Anyone moved to LED Lighting?

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 Most of Philadelphia's red ones installed in the 1990's and using an LED chemistry since superseded in traffic signal use are still working and in service, not relaced just for a few LEDs being out.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.

-- John Perry

I just had the the center-mount stoplight in my '03 Chevy Surburban fail. Appears to be a line array of 15 leds in a moulded plastic housing. Unit is completely dark. Replacement cost is over $200 not including install labor. Less than 60K miles on the vehicle. If incandescant, replacement would be a $1.25 bulb, self installed. Bummer!

Bob King

That's one area where automotive differs from marine. In most states there are minimum requirements for headlights, tail lights, etc. You're not required to have more than the minimum but if you add any they must all function. That said, I doubt many police will ticket anyone because one of his 30 LEDs isn't working.

Drive their autos less?

Hasn't been much of an actual problem in Philadelphia PA USA.

My experience in Philadelphia and its suburbs in 2 states is that minimum of 2 face each way.

Incandescent filaments suffering significant damage from thermal shock is mostly myth, despite existence of devices to remedy this. What mainly happens is that an aging filament becomes unable to survive a cold start a little before it becomes unable to survive continuous operation.

I even tried an experiment with a soft-starting device claimed to double life of incandescents. It was a NTC thermistor, and when fully warmed up it dimmed an incandescent enough to multiply its life by at least 1.5.

- Don Klipstein ( snipped-for-privacy@misty.com)

Due to someone not knowing how to implement the LEDs properly, though 15 years ago efficiency of LEDs was a lot less and maybe they could not have been implemented properly.

This problem is very easy to avoid with the green LEDs that are available nowadays, not too hard to avoid with green LEDs that have been available since about 2000-2001 or so.

Have a look at what just one modern good InGaN green LED can do with

5-10 mA now, or what one made by Nichia in 2001 can do.

Did you run controlled tests? I have heard of testing showing that most incandescents do not lose much life to cold starts. They do become unable to survive a cold start before they become unable to survive continuous operation, but not by a lot. The usual incandescent failure is from a hot thin spot in the filament, prone to temperature overshoot beyond its already-excessive temperature when a cold start is imposed upon it. This bad condition of an aging filament accelerates worse than exponentially, and an aging filament that cannot survive a cold start will kick the bucket soon no matter what.

- Don Klipstein ( snipped-for-privacy@misty.com)

The incandescents lasted forever (well at least 4-10 years) until they were turned off.

I believe I have the supplier mixed up. It wasn't OSRAM but another supplier with similiar type name???. OMRON or something..Been awhile now. These lED indicators were all crap and we tried many different styles and many different current levels. When run at their rated current (I think about

20mA) they all went up in smoke after a few years, anyway. The main (130vdc) ballast resistors were mounted elsewhere so they weren't a problem. The problem, as I saw it were they were designed as a 24v bulb with 24vdc worth of ballast in a miniature bulb....that's a no..no and did them in from localized heat. Finally, after about 15 years of experimenting with them and different breeds, the Engineering department decided to ignore the manufacturer's advice, went back to incandescents and replace the bulbs every few years when the device was de-enrgized, basically.

As I stated, the LED units are back without any diffusi>>As some of the articles point out LED testing may be done unfairly, is >>many

My experience of red, yellow and green LEDs at 20 mA, for ones characterized at 20 mA:

Red - my champion experience here so far is around 1.8 lumens at 20 mA. They appear to me to achieve about .8 lumen at 10 mA. (Nichia NSPR510CS)

Yellow - I got about .6-.7 lumen at 20 mA several years ago, likely now at least a little better. My experiece is generally 60% of red - so I expect Osram to have something delivering around a lumen at 20 mA nowadays.

Green - my champion experience so far here is 3.7-4.4 lumens at 20 mA, more than half of this at 10 mA, averaging .94 lumen at 3 mA and around .58 lumen at 1.7 mA, at which their efficiency is close to peak and much improved over that at 20 mA. Part number - Nichia NSPG520AS.

- Don Klipstein ( snipped-for-privacy@misty.com)

Yes. The usual white LEDs have blue-emitting chips coated by a phosphor that absorbs some-most of the blue light and converts it to a yellow/yellowish broad band whose spectral content typically covers mid-green to mid-red. Some of the blue light is not absorbed but passes through the phosphor, to mix with the yellow/yellowish light so that you get white light.

Nowadays, some of these blue chips used for white LEDs are achieving around 40-50% efficiency. The most efficient white LED on the market that I am aware of, Nichia NSPWR70CSS-K1 at 20 mA, is a goodly 40% efficient even after losses of the phosphor. At 20 mA, it is supposed to typically achieve 150 lumens/watt.

- Don Klipstein ( snipped-for-privacy@misty.com)

Things are definitely improving with this technology!

I still suspect, as the article in the link I pointed out (another post) the LED manufacturers are cheating the measurments a bit as they don't include ballast energy (they can't as they don't know the circuit) and they don't include the losses of the lens and/or filter and as you article describes, the input power vs output power.

Thanx!

I think the gentleman meant to type "so bright."

Regards, Robert L Bass

I have around 32 LED's on my M109R motorcycle. Once I pulled into the driveway and forgot to turn them off. After 2 days I went out to start the bike at night and noticed the LED's were on. When I turned the key and pushed the button the bike started up immediately. Nice.

Regards, Robert L Bass

I've got a real assortment of small LED flashlights, and a couple big ones. GREAT battery life. For home lighting they are still pretty pricy, but with incandescents being phased out, and the LOUSY luck I've had with CFLs, it sure is tempting!!!!!

The New York Times had an article earlier this week about a study (from a manufacturer) that indicates both CFL & LED lights use about 20% of the lifetime energy used by incandescents. That includes manufacturing and transport costs.

I don't no whether that reflects the high early failure rate for CFLs nor do I know whether mass production of LED lighting may lead to the same types of early failures which could severely skew the results.

Hmmm, I guess early failure actually means the CFLs use even less lifetime energy. ;-)