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Comments: 303 +- Technology: New York City Street Lights To Go LED on Friday December 19 2008, @11:15PM
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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."
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flicker crashes (Score:5, Interesting)
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.
Re:flicker crashes (Score:5, Interesting)
Assuming the line voltage is run through a full wave bridge rectifier, there would be a 120 Hz flicker, imperceptible to most people. Toss a large capacitor across that DC output and you've got dramatically less ripple.
Your directionality comment is apropos. It's also worth noting that some people don't like the light spectrum output on white LED's. Personally, I prefer the pink tint from high pressure sodium lamps.
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Re:flicker crashes (Score:4, Insightful)
Assuming the line voltage is run through a full wave bridge rectifier, there would be a 120 Hz flicker, imperceptible to most people. Toss a large capacitor across that DC output and you've got dramatically less ripple.
true but then you also have 100 times the surge current when you turn them on, or a slow turn on.
What you say is of course obvious to any EE, and yet i've never actually seen a single 120v LED lamp made that way. One wonders why.
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Re:flicker crashes (Score:4, Insightful)
These aren't headlights, they're street lamps. Do you really care if it takes them 3 minutes to warm up?
And even assuming they have ballasts featuring accelerated warm-up, the starting current will still be as much as double the normal operating current requirements. Really though, the starting current is negligible in the grand scheme of efficiency comparisons.
I'm not an expert on line voltage LED units designed to replace incandescents, but I would imagine including a bridge rectifier and capacitor would increase the cost and pose significant design constraints due to the components size.
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Re:flicker crashes (Score:4, Informative)
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Re: (Score:3, Interesting)
What you say is of course obvious to any EE, and yet i've never actually seen a single 120v LED lamp made that way. One wonders why.
I actually have a broken LED GU10 lamp on my bench at the moment. Inside is a small bridge rectifier, a smoothing capacitor and a tiny chopper PSU. The LED string is run at around 50D. The bridge rectifier and capacitor provide around 340V (240V mains) with about 10% ripple, but the chopper compensates for this and provides a 60kHz pulse-width modulated supply which is then
Re:flicker crashes (Score:4, Insightful)
I don't know what I hate more on slashdot .... seeing somebody spout off when it's obvious to anybody with even passing familiarity in the field in question that they're full of it, or seeing somebody get shat upon when they ask a perfectly valid question in an attempt to try to learn something new
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Re:flicker crashes (Score:5, Informative)
There are plenty of LED traffic lights around me and I've never noticed any flicker. I imagine it isn't a problem.
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Re:flicker crashes (Score:4, Informative)
The biggest problem with LED traffic lights is that the greens are REALLY bright. You'll be shocked, especially at night how bright the damned things are. In SoCal, we have LED traffic lights everywhere.
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Re:flicker crashes (Score:4, Interesting)
In SoCal, we have LED traffic lights everywhere.
In Québec we have them pretty much everywhere too. Sometimes when the snow is just the right consistency and falls in the right direction, it sticks to the traffic lights lenses, obscuring them. In the past, the heat generated by the incandescent bulbs would melt the snow, but the new LED lights don't produce enough heat. A city worker has to remove the snow with a kind of small broom attached to a long pole.
Two steps forward, one step back...
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Re:flicker crashes (Score:5, Informative)
Well, they have been testing these lights in my home town of Scottsdale, and they have three different types installed along one stretch of road way. They are super bright, and there is no flicker whatsoever.
The fact that they are directional is an advantage in this case since they are meant to throw light in a cone shape. The ones I've seen have no secondary lens. If there is any covering at all it is completely transparent glass.
Personally I like them because the light is white, not the orange of sodium vapor. Reminds me of when I was a kid before the move from mercury vapor to sodium vapor...
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Re: (Score:3, Informative)
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.
Re: (Score:3, Informative)
Mercury vapour is MUCH worse than led in terms of "spiky spectrum". They nearly have no continuum at all. LEDs do.
Re:flicker crashes (Score:4, Insightful)
Just because you don't have some trait doesn't mean that other people don't. In this case, that trait is how fast your eyes can see. Congratulations, you have slower eyes.
I am one of those people. It isn't just "flicker", I can see the image-black-image-black pattern of the CRT at 60Hz without doing any tricks like waving my hand in front of the monitor or using the side of my vision.
I can't stand to be in the same room as a CRT monitor running at 60Hz, it is almost physically painful to see. When I had a CRT I had to run it at 85Hz to be able to use it for any period of time, but still had to make the text white on black, turn the brightness down, and such.
If it doesn't bother you, then imagine replacing every CRT with a strobe light running fast, as bright as the monitor. That would be annoying and distracting, right?
Imagine that tail lights of cars and buses were red strobe lights. Around here, that is actually a reality, with most of the new buses and some new cars having tail lights running at 60Hz. It is extremely obvious to me, where I can instantly point out which cars in a long line have blinking LED tail lights.
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Re: (Score:3, Informative)
Cars and buses with LED tail lights are not running them at 60Hz. Nor are they being pulsed at any rate. The electrical system in a car is 12V DC. The LED assembly is either designed with enough LEDs in series such that the forward voltage drop over the set is 12V (roughly 10 LEDs) or they are in parallel with a buck-style switching power supply in front of it.
