COB Spacing and Power To COB Talk

[churchhaze]

Photosynthesis is powered by energy, not quanta of photons. It's those quanta of photons that carry the needed energy. More photons means more energy.

When spectrum is held constant, photon flux and radiant power tell you the exact same thing.

 

[churchhaze]

Watts PAR is a more intuitive variable to use than PPF when they literally mean the exact same thing. (when SPD is constant).

Using ppf rather than watts PAR is needlessly confusing to noobs.

 

[JimmyIndica]

Watts PAR is a more intuitive variable to use than PPF when they literally mean the exact same thing. (when SPD is constant).

Using ppf rather than watts PAR is needlessly confusing to noobs.

I had the same thought about hour ago and didn't reply, but after going back and reading the start of the thread. Its def more of average par# per sq ,than wall watts per square. The big debate is whats the par#s needed per sq too produce what your expecting?

 

[churchhaze]

I had the same thought about hour ago and didn't reply, but after going back and reading the start of the thread. Its def more of average par# per sq ,than wall watts per square. The big debate is whats the par#s needed to produce what your expecting?

Between 12-15W/sqft PAR is what I've been recommending for 2-3 foot plants.

 

[JimmyIndica]

Between 12-15W/sqft PAR is what I've been recommending for 2-3 foot plants.

umols?persq?

 

[churchhaze]

umols?persq?

For 3000k 80 cri cxa:
4.87umol/J * 15W/sqft = 73umol/s/sqft

 

[Sxott]

IMHO on cob spacing is to start with how many cobs your using to achieve the ppfd you want for your canopy and then space them out equally.

I like to divide my grow area in equal segments. The amount of segments its divided by is equal to the amount of COBs I am using and then center that cob over each segment.

For example Im using 8x cxb3590 in a light that is covering a 2'x4' space. The cobs will be spaced 12" apart. (1 cob centered over each of the 8 square ft of the growing area)

I have about 1300 ppfd that is equally distributed on my canopy when running full power.

Another light I have built is close to the same ppfd is a 10 cxb3070 covering a different 2x4 area. I cant divide a 2x4 area in 10 square shaped segments so... Each cob is centerd over a 9.6"x12" area. So I have 2 rows of 5 cobs that are a 12" apart but only 9.6" apart along the same row.

I feel this is the best way to get an even light intensity across the canopy. If I were going to try this same build in a 2ft square case, the light would be much stronger in the center than on the edges of the tent.

 

[churchhaze]

Saying that photosynthesis is powered by quanta of photons, not energy, is like saying car engines are powered by # of C-H bonds. It may be true, but it's an absurd way to measure the energy provided by your gas, and the amount of energy the engine burns. There's a reason we came up with the concept of energy and power and don't just treat all forms of energy as independent. (most people like to measure their engine power in horses, not C-H bonds broke per second.)

 

[Sxott]

My 2 lights to show what I mean:

 

[GrowGrowYumYum]

Who makes good fixtures with COB leds?

 

[Greengenes707]

Assuming the same spd...
More energy=more photons
More photons=more energy
Half full or half empty.
That doesn't make it correct for what we are talking about. Or a way to compare any light because it works with the same SPD...so does lumens. Is it close, and can be related...sure...but again, not correct. Your issue is with plant physiology which I find hard to over turn.

And also doesn't help when it comes to canopy intensity. PAR watts, and avg PPFD will not tell you instantaneous PPFD...which is not the same as avg PPFD. I can take sufficient PAR watts and hang it too high it will not perform. Then also the other side of it... I can take insufficient PAR watts but create acceptable canopy intensity for better growth than sufficient but not ideal in use. All coming back to the plants direct relationship with photons.

Plants require an avg PPFD of 700-1000µmols. But can handle instantaneous intensities of 1500µmols.

 

[PurpleBuz]

My 2 lights to show what I mean:

nice setup!

I was wondering why you chose four short heatsinks instead of two long heatsinks oriented the other way, lengthwise ?

 

[Sxott]

nice setup!

I was wondering why you chose four short heatsinks instead of two long heatsinks oriented the other way, lengthwise ?

