low pressure sodium lights

[cfz2882]

got an interesting outdoor light today-noticed it had a "weird"bulb,and further examination revealed it is a low pressure sodium-made diffently from high pressure sodium type:has u-shaped glass tube with filaments at each end and an outer glass bulb around that. 18 watt Bulb was made in Belgium by Philips and has a base like that found on some European household bulbs-fixture was made in the US 4/82.Tried it out and it took several minuits to warm up all the way-longer than my mercury and high pressure sodium lights.Light is very yellow instead of the more goldish light of HPS.Used to see these fixtures(and the distinctive yellow glow) on occaision in the 1980s,but seems low pressure sodium did not really"catch on"despite being very efficient watts/lumens.

 

[rp2813]

My town stupidly retrofitted mercury vapor street lamps with this type of light many years ago.  With Lick Observatory perched atop Mt. Hamilton above the valley, it was a well-intended gesture to reduce the amount of light reflected from the valley floor to help with astronomical research.

 

These lights are horrible.  Not only does everything beneath them appear to be monotone, but when driving the city streets at night, these lights are the same color as the amber lights on traffic signals and render that sequence of the signal useless.

 

LED street lamp replacements have been installed on a trial basis in various parts of town.  It appears they've been well received and I can't wait until they are retrofitted citywide and the last of the low pressure sodium lamps are smashed to smithereens.

 

[tolivac]

LP Sodium lights-Yes,have one in my collection-they were introduced in the US by Philips in the later 70's didn't catch on becuase of just that-their monochomatic yellow color.The claim they are the most efficient light source is true to a light meter-but NOT to the eye.Wideband light sources are more "efficient" to the eye as opposed to a photometer.The meter cannot distinguish colors as the eye can.HP lights are better than the LP ones-at least closer to white light.Metal halide,LED,some flourescents are the best sources of white light-natural light of course-blue sky sunlight.(thats free!!)
At this point monochromatic sodium and yellow LED of the same wavelength is useful for gemological and scientific purpoes than gen lighting.
Glad the LED light is replacing the LP sodium ones-and yes,mercury lights-esp phosphored bulbs(phospors like flourescent bulbs)improve the color and efficiency of mercury bulbs.I think the ban on mercury bulbs is poor-they are an efficient,long life,and inexpensive source of light.
Another thing--for protecting planetariums and other light sensitive items-its the FIXTURE design-not the light source that is the problem.The fixture should direct the light to where its really needed-IE streetlight-the light should be directed DOWN to the street and ground-not around or upward.I see so many "streetlight" fixtures that do a good job of lighting the tops of trees near them--but not the street or ground under the lamp-the area you want to light.Fixtures should be replaced with the direct downlight ones.And another bonus you can use a LOWER wattage bulb!

 

[tolivac]

Oh yes-if you smash LP sodium lights--put the remains in a bucket of water to dissolve the metallic sodium in their arc tubes--otherwise you may have a trash fire.When you treat the boken arc tubes in water be careful of the sputtering sodium-don't let it get on you-burns skin badly.Is fun-like when your chemestry teacher put a peice of sodium in water-and of course flammable items should be kept well away.HP sodium bulbs have a tiny amount of sodium and mercury in them-so little the arc tube in water does not much of anything.But again many lamp collectors like the LP lights-they do have their fans.When the LP fixtures are replaced-those folks go after the old LP ones.

 

[tolivac]

The "filaments" in your LP light are the electrodes-much like those in a flourescent bulb.They will "light up" as the bulb warms up-no current actually flows thru them.they heat up from the current drawn by the arc as the bulb gets up to wattage-the bright yellow glow.when the LP bulb is first started-it has a red glow-from the neon fill gas-that is easily started by the low secondary voltage of the ballast-some light collectors have run LP bulbs from flourescent ballasts of the same wattage as the LP bulb.

 

[rp2813]

Thanks for the tutorial on LP sodium.  I would very much enjoy smashing the two that are nearest my house.

 

Sometimes I'll spot a street lamp that's stuck in warm-up mode and never gets past the red glow.  I lived across the street from one like that for a while.  Then one day the bad lamp was replaced and the bright yellow light from the new one was comparatively offensive.  It was a short old-school 1930's light standard with reproduction "frosted" plastic globe.  A friend and I schemed one night and pulled my pickup next to it and with a ladder in the back we were able to reach the top of the lamp and spray the side of the globe facing my house with white paint, which effectively blocked the yellow glare.  This was unnoticeable to the uneducated eye during the day and remained that way for years.

 

I agree about directing light downward.  I've seen street lamps with shrouds that do exactly that.  I don't know why they aren't used more widely.  The local astronomers would be delighted by that solution.

