[PSUBS-MAILIST] LED Light test

[Stephen Fordyce via Personal_Submersibles]

Thanks Alan, your LED flip chip is quite interesting - my research has only
been into much smaller LEDs (CREE XML2) and it's cool to see such a big
one!  Pretty hard to argue with $6.50 too.

Cheers,
Steve

On Thu, Mar 9, 2017 at 8:40 PM, Alan via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> Thanks Steve,
> that's great to know about the heat on the acrylic lens & your testing.
> At the moment I am driving my lights with a buck / boost constant current
> driver
> that has a 60V input for my 48V system. It took a lot of work tracking
> down a
> unit that was suitable for 48V.
> A friend put me on to those linear regulators & is trying to convince me
> to go
> with them. I will keep your information in mind should I need to argue my
> way
> out of them.  They would be good for a Sub on a 36 V system, as most of the
> high power LEDs are 36V.
> Have a look at the flip chip LED I'm using if you haven't already seen it.
> Smaller than the usual cob LEDs.
> http://www.tyf-led.com/downloadRepository/82befdc2-
> 15b3-4ff0-a553-6f53a4d8e404.pdf
> Got mine with pigtails on for $6:50- each.
> Cheers Alan
>
>
>
> Sent from my iPad
>
> On 9/03/2017, at 9:54 PM, Stephen Fordyce via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
> Hi Alan,
> I'm glad your lights are going well!  There are a couple of things I may
> be able to contribute after several iterations of designing the circuit for
> my TFM caving/diving helmet lights.
>
> *1. Linear vs switching LED drivers.  *
> I looked at the datasheet for your LED driver chip and it appears to be a
> linear regulator - this in general terms means it creates a variable
> resistance to get the output current/voltage right, and as such can create
> a lot of heat which may be wasteful.  Ie. if you have a 12V supply and your
> LED needs 4V, 67% of the power will be lost in the driver!  But if you have
> a 12V supply and your LED chain needs 11.5V, then it's quite efficient.
> They are simple and easy, and small as you point out, with no external
> components.
>
> A switching driver uses very fast (MHz) PWM along with an external
> capacitor/inductor to drop and smooth out the voltage, and is ~90+%
> efficient over a big range of voltage drops.  This means it creates much
> less heat and saves power.
>
> I changed to switching drivers for my LEDS (input 7-8V, output 3-4V) and
> noticed a huge difference in heat and efficiency.  Just something to be
> aware of if you run into heat or runtime problems.
>
> *2. Acrylic windows*
> I have used lasercut acrylic (6mm) in my caving lights (which I've had up
> to 80degC according to the internal temp sensor.  Lasercutting allows me to
> get an oblong rectangular shape with holts for screws.  The lights have a
> full high temperature burn test out of the water and then multiple dives to
> 100m in my pressure pot, with no acrylic failures to date.
>
> Cheers,
> Steve Fordyce
>
> On Thu, Mar 9, 2017 at 6:12 PM, Alan via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
>> Tested my 80W LED light in a housing, to see how hot it got in & out
>> of the water.
>> The good news was it didn't get warm at all after running at 70W for
>> 25 minutes in the kitchen sink. Out of the water it hit 120F (49C) in 7
>> minutes. The LED has a maximum temperature rating of 60C so was keeping
>> back a bit from that.
>> I dropped the current down & ran it out of the water at 33W & 25W but it
>> climbed
>> to 125F in 20 minutes for 33W & 15 minutes for the 25W.
>> I am using a cast acrylic 8mm thick lens, & this didn't get hot either in
>> air
>> or water. Using acrylic instead of glass is saving me $90-.
>> Am making a few minor housing design adjustments for the final iteration.
>> Have also ordered a dozen of these 50 V 350 mA constant current regulator
>> &
>> LED drivers.
>>
>> http://www.onsemi.com/PowerSolutions/product.do?id=NSI50350AD
>> They are TINY; about 1/4" square & you run them in series to get the
>> desired
>> amperage. They have a wide input voltage & would be great for a 36V
>> system.
>> Alan
>>
>>
>> Sent from my iPad
>>
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