Does a bare emitter need to be electrically isolated?

tylernt

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If I want to use a bare Cree emitter (the 3.45mm square, not on a star), does the thermal pad on the bottom in the middle need to be electrically isolated? Or can it be electrically shorted to ground or to + (not to both at the same time of course ;) ).
 

alpg88

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most of cree leds have isolated thermalpad, which one are you talking about?
 

tylernt

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Mainly XP-E, XP-G, and XP-C. But I'm also curious about XR-E and XM-L.

By "isolated thermalpad", you mean it's OK to short it to ground or NOT OK to short it to ground?
 

AnAppleSnail

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Mainly XP-E, XP-G, and XP-C. But I'm also curious about XR-E and XM-L.

By "isolated thermalpad", you mean it's OK to short it to ground or NOT OK to short it to ground?

The datasheet will tell you if the thermal contact is electrically isolated. If so, then the thermal pad can touch the heatsink with no ill effects.

WARNING. Cree LEDs have electrical contacts on the bottom, too. Either grind them away carefully or use a spacer, or your +/- contacts will be shorted.
 

alpg88

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Mainly XP-E, XP-G, and XP-C. But I'm also curious about XR-E and XM-L.

By "isolated thermalpad", you mean it's OK to short it to ground or NOT OK to short it to ground?

you can short it to either,
 

tylernt

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Nov 25, 2009
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Ok, cool -- isolating + is not a problem. Shorting - and the thermal pad together makes things much easier.

Thanks guys!
 

eh4

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I'd get dyslexic about it after all the explaining, couldn't you just double check it as many times and ways as you needed to with the circuit continuity tester function of a multimeter?
 

tylernt

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Nov 25, 2009
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I haven't bought the bare emitters yet -- wanted a sanity check before spending the $$$.
 
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