[PSUBS-MAILIST] LED lights

[Rick Patton via Personal_Submersibles]

Thanks Alan and Chris
much appreciated and I can't imagine building a sub without this group!

Rick

On Sun, May 13, 2018 at 12:53 PM, Cliff Redus via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> Rick, based on my experience, I agree 100% with your electrical guy.  The
> problem is any of these high lumen Led arrays will quickly overheat and
> destroy themselves if you cannot move the heat away from the array. The LED
> lights I have will work continually even when not submerged.  They are
> housed in 6061-T6 aluminum case and are 1-atm air.  As Alan mentions, the
> key is having the arrays securely mounted to an aluminum base with heat
> conducting grease.  This aluminum base has to be designed to conduct the
> heat away from the array and into the cooling fins. Fins have to be
> designed to convect heat away from heat sink either by forced convection or
> natural convection when not submerged.  The problem you are having is the
> mineral oil that is surrounding the array just cannot dissipate the heat
> fast enough.  If you repeated the experiment with only one change,
> mounted the array to a finned heat sink, it probably would have worked just
> fine.  As Alan mentions you need a constant current driver.  Also I have
> had better luck with higher quality arrays like Bridgelux Vera 29.  These
> are cheap at Digikey.
> If you don’t want to do the engineering around designing the LED light
> system, Hank’s approach works.  Buy and off the shelf light that mates
> with your electrical system and hydraulically pressure compensate
>
> Cliff
>
> On Sat, May 12, 2018 at 3:51 PM, Rick Patton via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
>> I am still trying to come up with a viable working LED light system and I
>> think I have it boiled down to cheap arrays? I have a friend helping me
>> that understands electricity a lot better than I do and he seems to think
>> it's a heat issue, not dispersing it quick enough.
>>
>> I am using a 10,000 lumen array that is about 1 1/2" square and costs
>> $2.75 each and made in china. Well, you've herd the saying, you get what
>> you pay for? These are rated for about 100 watts and like to see around 34
>> volts so were running them threw a buck booster? and dialing them down to
>> that from about 38 volts and then running them threw a PWM and then to the
>> array.
>>
>>  I at first was putting them in a housing that I had fabricated for them
>> using a strain relief fitting to run the power cord threw as the housing is
>> full of mineral oil then setting the housing in a 5 gal bucket of cool
>> water and they are still burning out so I tried just hanging an array by
>> it's wires into a container of mineral oil and still only lasting a couple
>> of minutes so I got a thin cold pack from the freezer (without telling my
>> wife of course!) and sandwiched the array in it thinking that that would
>> eliminate any questions of the heat dissipation theory and it still only
>> lasted a minute!
>>
>> My friend is still insistent that its a heat problem and that the thin
>> layer of plastic that holds the frozen stuff in is enough to keep the array
>> from seeking the relief that it needs before melting down which I don't
>> agree with. He says he can hang an array by it's wires in a bucket of tap
>> water for a number of hours with no issues and that water disperses heat
>> much faster than oil.
>>
>> Sorry for the long post but I felt it necessary to let you guys know
>> exactly what I am doing for better input. I want to put this behind me so I
>> can get on to the next thing! It would be helpful to hear from those who
>> are using a small high luman LED array as to what you are using and where
>> did you buy it. PS: I snuck the cold pack back into the freezer unnoticed!😂
>> Rick
>> The fissures stopped spewing lava two days ago so will hope for the best
>> but looters are having a field day!
>>
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>>
>
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