Now, before you go on about how the switching power supply causes flicker, you should research how they work. You will find that for cost and siz
Re:flicker crashes (Score:4, Interesting)
You will observe, instead of a smooth trail of light (referred to on film as a "motion blur") like you normally would see, you can see individual "sets" of lights; very broken partial light trails. This effect is exaggerated enough to be realized in this case by the constant movement of your eyes.
Every set of LED tail lights I've ever seen could produce this effect. How can this be? Apparently, I'm not alone in my experiences, either. I'm certainly not one of those nut jobs who says WiFi makes them nauseous, hell I can't tell teh difference between 320kbps MP3 and WAV.
I can, however, hear a high pitched whine from an old CRT with no signal, 60Hz monitor refresh gives me a headache, and LED tail lights leave a strobe pattern instead of a smooth trail.
I believe this is dangerous as it can make determining the point of origin for such types of lights difficult when split-second instinctive brain functions take over. Instead of a line leading to the current position of the tail light, in that slit second my mind has 3 "still frame" snapshots to piece the scene together with - not quite enough information.
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Re:flicker crashes (Score:4, Interesting)
I've seen a definite flicker in some cars' tail lights as well, so you're not crazy.
I think the cars pulse the lights at ~50% most of the time, then switch to 100% when the brakes are applied.
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Re:flicker crashes (Score:5, Interesting)
*sigh* You remind me of the EE graduate student who was showing me and my classmates around his lab one day. To prove the point that humans couldn't hear a 16kHz tone very well he quickly turned the power up from 1 to 11, and through pain practically paralyzed the half of the class that still had their hearing intact.
Many cars have the flickering tail LED lights, and it has nothing to do with DC-DC converters or other sources of ripple in the supply current. It's simply a matter of the duty cycle timer, the tail lights are "dimmed" not by limiting the current but by turning them completely on and off at a low frequency. The ones I've seen are in the 40-80Hz range, just stick an oscilloscope on there if you don't believe me. The flicker stops when the lights go to full illumination (i.e. the break petal is depressed).
Now go outside and look at some LED tail lights! Even if you have very poor vision you should be able to see the ones flickering at 40-50 Hz.
PS If you are legally blind, just don't comment on lighting. You are bound to suffer from foot in mouth at times; go take on those annoying audiophiles buying 1000 euro power chords.
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Re:If you see flicker in taillights (Score:5, Informative)
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Giant LED light bulbs (Score:4, Interesting)
Re:Giant LED light bulbs (Score:4, Informative)
uh... because they do and you can buy them [google.com].
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Re: (Score:3, Interesting)
That's not what he means. The replacement 120v led lamps are a collection of a bunch of little white led's. Why can't they make a single led the size of a lightbulb instead of 100 small led's.
Is it possible to make a single, huge led?
Re:Giant LED light bulbs (Score:4, Informative)
You can buy a single 5 watt led that is the same brightness as a 50 watt incandesscant.
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Re:Giant LED light bulbs (Score:5, Insightful)
Why can't they make a single led the size of a lightbulb instead of 100 small led's.
Is it possible to make a single, huge led?
I don't know. Maybe it's the same reason that they can't make a tungsten filament the size of a whole light bulb. Instead, they keep selling us a tiny wire the size of a pubic hair surrounded by a huge void filled with argon gas. This has been going on for well over a century, and they never seem to fix it.
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metric vs. imperial (Score:5, Funny)
[...] Instead, they keep selling us a tiny wire the size of a pubic hair [...]
Please adopt the metric system. PLEASE!!!
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What's the metric equivalent? (Score:5, Funny)
[...] 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?
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Re: (Score:3, Informative)
The white LEDS are doped to generate three distinct colors of light (R,G,B) whose combination yield a very cold blueshifted white light (>6500 K). If one seeks to use these for video, better check to see if the camera works well with such light.
Re:Giant LED light bulbs (Score:5, Interesting)
Yeah. I've noticed that. What I don't get is why they choose to set the color temperature that way. Red LEDs are extremely cheap compared with producing light at the other end of the spectrum. Why in the world would they balance them towards the blue (expensive) end of the spectrum when that is both more expensive and visually unpleasant? About the only thing I can imagine about the current LED designs is that they were designed to be used in combination with standard incandescent bulbs. If you blend the two, you should get a fairly nice looking light spectrum, albeit probably a bit heavy in the yellows....
I'd buy LED lights instantly if they actually used three emitters. Unfortunately, most don't. They use two---one yellow, one blue. Because the yellow LED has a relatively narrow light spectrum compared with an incandescent, you end up with basically no light output down near the bottom of the visual spectrum. The result is light that is downright unpleasant to deal with in every way. The bluish light makes it hard to see color accurately, makes colors not reproduce well in photography or video, and really isn't good for you mood-wise. Basically, the current crop of LED lights have all the problems of CFLs except the mercury (well, and the LEDs should last a lot longer, I believe).
The question, then, becomes this: "When are we going to see properly designed white LED bulbs?"