I should have used longer heat sinks The other way and it would have used less angle iron and bolts. My third light is on my table right now. Its the same 10x cxb3070 build except its on 2 45" 5.88 profiles this time like your talking about.

Im just waiting on the 3 watt royal blues to go in between the cobs to finish it up.

Third light:

 

[Rahz]

canopy penetration with an underpowered cob? Why not run them on high so to speak! and replace the chips 6 months-1year for something better?

Sorry missed this so will address it now. Penetration is simply a matter of PPFD as far as I can deduce. Running more emitters under driven will give the same result if the PPFD is the same. Efficiency goes up, emitters last longer and use less wattage. The only reason to drive them at nominal or higher is up front cost, but in all my calculations the extra cost associated with under driving is recouped within about 4 years (electricity here is 12 cent per kilowatt). This doesn't factor in the AC savings so bonus if you have to run AC.

 

[PurpleBuz]

I should have used longer heat sinks The other way and it would have used less angle iron and bolts. My third light is on my table right now. Its the same 10x cxb3070 build except its on 2 45" 5.88 profiles this time like your talking about.

Im just waiting on the 3 watt royal blues to go in between the cobs to finish it up.

Third light:

cool like minds think alike, adding a bit of royal blues is the ticket, super efficient and balances the color spectrum. I'm doing similar with vero18s and 3' long 4.85" wide heatsinks.

 

[churchhaze]

Assuming the same spd...
More energy=more photons
More photons=more energy
Half full or half empty.
That doesn't make it correct for what we are talking about. Or a way to compare any light because it works with the same SPD...so does lumens. Is it close, and can be related...sure...but again, not correct. Your issue is with plant physiology which I find hard to over turn.

And also doesn't help when it comes to canopy intensity. PAR watts, and avg PPFD will not tell you instantaneous PPFD...which is not the same as avg PPFD. I can take sufficient PAR watts and hang it too high it will not perform. Then also the other side of it... I can take insufficient PAR watts but create acceptable canopy intensity for better growth than sufficient but not ideal in use. All coming back to the plants direct relationship with photons.

Plants require an avg PPFD of 700-1000µmols. But can handle instantaneous intensities of 1500µmols.

Wanna know what would really simplify things? Take the watts dissipated and multiply it by the efficiency on the efficiency chart. Take that number and divide it by the total area of your grow. Done. Who are you trying to sell lamps to anyway, Einstein? Also, what crazy SPD are you planning on using that doesn't have a very similar QER to cxa 3000k 80cri? Are you going boost the red and cut the blue as if that's a ticket to few free extra umol/s without increasing W? Just gotta turn a few knobs...

And that's my issue with the "it's not watts, it's umol/s" line of thinking. Photosynthesis is a process of transferring light energy to chemical energy. It takes energy to create the sugars, and that's why the nutritional value is not measured in the umol photons worth of sugars produced.

 

[PurpleBuz]

Sorry missed this so will address it now. Penetration is simply a matter of PPFD as far as I can deduce. Running more emitters under driven will give the same result if the PPFD is the same. Efficiency goes up, emitters last longer and use less wattage. The only reason to drive them at nominal or higher is up front cost, but in all my calculations the extra cost associated with under driving is recouped within about 4 years (electricity here is 12 cent per kilowatt). This doesn't factor in the AC savings so bonus if you have to run AC.

another part of penetration is the incidence angle. think of a stone skipping over water, as opposed to going kerplunk straight down

 

[Sxott]

cool like minds think alike, adding a bit of royal blues is the ticket, super efficient and balances the color spectrum. I'm doing similar with vero18s and 3' long 4.85" wide heatsinks.

Your the one that got me thinking about the blues after pointing out the efficiencies on the other boards. I went with the 3 watters thou because a 12 watt in between each cob would prob be too much blue. 8 three watters maxs out my driver perfectly. Thank you.

 

[JimmyIndica]

Ive been savin some cash for a meter,cause its something I wanna monitor? Right now enough par for me is dropin the fixture until the top buds glow!

 

[Rahz]

another part of penetration is the incidence angle. think of a stone skipping over water, as opposed to going kerplunk straight down

True and that idea supports more emitters.