Led design help

so I’ve been working on a vertical cob build for some time now. Finally all working i can’t get a ppfd meter but using a lux meter to get a general idea of its output is actually very disappointed.

I am running 4 citizen 1212 Feb 5 cobs per square foot. They should provide 50% efficiency at 15w each totalling 60w per square foot.

I’ve mounted heatsinks back to back so I have cobs facing away from each other and hydro towers built 90cm away from the cobs.

I was aiming for 1500 ppfd with this as I’ll be using co2. Based on calculations I did based on info available on forums I thought 60w per square foot would get me there.

However my measurements taken today I think even though they are in lumens it gives me a general idea - and the amount of lumens is way off?

I got the following measurements:

25klux 90cm away from cobs at “pot level”
57klux 40cm from cobs
61klux 30cm from cobs
68klux 20cm from cobs

I was planning on having the plants finish at 40cm from the cobs and have enough penetration left over to have solid buds all the way down the plant. But these numbers don’t look like I’m gonna get that?

Anyone have any input on what’s going wrong here or have I calculated my lux wrong etc?

Here’s a pic of part of the lights- can’t get a full pic as the whole fixture is 3m x 2m


320 cobs linked up to 8 600w drivers so there’s Quite a bit of spaghetti going on

I would add some reflective material top and bottom to redirect the side light, preferable using angled reflectors. It would improve your readings especially at the further distances. For that matter I woudn't put too much faith in the lux meter.

Rahz said:

I would add some reflective material top and bottom to redirect the side light, preferable using angled reflectors. It would improve your readings especially at the further distances. For that matter I woudn't put too much faith in the lux meter.

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Got white reflective sheeting on the floor, on the ceiling directly above the top cobs, and to the sides. You reckon angled reflectors would help? Which do you recommend baring in mind id need 320 of them

I am using MarsproII led, this light uses reflective cups to mix light and increase coverage

SamWE19 said:

Got white reflective sheeting on the floor, on the ceiling directly above the top cobs, and to the sides. You reckon angled reflectors would help? Which do you recommend baring in mind id need 320 of them

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I would try to get ahold of some 4x8 foam board with the foil film. Very cheap, very reflective and can be found at hardware stores. Place them at a 45-60 degree angle against the floor/rack... might not even need something to secure them depending on how they sit and the exact angle you need to get the best reflection. Easy to move when you enter the room For the top, if you can find some thin aluminum bar about 2 inches wide, cut into 3 foot pieces, drill a couple holes and make a bend at 6" mount them above the top cobs as brackets to hold the 4x8 sheets at same angle at the top.

If you use the reflective cups I would probably use the narrow ones (60 degree I think) only on the top and bottom two rows. Maybe leave all the middle ones without reflectors.

You can always do a run first to see how it goes. I know someone with a system I designed to be 1250 PPFD at 12" inches. They hang them at 24" no reflectors, flat white on the walls, despite my suggestion they move them closer, claims it stresses them. They grow trees 3-4ft. tall and happy with the output, sealed room using CO2.

We had discussed the room and how you can't move anything, but it would be ideal if you could. Barring that, getting the right reflective situation is going to make it work, but I was thinking about your setup. It would be possible to split the lamp in two and mount them on rails at the ceiling. If the rails are rated properly and secured to studs they should support the weight of your lamps. The you can move them to center out of the way with a push when you enter, and move them out to proper distances when you exit. No reflective material necessary and you can turn down the wattage during the veg stage, even dim a bit during peak flower.

We discussed wheels, but to mention it again you could consider welding a base on each of the lamps and adding casters. It would be a little more work to move the lamps than hanging them on rails, but with the right floor surface the weight wouldn't be an issue.

Both pretty major modifications, but something to keep in mind for the future if you're not happy with the output.

One other point before you make decisions on modifications, after looking around for lux intensity the target range is 25,000-50,000.

Added to that I think your 30cm reading (12") should be higher especially in the center of the grid, that's why I mentioned not putting too much faith in the lux meter.

Either way I think there would be a notable benefit to the top and bottom readings getting some angled reflective material in there. You could probably get the foam sheets in place for around $100.

But, even without any modifications you'll be hitting some good numbers and see a benefit using CO2.

So, while I would plan on doing something to improve the light distribution eventually, it wouldn't hurt to just crank it up as it and see how it performs before you do anything else.

Rahz said:

I would try to get ahold of some 4x8 foam board with the foil film. Very cheap, very reflective and can be found at hardware stores. Place them at a 45-60 degree angle against the floor/rack... might not even need something to secure them depending on how they sit and the exact angle you need to get the best reflection. Easy to move when you enter the room For the top, if you can find some thin aluminum bar about 2 inches wide, cut into 3 foot pieces, drill a couple holes and make a bend at 6" mount them above the top cobs as brackets to hold the 4x8 sheets at same angle at the top.

If you use the reflective cups I would probably use the narrow ones (60 degree I think) only on the top and bottom two rows. Maybe leave all the middle ones without reflectors.

