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Interesting about how the incandescent's heat had been
useful!
Looks like that isn't the only drawback of trying to go high
tech: All the way at the end of superbrightleds.com's listing they offer a
"loading resistor" to suck the power that incandescent bulbs would have!
It sounded like some automotive systems, maybe like blinkers, can't deal with
the low current draw of the LED replacements.
>>> "T Humphrey" <thumphrey mynra com> 11/24/2003 10:34:11 AM >>> Yeah those LED traffic light are catching on big time in NY too! Generally I like them, they have lots of advantages over the old incandescants. However they also have one MAJOR disadvantage, they are cool-running. Recently we had a snowstorm. Being early in the season it was a nasty wet snow and the winds were particularly brutal during this storm also. Well anyway the storm blew the snow straight onto the signal lights were it froze into a solid chunk of ice. The old incandescents made quick work of this ice melting off with all of there usually waste heat, but the LED's just sat there, completely obscured. Too make matters worse, the following morning was a cold, cold high pressure system, resulting in blinding bright sunshine, making the LED signals even harder too see. Not suprisingly, many fender benders occurred. Granted this doesn't occur very often, but when it does it's nasty. Unfortunately?, it wasn't enough snow to use the new thrower I got from Jon K. Thanks, Jon Stay Charged! Hump > > >-----Original Message----- >From: RJ Kanary [mailto:rjkanary nauticom net] >Sent: Saturday, November 22, 2003 11:39 PM >To: David Roden (Akron OH USA); elec-trak cosmos phy tufts edu; William >Korthof >Subject: Re: (ET) Ralph's LEDs > > > I have no scientific evidence to back up the idea of whether or not LED >signaling devices use PWM power technology. What I can tell you is that here >in the Commonwealth of Pennsylvania, LED signaling is taking root. All new >installs are of that variety, and most PennDot owned fixtures are being >updated. > I have noticed a perceptible flicker, in some units. I am blessed with >what computer geeks call 'Fast Eyes'. I have to have a refresh rate of 75Hz. >or higher on my monitor, or I can't stand to be in front of it . So, that >being the case, if there is a flicker there, indicating PWM operation, I'm >the person that would be likely to see it. > The signals I have noticed flicker on also appear to have a higher >number of dead elements in the arrays. Your thoughts ? >----- Original Message ----- >From: "William Korthof" <wkorthof earthlink net> >To: "David Roden (Akron OH USA)" <roden ald net>; ><elec-trak cosmos phy tufts edu> >Sent: Sunday, November 23, 2003 8:20 PM >Subject: Re: (ET) Ralph's LEDs > > >> David, >> >> I'm friends with the owner of one of the most established LED traffic >> signal retrofit manufacturers, and I've been following progress with >> them for 10 years. Every production unit I've seen uses some form of >> current limited power supply designed to approximates a constant >> current supply (with varying effectiveness). Where did you get the >> information that a pulsed power supply is common? >> >> /wk >> >> At 09:53 AM 11/22/2003, David Roden (Akron OH USA) wrote: >> >I recently read something fascinating about LEDs. Have you noticed >> >how intense the new LED traffic signals appear? (At night some are >> >so bright that the green ones actually are almost painful to view.) >> > >> >This is how it's done. The LEDs are driven by a pulsed waveform. >> >The on current is TEN TIMES their rating, but the duty cycle is only >> >10% - that >is, >> >on (for example) on 1 picosecond, off 9 picoseconds, repeat. Thanks >> >to persistence of vision, the human eye sees the peak intensity as >continuous >> >high intensity; but the LED "feels" the average current, which is >> >just >its >> >normal rated current. >> > >> >I'm sure the same thing could be done with automotive signals (if it >isn't >> >already). >> > >> >Clever, no? >> > >> > >> >David Roden - Akron, Ohio, USA >> >1991 Solectria Force 144vac >> >1991 Ford Escort Green/EV 128vdc >> >1970 GE Elec-trak E15 36vdc >> >1974 Avco New Idea 36vdc >> >= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = >> >Cutting the space budget really restores my faith in humanity. It >> >eliminates dreams, goals, and ideals and lets us get straight to the >> >business of hate, debauchery, and self-annihilation. >> > >> > -- Johnny Hart >> >= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = >> > >> > >> > >> > >> >_______________________________________________ >> >Elec-trak mailing list >> >Elec-trak cosmos phy tufts edu >> >https://cosmos.phy.tufts.edu/mailman/listinfo/elec-trak >> >> >> _______________________________________________ >> Elec-trak mailing list >> Elec-trak cosmos phy tufts edu >> https://cosmos.phy.tufts.edu/mailman/listinfo/elec-trak >> > > >_______________________________________________ >Elec-trak mailing list >Elec-trak cosmos phy tufts edu >https://cosmos.phy.tufts.edu/mailman/listinfo/elec-trak > _______________________________________________ Elec-trak mailing list Elec-trak cosmos phy tufts edu https://cosmos.phy.tufts.edu/mailman/listinfo/elec-trak |