Using Epoxy to stick the Cree Q5

[snipinglight]

I don't want to spend money on AA heat epoxy for one Cree emitter. I was thinking to use normal resin epoxy to hold it in place to a heat sink. A very thin layer will be applied. It will be driven to 890ma at 3V using two AA rechargable batteries. Will there be heat issues?
Thanks

 

[Lynx_Arc]

I don't want to spend money on AA heat epoxy for one Cree emitter. I was thinking to use normal resin epoxy to hold it in place to a heat sink. A very thin layer will be applied. It will be driven to 890ma at 3V using two AA rechargable batteries. Will there be heat issues?
Thanks

I don't think without proper heatsinking you can drive a Q5 at 900ma without frying it and unless you have a boost circuit direct driving it off 3v input will find you probably less than 250ma. Epoxy that doesn't have heat conducting material in its composition may act more like an insulator.

 

[snipinglight]

I don't think without proper heatsinking you can drive a Q5 at 900ma without frying it and unless you have a boost circuit direct driving it off 3v input will find you probably less than 250ma. Epoxy that doesn't have heat conducting material in its composition may act more like an insulator.

Now I can't use the Q5 for some reasons and changing it to a Seoul SSC P4 and attaching the LED base to the combo heatsink/driver unit using normal epoxy and driving current is 950ma at 3V. The distance between the heat sink and SSC P4 led is 0.42mm. Will there be any heat issues?

 

[Toaster79]

There will be some heat issues but not for long. The led will cook really fast. Which part of not using regular epoxy didn't you understand? You'd be better off sticking that led directly to the heatsink or using no heatsink at all, than using 0.4mm thick layer of insulationbetween the two.

 

[snipinglight]

There will be some heat issues but not for long. The led will cook really fast. Which part of not using regular epoxy didn't you understand? You'd be better off sticking that led directly to the heatsink or using no heatsink at all, than using 0.4mm thick layer of insulationbetween the two.

The base of ssc P4 is positive and the heat sink is battery negative, if there is direct contact with the heat sink, the whole thing will be shorted.

 

[Lynx_Arc]

Now I can't use the Q5 for some reasons and changing it to a Seoul SSC P4 and attaching the LED base to the combo heatsink/driver unit using normal epoxy and driving current is 950ma at 3V. The distance between the heat sink and SSC P4 led is 0.42mm. Will there be any heat issues?

I'm still not sure how you can get 950ma into a Q5 or SSC P4 at only 3v. Without knowing the heat conductivity of the insulating layer I cannot tell you how much heat is allowed through it to the heat sink itself but I am guessing that you need to get rid of 3-5 times as much as the LED itself can handle. I think there will be severe heat issues such that the LED will fry quickly if you are truly putting almost an amp into it.

 

[derfyled]

Just to come back on the epoxy subject, you can mix about 50-50 epoxy with some CPU thermal grease. I had good result with that recipe before I finally bought some Artic Silver. You can get a small tube of thermal grease in any computer store for 1-2$... Just be sure to properly mix it. I don't think it is efficient as a real thermal transfer glue but it works...

 

[snipinglight]

Just to come back on the epoxy subject, you can mix about 50-50 epoxy with some CPU thermal grease. I had good result with that recipe before I finally bought some Artic Silver. You can get a small tube of thermal grease in any computer store for 1-2$... Just be sure to properly mix it. I don't think it is efficient as a real thermal transfer glue but it works...

I just tried out this method and it works. My old Maglite is now alive and holding well. Its very bright compared to the Cree and Lumiled. Thanks.

 

[Scattergun]

I have made a few Maglites running XR-Es at around 1A with nothing other than regular epoxy holding them down... works for me.

 

[snipinglight]

I have made a few Maglites running XR-Es at around 1A with nothing other than regular epoxy holding them down... works for me.

Glade to hear that, don't want to spend big money on AA, too costly for me.

 

[schizeckinosy]

Reading through this, I can't help but wonder if folks are talking past each other. Gluing an emitter will surely fry it (if you could even get it to work at all), but if it is mounted on a star, then gluing the star would not be too bad for less than 1 amp if you mix in some thermal transfer stuff, as noted. I have tested (copper) star mounted emitters in air at 3a for several seconds at a time and they hold up just fine.

 

[Scattergun]

Reading through this, I can't help but wonder if folks are talking past each other. Gluing an emitter will surely fry it (if you could even get it to work at all), but if it is mounted on a star, then gluing the star would not be too bad for less than 1 amp if you mix in some thermal transfer stuff, as noted. I have tested (copper) star mounted emitters in air at 3a for several seconds at a time and they hold up just fine.

I think you are right, and I was talking about glueing a star. The emitter must be soldered if high currents are to be used.