• Here is a link to the full explanation: https://rollitup.org/t/welcome-back-did-you-try-turning-it-off-and-on-again.1104810/

COB efficiency Spreadsheets

EfficientWatt

EfficientWatt

Well-Known Member
Lower current => higher lumens/W but less light per cob.
Higher current => less lumens/W but more light per cob.

Therefore, for a target amount of light:
=> lower current, means more cobs are needed, so more upfront $$$, but higher efficiency and electric savings.
=> higher current, less cobs needed, less upfront $$$ needed, less electrical efficiency/savings too.

(Voltage drops a little at lower currents, and rises a little at higher currents, but it is thru current that we drive them (underdrive/overdrive))

EDIT : Churchhaze was quicker :oops:
 
AquariusPanta

AquariusPanta

Well-Known Member
EfficientWatt said:
Lower current => higher lumens/W but less light per cob.
Higher current => less lumens/W but more light per cob.

Therefore, for a target amount of light:
=> lower current, means more cobs are needed, so more upfront $$$, but higher efficiency and electric savings.
=> higher current, less cobs needed, less upfront $$$ needed, less electrical efficiency/savings too.

(Voltage drops a little at lower currents, and rises a little at higher currents, but it is thru current that we drive them (underdrive/overdrive))

EDIT : Churchhaze was quicker :oops:
Click to expand...
This was something I took note of many months ago, which was that there are two extremes when driving COBS.

Since then, some of the outcomes that I see by underdriving COBS is that by doing so requires more COBS in a given area, consequently increasing start up costs but subsequently saving on electricity bills and giving better distribution of light through different points of projection, thus leading to healthier and bulkier plants.

But then there is the Sun, which acts as one mega light. <---- (food for thought)

:joint:
 
Scotch089

Scotch089

Well-Known Member
Yea but I can walk all over my yard with my apogee meter and no matter what (as long as I'm not in shade) the reading sst VERY stable. With a cob that's definitely not the case.

Like the sun has a 360° viewing angle without any falloff. o_O
 
O

orangesabc123

Member
EfficientWatt said:
Lower current => higher lumens/W but less light per cob.
Higher current => less lumens/W but more light per cob.

Therefore, for a target amount of light:
=> lower current, means more cobs are needed, so more upfront $$$, but higher efficiency and electric savings.
=> higher current, less cobs needed, less upfront $$$ needed, less electrical efficiency/savings too.

(Voltage drops a little at lower currents, and rises a little at higher currents, but it is thru current that we drive them (underdrive/overdrive))

EDIT : Churchhaze was quicker :oops:
Click to expand...
Your explanation was much more concise though, really helped understand it. :D

Although I still have no clue what all those abbreviations mean.
 
ttystikk

ttystikk

Well-Known Member
AquariusPanta said:
This was something I took note of many months ago, which was that there are two extremes when driving COBS.

Since then, some of the outcomes that I see by underdriving COBS is that by doing so requires more COBS in a given area, consequently increasing start up costs but subsequently saving on electricity bills and giving better distribution of light through different points of projection, thus leading to healthier and bulkier plants.

But then there is the Sun, which acts as one mega light. <---- (food for thought)

:joint:
Click to expand...
The sun moves.
 
alesh

alesh

Well-Known Member
kamikaza

kamikaza

Well-Known Member
Hello guys

i am tring to calculate the efficiency of the CXB3070 using Cree Product Characterization Tool -

http://pct.cree.com/dt/index.html

but i can only choose the COB model and flux bin, not by CCT or CRI.

which does make sense, as we all know. 2700k 90cri lm/w isn't the same as 5000k 70 cri.

how can i tell the true efficiency, like supraSPL finds out at his charts?

thanks for any answer...
 
Greengenes707

Greengenes707

Well-Known Member
kamikaza said:
Hello guys

i am trying to calculate the efficiency of the CXB3070 using Cree Product Characterization Tool -

http://pct.cree.com/dt/index.html

but i can only choose the COB model and flux bin, not by CCT or CRI.

which does make sense, as we all know. 2700k 90cri lm/w isn't the same as 5000k 70 cri.

how can i tell the true efficiency, like supraSPL finds out at his charts?

thanks for any answer...
Click to expand...
The bin tells the tool what the lumen output is. The 2700k 90cri top bin is "Z2" and 5000k 70cri top bin is "BD". Those are very different. Then the model(3070, 2530, 3590) tells the wattage based on current and voltage.

