[PSUBS-MAILIST] LED lights

Sun May 13 18:53:42 EDT 2018

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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