Low Power LED Flasher  
  It doesn't get much simpler than this circuit. Four components counting the battery!
 
How can an LED be illuminated by a 1.5V circuit, when the forward voltage of an LED is about 2V? The LM3909 uses the 100uF capacitor as a charge reservoir, building up a voltage of about 2V before discharging the cap through the LED.
 
This circuit is used in emergency flashlights on airplanes and in other public places. Though you may not have known it till now, the LM3909 is everywhere!

 
 
  Flasher  
 
 
News: As of July 2006, I know of one source for the LM3909: Alltronix

I have known the owner of Alltronix for many years. They are a very reliable supplier.
 

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