The part of the efficiency equation that the tool doesn't have is the LER. We only know the LER's for the spectrums posted in the data sheet(3K 80cri, 3K 90cri, 4k 70cri, 5k 70cri), anything else will have to be some what of a guess.
3K 80cri: 325
3K90cri: 275
4K 70cri: 323
5K 70cri: 321? Forget this one off the top of my head.

Anyways efficiency is (lm/w÷LER).
So take the lm/w of your bin at what ever current you choose, and then divide it by the LER of your spectrum.

For the 2700K 90 cri I would guess around 270-273 for the LER.
 
kamikaza

kamikaza

Well-Known Member
thanks for your answer GG!

what the chart doesnt tell me, is at what color i am at.

for example, the chart says that cxb3070 AD bin at 1900ma Tj85 gives out 8538.9 lm.

but when i look at the product PDF chart for the 3000k 80 cri at the same bin, current, and Tj, it shoud give me 9000 lm.

so, if i want to know the lm/w at different currents for the 3000k 80 CRI i can only compare the % difference between 8538.9 and 9000?

of course i don't have the aknoweladge and equiqment to check it myself.
 
EfficientWatt

EfficientWatt

Well-Known Member
You must of made a mistake somewhere, or misread something ...

(luminous) bins are "groups", defined in terms of min/max Lum/W (at least for white CREE cobs they are)

2 Leds of different spectrum but same bin, will be in the same range of lum/W.
ie :140 lum/W of 2700K has more photons than 140lum/W of 5000K, that's where LER comes into play (as a conversion factor).
Both would be tagged with the same bin.

Hope this helps

EDIT : Just checked it, and you're right, tool gives about 2% less light than the spec sheet :???: Hope it's a bug on the tool side

kamikaza said:
thanks for your answer GG!

what the chart doesnt tell me, is at what color i am at.

for example, the chart says that cxb3070 AD bin at 1900ma Tj85 gives out 8538.9 lm.

but when i look at the product PDF chart for the 3000k 80 cri at the same bin, current, and Tj, it shoud give me 9000 lm.

so, if i want to know the lm/w at different currents for the 3000k 80 CRI i can only compare the % difference between 8538.9 and 9000?

of course i don't have the aknoweladge and equiqment to check it myself.
Click to expand...
 
Last edited:
Greengenes707

Greengenes707

Well-Known Member
kamikaza said:
thanks for your answer GG!

what the chart doesnt tell me, is at what color i am at.

for example, the chart says that cxb3070 AD bin at 1900ma Tj85 gives out 8538.9 lm.

but when i look at the product PDF chart for the 3000k 80 cri at the same bin, current, and Tj, it shoud give me 9000 lm.

so, if i want to know the lm/w at different currents for the 3000k 80 CRI i can only compare the % difference between 8538.9 and 9000?

of course i don't have the knowledge and equipment to check it myself.
Click to expand...
Finally someone else noticed. That is how it was with the cxA too. I have brought it up in the past but didn't get an answer. The tool is right on for the xbd data sheet. So I wonder what's up. It is definitely on crees tool end, because multiple analyses of the data sheet by different people have all confirmed each other more or less.
It is beyond me as well.
 
SupraSPL

SupraSPL

Well-Known Member
Yep the PCT is just a guide. The spreadsheets are more precise but just approximate because of variation from COB to COB. It does give us the general idea of where we are at and from there we can do empirical testing.
 
Shig87

Shig87

Member
Impressive data you collected here so far!!!
I was doing that by myself in the past days just without the knowledge like you guys have for real it's just unbelievable for me right now maybe I'm dreaming :shock:
I just have 2 questions

Which cob is the best and how should I undervoltage them? :roll:
Thank you for sharing
love you guys :peace:
 
S

sethimus

Well-Known Member
Shig87 said:
Impressive data you collected here so far!!!
I was doing that by myself in the past days just without the knowledge like you guys have for real it's just unbelievable for me right now maybe I'm dreaming :shock:
I just have 2 questions

Which cob is the best and how should I undervoltage them? :roll:
Thank you for sharing
love you guys :peace:
Click to expand...
that's up to you to decide, you have all the data. find the pricepoint you're comfortable with.
 
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