Introducing CobKits.com - specializing in DIY and Citizen COBs

I made a mistake and corrected my previous post

So, 43~45% efficiency @ 84W seems right, it clicks, but that still makes your "best guess" table over estimating by ~17% (!) well over what you'd call normal margin of error ..

Looks like Cree is still ahead, in most cases, on efficiency ...

CobKits said:

heres citi calc at 4000k 80cri, 85C Tj:

View attachment 3830359

42.8% efficient but that Tj is way high for 84W. 45% is more realistic.

and the citis seem to outperform the datasheets in practice. in my testing the 1818 at 84W was about as efficient as cxb@ 67W. pct says thats about 153 lm/W or 47% efficient on a 323 LER for 4000k 70 cri cree

question remains would you rather have a higher efficiency number if the LER is lower? or would you rather have straight lumens (/PAR)

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yeah thats a tough one.

assuming you are referring to this table here:

https://www.rollitup.org/t/introducing-cobkits-com-specializing-in-diy-and-citizen-cobs.916763/page-25#post-12961347

at the time i was just taking raw lumen measurements and comparing it with supra's cree spreadsheets (see "cree typ" sheet in this excel workbook: https://docs.google.com/spreadsheets/d/1nKfc12OCuDu7puJCa_6maefyCVm3gS5sBmzAXOlh06w/edit#gid=714232104)

so if you go to the chart for 4000K DB you'll see that for 67W the cree should be about 53-54% efficient. and the 1818 is putting off the same amount of PAR at ~84W, so we make the leap that, based on the efficiency numbers in that spreadsheet, that the citi is that same efficiency. now looking at that further they have different LERs so the efficiency number will be biased from that alone (in favor of cree)

obviously neither cree PCT or citi calculator is all that representative of what the chips do in real world. largely a reflection of the fact that our application is so far off the map with the low currents. Also the bias between manufacturers in hot vs cold binning and what they state for minimum/typical values and at what temperature.

im hoping that doing measurements on multiple chip samples with better temperature and current-controlled measurements with the sphere gets us better data to work with. i need to do at least 3 chips from each model i think to get a good indication of performance. cree in particular seems to have wide variations in a given bin/lot. i can grab 2 citis or veros and they generally test right along the same curve. ive seen +/- 5% from crees out of the same lot.

EfficientWatt said:

Looks like Cree is still ahead, in most cases, on efficiency ...

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looks like in the real world, citis or veros that cost about half as much as cree put off the same amount of PAR to your plants at equal umol/J efficiency...and if you want to compare flagship chips (3618 vs 3590) or even chips that cost the same (1825 vs 3590), at a given wattage, its not even a close race

@EfficientWatt
Try the Cree Calculator the cxb3590 cd bin is not 182lm/w as you read here on RIP. It is more like 166lm/w @50C.

minor sphere update: some shots:



with heatsink for scale



not much to it really. white sphere with a port and a baffle. The baffle is designed to prevent direct illumination of sensor to give repeatable readings of reflected light independent of beam orientation

closeup of port



port with vero29 for scale



closeup of baffle



other side of sensor port with photodiode disconnected



LI-COR li190 sensor in place of OG photodiode




the photodiode installed on the sphere would normally be read by a picoammeter (basically a benchtop ultra-precision low-current ammeter). It has a BNC and i tried to hook it up to my Li-Cor meter and it read, but read negatively (probably could be fixed with a polarity swap), but it pinned it. possibly resolvable with entering a new constant, and/or addign a resistor in line.

ultimately calibrating the ocean optics USB-2000 (similar to this but mine is the older "non +" model)
using this) is what id like to do as it will give us more data, as the licor has a sharp cutoff at 700 nm.

for now i think i will figure out how to mount the li-cor in there, which is somewhat calibrate-able as i have the constant from a semi recent (this decade) calibration:

https://www.licor.com/env/support/cal/2012-04/instruments/Q45044.pdf

what would be awesome is if anybody with a 3D printer could make me some mounts for these sensors. anybody up for it?

peltier coolers are horribly inefficient might as well use ice cubes.....lol!

