Osram, who makes incandescents, CFLs and LEDs, did a study indicating very well that only a very small percentage (about 2%) of energy used by all 3 of these throughout their life cycles, including manufacturing and transportation, is in everything other than the electricity consumed by them over their lifetimes.
There are now white LEDs more efficient than CFLs - but this level of efficiency is largely limited to cool white ones without high color rendering index, or to laboratory prototypes.
Nav lights involve colored lights, and LEDs have an extra advantage there from the fact that there are efficient LEDs specializing in producing one color or another of light. Incandescent red and green nav lights have filters that remove something like 70% of the light.
- Don Klipstein ( snipped-for-privacy@misty.com)
In , snipped-for-privacy@dog.com wrote in part:
Can you tell me where I can buy an LED exceeding 150 lumens/watt?
(I have ones claiming 150 lumens/watt - Nichia NSPWR70CSS at 20 mA drive current, 8.7 lumens at .058 watt, 5000 K color temp. with color rendering index appearing to me to be in the mid or maybe low 60's.)
- Don Klipstein ( snipped-for-privacy@misty.com)
Flashlight bulbs tend to mostly be less efficient than ones used for home lighting.
One advantage LEDs have for flashlights is that their energy energy only changes slightly (mostly improves slightly) when the batteries weaken, while incandescents greatly lose energy efficiency.
Another thing: The cost of LEDs needed to achieve an 800, 1600 or 1710 lumen light is fairly prohibitive, more so for warm white, and the amount of heatsinking needed is a tall order now to get into something the size of a regular lightbulb.
As for LED taillights: They make those. Cadillac has been using them for many years already. Some other cars are now being made with them.
An LED retrofit bulb to put into a taillight made for an incandescent is another story. It is quite a tall order to get an LED light source with the same emitter shape and size and same radiation pattern and suitable output so as to achieve the same optical results as with incandescent.
A light to serve a legally required function on a motor vehicle has to fall within both lower and upper limits of candela into a few dozen different specified directions, and must be properly certified to do so, in order to be street legal. An incandescent light with an LED retrofit bulb generally fails to achieve this, let alone be certified to do so with any particular mfr/part-number LED bulb. It is illegal to refit a legally required motor vehicle light with a bulb other than one it is certified to use.
- Don Klipstein ( snipped-for-privacy@misty.com)
There are nav lights out there sufficiently simple and non-critical in design such that someone can make an LED retrofit for the bulb that gets the light to meet the spec - despite the difference in emitting surface geometry and directional characteristics.
Motor vehicle lights are not as easy to make LED incandescent-retrofit bulbs for with achievment of legal requirements being maintained.
- Don Klipstein ( snipped-for-privacy@misty.com)
This thing has a couple items wrong. Not only do no lasers get anywhere near 700, but the chart also states incorrectly that xenon achieves 400. Xenon is doeing very well for xenon when it achieves 60.
The maximum possible is 683 - for a 100% efficient source of monochromatic light at the yellow-green wavelength at which human photopic vision is most sensitive.
- Don Klipstein ( snipped-for-privacy@misty.com)
My experience is that they are usually LEDs. Most but not all cars with LED tail/brake have dimming for tail function achieved by pulsing at a low duty cycle. (This is done because most LEDs do not have low-current performance sufficiently predictable from one run to another for certification.)
Such LED tail/brake lights in tail mode usually show a stroboscopic pattern if I move my eyes while looking at them.
There are now legal LED backup lights, although so far I have only noticed these as aftermarket replacements for truck backup lights or for manufacture of truck bodies and trailers.
- Don Klipstein ( snipped-for-privacy@misty.com)
If the light continues to meet the specification of upper and lower limits of candela in all required directions, then there is no way to deserve a ticket. If the percentage of LEDs being failed is small, chances are fairly good that the light will meet every letter of the legal requirement.
I would agree that a multiple LED light is likely to fall short of the spec sooner than a single-LED one is. However, since red LEDs usually honestly achie 100,000 hour life expectancy (white ones generally don't), I expect a multi-LED tail/brake light to meet the spec until the light has been used a few tens of thousands of hours. More, since most of the time it will not being used at full power as a brake light.
In a Crown Vic used as a police cruiser and after that as a taxicab, lights may have to run for a few tens of thousands of hours. Otherwise, any decent brake/tail or turn signal LED light should have little trouble outlasting the car unless it gets broken in a collision that does not total the car.
- Don Klipstein ( snipped-for-privacy@misty.com)
I haven't seen that but some of the cars have one incandescent bulb and a reflector with many small domes that make it look like many small lights. I have had friends mention them as LED lights because they look like an LED array until you look close and find the one actual bulb.
LEDs have typically been used where visibilty of the LED unit is required, but for visibilty for the user of the LED they have not proven very economical.
It is important to see the difference in these two usages. An LED for visibilty for other can be flashed on and off and become more visible but for a flashlight, for visibilty for the user (holder) flashing on and off reduces the visibilty.
