LED Veg lighting: 4' x 16"

I’m trying to determine the best structure/config for a room, exclusively for veg that will light 3 plants, ea. in 5 gallon cloth pots + drip pan, in a row.
I’ve determined that 4’ is just about right for the length.

I think I want 2 lights that I’ll wire in series & hopefully use 1 driver for both.
I’m looking at aluminum square tubing: 1" X 4’

First off, how can I determine how much light (ppfd) a given strip delivers.
What is ‘flux’ lm?
What is the correlation between lm/W and µmol/J ?
I don’t know what is ‘optimal’ for veg but I’m sure I don’t need more than 300 ppfd.

I’m looking at strips and I think I like 3 of these per light, separated to center over each plant.
I value dbrn32’s opinion and I think he might prefer Cree because it’s so small.
Again, I don’t know how much light one of these strips puts out.

So, I’d use thermal tape to stick the strips to the aluminum.
I’d drill holes at key spots to route wire.
I’d put a bigger hole w/ a rubber grommet into the back of the aluminum at one end.
I’d stick 18-2 wire stranded, flexible cable 12’ into the grommet.
Hmm, maybe 18-3 and ground the aluminum?

So again I was thinking of putting 2 of these lights in parallel over my 3 veg plants.
All 6 strips would be wired in series.
Is this a good idea?
How can I determine the driver for this?
How much light (ppfd) would it deliver?

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Hi - I don’t know much about the strips. I have QB boards and the only way I know to calculate average ppfd output is like something posted on HLGs sites for their boards with a table that references how much a given driver, board wattage, and umol/joule the board delivers. Then you can back into the ppfd for the square footage you are trying to cover. So for the table below, if I have a 2100a driver power two 288 boards, and the watss at the board are 102.83, the umol.j is 2.63, and I have a footprint that is one square meter, the average ppfd is 2102.832.63/1 = 540.83

The difference between lm/w and umol/J is that lm/w is overall light energy, where as umol per j is specific to a range of wavelengths for plants. progrowtech.com has a blog on it.


You’ve got a 4’x16" space. That’s 5.32 sq ft. The general rule of thumb for bridgelux strips is around 30-35w/ sq ft. So… around 180w for that space
I built a supplemental light with 4 BXEB-L1120Z-35E4000-C-B3 strips that puts out 188w. That would be enough for your space. You might do something similar.
Here’s a link. Project: Increase the lighting footprint with bridgelux light strips

Of course @dbrn32 is the genius around here. Perhaps he’ll chime in.


This is pretty much same questions as other thread but just a different sized space? I don’t see why you just didn’t post there. 6 of those strips at test current is going to be about a 40 watt light on the DC side, and those strips will run about 2.5 umol/joule at that current.

Thanks. yea, that thread started about CO2 and by the time I was asking about this light I feared I might be aggravating moderators - off topic. So, I decided to move it to a new thread.
Frankly, I was hoping you’d answer this. Thanks:)

The closet is 2X14X8. The 4’ by 16" is the area I have figured specifically containing the plants.
So, if I’ve learned from you correctly, 40 * 2.5 = ppf = 100/1.62 = ppfd = 61.72
Did I do that right? If so, that’s not anywhere near enough light.
I’d really like to learn how to buy strips & match them to drivers.

Again, I’ve got 3 5 gallon pots in pans in a row that just fit comfortably in 4’.
Truth is I really need something for clones too but I haven’t figured that part out yet.
What would you suggest I do?

40 watts at 2.5 umols per second/watt is a ppf of 100. 4’x 16"=5.3 sq feet, that’s almost exactly half a square meter.

So, 40 watts of strips is going to put you around a ppfd average of about 200 umols per second. For a veg space, you want to target a ppfd average of about 400 umols per second. An lpc 100 driver full would be in that neighborhood.

OK, so 5.3 sq ft ≠ 1.62 sq meter. I still don’t see how you’re getting µ(alt 230) mol/joule off those specs.
I’m guessing just your experience with them? Can we 2.5/6 to find µmol/J per 280mm strip?

I don’t like my design anymore & I’m still not convinced I won’t end up flowering 4 5 gal plants in that space. Bergman said in small spaces use tall skinny pots. I interpreted it: ‘get dirt/roots under the foliage’. My past experience in that 2x2 space validates it. Tall is good. Then again, Banana Kush? Tall? :-/

4 5 gal plants in flower means I’d have to veg 4, not 3.
That would force me to redesign my veg area - maybe 16" bench to 24" bench.
Maybe make the veg area 2x2 so I can train them to live in that space.
Yea, that makes sense.

OK - Topic Change (topic modification?) 2X2 veg area. That’s easier to come up with a light.

I think I get how to match strips with drivers. Match current and add strip voltage drop until the sum is within the driver’s voltage range. Thank you:)

So, for a 2x2 veg area what do you think of this? QB 65W.
Looks like it’s just shy of 400 (@ ppf/.37) but close.
I’m pretty sure I can stay about 18" off the plants’ tops. Maybe closer.
I use venetian horizontal blind mechanisms to be able to move the lights up & down.

Is that 65W at the wall? The wife couldn’t complain about that! lol

then for the clones . . .

4’ x 16" isn’t 1.62 square meters, that’s where we come up with different numbers. It’s only about half of a square meter.

Hlg-65 is pretty ideal for vegging a 2x2, that would be a good choice.