DIY COB LED Calculator

bggrass

bggrass

Well-Known Member
threetwobravo said:
@bggrass

Thanks for making this calculator man, any chance you can add the CXB3590CD 72V 3500K? I can't seem to find a spread sheet for it.
Click to expand...
I haven't done the spreadsheets myself. We all owe it to Supra for that. That being said, currently, if Supra hasn't made the sheet, I can't add it. That is the reason also that you get 0 for some of the calculations at different amps. I don't think I have enough time currently to look up how to get the values myself as I'm sure it requires focus and takes time
 
threetwobravo

threetwobravo

Member
bggrass said:
I haven't done the spreadsheets myself. We all owe it to Supra for that. That being said, currently, if Supra hasn't made the sheet, I can't add it. That is the reason also that you get 0 for some of the calculations at different amps. I don't think I have enough time currently to look up how to get the values myself as I'm sure it requires focus and takes time
Click to expand...
all good bro cheers
 
bggrass

bggrass

Well-Known Member
alesh said:
Nah I was just pointing that you've got the terms mixed up.
PPF - photosynthetic photon flux - total photon output in a range (400-700nm or 380-780nm)
PPFD - photosynthetic photon flux density - total photon output in a range (400-700nm or 380-780nm) per area
So you can convert lumens to watts, then watts to moles of photons per second and that could be converted to average density.

But no wonder that people are confused even mfgs can't get it right - just found this gem.
Click to expand...
So alesh,

totalLumens / lumensPerWatt = Watts
Watts . umol/s/W = PPF
PPF / area(in sq. ft) = PPFD

for 4 CXB3590CD72V3000K @0.7A 80CRI 4.66 umol/s/W

32746 / 167.93 = 195 watts
195 x 4.66 = 908.7 umol/s/W Total
908.7 / 4 sq. ft = 227.175 PPFD

Did I do this right?
 
Last edited:
bggrass

bggrass

Well-Known Member
Calculator updated. Thanks to @SupraSPL and @alesh for explaining how to come up with the ppf and ppfd numbers. If you guys want to I can put your names on the calculator, to show the credit given and appreciation. Wasn't sure if you care about it, but let me know. If someone find discrepancies, please let me know, I'll update it. Same link for the update.
 
bggrass

bggrass

Well-Known Member
So the ppfd value that the calculator displays might be the value at the source of the light. That value probably changes at different distance. @guod posted today the inverse square law in Supra's thread, but then alesh doesn't seem to think it's necessary and Supra says that the leds beam the light in a different way then the sphere way that is used in the inverse square law. I respect both of them opinions, I've learned most of it from them. I felt like trolling in Supra's thread, by asking too many questions, so I thought I'll post here, see if anyone has an opinion.

Considered that the calculations are an estimate, how much difference would it make whether the light is beamed as sphere or flat, considered that the distances from light to canopy don't seem that long. If we find a consensus, I can add an input box for distance from canopy and get different ppfd values at different distances.

What do you guys think?
 
threetwobravo

threetwobravo

Member
bggrass said:
I haven't done the spreadsheets myself. We all owe it to Supra for that. That being said, currently, if Supra hasn't made the sheet, I can't add it. That is the reason also that you get 0 for some of the calculations at different amps. I don't think I have enough time currently to look up how to get the values myself as I'm sure it requires focus and takes time
Click to expand...

@bggrass just found this in one of supras threads if you find time to add the 72V that would be greatly appreciated

 
bggrass

bggrass

Well-Known Member
Added a par per sq. ft box and made some clickable reference buttons which when clicked, it takes you to the thread in RIU. Let me know if I need to add some more links. Same link for the update.
 
Last edited:
You must log in or register to reply here.
Top