Part of the thrust in going to LED's (in addition to the lifetime savings on
electric cost compared to the increased bulb cost) is the increased life and
hence the reduction in the cost actually replacing the bulbs over a period
of years, ignoring the cost of the bulbs.  I.e., the cost of a municipal
truck, with a high loader and a crew of at least two each time a light bulb
needs changing.

Marc Reinig
System Solutions

-----Original Message-----
From: pic microcontroller discussion list [mailto:PICLIST@MITVMA.MIT.EDU]On
Behalf Of Harold M Hallikainen
 Subject: Re: [EE]: Bulb Life

>        In the past couple months, pretty much all the traffic lights here
have
> been changed to LED. I kinda wonder what the electronics to run an LED on
> 120VAC looks like. I'd expect some sort of boost switcher acting as a
> constant current source into a bunch of LEDs in series. Not really very
> simple or cheap.  In an effort to save electricity, you certainly don't
> want to just use a big current limit resistor!

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