 

[kb0nes]

Full Cutoff Lighting

As an amateur astronomer I have witnessed the amazing growth of light pollution over the past 15-20 years or so. I used to be able to stand in my suburban backyard and make out the knot of the Milky Way overhead. Today there is not a hope of that. I've even tried imaging with my camera and all I get is man-made sky glow

Full cutoff refers to lighting fixtures which don't radiate any light upwards towards the sky. In the vast majority of cases there is no reason to spill light into the sky, there is no reason to light the clouds and the bottoms of airplanes. Its poor design and a waste of money and energy.

There is a group called the International Dark Sky Association that pushes to preserve the night sky by trying to effect change in the way we use lighting. I always found it funny how people would immediately react to call these groups "tree-huggers" or "environmental Nazis" etc. Why is the use of controlled and efficient such a controversial issue? I suppose people just like paying more for electricity by using poorly designed high-glare fixtures.

The big change that will eventually come is using standby lighting in parking lots etc. that will be controlled by motion or proximity sensors. The ability to have this comes with LED technology as solid state light sources don't suffer the turn on problems that plague other forms of lighting. Imagine a parking lot that is totally dark at night until someone drives on to it. It is more secure as the presence of light means someone is there, attracting attention that constant on lights don't do.

A few months ago Cree introduced a 25 & 41 watt LED street lamp fixture that is a bit of a game changer by breaking the $100 barrier. I'm starting to see more and more of the new roadway lighting here in MN is all LED. And from what I see both aesthetically and performance wise it beats what was there before it.

 

[d-jones]

I've lived most of my life here in L.A. and I can recall a number of trips to the local mountains over the years where I was able to look out over the city lights at night. In my earliest memories those lights all had the soft warm glow of the basic incandescent light bulb, but over the years I saw them gradually change to the pale cold blue tint of mercury. Then came the very strong deep yellow of the low pressure sodium. They gradually spread across the city displacing most of the mercury bulbs, but not all. As others have mentioned, the color wasn't very pleasant to look at, so when the bright golden light of the high pressure sodium came along and displaced the vast majority of the low pressure bulbs, it was a welcome change.

Now on any given night from any hill or mountain one can look out over the city and see all three of these more modern bulbs in use. The vast majority are high pressure sodium bulbs, which give the city a nice golden glow, but if you look around a bit you can still spot large numbers of mercury bulbs in use and even a number of the low pressure sodium. I actually recall reading an article a long time ago that claimed the light from these low pressure bulbs was so unpleasant that they were sometimes installed by businesses to repel loiterers at night.

 

[cfz2882]

mounted up the sodium light to illuminate the front yard and driveway-does the job nicely and I expect the yellow light will reduce the bug attraction during bug season.Though the bulb is rated 18w,i checked current of the fixture and it was 1 amp-a little over 100w consumed with the old skool magnetic ballast in the 1982 verd-a-ray brand fixture-I tried a 100w inchandescent yellow "bug light" for compairison and the sodium did light a bigger area.For dimmer outdoor lights I leave on,i like LED- got a couple"lights of America"LEDs(more on those in a later thread I will create )

 

[sudsmaster]

Ralph,

I remember being repelled by the LP lights when I first started driving around San Jose at night in the 1990's. They really do cast a disgusting light.

There's an HP sodium light a couple of doors down from my house in the cul-de-sac. I'm not too fond of that one, either. Not as yellow as LP sodium, but still unnatural and, well, icky. The color rendition sucks badly. When it burned out some years ago I remember being pleased at the effect of... no street light. Unfortunately it was replaced. It's a War of the Worlds type of pod light fixture, which would be difficult to paint, let alone reach.

LED street lamps with decent CRI would be very nice indeed.

 

[arbilab]

"Dark at night" would be very nice. I only recognize a handful of constellations, from my youth and later in Hawaii. But here, now, I can't even find the big dipper fer gawdsake. And only the 4 primary stars of Orion. Cassiopea? Pleiades? Fugettaboutit.

Last week a nearby merchant rented a searchlight. You know, those 15kW 8M candlepower carbon-arc artifacts from WW2 made by Sperry and GE for $40,000 WW2 dollars. Their 5-foot diameter is 3 times the same size circle intensity as the Sun. Had to squint to see it.

But in 1955 there wasn't a boogeyman lurking in the dark every 20 feet, so no need for 500W of light every 20 feet. Why do I feel like Cher? "If I could turn back time."

 

[tolivac]

Yes,as a light fan I can agree about preserving the night skys-it is nice to be still able to see heavenly bodies up there at night.All that is really needed is to do just that-install downlight street lights and cutoff type parking and building lights.Then we can have both worlds.AS I mentioned-the cutoff and downlights can use lower wattage bulbs-an example-say you have a 250W HP sodium "dome lens" cobra head streetlight-replace it with a full downlight cobrahead fixture-the bulb wattage can be decreased to 150W HP bulb.The downlight fixture optics focus the light from the smaller bulb onto the street and ground where its needed.No sense in lighting the trees and skys.I guess if there is an advantage to LP and HP sodium lamps-its that the bugs don't like them-and well,people don't,either.But---if you have a HP light fixture-you can use a Philips Mastercolor Retro white ceramic metal halide bulb in it-beautiful white light!And all you had to do was replace the HP sodium bulb.They are in 250W,400W sizes.Venture and GE make sort of similar "conversion" bulbs-but they have the standard quartz arc tube-Philips has the patents on the ceramic ones for the most part.The Venture bulbs work well in HP fixtures,250W,400W.So you can get nice white light from the HP fixture instead of putrid yellow-orange-white light.They have a HP sodium "flag light" here and it makes the flag look horrible.Sadly there are no retrofit MH bulbs for low wattage HP fixtures.I would love to sneak one in that lamp.

