# Awesome CREE calculator



## zemike (Sep 3, 2007)

http://pct.cree.com/

This is a calculator for Cree leds. Example - it allows a quick comparison of all white Cree leds in terms of Lm/W, Lm, watts, total LED cost.


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## zemike (Sep 3, 2007)

Using Cutter prices for neutral white LEDs on stars I made a calculation for a 1200 lm system with 90% optical efficiency (in $AUD):
MC-E K bin $93 3 leds
XP-E P3 $84.7 11 leds
XR-E Q3 $81.9 7 leds


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## markj2k4 (Jan 20, 2009)

i think whats pretty clever about that calculator you can quickly look at various currents and instantly see lumen output as well as voltage draw. this would be helpful for someone looking for a fixed resistor dimming switch, or someone on the fence as to which driver to run and at what current. sure you can figure out price and lumen output yourself but theres a ton of guess work as your squint an guess at graph provided by cree. good find


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## bikerjay (Sep 16, 2007)

Well timed, I was about to ask about finding the equation for the curve of the Cree lumen vs current chart. With the equation it would be much easier to calculate exact outputs for lower than 350ma drive currents but this is ever better.


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## ifor (Apr 15, 2008)

Too bad I can not see how to fix the number of leds. Then the curent table would be better for the specific lights I already have.

Ifor


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## markj2k4 (Jan 20, 2009)

ifor said:


> Too bad I can not see how to fix the number of leds. Then the curent table would be better for the specific lights I already have.
> 
> Ifor


im assuming your talking about the number of leds it indicates you need for your system. that changes in relation to your target lumens you specify. default is 1200 i think. so say, if your running 3 r2's at an amp you would want to indicate your looking for 750lm output. furthermore if your looking for a target output for a dimmed state, change the target lumen output to what your hoping to achieve then look down the system led column until you find the number of leds in your system then look over for amp output needed to obtain that state. i hope i didnt misunderstand your question.

-m


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