19012fc4   
   XPost: sci.physics, sci.electronics.misc   
      
   In sci.physics RichD  wrote:   
   > On Jan 12,  Helmut Wabnig  wrote:   
   >> >I was looking at some LED flashlights, with ratings   
   >> > from 50 to 150 lumens.  A p-n junction is a p-n   
   >> > junction, how do they get such varied outputs?   
   >>   
   >> >I examined the working end, they all look alike,   
   >> >with a single bulb.   
   >>   
   >> The more current you  force through a p-n junction,   
   >> the more light will come out.   
   >> With veryvery much current, it will flash very brightly,   
   >> for a short duration.   
   >   
   > Thay all use the same batteries,  so it's as simple as   
   > a series resistor?  But then why does the higher   
   > output cost more?   
      
   High power parts generally cost more than low power parts.   
      
   > Also, there are flashlights which use multiple LED -   
   > you can count them in the housing - why would the   
   > manufacturers do that, paying for extra parts, rather   
   > than using a single LED with high current?  And   
   > some of those multiple LED units cost less than   
   > the single ones I checked.   
      
   Because high power parts cost more than low power parts and it is often   
   cheaper to use several low power parts than one high power part.   
      
   Also, when 1 LED out of a 10 LED array goes bad no one notices but if   
   there is only 1 LED it is pretty obvious if it fails.   
      
   That's the main reason the LED traffic lights are arrays.   
      
      
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