 

[tolivac]

I still can't fully endorse LEDS just yet-they do-at least the ones at the new Wal Mart here-have a sickly blue-white light to them-the neghboring Food Lion store with their MH bulb lights looks MUCH better.I think in a few years the LED lights will improve more-and they will be as bright and same colors and brightness as MH lights.Do like the idea of the LED lights shutting off when not needed.This isn't good for HID lights since there is a resatart time involved-and frequent starts shorten the bulb life-with HP sodium and pulse start MH-the ignitors life will be shortened.LEDs don't care if they are turned on and off.

 

[arbilab]

As has become the norm, the more alternatives offered, the worse the bureaucratic choices. Yes lighting can be directed where it's intended. Yes it usually isn't, probably because directed lighting costs $20 more per fixture. Though it saves that much every 6 months it's in service. But bureaucrats, like shxtty drivers, never look beyond their hood ornament.

 

[davetranter]

Street lighting / Street Furniture

Interesting discussion on various types of lighting. On this side of the 'pond', LP Sodium was pretty much Universal for many, many years as street lighting. There has been a gradual (now almost complete) change to HP Sodium. I have seen very few mercury fittings on my travels.

I did, however, make a very interesting observation only a couple of weeks ago... The 'Belisha' beacons positioned at our 'Zebra' type pedestrian crossings (I don't think you have them 'Stateside'), flash on and off with an approximately 4-second cycle (2 on, 2 off) 24hrs a day. They were fitted with 'hard duty' incandescent filament lamps (150W, I think). I recently passed a beacon from which the 'globe' had been displaced, revealing a LED lamp, which I would imagine was 'purpose-made' as it is a 'double-sided' lamp, designed to throw most of it's light output along the road in both directions, although diffused somewhat by the orange plastic globe. Considering how many of these beacons exist in the U.K., it has probably been cost-effective for some manufacturer to 'custom' design and produce a lamp for the purpose. I assume that the 'flasher' is now built into the lamp, as formerly the lamp was cycled by a current-heated bi-metal type flasher, similar to the older type of automotive indicator flasher unit.

Hope this is of some interest

All best

Dave T

 

[rapunzel]

I love the LP and HP sodium lights. Love the soft yellow/orange light it's easy on the eyes and, as mentioned above, the bugs hate it.

Unfortunately the trend now is to replace HP with this new, stark and cold induction lighting, which is horribly white and much too bright. It may be more energy eficient, but it causes too much light pollution.

 

[tolivac]

Induction lamps-these are more like a flourescent light than HID.They could for practical purposes be called a flourescent light that is electrodeless and energized by a special RF generating ballast.The bulbs are efficient and very long lasting-becuase of no electrodes.But they do have a softer,colder blue white light.They don't have the bright,crisp,white light Metal Halide lamps generate.

 

[sudsmaster]

LED's by their very nature are directional, so they are a good choice for downlighting street lamps. In fact it looks like it's been challenging for LED light mfgs to design and produce an LED "bulb" that casts a 360 degree light pattern. It seems the solution is multiple LED's in an array on a stalk. That then introduces cooling problems for the LED's, reducing the wattage and lumens possible. Another solution is reflectors, but they cast their own shadow. But you want directional for a street lamp anyway.

 

[tolivac]

The LED "chips" used in lighting devices are indeed directional-they have a lens built into them and the LED chip under the lens is flat.A reflector-as in a LED flashlight-makes the LED even more directional-depending on the reflector-the LED light beam from the flashlight has a very strong center hot spot-and low amount of "spill".The LED chips and the driver circiuts have to be heat sinked-otherwise they can fail.And something weird and interesting about LED lights-they can fade over time in light output like HID and flourescent.The thing on HP sodium and even LP sodium bulbs is their light output is consistent over the life of the bulb.At "end of life" the bulb cycles on-off never reaching rated brightness or color.LEDS will fail-just won't light.Mercury and Metal Halide bulbs lose brightness and "color" as they age-and can have "non passive" failures-the arc tube ruptures-causing the bulb to explode in the fixture."open" fixture rated MH bulbs have a thick glass or quartz cyclinder around the arc tube to contain it if it ruptures-in ceramic halides-a thick coil of wire or the thick quartz tube around the arc tube.The ruptures are still quite rare-usually if the bulb is burned well beyond its rated hours.