- Test was performed exactly as all of my emitter tests - which is mounted to a 1lb piece of copper barstock imbedded in a 25lb block of aluminum.
- Heat is the key. The cooler an led can be kept, the more power it can be fed to produce more light.
- I have @ 10 150w peltier coolers at work that I could stack together to get an led close to cryogenic...but other than academic interest a test like that wouldn't have much bearing on what could be done in relation to a flashlight.
The results from that test are here. For Justin's benifit, I sent him a graph depicting all three tests.
I agree, you can’t easily put a peltier cooler into a flashlight, so i guess its more of an academic interest. I assume at some point the wires and junctions in the led will fry from the voltage and current if you keep the temp low enough for that to happen.
We could always start a betting pool to see what amperage and lumens a U2 XM-L can take before non heat related failure
I centered these just by setting the led on the pads by eye. Then I hit each outer pad with a solder gun just long enough to heat the low melt solder and last is to heat under the center pad, until it’s solder melts. If the solder is done very thin, it works pretty good.
thanks. Looks like the only main difference between OL Cu star and direct copper mount is at very high amps (>4.5A), so within the realms of sane use OL’s method should be equivalent and a smidge easier
I was looking up kapton tape and found a document on off gassing from the adhesive here
I don’t know if it’s relavant or not. It seems to relate to condensation of the gasses on switch contacts but I thought it might also affect reflectors adversely. Do people use kapton often on stars without problems? If so then ignore this post. This is a great idea, just want to avoid later disappointment. Thanks
I’ve done something similar, I made my own copper star by sanding a penny until it was flat. Copper is surprisingly expensive material and one convenient thing about the penny is before 1982 they were pretty much solid copper. You’re actually getting more than 1 cent worth of copper for every penny so there is no cheaper way to make a copper star than by sanding a penny flat.
Instead of soldering a base to raise the center you can actually just use the solder itself to bridge the thin gap between the kapton gasket and star. Instead of using copper sheet as conductor you can use copper foil. This way there is minimum thickness between the conductors/gasket and the star allowing the solder to fill the gap in completely. That makes it only one solder joint from the led thermal pad to the star. Solder joints are a big bottleneck for heat conduction so you want to keep them to a minimum.
The Polyminide tape I am using is supposed to have a Teflon Silicon adhesive, not Acrylic. Probably still has off gassing as any adhesive probably would. I imagine even the Silicone domes on leds have some form of off gassing, however minor it may be.
Not trying to be a party pooper and the article did look old. I have not used kapton and don’t know what changes have been made in the adhesive. The article just made me think of the effect super glue can have on domes and lenses. As Gilda Radner said,“never mind”.
