How to calculate PPFD for my build?
- Thread starter Joe34
- Start date
George2324
Well-Known Member
For optimal light for co2 1500 par is what I aim for.
If I get bleaching I'll just dim them down. I'd rather have too much than too little I suppose. It's costing me 350 dollars in shipping alone and nearly 5000 dollars for all the stuff I need from Alibaba so don't wanna have to order again if I get too little or wrong stuff.
I can use 4 1818s at 75w on a 1400a 320h driver I can use 4 cobs with 21v left on each driver. Are there any good 5w led chips that can be run at 1400a?
The issue I can't get my head around you say that 33 par w is 1500 ppfd but in reality the canopy could and theoretically should be way less than that?
If I get bleaching I'll just dim them down. I'd rather have too much than too little I suppose. It's costing me 350 dollars in shipping alone and nearly 5000 dollars for all the stuff I need from Alibaba so don't wanna have to order again if I get too little or wrong stuff.
I can use 4 1818s at 75w on a 1400a 320h driver I can use 4 cobs with 21v left on each driver. Are there any good 5w led chips that can be run at 1400a?
The issue I can't get my head around you say that 33 par w is 1500 ppfd but in reality the canopy could and theoretically should be way less than that?
George2324
Well-Known Member
I've pretty much dialed in my grow now. Last thing to dial in is the amount of light. I may sound like I'm being crazy about getting these numbers but I have a nice little environment going on. Last two things I have to get control of is light and co2.
CobKits
Well-Known Member
thats 33 par W/SF and is a lot of light, most people run 20-25
George2324
Well-Known Member
33par w/sf is 1500 ppfd but at how far from the cob?
CobKits
Well-Known Member
its not related to light source
par watts per square foot and ppfd are both measures of par intensity per area
how much par your cobs produce are determined by a host of factors including:
-cob spectrum
-cob efficacy
-current
-driver efficiency
how much of the light produced by the cobs actually falls on the canopy is determined by:
-distance
-# of cobs per a given area
-optics efficiency and directivity
-% of light wasted by misdirection
-% of light that is reflected
-reflectivity of reflective surface
you say you are in large open areas so reflectors or lenses would be a must even thought they eat 5-10% of the light
par watts per square foot and ppfd are both measures of par intensity per area
how much par your cobs produce are determined by a host of factors including:
-cob spectrum
-cob efficacy
-current
-driver efficiency
how much of the light produced by the cobs actually falls on the canopy is determined by:
-distance
-# of cobs per a given area
-optics efficiency and directivity
-% of light wasted by misdirection
-% of light that is reflected
-reflectivity of reflective surface
you say you are in large open areas so reflectors or lenses would be a must even thought they eat 5-10% of the light
George2324
Well-Known Member
Each cob will be directly above canopy if I was to use a 90 degree lense as far as I remember from reading the diameter of coverage is equal to the distance travelled at 90 degrees so at 12 inches away that would be a foot of coverage.
That should make each cob cover exactly 1 sqft each with no overlap.
So if 1 cob is covering one sq ft with a lense I would lose 10% of that ppfd?
So if I had 33 par watts per cob (1500 ppfd) I would lose 150 ppfd making it 1350 ppfd.
However that ppfd should also drop the further away from the cob the measurement is taken right?
That should make each cob cover exactly 1 sqft each with no overlap.
So if 1 cob is covering one sq ft with a lense I would lose 10% of that ppfd?
So if I had 33 par watts per cob (1500 ppfd) I would lose 150 ppfd making it 1350 ppfd.
However that ppfd should also drop the further away from the cob the measurement is taken right?
captainmorgan
Well-Known Member
Reflectors with snap in defusers is a good option. I run just the reflectors and can put little zip locks bags on them if I need to spray.
CobKits
Well-Known Member
not as much as you'd think because as you go lower now other cobs are shining into that same space and the irradiance is additive
George2324
Well-Known Member
If I use 90 degree lenses though other cobs will only start to shine on same space once 13 inches Away. If canopy is set at 12 inches away there would be no overlap.
It looks like the calculator on RIU for these cobs is wrong as it states 31 par watts is 1800 pffd
It looks like the calculator on RIU for these cobs is wrong as it states 31 par watts is 1800 pffd
Big smo
Well-Known Member
I'd much rather run more 1212's at lower amperage to meet the 3590 specs and it would still most likely be less expensive. In the end you have more heatsinks and drivers but those things are all reusable as tech progresses.
For instance 2-1212's at 700ma vs 1 3590 at 1400ma. I'm sure the price to purchase this is still in favor of the 1212. When a new 70% efficient cob comes out you throw away the 1212's and have 2 heatsinks.
For instance 2-1212's at 700ma vs 1 3590 at 1400ma. I'm sure the price to purchase this is still in favor of the 1212. When a new 70% efficient cob comes out you throw away the 1212's and have 2 heatsinks.
wietefras
Well-Known Member
That's why you need to go higher if you use reflectors. Without overlap indeed you would get hot spots and dark spots. Using 90 degree reflectors you need to just about double the height you'd use for bare cobs to get similar uniformity. Even then it will be worse though since the reflectors project circles and not a nice diffuse pattern as the bare cobs do produce.
DankaDank
Well-Known Member
Kind of like this.
4x1212's @700ma(95w) cost me £7.5 per chip. all 4 chips combined where £15 cheaper than a 3590(not including holder) and way more efficient than a 3590 at 95w.
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CobKits
Well-Known Member
thats kinda the reason i like the 28mm cobs
citi 1212, 1812,1818, luminus cxm22 and several other cobs all use same size holders so youre not redrilling and BS if you want to change up later
CobKits
Well-Known Member
thats more efficient than any chip out there basically. you have 576 dies over a really nice large heat transfer area. a 3618 is 648 dies crammed into a much smaller space
what size heatsink is that? 180mm?
CobKits
Well-Known Member
^this
i dont use reflectors at all (tent). if i had an open space id prob only use them on the edge
Big smo
Well-Known Member
I was the same until I did some spot testing and saw an increase over the whole 2x2 space up to 25% in places. I even went as far as testing areas around the plant with reflectors vs no reflectors in a properly sized tent.
DankaDank
Well-Known Member
Yup 180 by 70mm.
Since buying one large heatsink is usually cheaper than multiple smaller ones and only one 100mm lens is required ,this config would make the ultimate compact high powered passive module with this heatsink (3-797925g).
The thermal resistance of 0.3°C/W will allow the 4 chip module to be run at 1400ma.
One day
