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Last Updated on: Thursday, November 30, 2017 07:43 AM

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White LED Lifetime Tests 
By: Dave Johnson  --   March 1, 2010

Problem:  All white LEDs fade over time.  I find that some LEDs fade in intensity very rapidly while others fade more slowly but every one I have tested would be worthless in a few months to a year.

Solution:  To speed up the testing process I have modified my constant current LED driver circuit as shown below. 

 
 



White LED Lifetime Test Circuit
This new circuit can test 4 LEDs at the same time.  I have a separate photodiode monitoring the light output from each device.  I have also mounted a battery operated hour meter to the circuit.  This should make it easier to plot light output Vs time curves for several parts.

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DC Magazine, Issue 7, Page 4:  White LED Lifetime Tests


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