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CobKits

CobKits

Well-Known Member
sure thing "VegasWinner". sorry i dont have time to pick thru all your points one by one. ill let the thousands of cobs in hundreds of rigs out there running in parallel speak for themselves.

to address one point: 96% is indeed substantially more efficient than 93.5%, esp when it can be achieved for pennies a watt and people are tripping over themselves to get incremental efficiency with cob and cooling selection and current reduction
 
CobKits

CobKits

Well-Known Member
burnpile said:
If making a linear fixture with these what is a good spacing? They will be run at approx 60 watts ea, the fixture is similar to a tube, one side is a heatsink that the cobs are mounted to. There is a fan at one end to move air over the heatsink. I was thinking about 10" c-c, the whole fixture would be approx 36" long.

Meant to say Luminus CXM22 Gen3 3000K 90 CRI.
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10" center to center at 60W sounds fine you could prob go 12"

depends on width of coverage and if there are cobs in the other direction
 
GrowLightResearch

GrowLightResearch

Well-Known Member
nxsov180db said:
Still wrong.
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Yes you can wire them in parallel and they will light up. The problem is the current flowing in each CoB will be significantly different. If you do not care about not having any uniformity and having hot spots, continue to wire them in parallel.

Each CoB has a slightly different forward voltage. When wired in parallel they will all have the same voltage because they are all connected to each other. It's simple DC fundamentals being violated.

I'm just saying wiring them in parallel is wrong. If you think you know more than me, ignore this.
 
Humanrob

Humanrob

Well-Known Member
GrowLightResearch said:
Yes you can wire them in parallel and they will light up. The problem is the current flowing in each CoB will be significantly different. If you do not care about not having any uniformity and having hot spots, continue to wire them in parallel.

Each CoB has a slightly different forward voltage. When wired in parallel they will all have the same voltage because they are all connected to each other. It's simple DC fundamentals being violated.

I'm just saying wiring them in parallel is wrong. If you think you know more than me, ignore this.
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How much variation do you think there is between COBs (you say "significantly different")? They are built to a spec with certain tolerances, I'm wondering if its 2%, 5%, 10% +/- is the normal variation from one to the next?

For my lights, so far I have one in parallel (only two COBs connected to the driver) and all the others are in series, but I was thinking about building another in parallel. Honestly, if they are off by less than 5% I'm OK with that.

Also, in your second sentence you say, "When wired in parallel they will all have the same voltage because they are all connected to each other." Did you mean to say "in series"? Otherwise, I'm confused.
 
T

TD816

New Member
Hows it going everyone, new member and just placed and order with cobkits last night. Man theres alot of info through out these 156 pages and its best to smoke after reading I've figured out haha.

Just wanted to say thanks to Cobkits for providing a great service at great prices.

Looking forward to growing with these 5 citi 1212's just need a driver for them. Would a Mean Well HLG-240H-C1400A be enough to run them or should i be looking at a different driver?
 
CobKits

CobKits

Well-Known Member
BuddyColas said:
Same results I have seen as well.
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he is misinformed and doesnt understand these systems, at all
yes there are current variations between cobs, no its not enough to cause hotspots. there are also flux and voltage variations when cobs are run in constant current in series, same deal

"growlightresearch" appears to be another in a long line of trolls which is why hes in this thread and not out there making his own thread about the "dangers" of parallel wiring
 
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BuddyColas

BuddyColas

Well-Known Member
CobKits said:
he is misinformed and doesnt understand these systems, at all
yes there are current variations between cobs, no its not enough to cause hotspots. there are also flux and voltage variations when cobs are run in constant current in series, same deal

"growlightresearch" appears to be another in a long line of trolls which is why hes in this thread and not out there making his own thread about the "dangers" of parallel wiring
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I was not agreeing with growlightresearch. He's a legend in his own mind. Just saying I've had good success running both series and parallel cobs. Much respect to your patience in answering 150 pages of questions...with many repeats, and for your detailed tests and comparisons! Thanks.
 
CobKits

CobKits

Well-Known Member
was planning on replacing 1818 with cxm22 but peopel keep asking for them so i jsut put anorder in for them in 3000/3500k and 80/90

~4 weeks
 
nfhiggs

nfhiggs

Well-Known Member
GrowLightResearch said:
I just ran a test on two CoBs. At 600 mA the measured Vf were 33.4V and 34.2V powered by a HLG-60H. At 1200mA wired in parallel the currents were 768mA and 463mA respectively and the forward voltage 34.9V (higher than either of the individual Vf).
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I call bullshit. Your numbers do not add up. If the parallel voltage applied was higher than both Vf's of your 600mA individual tests, then BOTH would have pulled more than 600 mA at 34.9V. You are either lying or incompetent.
 
