Questions about 5mm leds???????????

[metlarules]

I am working on a project that requires me to put a 5mm led in a plastic housing. Is there anyway to heat sink the led? Also, the led I will be using is the Cree 5mm as seen here. http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=LC503FWH1-15P-A0-ND What resistor value would I need to run it at 20ma runnin one off of 3aa batteries? Thanks!

 

[kuksul08]

I don't think that type even get hot.

It depends whether you're using alkalines or rechargeable AA's, but I'd say

V=IR
V=(3*1.35 about average voltage for either kind - 3.2 Vf of the LED) = .85V

I=20mA=.02A

-> R=42.5 ohms and you'll probably be safe rounding down to the next resistor since this one is rated for 25mA max.