Click to expand...

im actually doing this today myself,

Rahz said:

I would try to get ahold of some 4x8 foam board with the foil film. Very cheap, very reflective and can be found at hardware stores. Place them at a 45-60 degree angle against the floor/rack... might not even need something to secure them depending on how they sit and the exact angle you need to get the best reflection. Easy to move when you enter the room For the top, if you can find some thin aluminum bar about 2 inches wide, cut into 3 foot pieces, drill a couple holes and make a bend at 6" mount them above the top cobs as brackets to hold the 4x8 sheets at same angle at the top.

If you use the reflective cups I would probably use the narrow ones (60 degree I think) only on the top and bottom two rows. Maybe leave all the middle ones without reflectors.

Click to expand...

I’m confused a bit by this. I put reflective sheeting directly perpendicular to the light fixture flat.

I can’t get my head around the angle you mean do you mean like the picture below:


Also I think I’m gonna move my vertical hydro system slightly closer. Not sure how much closer yet

I’m thinking to aim for 60cm tall plants that will end up being about 45 cm horizontally due to 45 degree angle of growth.

So I could push the hydro system to around 75cm Away from the light fixture which will have the canopy at 30cm

I read that 25000 - 50000 lux was for slow growth I guess that was wrong or I remember incorrectly

Only downside to moving pots forward is I won’t have enough room between canopy and lights to walk between them and check on the plants in the back. But I guess if the plants in the front look fine the ones in the back should be since they’re all clones

Hell of a light you got there!

coreywebster said:

Hell of a light you got there!

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Yeah, i totally forgot to mention that myself, bitchin rig for sure.

One source for canna :

1000 - 5000 lux Min. necessary for life
10000 - 15000 lux Min. necessary for consistent but sparse growth
20000 - 25000 lux Min. necessary for robust growth
25000 - 30000 lux Max. Efficiency for Sub Tropical varieties
25000 - 50000 lux Max. Efficiency for Equatorial varieties

I assume this is for 12/12.

I see another source mentioning getting close to full sun (90-100,000 lux) but full sun can be over 2000 PPFD and isn't going to be ideal at all indoors at 12 hours a pop.

Reading around a little more, it seems lux meters can have trouble providing accurate results under LED. I would check with the manufacturer to see if there's a correction factor for the LUX readings under LED. So, it's not at all clear at this point that you need to move the pots forward and inconvenience yourself when working with the plants. If anything I would put more thought into the reflective situation.

Even if your meter is reading low and you do a grow before making any more modifications and get fantastic results, you can still add angled reflectors and improve the results at the top and bottom margins. The sketch is basically correct. Looking at the photo you provided it looks like you've got some space between the lower line of cobs and the floor, so you would want the reflectors extending out at least to the final canopy distance. To get in the space you just grab the lower reflectors and pull them out.

Unless you're using full sheets you won't need 30" arms on the brackets.


Bottom line is, you do have a hell of a light and you're probably worrying too much over some lux readings.

i agree, if anything the farthest outside might lack intense photons, but overall, what you gain on the inside will make it not even a factor. unless of course the grow is in the middle of a warehouse with 1-2 feets from edge to wall.

Im waiting on my PAR meter, should be here in 10 minutes, cant wait, lol. Then i can calibrate my Lux,

Rahz said:

I would add some reflective material top and bottom to redirect the side light, preferable using angled reflectors. It would improve your readings especially at the further distances. For that matter I woudn't put too much faith in the lux meter.

Click to expand...

I use cardboard too, from packaging etc and cover it in diamond Mylar, stick it with Gorrilla tape. Cheap n cheerful.
Works a treat. I've big medium and small pieces I slot in.
It's all about the reflection

Alright I’ll do a test run and see how it goes and now I think about it I don’t even need a mounting bracket to do the reflectors you suggest raz as the shape of my ceiling is actually beneficial for that i can just rest the foam on the slope.

Excuse my shitty diagram but it should explain it. I’m building this in a rather large European loft with sloped roof

I’m just waiting on a batch of seeds I fertilised to be ready to pick and I need to pick a new nute line to use with this system.

Veg+bloom by hydro research is supposed to be shipping to Europe in a month or so I’m hoping that’s a decent price as this has a 130 gallon tank don’t want to be spending thousands on liquid nutes

My hacked Lux meter, is exact to my PAR readings, so thats awesome, because my lux meter is more stable in readings. going to do a mapping of the PAR, and send this sucka back for refund, saved $130, lol..

InTheValley said:

My hacked Lux meter, is exact to my PAR readings, so thats awesome, because my lux meter is more stable in readings. going to do a mapping of the PAR, and send this sucka back for refund, saved $130, lol..

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Yeah I’d have to order mine from the USA for 130 usd then pay 50 usd shipping then probably 80 usd for import charges if I wanted to then return it I’d have to spend another 80 usd on shipping and only get 130 usd refund. Only one website I found selling a par meter here and their website has been crashing with php errors for months I emailed them asking about it and got no reply