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CobKits

CobKits

Well-Known Member
the gt2828 and 3838 are identical in dimension to the clu048 and 058 and can use the same holders. they were impressive for their price. cheap and both of the 3838 beat cree across the board. the 2828 fell short of the citi 1212 which is stil the best value out there in par/$

https://www.rollitup.org/t/why-are-cobs-better-and-whats-so-great-about-the-3590.920480/#post-12944216

for a few more bucks i think citi is probably a better value. if i stocked these they wouldnt be that much cheaper than the citis, and major advantage would be lead time.

what i didnt like about them is their flagship chip gt3838-164 which did well was 100v which is a bit unwieldy. if i stocked those they would be ~$33.

the gt3838-117 did pretty well at higher currents though, beating the1818 out past 40W and the new veros out past 75W. if i stocked that it would be ~$24

leaning towards stocking the gt3838-117, their lead times are better than citi by a few weeks at least
 
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PSUAGRO.

PSUAGRO.

Well-Known Member
CobKits said:
it is 100% relative to cree which is why i always try to mention it as an "approximate, estimated, or relative" efficiency. There was a discussion recently where someone said that cree PCT was actually accurate to "the spreadsheet" within a fraction of a percent. In reality either cree is overreporting lm/W or citi is underreporting lm/W as their data doesnt jive. people are obsessed with their efficiency numbers but in reality if cob A is consistently brighter than cob B at a given wattage, are you going to use the real-world testing data or what the manufacturer told you?

Those mfr-provided tools are great for comparing various intra-manufacturer models and setups but clearly there is a bias when compared with other manufacturer's data
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You damn well better believe that Cree's lm/w #s on the data sheet is the reality , NO inflating===== legal department would have a shit-fit. They have enough problems with t8 retrofit bulbs being recalled twice in a row

possible that Citi is underrating to stay within their specs/ no binning

Also possible your tests aren't dead accurate
 
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CobKits

CobKits

Well-Known Member
no they are ala-carte
https://cobkits.com/product/clu048-1818-active-light-engine-single/

those are setup to run in parallel, 2 per hlg185-48a, thats 300V rated 18/2 wire coming off there, 18" leads for wagos

those actives are built to run hard on cooling they can take the full 250W that chip can deliver, id say passive heatsinks are the best choice below 100W and the actives are the best choice above 100W, but they can be run soft too. fans arent too noisy and in a low current situation you can just feed em 5V and they are silent

those ones in the pic use the 3A/150V rated bjb holders so id recommend either the constant voltage drivers (either a 2.95A/150W HLG120-48A per engine, or a 4.25A/225W hlg185-48A running 2) an hlg240h-c1750 and 2100 would also work

just getting going but im trying to offer options with those like:
1. idela holders: cheapest option (no holes to drill, just run tap)- 4A/250V can handle msot driver setups and chip can be run up to 225W or so- open chip only does not accomodate reflector
2. BJBs: next cheapest option (no holes to drill, just run tap)- limited to 3A/150W- can use reflector. really sameprice as idel+ $5for reflector if you want it
3. direct mount soldered chip with ideal reflector adapters (more expensive - 2 holes to drill and tap plus i have to solder the chips which is time and always a risk with the citis) -offers best driver options and can run out to full 4.14A/250W with the right driver
 
JorgeGonzales

JorgeGonzales

Well-Known Member
CobKits said:
it is 100% relative to cree which is why i always try to mention it as an "approximate, estimated, or relative" efficiency. There was a discussion recently where someone said that cree PCT was actually accurate to "the spreadsheet" within a fraction of a percent.
Click to expand...
I'd like to see how that is possible below 1400mA/36V since Cree doesn't actually provide that information. But sometimes I get sick of arguing. Having productive conversations is a thing of the past with certain people.
 
