With cobs - Why a panel?

OneHitDone · May 3, 2015

Was just thinking - if most of the high powered cobs will cover approximately an 18" diameter circle, why are people packing them in rectangular layouts and not evenly spaced on heatsinks?

Don't mind the 2 second sloppy kindergarten sketch but it seems it would make more sense to lay them out more like this in a 5x5 area, does it not? Each grid represents 2"

solksagen · May 3, 2015

Those people don't wanna be square (even their tents are rectangular), and you're right, 16 clones equally spread would be perfect in your 5'×5'.

KarmaPaymentPlan · May 3, 2015

OneHitDone said:
Was just thinking - if most of the high powered cobs will cover approximately an 18" diameter circle, why are people packing them in rectangular layouts and not evenly spaced on heatsinks?

Don't mind the 2 second sloppy kindergarten sketch but it seems it would make more sense to lay them out more like this in a 5x5 area, does it not? Each grid represents 2"

View attachment 3409941

i don't think a cob instantly translates to a 18 circle or what ever shape your light source may be considering intensity of each individual light and on top of that it's a simplicity factor i actually prefer them all spaced out like you brought up i also have them driven harder to help achieve the spread i desire but it was kinda a hassle running all the wire and stuff

bicit · May 3, 2015

I think the biggest reason is that it's a pain in the ass. Especially with the wiring.

Then if you're going actively cooled you will will need fans for each heatsink. Which will also require more wiring, and a bigger power supply for the fans. Which also reduces the efficiency of the system.

With one rectangular heatsink you can cool 200w with a single 2-5w fan. As opposed to 16 fans.

Oh and cobs don't light a perfect 18" circle without a lens or a reflector. Also without a lens or a reflector the light is not distributed evenly through the 120* angle. Rather the outer 60* is about 50% less intense than the inner 60* further complicating things.

bicit · May 3, 2015

There are quite a lot of variables to account for

Rahz · May 3, 2015

Because it costs less.

OneHitDone said:
Was just thinking - if most of the high powered cobs will cover approximately an 18" diameter circle, why are people packing them in rectangular layouts and not evenly spaced on heatsinks?

Don't mind the 2 second sloppy kindergarten sketch but it seems it would make more sense to lay them out more like this in a 5x5 area, does it not? Each grid represents 2"

Rahz · May 3, 2015

With DIY you can do whatever you want.

captainmorgan · May 3, 2015

I have mine on CPU coolers with the drivers outside the grow area,I like it because it's more flexible and I can cover a area very evenly but it's a spaghetti mess of wires.

OneHitDone · May 3, 2015

If one is to "outperform" the good old hps which seems to still be the thing to beat I was thinking they would have to be evenly spaced out like that so you will get a more consistent product all the way out to the edges of the space. No areas of lower intensity.
That was my thinking anyway

If a large enough heat sink could be used on each cob the fan wiring could be eliminated.
But just how large would it need to be?

bicit · May 3, 2015

OneHitDone said:
If one is to "outperform" the good old hps which seems to still be the thing to beat I was thinking they would have to be evenly spaced out like that so you will get a more consistent product all the way out to the edges of the space. No areas of lower intensity.
That was my thinking anyway

If a large enough heat sink could be used on each cob the fan wiring could be eliminated.
But just how large would it need to be?

Depends on how hard you're driving the cob. 25w or less and you could use a 5.886x6" heatsink per cob. A 50w cob requires a rather large heatsink for passive cooling. To the point where you end up using long bars of heatsinks instead. I don't have my heatsink calculator with me to get a better answer than that

Distribution like that isn't really all that critical. Most cobs are already outperforming hid simple because all the photons are going in the right direction.

Rahz · May 3, 2015

I wish HSUSA would offer radial heat sinks. I'm sure they would be less expensive than the Ebay ones.

OneHitDone · May 3, 2015

bicit said:
Distribution like that isn't really all that critical. Most cobs are already outperforming hid simple because all the photons are going in the right direction.

But, what about the whole distance from the lamp (cob) thing? Seems an even distribution of the cobs would give the best even lighting over the whole area

Positivity · May 3, 2015

Your assuming everyone needs perfect light distribution. In that case greengenes has shown that produces awesome results, most probably the best. Can't really argue with a light meter..lol

Speaking for myself...

Perfect distribution means a fixture near the size of the area. Easily achievable with multiple long and not so wide heatsinks.

But hid has proven you can still have a very productive light with a point source and reflector.

So I basically shoot for a middle ground. A light that has a better footprint than a hid but still has a easily manageable fixture size. Pretty simple really..

churchhaze · May 3, 2015

Positivity said:
Speaking for myself...

Perfect distribution means a fixture near the size of the area. Easily achievable with multiple long and not so wide heatsinks.

This is exactly what I do. I take the width of the tent and subtract a few inches of padding. If/when I make another DIY, It will likely be with 2 long 5.886" profile, "long enough" length.

Another reason people might design things the way they do is because of how many cobs fit on their driver. If you have a driver that supports 8 cxb2530, you're thinking in multiples of a factor of 8. That means 1 wide bar with 8 cobs, 2 bars with 4 cobs each, or 4 bars with 2 cobs each.

But if you have a driver that supports 11 cobs... 11 is a prime number... Why couldn't you be 12!!!!! (that explains my latest asymmetrical design :wall:

)

bicit · May 3, 2015

OneHitDone said:
But, what about the whole distance from the lamp (cob) thing? Seems an even distribution of the cobs would give the best even lighting over the whole area

It would, I just don't think it's really worth the effort to a range them that meticulously.

Like pos said, I aim for a middle ground because I hate exposed wires. Im a clutz with flailing limbs. I like everything to be rock solid.

SupraSPL · May 4, 2015

If you are determined to maximize spread, you can manage the wiring and have a hard hat, it can be done. Lighter and cheaper if I had used the 12" profile

Or you can use the 3.5" profile heatsink for active cooling and get good spread that way (lamp being tested)

Doer · May 4, 2015

OneHitDone said:
If one is to "outperform" the good old hps which seems to still be the thing to beat I was thinking they would have to be evenly spaced out like that so you will get a more consistent product all the way out to the edges of the space. No areas of lower intensity.
That was my thinking anyway

If a large enough heat sink could be used on each cob the fan wiring could be eliminated.
But just how large would it need to be?

You can take advantage of all these little nuances of light spread.

So, if you overlap 2 cones' outer 60% of area that only get 50% of the radiation, you get what?

100% of the radiation in the overlap.

With cobs - Why a panel?

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