On the other hand, while they suck for homes, the existing LED lights are perfect for street lights. First, there was one experiment [psychcentral.com] that suggests that suicides and crime may decrease when street lights are replaced with bluish lighting. Second, the color temperature of blue LEDs are virtually indistinguishable from the mercury vapor lights (~6000K) that are already used in a lot of places.
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Re: (Score:3, Informative)
The company I work for has actually done a good amount of research on the technologies available for high efficiency lighting right now and they do indeed make warmer white LEDs. They look pretty nice and have an adequate CRI, however, their efficacy is poor enough compared to the cool white LEDs that they are in fact only about as efficient as compact florescent.
I think it has to do with the fact that the visible light generating part of white (and blue) LEDs are phosphors pumped by what is actually a ultr
Re: (Score:3, Insightful)
Could be, but an LED that uses phosphors eliminates any interest in my book because it means the color spectrum is a spiky mess.... :-) Either way, though, I'd gladly accept much less efficiency to get better light quality. I hate CFLs (even the so-called daylight CFLs) so much that I'm planning to start stockpiling incandescent bulbs soon in preparation for the U.S. ban on them. That cold, lifeless lighting just really bugs me.
Re:Giant LED light bulbs (Score:4, Informative)
First, the GP is right: most high power white LEDs are actually blue or UV LEDs with a yellow phosphor in the plastic packaging.
As for phosphors yielding a spiky mess for a spectrum: how exactly do you imagine the spectrum of an RGB LED looks? The individual primaries in such combinations are VERY narrow band, so rather than a continuous spectrum you get three distinct peaks. Phosphors are actually smoother by comparison.
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Re:Giant LED light bulbs (Score:4, Informative)
LED light bulbs do exist (they're a bunch of small LEDs, not one jumbo one -- I don't know if that's feasible).
I think you hit on the problem in your post though, power. 220V (or 120V) AC certainly has enough watts, but it's not in a usable form for LEDs. They require direct current (DC) at a much lower voltage. So you need some power conversion electronics to make them work. Then, to make them work efficiently, you need more electronics to regulate the current through them. For a standard electronics project, you just use a resistor, but then you're wasting power (to the tune of P=R*I^2). Off the shelf components that regulate the power more efficiently exist, but it adds expense.
Fluorescent lights need some electronics to work too, but I don't think they're as complicated (and are thus, cheaper). Cost is a big factor here, because old incandescent light bulbs don't cost much to purchase.
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Re:Giant LED light bulbs (Score:4, Interesting)
> and they break when they get too hot.
actually, high-power LEDs such as Philips's Luxeon series are quite robust in the face of surprising amounts of heat. I've run enough current through them so that they melted their soldering several times, and while its true their efficiency declines with heat, they suffered no permanent damage. When you put an amp and half through one of those suckers, they're literally stunningly bright.
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How (Score:5, Funny)
Re:How (Score:5, Funny)
What's it to you, pal?
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Re: (Score:3, Funny)
None. They don't work because someone stole all the copper wire.
Seriously, this happens all the time in the parks.
Won't anyone think of the astronomers? (Score:4, Insightful)
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 [wikipedia.org]
Re: (Score:3, Interesting)
NYC is a lost cause as far as astronomy is concerned, but I have hope that smaller cities and towns will see this and adopt it. LEDs are inheirently directional, whereas most fixtures tend to waste a lot of their light going out and up. So LEDs should be a win for astronomy.
Re: (Score:3, Interesting)
Bad plan in snowy environment... (Score:5, Interesting)
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.
Re:Bad plan in snowy environment... (Score:5, Funny)
So all the LED streetlights in Portland are covered in snow and cannot be seen.
Since LEDs are more efficient (more lumens per watt) the colder their tmperature, you can at least take comfort in the fact those snow-encrusted street-lamps are very efficiently lighting up the inside of the snow.
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Sodium Vapor vs LED (Score:3, Interesting)
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.
LED signals in Osaka for 5+ years (pics) (Score:3, Interesting)
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 [jsdi.or.jp]
Pedestrian Crossing [michioakita.jp]
Green, Amber, Red [yahoo.co.jp] (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.
We have lights. Stop spending, cut taxes. (Score:3, Insightful)
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.
Re: (Score:3, Insightful)
Is it?
Cost of running existing bulbs for the next 5 years: $10 million
vs.
Cost of replacing with LEDs: $2 million
Cost of running LEDs for the next 5 years: $2 million
Numbers are pulled out of thin air, but I wanted to illustrate a point - it sometimes pays to replace something that is working.
Presumably whomever is in charge of the replacement has done this math, and found it comes out ahead to go ahead and switch before
Submitter needs to visit wikipedia. (Score:4, Interesting)
"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.
Re:one million? (Score:5, Informative)
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Re:I hate leds!! (Score:4, Informative)
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 [google.com]
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Re:Isn't HPS more efficient? (Score:5, Insightful)
Some of the newer LEDs can go above 100 lumens/watt [gizmodo.com].
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.
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Re:Isn't HPS more efficient? (Score:5, Informative)
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.
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