CobKits

CobKits

Well-Known Member
oh yeah - i forgot that all 3590 data below 50W is entirely extrapolated from a different chip series lol

what would be valuable is if @bggrass could use what he learned manipulating the hidden page in the citi tool workbook to generate us curves from the formulas there, and compare those with real world testing
 
Abiqua

Abiqua

Well-Known Member
CobKits said:
the gt2828 and 3838 are identical in dimension to the clu048 and 058 and can use the same holders. they were impressive for their price. cheap and both of the 3838 beat cree across the board. the 2828 fell short of the citi 1212 which is stil the best value out there in par/$

https://www.rollitup.org/t/why-are-cobs-better-and-whats-so-great-about-the-3590.920480/#post-12944216

for a few more bucks i think citi is probably a better value. if i stocked these they wouldnt be that much cheaper than the citis, and major advantage would be lead time.

what i didnt like about them is their flagship chip gt3838-164 which did well was 100v which is a bit unwieldy. if i stocked those they would be ~$33.

the gt3838-117 did pretty well at higher currents though, beating the1818 out past 40W and the new veros out past 75W. if i stocked that it would be ~$24

leaning towards stocking the gt3838-117, their lead times are better than citi by a few weeks at least
Click to expand...
Which bin are these? they say 3838- but no mention of 164,117 etc. :peace:

http://getiangroupled.en.alibaba.com/product/60468016301-801983454/LED_Manufacturer_Low_Light_Decay_Aluminum_Based_ra90_170lmw_High_Power_LED_COB_200Watt.html
 
CobKits

CobKits

Well-Known Member
164 and 117 are nominal wattage not bins

those certainly arent 3838s at that price. the only chips on the pricelist that cheap were tiny LESs those look like 1313 price. didnt bother to test the small ones. even the smaller 37W 2828s offer very nominal savings over the fantastic citi 1212 with the associated import and tooling costs. the 54 and 86W 2828s underperform relative to 1212s and cost more so are out for me. ill give you a 1919 if you want to play with it. the 1919s are 25W chips and top out around 50W, I havent run a test on them yet.

factory direct they only have 4000 and 5000k, if you want other color temps it costs 10% more and is min 100 pc order.

the alibaba ads are ambitious to say the least. i was only able to get one "170 lm" bin which is really 160-170, and thats 5000k 70 cri 37w 2828. i dropped $600 and asked for top bin of everything i wanted. i dont think "ra90 170 lm/W" per that ad is even in the conversation, as you can see the 90 cris i got were 130 bin

what is tested in that graph:

upload_2016-9-12_17-46-21.png

id like to say they are a great deal, they have a few comers. mostly in the high wattage/low efficiency range. if you you look a the graph of chip economics on pg 3 of that thread, you'll see 1212 still at the top in the 50-70% efficiency range we want to target

https://www.rollitup.org/t/why-are-cobs-better-and-whats-so-great-about-the-3590.920480/page-3#post-12945281

the 37W 2828s seem like a good deal but at a given efficiency youre getting less watts per chip so any advantage it might offer quickly gets eaten up in handling/mounting etc of small LES package

in any case "lumens/watt" is a hard measure to wrap your head around looking at different chip series as that figure is pegged at a nominal wattage that is unique to each series. the curves i generate and esp the cost effectiveness curves are far more useful (to me) - i hope they help you guys as well
 
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C

camdengolf

Well-Known Member
CobKits said:
ill mount those chips for you if you want and ill throw in another 5 pin wago which you'll need. you'll just have to mount the sinks, throw an AC plug on the end of the driver, and hook the wires to the wagos
Click to expand...
That would be very much appreciated! Thank you so muchl
 
CobKits

CobKits

Well-Known Member
any number of drivers would work.
an HLG-120H-48A would drive one to 2950 mA = 160W
an HLG-185H-48A would drive two to 2125 mA = 110W x 2
an HLG-240H-C2100 would drive two out to about 2400 mA = 125W x 2
an HLG-320H-C2800 would drive two out to about 3000 mA = 160W x 2
etc

yes all of those are dimmable. the former two to 40%, the latter two to 10%

that first option is 160W out the door with driver, heatsink, chip for under $120 shipped. beat that..... all you need is a $2 12V wallwart for the fan

:: orders those::
 
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CobKits

CobKits

Well-Known Member
beauty of those setups is the 1825 is a burly chip that can take 5700mA. heatsinks can take 300W. even runing two of them on a 185-48A in parallel, if you dropped a cob youd be fine. the second cob wouldnt even take the full 4.25A of the driver as it would top out on voltage at 53.5 around 3A.....the 48V drivers are almost like built in safety in that regard. excellent driver utility using it near the top of its voltage range

I'm gonna work on building stock on those, right now ive got 2x 1825 2700k 90 cri built if anybody wants a quick ship. please buy em before i put em into use :bigjoint:
 
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