Water cooled cobs

shimbob

shimbob

Well-Known Member
mahiluana said:
You can always add some adequate led-chips into the row, if you want a higher Vf
Click to expand...
I'm willing to entertain this idea. There's 28v @ 2.1A to play with, or 37v if going by the open circuit voltage of 105v.

I actually bought 5 of these cobs, one extra in case I goofed. I could wire it in series with the other four and place it centered on the board. At 2.1A it'll need ~35.8V. That's a tight fit, between the top of the V range and the open circuit V, will it light up? I'd slap it on a spare socket 775 cooler I have.
 
pirg420

pirg420

Well-Known Member
any one have problems with condensation dripping off the cool water lines that run to the fixtures? or condensation anywhere on the light?
 
Randomblame

Randomblame

Well-Known Member
ttystikk said:
I had that problem.
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Probably because of too low water temperatures, right?
I remember you're using a chiller to keep water temperatures down?
What water temperature settings do you need to avoid condensation?
At 30°C water and environment it should actually not happen,
At 30°C ambient temperature but 20°C coolant temps it is more likely.
 
shimbob

shimbob

Well-Known Member
Randomblame said:
What water temperature settings do you need to avoid condensation?
Click to expand...
All you need to prevent condensation is a chiller that monitors the ambient temperature and relative humidity. From that it can calculate the dew point and only chill down to that temp. Easy peasy in theory. The dew point will always be lower than ambient, if it isn't then you live somewhere where the laws of psychrometrics don't apply, abandon all hope ye who live there.
 
Randomblame

Randomblame

Well-Known Member
I have a cheap thermometer with dew point display. But something like this connected to a chiller and able to switch temp settings according to ambient/dewpoint. Maybe you should collect money with the idea online, lol!. Or do you mean it already gives something like a dew point based thermostat? Pretty sure something like that will be needed more often. Especially in the commercial sector.
 

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ttystikk

ttystikk

Well-Known Member
Randomblame said:
Probably because of too low water temperatures, right?
I remember you're using a chiller to keep water temperatures down?
What water temperature settings do you need to avoid condensation?
At 30°C water and environment it should actually not happen,
At 30°C ambient temperature but 20°C coolant temps it is more likely.
Click to expand...
Lots of bad things happened with cold water in the lights. Some of my lenses filled up with water, literally drowning the COB chips!
 
mahiluana

mahiluana

Well-Known Member
shimbob said:
will it light up?
Click to expand...
:peace: if you start your fixture at very low ambient- or led temp. --- with Vf too close to the open circuit voltage(105V) -
you may see your lamp blinking (Shut down o/p voltage, re-power on to recover)

- because low temp. ---> higher Vf

in case - you can dimm your driver a bit down - or better buy another cxb3590 to run 2 series of 3 cobs in paralell. (max. load of the driver + >180lm/w + better spread)
 
ttystikk

ttystikk

Well-Known Member
Randomblame said:
Probably because of too low water temperatures, right?
I remember you're using a chiller to keep water temperatures down?
What water temperature settings do you need to avoid condensation?
At 30°C water and environment it should actually not happen,
At 30°C ambient temperature but 20°C coolant temps it is more likely.
Click to expand...
My coolant temps were in the teens C, about 55-60F.
 
shimbob

shimbob

Well-Known Member
Curiosity got the best of me and I threw my 5th cob in series with the other four. It lit up!!!
However; there's now 0.48A on the AC side and 64V on the DC side, compared to the usual 0.68A AC & 67.8V DC with just the 4 cobs. That's unexpected.
 
nfhiggs

nfhiggs

Well-Known Member
shimbob said:
Curiosity got the best of me and I threw my 5th cob in series with the other four. It lit up!!!
However; there's now 0.48A on the AC side and 64V on the DC side, compared to the usual 0.68A AC & 67.8V DC with just the 4 cobs. That's unexpected.
Click to expand...
You're running outside the drivers voltage envelope, so its cut back the current and power.
 
mahiluana

mahiluana

Well-Known Member
shimbob said:
I threw my 5th cob in series with the other four
Click to expand...
if you wire your 5th cob in series - you drive all the current (2100mA) through it - and then you split it up in 2 series of 2 CXB ? --- you should measure a Vf close to 100VDC o_O

can you take a pic of your wires ?
 
shimbob

shimbob

Well-Known Member
mahiluana said:
if you wire your 5th cob in series - you drive all the current (2100mA) through it - and then you split it up in 2 series of 2 CXB ? --- you should measure a Vf close to 100VDC o_O

can you take a pic of your wires ?
Click to expand...
You can see most of the wiring back on page one of this thread, in the second group of pictures. You're right, 5th cob in series with 4 others in 2S2P means a Vf of around 104. Was just wishful/hopeful there might be enough slack in the numbers that the driver could handle it. Just sheer morbid curiosity to play with it, after finally finding the spare CPU cooler. But nope, like nfhiggs said, the driver's in limp mode.

In other news, after removing the 5th cob and returning to normal, tried a lux meter app on my Nexus 7 tablet (because for some reason lux meter apps on my HTC m9 max out at 8000lux) and measured 30k lux at ~10" directly under a cob.

I'm happy with this light. It's not the most cost effective way to deliver 170watts of light but for an engineer it's pure mental masturbation.
 
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