HolyGhost23 said:

if you look at the lm/w the 1825 is the best at that amperage. so if you get me a 185-54 ill buy your 1825 light "engine".. i might swap out the fan for a Peltier cooler to it .. to experiment.

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Wow! you don't have to anymore?? Must be nice........lol!

CobKits said:

the good old days where you doubled back around on your drive to the hydro store

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Now here's where I have a problem with this vague statement every time I see it. 600-1200 ppfd in WHAT environment? When you start getting over 600 ppfd your gaining little unless your also running CO2. Max light is only useful when every aspect of your environment is tuned to run at max potential. You can put a 500 cu in V8 on a gocart, doesn't make it useful.

CobKits said:

i'll try to make the driver page more explicit.

trying to be polite here, but its kind of not up for debate. Youre the only person who advises 400, every other person on this site would say 600-1200. and there is plenty of science to back that up. But there are other threads for that. im all for 400+ on the bottoms but top canopy really should have 600+

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r

pop22 said:

Now here's where I have a problem with this vague statement every time I see it. 600-1200 ppfd in WHAT environment? When you start getting over 600 ppfd your gaining little unless your also running CO2. Max light is only useful when every aspect of your environment is tuned to run at max potential. You can put a 500 cu in V8 on a gocart, doesn't make it useful.


r

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This is false. 600 PPFD's about 75% growth rate. 900-1100 is pretty much 95-100%. Over 1200, you start to reach photoinhibition saturation points. 1500 can start to cause cell damage and legitimate harm to a plant.

You don't need CO2 unless it's also hot, but obviously it does contribute. Not necessary to achieve optimum growth rate at proper PPFD, though. People typically crank heat to 85-90°F in combination with CO2 to increase respiration and metabolism (open up the stomata) for even faster growth.

Temps aside, PPFD usually is counted in a square meter. All other environmental factors don't interfere with PPFD unless you, for some fucked up reason, humidify your grow room so much that a haze forms between your canopy and your light.

ive read that co2 is useless below 1000 ppfd. not sure i agree with it, maybe they meant below 1000 ppfd more light is easier to add/cost effective to increase growth compared to co2.

There has only been one scientific study on CO2 enhancement and they only went to 700ppms, but showed definite increase in plant mass

CobKits said:

ive read that co2 is useless below 1000 ppfd. not sure i agree with it, maybe they meant below 1000 ppfd more light is easier to add/cost effective to increase growth compared to co2.

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I'll see if I can find it. I read about it in the book: Marijuana Cultivation Reconsidered by Read Spear

where's your data to make the statement my claim is false ? You've provided nothing more than the same vague, generalized statement. under WHAT conditions is this true? What was the garden environment that provided those numbers? According to what you say, my garden will increase its yield tremendously just by adding more ppfd. Increasing the ppfd alone is enough? My plants won't want more: Water, nutrients, CO2? Doesn't photosynthesis need across the board increases?

I'd love to see a side by side comparison done at 400-600 PPFD, with and without CO2, and again at 1000 PPFD, thats the only way to really answer this. IMO, I think, the gains in plant mass will not match that from say, 300 to 600 PPFD, and will drop off rapidly without CO2

Olive Drab Green said:

This is false. 600 PPFD's about 75% growth rate. 900-1100 is pretty much 95-100%. Over 1200, you start to reach photoinhibition saturation points. 1500 can start to cause cell damage and legitimate harm to a plant.

You don't need CO2 unless it's also hot, but obviously it does contribute. Not necessary to achieve optimum growth rate at proper PPFD, though. People typically crank heat to 85-90°F in combination with CO2 to increase respiration and metabolism (open up the stomata) for even faster growth.

Temps aside, PPFD usually is counted in a square meter. All other environmental factors don't interfere with PPFD unless you, for some fucked up reason, humidify your grow room so much that a haze forms between your canopy and your light.

