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New York City Street Lights To Go LED
eldavojohn writes "Wired has a short piece on NYC's new street light project. I don't think we need to belabor the many benefits that LEDs hold over traditional light bulbs, but the finishing touches are being addressed, and they will hopefully be put into place sometime next year. This design won a competition back in 2004, and OVI has been whittling down the prototypes. At $1.175 million, this sounds like a pretty cheap deal considering the DOE forked over $21 million to 13 R&D projects along the same lines."
The thing that is awful about led lamps is that most of them are run straight off the AC voltage and have massive 100% brightness flickers. If you are moving it's like a strobe. You don't see it in car lights since they are run off DC. but most, perhaps not all, AC socket lamps I've seen have really bad flicker.
I also how they have secondary lenses since LED's can be very directional the way they are typically resin cast.
Some drink at the fountain of knowledge. Others just gargle.
This is something I've been wondering about for awhile. LEDs (especially the white ones) are really bright for being so small, and they don't have that yellow tint that incandescent bulbs do. Compact florescent bulbs are nice, but they aren't perfect for every situation. I'm not an expert on the subject, but I've always wondered why they don't make giant LEDs that can replace ordinary light bulbs. It seems like 220 AC would be more than enough to power them.
"It is a denial of justice not to stretch out a helping hand to the fallen; that is the common right of humanity."
many NewYorkers does it take now to change a light bulb?
FTA, the ~$1million is for building and testing six working prototypes. The design will then be added to a catalog the city uses, and they can then install them as they see appropriate.
I'll never make that mistake again, reading the experts' opinions. - Feynman
Are there any major observatories near NYC? (hmm large mountains close to NYC?)
Are these new lights narrow or wide spectrum?
See: http://en.wikipedia.org/wiki/Light_pollution
Blue Light hazard? No wonder my eyes hurt after shopping at K-Mart.
Submission as evidence constitutes plaintiff and/or prosecutorial misconduct.
The lighting product manufacturers quote efficiency in lumens-per-watt(lpw). What they don't shove in your face in marketing is that the devil is in the details.
CFLs, LEDs, incandescents, HPS and metal halides all have drastically different spectrum outputs. Incandescents have a very broad spectrum but their lpw is astonishingly low.
CFLs have as much as 80 lpw, whereas MH and LEDs are currently at about 100 and HPS can be even higher(around 140 lpw initial, which declines over time). LEDs have the potential to be higher than HPS but across the lifetime of the HPS bulb the LED may end up with a higher average lpw and definitely much longer service life.
There are CFL's with a broader spectrum but they're less efficient. While not completely monochromatic, there is a big spectrum spike in reds and yellows for HPS bulbs. Most people find this light to be soothing. Metal halides have a broader spectrum than HPS but are less efficient than even fluorescents. There are new white LEDs in research that produce as much as 145 lpw, but these are not commercially produced yet. Philips produces a 115 lpw white LED which is available in large quantities. You're right about the blue light hazard though - phosphor based white LEDs have a large spike around 465nm.
Interested in reading more about Lighting? Read the book the pot growers read. They have the best lighting money can buy. The Best of the Growing Edge
You can't legislate goodness. Let each to his own destiny, by will of his freely made choices.
Some of the newer LEDs can go above 100 lumens/watt.
One thing about HPS is that it spreads light everywhere, whereas LEDs are more directed, which you want in a streetlight facing down. Omnidirectionalness can be fixed with good fixture design, but most cities use crummy fixtures.
Not a typewriter
Here in Portland, OR, we have already started to use LED street lights. And now that we're in a snow storm, these lights aren't working. LEDs don't produce heat (that's why they're efficient). By not producing heat, they don't melt the snow away from them. So all the LED streetlights in Portland are covered in snow and cannot be seen.
The old lights produce enough heat to melt all the snow. Snow in Portland is rare, so it's not that big of a deal. In NY, it's quite the opposite.
Actually, LEDs get dimmer as they get used. If they don't fail due to the semiconductor turning into molten metal, they get dimmer and dimmer and dimmer. The 100,000 hour lifetime figure on LEDs is usually the time until 50% brightness (considered to be the point where one would notice the light being dimmer).
There are many reasons for this - degradation of the junction itself, but the semiconductor itself leads to a large index of refraction - a lot of the light in a LED gets reflected back into the semiconductor. And then there's degradation of the epoxy used to seal the LED. All these conspire to make the LEDs much dimmer, and get dimmer over time.
Personally I'd miss sodium vapor street lights if LED replacements became fashionable. Perhaps it is a romantic notion, but it seems to be that one of the reasons sodium lamps have become so popular is that the orange light they emit is reminiscent of fire, and in colder northern climates their warm glow is comforting to people at some deep instinctual level.
"I bless every day that I continue to live, for every day is pure profit."
