[PSUBS-MAILIST] LED Light

Tue Feb 7 12:48:13 EST 2017

Thanks Cliff.
Yes, no chamfer or fillets on the drawing; it was to give a general
idea of design. However hadn't thought about filleting for anodising.
   From a machining perspective, I am not sure how thin & deep I
can get the grooves for the fins. This will be trial & error.
   Good point about the thermister. I could probably fit one under
the plastic wire cover. BTW the wire covers fit the LEDs & are supplied
by the manufacturer, so should take the heat.
I have a friend on board whose day job is running up to 800,000 LEDs
at a time on advertising hoardings. He also did electronics on nuclear subs.
He keeps telling me I run the LEDs too hot & is analysing my LEDs
to find the right driving current. So this may help with the temperature.
Still finding out here.
With regard to the bulkhead; I want to make a mould for forming the
elastomer around the wires, so the process may be quick & more reliable
than a bulkhead with O-ring fitting. Definitely Cheaper.
   I went with the double O-rings after reading the "Prevco" underwater
housing literature. https://prevco.com/products/subsea-housings/seal-configuration/face-and-piston-seals
A double seal seems standard & isn't much more of an expense.
Also if salt water gets in, it can generate hydrogen through electrolysis
& cause a build up of pressure inside the housing. Remember that part
of yours I had to dive for :)
There are clearances. Have .125mm between the lens & housing & between
the base & housing. I will be machining this so even though I say .125 it
will be what I consider a good fit.
I am getting the LEDs with pig tails attached & will feed my main wire up
the wiring holes, attach to the pig tails, then pull down in to the wiring gland
when I attach the LED to the base.
Thanks again for the comments.
Alan

Sent from my iPad

> On 8/02/2017, at 4:04 AM, Cliff Redus via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> Alan, looks like you are making great progress on light.  A couple of comments:
> 1) If you plan to anodize, then I would chamfer the outside edges (85mm) to mitigate wear
> 2) I would use a small Subconn bulkhead connector rather than DIY penetrator.  These OTS fittings are cheap.
> 3) double o-ring seals are probably overkill
> 4) LED panels get very hot.  I worry about the plastic wire cover melting
> 5) Not showing any clearance for socket head screw heads
> 6) Not showing any clearance between the acrylic lens and housing
> 6) You would dramatically improve heat transfer away from unit if you made the fins thinner.  As designed not sure these fins and shell will dissipate 80W of heat when in the air.
> 7) As drawn I don't see any space for wire movement for makeup after you solder the leads and start to assembly the light
> 8) Don't see any RTD or thermistor for measuring temperature to enable the driver circuit to protect against overheating when unit is inadvertently turned on out of the water.
> 
> Cliff
> 
>> On Tue, Feb 7, 2017 at 4:43 AM, Alan James via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>> Rick, Cliff & anyone else that's interested.
>> Attached is the latest version of my 80W LED light.
>> In one drawing it shows a larger diameter top retaining ring.
>> This is to enable mounting in to a recess. By using longer bolts the
>> light can be mounted on a plate at the back.
>> What I like about this design is I only have to do 2 small threads for screws
>> that hold in the LED. This will also help avoid bolts seizing in threads.
>>    I am machining a grooved protrusion in the base to key in the rubber compound
>> for sealing the wires. Inside the base I will be epoxying the wires.
>> I have gone to an acrylic lens that will be 10mm from the emitter. This is because
>> the small flip chip LEDs I am using are cooler out the front. I can back off the power
>> if 80W is too much for such a small unit.
>> These could be used as navigation lights with lower power.
>> It should be good for over 2000ft.
>> Alan
>> 
>> 
>> 
>> 
>> 
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