Minimum distance on PCB between XP-G
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jtr1962
Flashaholic
You might want to look at this, particularly page 7 and pages 12-16. Although this document pertains to Rebels, the same principles apply with similar LEDs such as the XP-G, except of course the pad layout is different. The idea is to use thermal vias which conduct heat from the LED's thermal pad to the heat sink. The thermal vias let you use conventional FR-4 circuit boards instead of much more expensive MPCBs.
And to answer your question, you should be able to put the XP-Gs practically touching at either 150 mA or 350 mA, provided you have an adequate size heat sink to attach the circuit board to. The XP-G is very efficient, meaning it doesn't produce as much waste heat as less efficient LEDs. At 350mA roughly 40% of the input power comes out as light, not heat. At 150 mA roughly 45% is light, and the remaining 55% heat. In terms of heat, that's roughly 0.65 watts of heat at 350 mA, or 0.25 watts at 150 mA.
And to answer your question, you should be able to put the XP-Gs practically touching at either 150 mA or 350 mA, provided you have an adequate size heat sink to attach the circuit board to. The XP-G is very efficient, meaning it doesn't produce as much waste heat as less efficient LEDs. At 350mA roughly 40% of the input power comes out as light, not heat. At 150 mA roughly 45% is light, and the remaining 55% heat. In terms of heat, that's roughly 0.65 watts of heat at 350 mA, or 0.25 watts at 150 mA.
jtr1962
Flashaholic
No, at 150 mA it would give fewer lumens. Here's my test results for the XP-G R5:
As you can see, you get 145 lumens at 350 mA but only 65 lumens at 150 mA. Link to post with XP-G R5 test results
jtr1962
Flashaholic
Yes, the lm/w is higher at 150 mA compared to 350 mA. The figures are 138 lm/W at 350 mA and almost 152 lm/W at 150 mA. Remember however that these results are from a test of an R5. The lm/W for an R4 would be a little lower at both currents.
What could be light color output of R5 6500K? Something like this?
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jtr1962
Flashaholic
Yes, the R5s I have look pretty much like that.
Could this be 5000 or 5500k?
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jtr1962
Flashaholic
Yes, more or less, provided the picture's white balance hasn't been altered.
Very nice, pure white light, warm and comfortable.
DM51
Flashaholic
Linger
Flashlight Enthusiast
http://www.candlepowerforums.com/vb/showpost.php?p=3164688&postcount=3
No distance is needed, they work great side by side.
edit - missed 1/2 your question - I drive them @ 1400ma each
No distance is needed, they work great side by side.
edit - missed 1/2 your question - I drive them @ 1400ma each
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