Micro Illuminator - gets warm!

[StoneDog]

I wasn't sure about the micro-illuminator's heat transfer capabilities, but since the LS is driven at (I believe) 150ma, I didn't think it was all that necessary.

Well, I'm here to report that it does get quite warm and the heat transfer appears to be just fine. The light was in my pocket on Friday and had accidentally been clicked on. I don't know how long it had been on but I gradually became aware of an uncomfortable feeling in my pocket. When I realized what it was I quickly removed the light and turned it off. The poor little Legend AAA was almost uncomfortably hot! Heat seems to have transfered from the pill to the body of the flashlight quite well. /ubbthreads/images/graemlins/smile.gif

Well done Arc Mania and Lambda!!! /ubbthreads/images/graemlins/grin.gif

Jon

 

[Doug S]

[ QUOTE ]
StoneDog said:
I wasn't sure about the micro-illuminator's heat transfer capabilities, but since the LS is driven at (I believe) 150ma, I didn't think it was all that necessary.

Well, I'm here to report that it does get quite warm and the heat transfer appears to be just fine. The light was in my pocket on Friday and had accidentally been clicked on. I don't know how long it had been on but I gradually became away of an uncomfortable feeling in pocket. When I realized what it was I quickly removed the light and turned it off. The poor little Legend AAA was almost uncomfortably hot! Heat seems to have transfered from the pill to the body of the flashlight quite well. /ubbthreads/images/graemlins/smile.gif

Well done Arc Mania and Lambda!!! /ubbthreads/images/graemlins/grin.gif

Jon

[/ QUOTE ]

Jon, you share a misconception that is held by many people. Your observations under your accidental test conditions contain absolutely no data about the heat transfer path from the LED to the external surface of the flashlight. All that you have shown is that when you inhibit the heat transfer from the surface of the flashlight to the environment by having it in your pocket it will get hotter than it would if it were in free air. Regardless of how good or poor the thermal path from the LED to the flashlight surface is, the flashlight surface will attain the same temperature assuming that the power input to the pill/LED remains the same.

 

[StoneDog]

Re: Micro Illuminator - gets warm in your pocket!

Ok, fair enough I suppose. The path appears to go through the top board (via what appears to be gold? wire) to the ring on the underside fo the pill's top board. This ring makes direct contact with the battery tube. I'm no expert and won't argue what you're saying, but until someone proves the pill has poor heat transfer I'm going to believe the path is good. /ubbthreads/images/graemlins/smile.gif

Jon

 

[kakster]

Re: Micro Illuminator - gets warm in your pocket!

To see whether the thermal path is good or not, you,d be better off measuring the time it takes to feel the warmth after switching it on.

 

[trailstoride]

Re: Micro Illuminator - gets warm in your pocket!

I've had the same thing happen with the Solitaire LS Mod. It is quite a suprise the first time it happens /ubbthreads/images/graemlins/blush.gif

 

[Doug S]

Re: Micro Illuminator - gets warm in your pocket!

[ QUOTE ]
kakster said:
To see whether the thermal path is good or not, you,d be better off measuring the time it takes to feel the warmth after switching it on.

[/ QUOTE ]
Kakster,
Not much better off in this instance. There is a sound theoretical basis for what you are thinking but for the case we are talking about where the mass [or more correctly, the thermal capacity] of the LED/pill assembly is very small relative to the flashlight housing and there is poor thermal connection to the thermal capacity of the cell, the "touch test" plus stopwatch would not be sufficiently sensitive. BTW, I have attempted to use a variation of what you are thinking to measure the thermal resistance from a Luxeon die to its slug and also from the slug to a heatsink. Very high speed instrumentation was involved [Digital storage scope].

 

[kakster]

Re: Micro Illuminator - gets warm in your pocket!

Glad to see someone with brains is working on this. From the little experience ive had with LEDs, ive come to the conclusion that the limiting factor for LEDs is the heat produced, and the less-than-ideal methods currently employed to deal with it. Current LED (including the luxeons) packages seem to be optimized for surface/PCB mounting. If a Luxeon could somehow be manufactured with a metal case with threads around the outside, much better thermal transfer could be acheived.
BTW, i have no idea what a digital storage scope is or does, but it sounds way more impressive than my pinky and my wristwatch /ubbthreads/images/graemlins/thumbsup.gif