From: and4y2@turnquist.name.invalid   
      
   I'm curious about what happens to an LED when it is exposed to a   
   moderate overcurrent situation.   
      
   This question came about as I was troubleshooting some small white LED   
   lights I built using 3 5mm LEDs and a current limiting resistor to run   
   on 12Vdc (supplied by a lead-acid battery charged by solar).  After some   
   time, many of these strings would start to flicker or blink.   
      
   I was about to post a question about that, when I redid my resistor   
   calculation.  I had originally calculated that a 100 ohm resistor   
   would be sufficient to keep the current around 20mA (assumed 12.5V -   
   10.5V total LED drop).  But on recalculation, that would result in 30mA   
   (the absoulte maximum rating) at 13.5V, the low end of charging range.   
   Adding another 47 ohm resistor seems to have helped.   
      
   So now I'm curious what happens inside the LED when the current   
   exceeds the absolute max current by a modest amount (i.e., not the   
   obvious overcurrent of leaving out the resistor entirely).  The LEDs   
   I'm using seem to return to normal operation when the current is   
   reduced, and seem to produce a momentary open-circuit condition during   
   overcurrent, presumably from overheating.   
      
   Anyone know what's happening to the semiconductor material in this   
   situation?   
      
   Thanks,   
   --Andrew   
      
   --   
   Andrew Turnquist, Short Tract, New York, USA (USDA Zone 5)   
   (Remove numbers and .invalid for email address)   
   "Do what you can with what you have where you are." -T Roosevelt   
      
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