BTW: LEDs >> >>
They had their choice and they decided to be born that way! It's not **our** faults!
Because, overall **white** LEDs do not put out much more, if any, light than an incandescent bulb for the energy used!
LEDs are more efficient in their usage than incandescents, can be. They are directional, focusing all their output in one direction. The only produce one colour of light, efficiently and do it well. An incandescent bulb with a filter only wastes energy from heat, losing all the other colours. LED's are also quite small with intense output, making them more esily seen to the human eye (noticable). When it comes to flood illumination white LEDs are too costly to compete for the small increase, if any, efficiency.
In article , Josepi wrote in part:
I have plenty of experience where I have been able to track individual units due to fading and/or a few LEDs being burned out and/or LEDs of a particular spectral characteristic are obsolete for the purpose due to lower efficiency than more modern ones. I can tell you that LED traffic signal units have a very high rate of lasting a lot more than 2 years - more like 5-10.
- Don Klipstein ( snipped-for-privacy@misty.com)
This all may be replaced soon with ESL bulbs. I know they have been talking about this for along time. Time will see if it is vapourware, like so many other tech announcements.
Cost is an obstacle, but plenty of available white LEDs are now a lot more efficient than incandescents. Efficiency like that of CFLs is now the cutting edge for available warm white ones, and cool white ones without high color rendering index now get as efficient as T8 fluorescents.
Osram recently put an 8 watt LED bulb on the market in Europe, with as much lumen output as an 8 watt CFL.
- Don Klipstein ( snipped-for-privacy@misty.com)
The traffic light people cannot afford failures. The legal implications are too great. I am not sure if it is based on manufactures warraties, recommendations or history but we still ocasional segments missing.
With LED experience this may also be a heat problem with retrofitting old units and heat not being drawn away?? When you push LEDs too hard they don't last long. This is only from a small sample area with slightly over $500K population.
I meant being kept in service for 5-10 years. Most of Philadelphia's red ones installed in the 1990's and using an LED chemistry since superseded in traffic signal use are still working and in service, not relaced just for a few LEDs being out.
Now that they are making them with power consumption as low as 7 watts for ones 8 inches in diameter and 8 watts for the ones 12 inches in diameter, heat is not that big a deal in traffic signals that had incandescents of 92 or 116 watts. Such huge reduction in power consumption occurs in part from not having 70-75% of the light blocked by red and green filters.
If any failure is so intolerable, then why were incandescents acceptable?
- Don Klipstein ( snipped-for-privacy@misty.com)
As some of the articles point out LED testing may be done unfairly, is many cases. The manufactures show lumen output for bare elements and then add the reflectors, lenses and other external parts later.
The ballast in not usually included in the efficiency testing, either.
Are these the white phosphour screen based LEDs, you refer too?
As a side note our company put in hundreds of OSRAM indicator pilot lamps on electrical control panels. After 10-15 years of replacing bulbs, burnout, sock melting, changing ballast current limiters, lenses and filters, we changed them all back and retrofitted them to incandescent bulbs.
Certain colours, green especially, could not be dicerned, when illuminated, if there was any windows with sunlight entering into the buildings. If we put a similar green pilot lamp with a lime green filter in it (unlit) beside a normal green illuminated unit, no difference could be detected. When we increased the drive current, the bulbs only lasted a month or so (at a cost of about $5 per bulb). These were very tiny LED segments with about 9 elements in each bulb. The ballast resistor dropped the current from a
130vdc battery bank and was a burn hazard for humans. Inverter technology was a much better proposition but too expensive a retrofit for so many bulbs. They spent tens of thousands of dollars trying all of OSRAM's tehnologies they had availble for about 10 years and finally went back to incandecent bulbs with low current supplies (less than the LEDs) and the bulbs last about 10-15 years (or until your turn them off, after a few years of usage...LOL).In the last few years the pilot lamps got smarter and went to a non-filtered LED holder, so the area of illumination decreased and the LED elements were now visible. This made the LEDs visible and workable but the whole thing dazzled the eyes like a Christmas tree.
Incandescents were not so acceptable. They were experiemtning with LEDS to lower the maintenance on incandescent systems.
Somebody ehre was roght about the lack of heat too. Snow storms can fill the lamp projector lens in and the status cannot be told during the day. (No we aren't moving to Florida, Robert...LOL)
After a debate on the job, we ran into a traffic light maintenance crew and pulled over to chat with them. IIRC, they informed me they replace the incandescents every year or on report. We always have multiple lamps for out traffic lights. I assume you are in the USA where they classically may have only one traffic head facing each way. We have at least two and on big intersection, three or four, sometimes. (we get lower sun in the winter. There always seems to be the main one with a sunset right beside it)
I would imagine an incandescent, pushed and heated that hard and then blinked on and off would wear the filiament out (thermal shock) very quickly, too.
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