Click to expand...

pop22 said:

where's your data to make the statement my claim is false ? You've provided nothing more than the same vague, generalized statement. under WHAT conditions is this true? What was the garden environment that provided those numbers? According to what you say, my garden will increase its yield tremendously just by adding more ppfd. Increasing the ppfd alone is enough? My plants won't want more: Water, nutrients, CO2? Doesn't photosynthesis need across the board increases?

I'd love to see a side by side comparison done at 400-600 PPFD, with and without CO2, and again at 1000 PPFD, thats the only way to really answer this. IMO, I think, the gains in plant mass will not match that from say, 300 to 600 PPFD, and will drop off rapidly without CO2

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https://www.tastyled.com/
Scroll down the front page.

And yes, more PPFD = better yield. Simple as that.

CO2 is more important if the heat is high and the stomata is open.

Nutes sustain the plant, but light has more influence over plant size and final yield. Your plant just needs properly fed to keep thriving. Light intensity is more important in determining your weight and density.

Anyone ever used this for Thermal paste for cobs? I ordered thermal pads with my cobs but the protective plastic layer won't peel off at all without tearing holes in the thermal pad.

It contains graphite and zinc in the compound. I used the thermal pads before on my other 4 cobs and had no problems with them but these just wont peel away from the protective plastic. This Ox-Gard is all i can source locally. Guess i can wait another 2 days and order Arctic thermal paste off Amazon.

Olive Drab Green said:

View attachment 3830790
https://www.tastyled.com/
Scroll down the front page.

And yes, more PPFD = better yield. Simple as that.

CO2 is more important if the heat is high and the stomata is open.

Nutes sustain the plant, but light has more influence over plant size and final yield. Your plant just needs properly fed to keep thriving. Light intensity is more important in determining your weight and density.

Click to expand...

Yes, keep in mind that double ppfd doesn't double yield.............balance is key

VenomGrower6990 said:

Anyone ever used this for Thermal paste for cobs? I ordered thermal pads with my cobs but the protective plastic layer won't peel off at all without tearing holes in the thermal pad.
View attachment 3831862 View attachment 3831863
It contains graphite and zinc in the compound. I used the thermal pads before on my other 4 cobs and had no problems with them but these just wont peel away from the protective plastic. This Ox-Gard is all i can source locally. Guess i can wait another 2 days and order Arctic thermal paste off Amazon.

Click to expand...

wait on the arctic paste grower

VenomGrower6990 said:

Anyone ever used this for Thermal paste for cobs? I ordered thermal pads with my cobs but the protective plastic layer won't peel off at all without tearing holes in the thermal pad.
View attachment 3831862 View attachment 3831863
It contains graphite and zinc in the compound. I used the thermal pads before on my other 4 cobs and had no problems with them but these just wont peel away from the protective plastic. This Ox-Gard is all i can source locally. Guess i can wait another 2 days and order Arctic thermal paste off Amazon.

Click to expand...

I used the MX2 graphite paste and it worked fine.

@PSUAGRO. @Uberknot Thanks for the feedback. I just went ahead and ordered the Arctic thermal paste. I can wait a couple more days because i want to make sure i do this right with the time and money already invested.

I need a little help. I made an order from cobkits.com and can't get my stuff working. Here is what I have.

4 bjb holders for clu048
4 citizen clu048-1212
4 passive pinfin heatsinks
1 meanwell hlg-120h-48a driver

I went and built a pretty kick butt frame for these out of electrical conduit and some screws which cost a whole 7 dollars, I can tilt the lights and everything.

The problem is I can't get all the lights to light up at the same time. I can get all 4 to work individually buy jumping with a wire, all the cobs are working and all the connections are good. I'm getting 48 volts from the driver, but I can't get even two cobs to work at once.

Now I have them hooked up in series because that is the way everyone says it has to be done.

What do I need to look at to make this thing work?

Silver or lead said:

Now I have them hooked up in series because that is the way everyone says it has to be done.

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That driver only works in parallel