DIY COB LED Calculator

bggrass

bggrass

Well-Known Member
Alright. For those who liked it, I just posted version 2 of the Calculator. Couple things to notice, in order to get the numbers to come out you need to enter values in the canopy, driver efficiency, electricity cost text fields. If you don't know your driver efficiency just type 100, but the watts out the wall won't be accurate. I've added an export button. When you do the calculation, the whole thing pops in the calculator built in screen. You can keep playing with different configurations and they will be adding up on the screen. When you hit the export button, the first time, the calculator will crate a .txt file and print the last configuration you did in the text file. To make it simple, if you put your calculator on the desktop, it will create the text file on the desktop. Prices on cobs I used are from Cutter, Kingbrite, and Digikey. Enjoy

Same link in the first post of this thread for the update.

Let me know if any bugs show up. I just completely re-did it so it might have some....
 
Last edited:
klx

klx

Well-Known Member
bggrass said:
Alright. For those who liked it, I just posted version 2 of the Calculator. Couple things to notice, in order to get the numbers to come out you need to enter values in the canopy, driver efficiency, electricity cost text fields. If you don't know your driver efficiency just type 100, but the watts out the wall won't be accurate. I've added an export button. When you do the calculation, the whole thing pops in the calculator built in screen. You can keep playing with different configurations and they will be adding up on the screen. When you hit the export button, the first time, the calculator will crate a .txt file and print the last configuration you did in the text file. To make it simple, if you put your calculator on the desktop, it will create the text file on the desktop. Prices on cobs I used are from Cutter, Kingbrite, and Digikey. Enjoy

Same link in the first post of this thread for the update.

Let me know if any bugs show up. I just completely re-did it so it might have some....
Click to expand...
Lookin good. Any chance of adding 1750mA as a drive current?
 
klx

klx

Well-Known Member
HLG-240H-C1750.

No worries if you cant be arsed. Just seeing more people run at this current.

Output voltage 71 ~ 143V - just fits 4 x CXB3590 36V COBs at max efficiency 94%.

lm/W = 163.6 for CD bin.
 
bggrass

bggrass

Well-Known Member
klx said:
HLG-240H-C1750.

No worries if you cant be arsed. Just seeing more people run at this current.

Output voltage 71 ~ 143V - just fits 4 x CXB3590 36V COBs at max efficiency 94%.

lm/W = 163.6 for CD bin.
Click to expand...
I see that driver, but it's the cob efficiency, lm/w and voltage forward I need. Here's a spreadsheet I have on that cob, but I don't have the numbers @1.75A for it...
 

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bggrass

bggrass

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klx said:
From http://pct.cree.com/dt/index.html

CXB3590 36V CD bin @ 1750mA: (optical efficiency 90%, electric efficiency 90%)

lm = 10161
lm/W = 163.6
Vf = 35.49
W = 62.111

What reading do you need for COB efficiency?
Click to expand...
I completely forgot about that tool. I tried to use it at some point and just tried it again but the numbers don't show up for me. I don't know what I'm doing wrong. I can get the efficiency based on Supra's spreadsheet and the lm/w you gave me. Comes down to simple math:
161.06 / 49.71 = 163.6 / ?
? = 49.71 x 163.6 / 161.06 = 50.49%
I'll add it to the calculator. Any chance you can pull up the lm/w and Vf @1.75A for the following cobs?
CXB3590DB36V4000K
CXB3590DD36V5000K
CXB3590CD72V3000K
CXB3590CD72V3500K
CXB3070BD4000K
CXB3070AD3000K
CXA3070AB3000K

If you can, I'll add a calculation for all the crees @1.75A in the calculator.

I wonder what would the Vero18 4000K and Vero29 4000K lm/w and Vf be @1.75A as well... I can add a calculation for them too...
 
klx

klx

Well-Known Member
Sure man. When using the tool dont forget to set the current range in the top right then scroll down.

lm/W Vf

CXB3590DB36V4000K
177.2 35.49

CXB3590DD36V5000K
190.9 35.49

CXB3590CD72V3000K & CXB3590CD72V3500K
121.5 76.67

CXB3070BD4000K
158.7 36.4

CXB3070AD3000K
142.8 36.4

CXA3070AB3000K
134.9 36.4
.
Not sure if there is a tool for the Veros. Maybe a Vero guy can chime in
 
bggrass

bggrass

Well-Known Member
Got it. Set up the top right corner menu to coarse.... I don't get any numbers for under 1.4A. Does that sound right?
 
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klx

klx

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But the numbers you used to get the efficiency were direct from Cree so they would be the most accurate no?
 
bggrass

bggrass

Well-Known Member
klx said:
But the numbers you used to get the efficiency were direct from Cree so they would be the most accurate no?
Click to expand...
Well, they gave us Vf and lm/w and I just assumed the the relation between efficiency an lm/w is linear (in the way I calculated it). The formula that's posted above calculates efficiency using some constants and the current. I've been thinking about it and those constants are probably specific just for the cxb3590 36v 3500k otherwise all the efficiencies of all different cobs will be the same at the same current, which is not the case with different bins.

Bottom line is, I can use that formula to fix the efficiency of the cxb3590 36v3500 @1.75A, but all other cobs efficiencies @1.75A will be a little off. Unless I know how to calculate those....
 
bggrass

bggrass

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What we're talking about is, I got the efficiency at 50.49% @1.75A, but following that formula, it gives us 52.87% @1.75A.... So it is currently incorrect by ~2%. Probaly in the same range for all cobs I did @1.75A....
 
BOBBY_G

BOBBY_G

Well-Known Member
bggrass said:
Looking at the formulas posted there, it seems that the numbers I got for efficiency @1.75A are a little off, not by much but still...

E=0.8948 * I^2 - 13.203 * I + 73.234

I can modify them to reflect this formula, but before I do that, do all the constants used in it apply for all cobs or just for the cxb3590 36v3500K?
Click to expand...
those apply to the one single chip that supra measured. you could easily derive an equation from crees data as well *IF* they presented data below 1.4A which they do not, which is why i used supras data
 
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