-----Original Message----- From: Michael C. Reid [mailto:mikecreid@qwest.net] Sent: Friday, July 06, 2001 4:29 PM To: rottosen@idcomm.com Subject: RE: [EE]: Bulb Life At Light fair international, held in Las Vegas in May, our booth (Centralite Systems, we make low voltage lighting control systems for luxury homes) was next to an LED fixture company. In their small incandescent replacement LED's, they use the reactance of a capacitor in series with the 120 vac input to drop the AC down to a level where they can power the LED's. They also I believe had some type of voltage regulator in the circuit. They said the problem is with heat dissipation from some types of LED's, such as the blue LED's, as they consume more current. The crowds were sure attracted to the fixtures they were displaying. -----Original Message----- From: pic microcontroller discussion list [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Richard Ottosen Sent: Friday, July 06, 2001 11:30 AM To: PICLIST@MITVMA.MIT.EDU Subject: Re: [EE]: Bulb Life Harold M Hallikainen wrote: > > On Wed, 4 Jul 2001 00:00:50 -0400 Brandon Fosdick > writes: > > > > The Feb 2001 issue of Scientific American has an article that > > answers your > > question. Unfortunately its not accessible from their web site. The > > short answer > > is that its a cost/consumer acceptance problem. Its not yet cheap > > enough to > > compete with conventional lighting in the home market, but its > > making headway in > > commercial and utility applications, namely traffic lights. The > > article also > > says that only 10% of the traffic lights in the US are LED based. > > > > 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! > > Harold > The traffic light my friend Al Brown reverse engineered used a capacitor to limit the current. Roman Black was kind enough to put Al's schematic on his web page at: http://centauri.ezy.net.au/~fastvid/tube4w.htm -- Rich > ________________________________________________________________ > GET INTERNET ACCESS FROM JUNO! > Juno offers FREE or PREMIUM Internet access for less! > Join Juno today! For your FREE software, visit: > http://dl.www.juno.com/get/tagj. > > -- > http://www.piclist.com hint: PICList Posts must start with ONE topic: > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.