We've had LED signals here in Osaka for 5+ years how and they work very well. Here are some links (in Japanese) with photos showing what they look like:
Red Light, Green Arrow
Pedestrian Crossing
Green, Amber, Red (the amber is actually brighter than it seems in this photo)
I haven't experienced any problems with them and I drive daily here. There is no noticeable flicker and they are a lot brighter than the traditional signals they replaced.
Some people are like slinkies--basically useless but they bring a smile to your face when pushed down the stairs.
I'm not one of those wacky conservative nuts but here in NY, we're about to be forced to pay all new kinds of taxes on various things such as Non Diet, Soft Drinks.
I'm all for the LED's if they're better in the long run and cheaper than maintaining the current lights but is it necessary right now?
Our politics are all screwed up here in NY. Its the blind leading the blind... literally.
"We don't need to belabour the advantages of LEDs over traditional lightbulbs"?
Actually, we do, since we've had lightbulbs other than incandecent for over a decade, and incandecents are never used to light streets. LEDs manage about 100 lumens per watt, similar to high pressure sodium lamps. The old orange low-pressure sodium lamps are still king of the hill at 200 lumens per watt.
So what were those advantages again? Compared to high-pressure sodium lsmps, they're the same efficiency and lifetime, but a lot more expensive. The only advantage to low pressure lamps is colour, but they loose a factor of 2 on efficiency.
SJW n. One who posts facts.
LEDs only produce light in narrow bands of spectrum, so even if those bands are far apart, so the light looks white, the reflection from various materials may look nothing like the color seen under wide-spectrum source such as sun, incandescent or mercury vapor light.
Contrary to the popular belief, there indeed is no God.
Mercury vapour is MUCH worse than led in terms of "spiky spectrum". They nearly have no continuum at all. LEDs do.
HI O WISE PRINCE. WHT TOOK U SO DAM LONG?
[...] Instead, they keep selling us a tiny wire the size of a pubic hair [...]
Please adopt the metric system. PLEASE!!!
You need to look at the LED taillights on a Cadillac in moving traffic. In the dim mode used for tail/marker lights (not the full brightness mode used when the driver presses on the brake pedal), the taillights are being dimmed by PWM with no filtering. The flicker is extremely annoying and gives a strobe-like appearance where your eyes see multiple images of the lights in moving traffic.
Why Cadillac chose to dim their LED taillights this way is beyond explanation. It makes the cars look cheap, but it can't be a cost saving, because you can dim an LED array with a simple resistor and eliminate the PWM circuit altogether. LED taillights for heavy trucks use a diode and a resistor for the lower light output level and they look great.
The effect is more noticeable when you're traveling at a different speed than the Cadillac, or if you move your head side to side while looking at the taillights. It's really obvious and undeniable.
Putting moderation advice in your
[...] Instead, they keep selling us a tiny wire the size of a pubic hair [...]
Please adopt the metric system. PLEASE!!!
Pray tell, can you enlighten us to what the metric equivalent of a pubic hair is?
5.3 centicurlies?
Putting moderation advice in your
The flicker is not in his head, it's in the taillights. I've seen the flicker, it's caused by a pulse width modulation circuit to make the taillight mode of a combination taillight/stoplight appear dimmer. A quick google search pulls up this article http://findarticles.com/p/articles/mi_m0EIN/is_2006_Nov_8/ai_n27039046 about an automotive product specifically designed to address this issue and stop the flicker by eliminating the pwm circuit. It works by reducing the DC drive to the LEDs in taillight mode instead of using pulse width modulation to reduce the average current and effective brightness.
Oh really ?
Those tail lights were not flickering to the naked eye, it was not a police vehicle - it only showed up through the video camera. And BTW, I can see flicker too, not the extent revealed by the video, but almost imperceptibly. I know it exists. Whether it's a DC circuit or not is irrelevant, as the flickering is to do with duty cycle not frequency.
A dutch company seems to have solved that problem (color recognition) by using a mix of mostly green and some red leds.
They use green leds because the human eye is most sensitive to green light in the dark, so the green light gives the best visibility at night. But to enhance the color recognition (which is basically zero with the almost monochromatic green light from the leds) some red leds are added.
Here you can find a nice presentation (with explanation) of the product.
Incorrect when talking about LEDs. "White" LEDs are covered with a phosphor that takes a blue LED's light and shifts it down. The output from the phosphor is broad spectrum, even if the original LED was a narrow band blue. Thus, these LEDs are a good wide spectrum light, instead of an approximation made from mixing red, green and blue LEDs. Of course, the problem you described can exist, but is commonly seen only with fluorescent bulbs.
This is incorrect. Modern white LEDs are quite similar to fluorescent bulbs. They use a high frequency (large bandgap) junction to generate UV light, which is "down converted" by a cocktail of phosphor chemicals, to produce a smooth output covering wide swatches of the visual light range. It is customizable, but it is based on what our eye and brain actually consider to be white (our eye and brain have a very nonlinear response to different wavelengths of light). We're not used to it since other lights are not as white as LEDs are.
Look and page 19 and 20 of this PDF to see what I mean: http://www.philipslumileds.com/pdfs/DS51.pdf