Humanrob

Humanrob

Well-Known Member
CobKits said:
was planning on replacing 1818 with cxm22 but peopel keep asking for them so i jsut put anorder in for them in 3000/3500k and 80/90

~4 weeks
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I'm adding to an existing build, so I was just continuing with what I used before. But in this case each pair is on a separate driver, so I suppose I could switch over. It's nice that they use the same heatsinks and holders.
 
Humanrob

Humanrob

Well-Known Member
Got the graph paper out and I'm mapping out the layout. For this iteration I'll have 6 cobs in a 3x3 tent. What is the optimal distance apart for 75w cobs?
 
CobKits

CobKits

Well-Known Member
6x75 in a 3x3 is a fair amount of light, i imagine you'll be dimming a bit.

easy way to map it is to take your 36" and divide it by number of cobs and go half that spacing from each wall on both ends

so if your 6 cobs are in a 2x3 grid, in the 3 cob direction it would be 36/3= 12 or in other words from the wall cob#1 is at 6", cob 2 at 18" cob 3 at 30"

in the 2 cob direction they are 18" apart and 9" from the wall

in practice (esp in bigger tents) to keep frame size down you can cheat toward the middle a little. esp if hanging your fixture high
 
Humanrob

Humanrob

Well-Known Member
CobKits said:
6x75 in a 3x3 is a fair amount of light, i imagine you'll be dimming a bit.
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My end game is 9 cobs running at between 40-50w each in a perfect 1 sq/ft per cob pattern. Could happen next year.

CobKits said:
easy way to map it is to take your 36" and divide it by number of cobs and go half that spacing from each wall on both ends

so if your 6 cobs are in a 2x3 grid, in the 3 cob direction it would be 36/3= 12 or in other words from the wall cob#1 is at 6", cob 2 at 18" cob 3 at 30"

in the 2 cob direction they are 18" apart and 9" from the wall

in practice (esp in bigger tents) to keep frame size down you can cheat toward the middle a little. esp if hanging your fixture high
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Thanks for those guidelines! When it comes time to actually build it, I'll probably do something like that. But I got stoned and started thinking...

All I could find was really small graph paper... but that didn't stop me (it only slowed me down). I started playing with distances, trying to figure out the most even light spread configuration. My first locations had too much overlap, so I moved them apart a bit and redrew my imagined per-light coverage radius with a colored pencil. The top left and bottom left are 16" apart (on center), the bottom middle one is about 12" from the left and right bottom ones.

This layout does leave a weak spot in the middle, and would come with some building challenges (!!!), but it was fun to think about. When I'm faced with the actual measuring and cutting, I'm sure I'll reread your response. :)

3x3_w-6cob-layout.jpg
 
D

Dave455

Well-Known Member
Humanrob said:
My end game is 9 cobs running at between 40-50w each in a perfect 1 sq/ft per cob pattern. Could happen next year.



Thanks for those guidelines! When it comes time to actually build it, I'll probably do something like that. But I got stoned and started thinking...

All I could find was really small graph paper... but that didn't stop me (it only slowed me down). I started playing with distances, trying to figure out the most even light spread configuration. My first locations had too much overlap, so I moved them apart a bit and redrew my imagined per-light coverage radius with a colored pencil. The top left and bottom left are 16" apart (on center), the bottom middle one is about 12" from the left and right bottom ones.

This layout does leave a weak spot in the middle, and would come with some building challenges (!!!), but it was fun to think about. When I'm faced with the actual measuring and cutting, I'm sure I'll reread your response. :)

View attachment 4041352
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Be nice to see PAR map on light layout. Believe you will find photon overlap in center will
be high enough to avoid added COB..
 
SSGrower

SSGrower

Well-Known Member
Found out some good info I think with regard to safety. First off its pretty cheap even though it may be overkill. Also I may have misinterpreted some of the electrical code (I'm talking about NEC class 1 wiring methodology). My boiler uses awm rated wire 600v (one component relay with 1000v) I think for two reasons temp and ampacity requirements and in a particularly thin gauge of wire 16 or 18. Most of us use 18 in our builds, this awm rated wire runs about 40 bucks for 500 ft in 18g, i could only find it at a wire distributor.
I will be rebuilding the led side of my lights with this wire as I only used about 150 ft of it to relocate my boiler power vent and hopefully make buildung inspector boy happy so we can move on with the rest of the remodel project.

Anyway, Thoughts on awm rated wire?
 
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