get this going immediately and may even be able to build the 2nd light by the time the first grow goes into flower. I’ve got some seedlings going already under T5 bulbs so I guess I need to get a move on. Let’s do a really good light for a 4x4 tent - one that, if anything, favors flowering. I figure if it favors flowering in this one I can finish with it and the next light I’ll build can be a more veg-oriented light. Is this possible or foes it make sense?

Where do I start?

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Start with deciding whether you want to do cobs or something with mid power diodes. If you want to lean towards flower, you can easily get 90cri cobs. But that will be a little more effort on the build.

I have NO idea what “mid power diodes” are, lol! What’s the advantage of one vs the other? What would you do?

Honestly, I’m prolly just going to take your advice on which way to go since I don’t know enough to make a good decision.

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Strips and qb’s use mid power diodes.

I could go either way.

You can buy that from hlg for significantly less.

@DTOM420 I’m a neophyte, myself, but ordered the 300 v2 kit. After reading through others’ builds, paying attention to @dbrn32, and watching a couple vids, it seems ridiculously simple to build one of those kits.

Now, if I was told to gather all the things myself & pick the proper connectors & make my own heat sink or something, no matter how simple those things might be, I’d probably just go with a prebuilt light.

Dbrn’s got your back.

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Do you have a link for that information? I’m looking to double up on them. I have a 4x8 footprint.

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