A problem with LEDs

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When used in traffic signals, the lights don't get warm enough to melt snow. The snow obscures the signal and people die.
"Cities around the country that have installed energy-efficient traffic lights are discovering a hazardous downside: The bulbs don't burn hot enough to melt snow and can become crusted over in a storm - a problem blamed for dozens of accidents and at least one death."
http://news.yahoo.com/s/ap/20091216/ap_on_re_us/us_snow_covered_stoplights
Some cities are considering hiring midgets to sit atop the signals with hair-dryers and long extension cords to keep the traffic signals clear. (Some species of monkeys could be trained to do the job, but the training time would take too long to be effective this season.)
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HeyBub wrote:

I can see a couple of ways to prevent the problem and one is to use the type of heater that is used in outdoor CCTV cameras. Another way would be a simple snap on clear plastic cover that would prevent snow from getting into the hooded area. Oh yea, teeny little windshield wipers.
TDD
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On Wed, 16 Dec 2009 11:14:28 -0600, The Daring Dufas wrote:

Yes, that would work. Wouldn't need much heat at all, either, I suspect.
Problem might be designing something and getting it all properly safety tested before it can be used out in the wild; I expect LED lights have been in the pipeline for a few years and for some reason some idiot never thought of the cold-weather issues.
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On Wed, 16 Dec 2009 11:41:40 -0600, Jules

There are an awful lot of places where it simply isn't an issue.
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As it turns out, I have yet to see even one LED traffic signal effectively obscured by snow or any other form of water in Philadelphia and that city's suburbs. It does snow there, with only one of the past 135 winters there officially having only a trace of snowfall, an average one having about 21-22 inches of snow, and the worst one of the past 135 (1995-1996) having 66-67 or so inches of snow, including over 30 inches in a record-breaking storm. And by-and-large, northwestern parts of the city that I grew up in and most of the city's northern and western suburbs that most of my family has lived in since 1991 and that I know well usually get substantially more due to higher elevation.
And quite the share at least of the snow there is the wet sticky kind blamed for obscuring LED traffic signals. And most of it falls with wind in the range of "moderate breeze", "fresh breeze" or "strong breeze".
- Don Klipstein ( snipped-for-privacy@misty.com)
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Don Klipstein wrote:

I used to live in Bolingbrook, IL, a southwestern suburb of Chicago. All the traffic light are LED. I have seen them obscured when there is a wind blown wet snow. But, it usually doesn't last long, so I don't know how much an issue it really is. BTW, they also had UPSs on every traffic light, so power failures didn't affect the lights. I don't know how many hours the lights would keep working.
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On Thu, 17 Dec 2009 21:24:20 -0500, Art Todesco wrote:

Y'know, I think most of ours in town here in northern MN are incandescent still, but I've still seen them full of snow. I think all it takes is for there to be a little space open above the snow pile; the cold air gets in behind the pile and makes the heating effect from the bulbs irrelevant.
What they perhaps need are separate heaters at the bottom of the shrouds, but I'm not sure how that could be (reliably and relatively maintainance-free) switched so that the heaters only ran when they needed to. Perhaps there's some way of detecting how much light from the bulb is being reflected back (due to snow build-up) and tripping the heater that way.
cheers
Jules
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The Daring Dufas wrote:

I would expect it wouldn't be that difficult to install an optical sensor at the end of the hood looking back at the light and use that to switch on a heater if it did not detect sufficient brightness when the signal light was on. No extra energy use unless there actually was snow obscuring the signal. Probably around $20 manufacturing cost, so sell for $200, a fairly insignificant cost given what the signals themselves cost. Also only needed in climates that have blowing sticking snow.
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Pete C. wrote:

Using the same material as used in the manufacture of self regulating heat tape, an inexpensive add on heater that worked automatically could be produced.
TDD
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The Daring Dufas wrote:

No point in heating all the time, or even just when it's cold. Much better to heat only when it's cold and something (snow) is obscuring the light. The minimal cost of the extra control components will be far outweighed by the lifetime power savings of only having the heater active during sticking snow events.
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Pete C. wrote:

Birds have actually built nests in the lights so turning on a heater every time a bird lights in the light (pun) you would turn on heat.
TDD
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The Daring Dufas wrote:

Yes, but that's an entirely different problem, and one that would afflict both LED and incandescent signals.
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Pete C. wrote:

If it's a Hippie bird, it would build its nest in a flashing light because it's psychedelic. *snicker*
TDD
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The Daring Dufas wrote:

I think a Hippie bird would choose the red lights with the flashing white strobe light in it. Cool man. That's cool.
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Tony wrote:

Nah man, it's GROOVY.
TDD
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[Christmas presents]
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The Daring Dufas wrote:

But the heat would serve to incubate the eggs, leaving momma free to flirt with the flight. The chicks would then end up as unsupervised avians leading to the spread of "feather delinquency."
What the heck's wrong with the "midgets with hair-dryers" proposal?
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wrote:

Not enough "midgets" to fill the job demand?
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Oren wrote:

You would have to find the cast of "Under the Rainbow" and put them to work.
TDD
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The Daring Dufas wrote:

sounds like a good project for obama to create jobs and put folks back to work. would it work better with tall people instead of short people on ladders? Maybe a Cash For Blinkers program.
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