[Aavso-photometry] LEDs

[Rumrill, Donald M (US SSA)]

My experience in the past with IR LEDs, is that they decrease in light output by around 10% per decade hours.  This is probably a good approximation for visible light LEDs too; at least the Reds and Greens.  So it is probably a good idea to burn them in for 100 - 200 hours before using them as a reference.  White LEDs are a secondary emission type, with a white fluorescent material excited by (I believe) a blue LED.  I do know that the fluorescent material does have a significantly more rapid degradation than the typical LED does, but I'm afraid I don't know that rate.  Be cautious of inexpensive White LEDs, as they have been know to degrade a great deal in just a few  hours.

The 10% per decade decrease appears to be driven by an "annealing" process relieving internal crystal stresses.



Don Rumrill

Principal Design Engineer

Components Engineering

607-770-3590



BAE Systems

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Johnson City, NY 13790