Noob needs opinions on diy cob build

Rahz

Rahz

Well-Known Member
batrgrower said:
I totally don't know what these acronyms mean that you guys keep using.

SPD, LER, PPF, and such.
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SPD is Spectral Distribution, usually presented as a graph showing relative intensity per wavelength of a light source.

LER is Luminous Efficacy of Radiation, the number of lumens in a radiant watt for any specific SPD.

PPF is Photosynthetic Photon Flux, the number of photons a light source will output.

batrgrower said:
Where do we find the information about the chips being more efficient at lower amperage?
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The chip datasheets generally provide lumens per watt at nominal (recommended) current, along with a graph labeled "relative flux vs current". These charts will show you a percentage of nominal flux at respective currents. Or you can do what @CobKits does and take readings at various currents and make your own graphs.

batrgrower said:
How do we make a calculation for any given chip to tell us what amperage to run it for maximum efficiency?
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Like RandomHero says the max efficiency will be with the chips dimmed as low as possible. At some point it begins to cost more than it's worth. It can make sense to run any particular chip at 45-60% efficient (maybe a little higher for some chips). Higher efficiency = more chips/cost required but less electricity/cost used over time. If you want to do the math yourself you can use a graph digitizer to digitize an SPD and feed that data into the spreadsheet here: https://www.rollitup.org/t/math-behind.868988/ to find the LER of a spectrum. The L/W as a percentage of the LER will provide the efficiency level.
 
RandomHero8913

RandomHero8913

Well-Known Member
Rahz said:
SPD is Spectral Distribution, usually presented as a graph showing relative intensity per wavelength of a light source.

LER is Luminous Efficacy of Radiation, the number of lumens in a radiant watt for any specific SPD.

PPF is Photosynthetic Photon Flux, the number of photons a light source will output.



The chip datasheets generally provide lumens per watt at nominal (recommended) current, along with a graph labeled "relative flux vs current". These charts will show you a percentage of nominal flux at respective currents. Or you can do what @CobKits does and take readings at various currents and make your own graphs.



Like RandomHero says the max efficiency will be with the chips dimmed as low as possible. At some point it begins to cost more than it's worth. It can make sense to run any particular chip at 45-60% efficient (maybe a little higher for some chips). Higher efficiency = more chips/cost required but less electricity/cost used over time. If you want to do the math yourself you can use a graph digitizer to digitize an SPD and feed that data into the spreadsheet here: https://www.rollitup.org/t/math-behind.868988/ to find the LER of a spectrum. The L/W as a percentage of the LER will provide the efficiency level.
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Great answer Rahz
 
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batrgrower

Well-Known Member
Yes, thank you for that Rahz.

So, I'm leaning more towards 6 cobs per rail for a total of 12 over each 50"x30" system. I'm thinking the 1212 80cri at 3000k (just to clarify, this color is okay for flowering only? Light won't be used for veg at all)

I'm thinking I'll run each rail of 6 with an hlg240-1050b.

And for the heatsinks I'll use the alpine 11 plus for each chip so I'll need 2 apv 12-12 power supplies for each light rail. 3 on each power supply.

Does anyone have any better ideas for this budget build?
 
HydoDan

HydoDan

Well-Known Member
batrgrower said:
Yes, thank you for that Rahz.

So, I'm leaning more towards 6 cobs per rail for a total of 12 over each 50"x30" system. I'm thinking the 1212 80cri at 3000k (just to clarify, this color is okay for flowering only? Light won't be used for veg at all)

I'm thinking I'll run each rail of 6 with an hlg240-1050b.

And for the heatsinks I'll use the alpine 11 plus for each chip so I'll need 2 apv 12-12 power supplies for each light rail. 3 on each power supply.

Does anyone have any better ideas for this budget build?
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Why not use passive pin-fin heatsink.. A lot less wiring... Don't have to worry about a fan breaking down..
Just a thought...
 
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batrgrower

Well-Known Member
HydoDan said:
Why not use passive pin-fin heatsink.. A lot less wiring... Don't have to worry about a fan breaking down..
Just a thought...
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That was a thought when I was going through everything.

I like the idea of less wiring and all that. I had some concerns that my lack of knowledge would cause me to get heatsinks that were too small.

Also, those seem expensive compared to the pc fan type. Or am I missing something?
 
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batrgrower

Well-Known Member
So I'm just rewatching some of growmau5s videos and he's calculating heat watts from watts from the wall and multiplying that by the percent efficiency. And then using this number to determine how large his passive heatsinks need to be.

Where do we get the percent efficiency number?
 
CobKits

CobKits

Well-Known Member
mfrs dont usually report them, you need to calculate it from the spectral chart, which has been done for a lot of, but far from all of, different colors of chips
 
CobKits

CobKits

Well-Known Member
the "LED Efficiency" spreadsheet thts been kicking around for a few years has a bunch for cree and vero

the "cheap and cheerful using citizen" thread has a bunch of charts with SPDs calculated. those are gen5, gen 6 phosphor is a slightly different spectrum
 
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batrgrower

Well-Known Member
Excellent.

Is it possible to wire up 2 of those drivers with one power cord? Like a daisy chain option or something?
 
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