Different size COB differences

[catoblepa]

Hello everyone.
I've been researching the cob market for quite a while in order to make a diy grow light. I finally decided to use CITIZEN CLU038-1205C4-403H7K4 4000K 97 CRI for a full cyle, 18 cobs powered by two 240w HLG drivers.
I've seen a lot of builds, and no one uses CLU038, but instead CLU048, CLU058, cree cxb3590 bridgelux VEROs, which are much more powerful but much more expensive, or quantum boards.
Why is everyone using those big cobs? What's the difference in using many little cobs which have the same spectrum and CRI?

 

[Koondense]

More components = higher chance of faults
I was having similar thoughts a while back, figured the designs are simpler for big cobs, probably overall cheaper.
Depends on your goals.

 

[catoblepa]

More components = higher chance of faults
I was having similar thoughts a while back, figured the designs are simpler for big cobs, probably overall cheaper.
Depends on your goals.

Yeah that's right, didn't think about chances of failure because top brand LEDs paired with top brand drivers should be a reliable duo.
As for the design it is simpler but they're less efficient (fewer cobs need more amps to keep the same total power) and with less uniform light distribution.
After some maths, i found out that in this case the smaller cobs put out twice the ppfd with the same price and with the same area
that's why i was wondering why no one uses those smaller clu038 cobs

 

[f-e]

IIRC the 048 can use about 100w which seems big, but with realistic expectations of cooling and lifetime, 50w is a more typical power level for them. They cost about £10 each and so does the heatsink to mount them on. Then the mounting gear, which might mean drilling and tapping M3 holes, which snaps more taps than gives success. The heatsink cost is the real factor while at the design phase. At 50w it's worth looking at cpu coolers, which is a competitive market. At 30w you are still looking at the same cpu coolers. Just more of them. Which cost more than the cobs. There is a great big hole in the market, between the well priced consumer gear aimed at PC's and the heatsinks hobby electronics people buy at much less competitive prices.

My last heatsink was over 100w and cost about £3 delivered. There is a constant supply of them, taken from old computers as part of the tech recycling that big business has to be enrolled in. Offices swap out the lot and need the paperwork from selling them, to officially reduce the companies worth. Recycling companies are the only people that will take van loads of old worthless tech. Heatsinks don't age though. They all find their way back onto the market at disposal costs. I couldn't post that 100+w heatsink for £3

Of course if your going to pay top dollar for some pin design, then they will be priced more closely around weight. So buying more smaller ones won't hurt. They may come drilled for the job. It depends on your build needs. My last build was a 20w green cob and cost £4 (I already had a plug)