Matching Drivers and COBs

Airwalker16

Airwalker16

Well-Known Member
PhotonFUD said:
Or if you had a bunch of cheap ~50v ~35-50w drivers, you could just run 1212s in parallel as many as you wanted. Worst case scenario the last one would still be able to handle the full power of the driver.

Another benefit to under drive, safety.
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What's the Fv of 1212's?
 
PhotonFUD

PhotonFUD

Well-Known Member
Airwalker16 said:
What's the Fv of 1212's?
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My, bad I was thinking 1812s. You could also go 2 1212s in series using ~50w drivers running 700ma that max at 70-75v. Run those series string in parallel as much as you want.

As for how many? As many as possible till I hit the magic 77% efficiency at 3.1w thanks to cobkits data. Works out to around 18, each per 50w driver :)
 
CobKits

CobKits

Well-Known Member
heres 1818s btw. the constant voltage 48V drivers on my site go out to about 53.5V so these fill them nicely as do the 1825s. that 1818 is pushing a respectable 40% efficiency at 200W

upload_2016-9-11_1-12-58.png
 
PhotonFUD

PhotonFUD

Well-Known Member
wietefras said:
Typical beam angle is around 115 degrees. Easy to calculate coverage from beam angle and height.
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LES size will have an impact on coverage that seeing as there is quite a bit of difference in size between the chips.

You are absolutely correct. I was working with 120 degrees instead and wanted to see how far the math would be off from what was found real world. Playing with overlap is going to be the next task at hand. Currently my next project is starting to look like a cookie sheet cram packed full of emitters running uber passive as cobkits calls it. If there is a price drop on the already low price for the 1212s then it isn't that expensive to challenge what you can do with only 400w of power.
 
wietefras

wietefras

Well-Known Member
So you are saying that you had already calculated that it would be a circle of around a meter in diameter and that you then worry about the difference between 12mm or 18mm for the LES of the COBs we're talking about?
 
wietefras

wietefras

Well-Known Member
Yeah that's going to make a massive difference /s. Now work out the difference in footprint caused by those 6 mm difference in LES and you're good to go :)
 
PhotonFUD

PhotonFUD

Well-Known Member
wietefras said:
Yeah that's going to make a massive difference /s. Now work out the difference in footprint caused by those 6 mm difference in LES and you're good to go :)
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Yeah, yeah, keep in mind that I am planning to run 100w chips at 3w so 10% here and there might add up. Rather check and be wrong so I can correct early.

At 6 inches the diameter is 50cm; the distance from the cob to the outer edge of coverage is ~12 inches. Will have to figure the output at different heights. Lots of variables to play with!
 
wietefras

wietefras

Well-Known Member
It's not a hard circle anyway and the beam angle is a "typical" value. For Cree at least. Don't know what it's exactly for Citizen. perhaps 120 :)
 
Humanrob

Humanrob

Well-Known Member
Question:
When I originally built my light, I had 4 CXB-3070's running off of a single HLG-185H-1400.
I've rebuilt the light, and for various reason am now running only 2 CXB-3070's off of the same driver.

Can this cause problems? My understanding is its "less efficient", but my understanding ends there... does inefficient mean it will run hotter, shorten the life of the COB.... harm something?

I have not run this for any long periods of time, only wired it and tested it.

Thanks!
 
CobKits

CobKits

Well-Known Member
you have to hit minimum voltage (50%) to operate that driver correctly. 71V in this case which your two 3070s barely hit and 3590s would not

datasheet has efficiency flat down to 50% load so no loss there

cobs dont care, 1400 ma is 1400 ma they dont care if they have neighbors. at that lower load your driver will now last forever and a day (as opposed to forever). the only thing you are 'wasting' is driver capacity but its there waiting for when you need it again
 
Humanrob

Humanrob

Well-Known Member
CobKits said:
you have to hit minimum voltage (50%) to operate that driver correctly. 71V in this case which your two 3070s barely hit and 3590s would not

datasheet has efficiency flat down to 50% load so no loss there

cobs dont care, 1400 ma is 1400 ma they dont care if they have neighbors. at that lower load your driver will now last forever and a day (as opposed to forever). the only thing you are 'wasting' is driver capacity but its there waiting for when you need it again
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Thank you! I really appreciate your taking the time to explain that to me. I will worry no more. :)
 
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