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Originally posted by gunnut View PostLED might generate a small amount of heat, but not enough to melt ice. You have to remember traffic lights don't stay on constantly. They change.
modern high power leds generate enough heat , so it becomes real problem in portable applications, and require sophisticated heat sinks. also as leds heat up they dim, and turn blue. halogen OTOH loves heat,
believe me, flashlights are my hobby, i build about 50 in the last 3 years, heat sinking is a serious problem, modern 30w leds need a copper heat sink that weights a pound, in 5 min it will heat up so much you will get serious burns if you tough it.
if you talking about 5mm leds, that yes they don't produce much heat, neither they make much of the light, lm\w ratio is horrible. you are a lot better off with fluorescent than with 5, or 10mm leds. there are also 3 and 5 chip 5mm and 10mm leds, but they are even more inefficient than single chip led.
but traffic light are a bit different, they don't need to produce much light, btw in NYC most if not all traffic lights were retrofitted with leds, now you can hardly find green that doesn't have dead clusters, some have only half of the leds on. talking about service life.Last edited by omon; 14 Sep 10,, 18:47."Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote!" B. Franklin
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Originally posted by omon View Postlol yes that is true, nasty unintended consequence
modern high power leds generate enough heat , so it becomes real problem in portable applications, and require sophisticated heat sinks. also as leds heat up they dim, and turn blue. halogen OTOH loves heat,
believe me, flashlights are my hobby, i build about 50 in the last 3 years, heat sinking is a serious problem, modern 30w leds need a copper heat sink that weights a pound, in 5 min it will heat up so much you will get serious burns if you tough it.
if you talking about 5mm leds, that yes they don't produce much heat, neither they make much of the light, lm\w ratio is horrible. you are a lot better off with fluorescent than with 5, or 10mm leds. there are also 3 and 5 chip 5mm and 10mm leds, but they are even more inefficient than single chip led.
Originally posted by omon View Postbut traffic light are a bit different, they don't need to produce much light, btw in NYC most if not all traffic lights were retrofitted with leds, now you can hardly find green that doesn't have dead clusters, some have only half of the leds on. talking about service life."Only Nixon can go to China." -- Old Vulcan proverb.
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Originally posted by gunnut View PostDon't worry. I wouldn't hedge my retirement on CFL technology. LED will replace it in about 10 years.In the realm of spirit, seek clarity; in the material world, seek utility.
Leibniz
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Originally posted by Parihaka View PostIt's replacing it now. When I did up our kitchen and bathrooms it was with a combination of halogen and LED"Only Nixon can go to China." -- Old Vulcan proverb.
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Originally posted by gunnut View PostCool! I may have to hit you up on some pointers and questions.
That's strange. I rarely see dead elements/clusters in traffic lights near my area. We have had these LED traffic lights for maybe 5 years.
strange it is, a wont be lying if i tell you entire ocean parkway has no green lights, that have all leds on, red are almost all just fine, 5 years ago sounds about right. and they never replaced yellow, they are still all incandescent, (never seen yellow burn out, lol)
the thing is, leds unlike bulbs are almost always wired in series, parallel clusters, one burns, takes out entire cluster, there are very few (actually 2 cree and nichia) manufacturers that build quality 5mm leds, china supplies billions of leds, but their quality is not that good, they are fine in cheap even not so cheap flashlights, since you don't run them long, but when they are in lights that are on 24\7 it becomes a problem, the same story in express busses reading lights, 12 bulbs, 4 clusters of 3, not many affected since they aren't on for too long, but still planty have 3 or 6 some even 9 leds dead.
i'm not a big fan of leds, that are cool white (look blue) cuz of low cri (color rendering index), nothing beats halogen at that, even warm white leds still are not as good, in the woods at night i wanna have halogen, for a simple reason, dark brown and dark green all look the same black in cool white led light.Last edited by omon; 14 Sep 10,, 20:50."Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote!" B. Franklin
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