[PSUBS-MAILIST] LED lights

Sun May 13 01:23:08 EDT 2018

Rick,
is your buck converter constant current, constant voltage?
Needs to be constant current as when the LEDs heat up they draw more
current & can burn themselves out. 
   At a certain voltage the current can be kept under control but I've seen
graphs where just 1 more volt will cause the current to really climb.
   You need to screw the LEDs down hard on to a heat sink with a thin layer
of heat sink paste between. They will burn out if this is not done properly.
   I have been told that people drive the LEDs too hard & that competing
manufacturers tend to over rate their lights; so it might pay to drive them at
80W rather than 100  W.
   I have glass lenses & no compensating oil. When I tried an acrylic lens it
trapped the heat in! You can feel the heat pour out the front with the glass
(pressure & heat resistant borosilicate) lens.
   I am using buck boost constant current drivers with dimming that I had made
up for me in China. They work well but there are a few things I want changed.
One of the components needs heat sinking as it gets too hot when the LED
is on high power; the on off switch is on the pcb board & I need it to be remote.
It is really fiddly taking off this switch & soldering an extension wire. Also
the default mode for a disconnected / broken wire on both the dimmer & on off 
switch is that the light stays on & this would kill the light if a wires soldering 
broke when the light was out of the water.
Will get them to change these things some time. If you get desperate & want
some of these drivers I will get on to it & order a few more. Mine are 12-54V
buck boost constant current with dimming.
Glad you haven't had a volcano pop up in your garden. Have been watching
the news footage & it looks pretty spectacular. 
Cheers Alan 

Sent from my iPad

> On 13/05/2018, at 8:51 AM, 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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