quick heat question

[LED4LYF]

Build: 7 xpg-r5 driven with blue shark at 1 amp all mounted on huge heatsink.

xpg- mounted with artic silver 5
blue shark- mounted with AA

When I turn on my flashlight you can feel the heat from the front out of the leds. I have cutters 6 degree optics.

My qestion is how much heat can the optics take?
In general how long should I run the light, till I cant touch it anymore?

I have not run it long enough to where it is so hot I can not touch it. The heat sink has barely gotten warm.

 

[LukeA]

PMMA has a maximum working temperature of 80-90˚C.

 

[Justin Case]

The Blue Shark uses a boost IC with a max junction temp rating of 125C. If you go to the taskled web site and read the technical section for the MaxFlex5 driver, you should get a good idea as to the heat sinking necessary to keep the Blue Shark running. In particular, read the thermal design PDF document. These two drivers use the same boost IC and should face the same thermal management issues.

FYI, I am uncertain as to the wisdom of sinking the Blue Shark and the LEDs to the same heat sink.

Seven XP-Gs at 1A drive could mean a power draw of about 7*3.2V*1A=22.4W. If 80% of that is waste heat, then the heat sink has to handle about 18W of waste heat.

Depending on your Vbatt, you could have a driver efficiency as low as ~85% or as high as ~95%. If possible, I would recommend as high a Vbatt as you can generate, as long as Vbatt<Vf. If we assume 85% efficiency to be conservative, then the driver has to pull about 26.4W of power, and thus generates about 4W of waste heat. That is a very high amount of heat to dissipate. At that level, George at taskled recommends heat sinking the inductor, as well as the boost IC (which you will already be doing by thermal gluing the Blue Shark's copper C to a heat sink).

Getting back to the issue of sharing heat sinks for the LEDs and driver, the problem is that 18W of LED waste heat are going to saturate your heat sink very quickly. That will affect the driver. If you can sink the LEDs and driver separately, IMO that will be a lot better.

What is your planned host? Do you have a photo of your heat sink?

 

[ti-force]

When I turn on my flashlight you can feel the heat from the front out of the leds. I have cutters 6 degree optics.

My qestion is how much heat can the optics take?

Click here, is this the optic you're inquiring about? If so, looking at the datasheet, these optics have an operating temperature and storage temperature range of -40 to +120 degrees Celsius or -40 to +248 degrees Fahrenheit. They're designed to work with those emitters, so the optics should work fine:thumbsup:. Most of the time, if a datasheet exists for the product you're inquiring about, the chances are good that you can find the information you seek right there.

 

[LED4LYF]

The heatsink and battery holder are all one unite and it slides in to a polished copper tube. The heatsink is pretty big so I thought it would not be such a big deal to mount the led and driver to the same thing. The flashlight is not that practical I just wanted to make something from scratch and something cool.

Here is a pic of the unite that slides into the copper tube.

http://yfrog.com/3dp1010374lj

 

[Justin Case]

I'd say that the heat sink appears to be comparable to the chunk of Al bar stock that George at taskled used in his MaxFlex thermal design PDF. But at an estimated 4W waste heat generation by the driver, you may also need to sink the Blue Shark's inductor.