LED lights questions and answers

Fred, you might enjoy the offerings from this place.

http://www.superbrightleds.com/

I found them several years ago but never bought anything.

SMITTY wrote:They get hot.

Actually I have to retract that statement .... I was thinking of CFL's - those get very hot. LED's don't get very hot at all. I remember when all the trucks switched to LED's on the trailers, we started having problems with them getting covered in ice & snow. The regular bulbs always kept them warm enough to burn all the snow off.

SMITTY wrote:

SMITTY wrote:They get hot.

Actually I have to retract that statement .... I was thinking of CFL's - those get very hot. LED's don't get very hot at all.

LED's do get hot. In some cases very hot. I'm talking about the LED device, the semiconductor die that convert input dc current to photons. The more current you put into them the more light output you get. The limit is 100's of degrees, degrees C not F. So the design criteria for putting a LED in a practical product is a trade off. How hard do I drive it vs. the light output. In a Edison socket (standard light bulb) the ability to shed conducted heat is limited. That's one reason many LED bulb replacement products on the market do not produce much light.

What's coming are entirely new fixtures with LED's built-in. The design is optimized for heat conduction from the LED, so it can be driven harder. There are several design approaches, which one wins in the market place is yet to be determined.

I was doing some reading on LED's and stumbled on something called "induction lighting". First I have heard of this technology, and it looks like it is making some ground into the "streetlight" market. I found a site that has dusk to dawn lights listed, but no prices...

http://www.neptunlight.com/productdetai ... eries.html

I am still running Mercury Vapor outside lights because I can't stand the pukey orange light of high pressure sodium. Metal Halide looks like the best alternative, but the 100,000 hr advertised bulb life of the light in the link above has my attention.

Yanche wrote:LED's do get hot. In some cases very hot. ..........

I stand corrected on that then. I was going by the light in my barn & the ones on the trucks - those run much cooler compared to regular incandescents. My LED flashlight also is cool ... but none of those runs on 120V except for the one in the barn. But that one is in a fixture. I guess I haven't left it on long enough to notice.


I have one of those ... either mercury vapor, or H/P sodium .. on my barn. It's been lit 365 nights a year since I moved here 8 years ago & still works great. Looks to be built in the early 80's, so that explains the quaility

Yowza! Those induction lights looked neat so I looked them up.... Grainger sells them.... got $1,500 to spare? I did see one 40 watt interior one for *only* $450. Most of the exterior ones ran $1,200 to two grand!

OK.... drive the LED's to make heat.... I gave it a try. I took two of my red free samples & gave one it's rated 12V and the other double the rating, 24 volts. The 12V one got up to 88* & stayed there. The one driven at twice it's rated voltage ...was real bright!....and the temp went up....up...up.... over a 30 minute period it got up to 192*! Then, after another 15 minutes, the temp started going down. I thought it odd until I realized it was getting dim LOL. After an hour it was down to 160* and not too much brighter than the 12V one. I discontinued the test at that point.

I do think that CFL's are a temporary thing. As Yanche says, new LED's are on the way & I think once they get it figured out they will be the thing to have.

I see where LED light bulbs that are thread in replacements for standard 120 VAC incancdescant light bulbs are either out already, or will be soon from about a half a dozen manufacturers (names like Cree, GE, Sylvania, and Phillips, among others). Estimated retail prices range from about $25 to $50 per bulb (OUCH!!!). 60 Watts equivalent light output in lumins (roughly 800 lumins) is the highest output I've heard of so far. 25,000 to 50,000 hours life expectancy. The 60 Watt equivalent output versions draw in the actual range of 12.5 to 13 Watts.

UPDATE: A Phillips 75 Watt equivalent A19 style (I.E., looks and functions like a standard Edison type light bulb) giving off 1,100 lumens of light is available online at Home depot for just under $40. This bulb draws 17 Watts of electricity. The Phillips 60 Watt (800 lumens) bulb which draws only 12.5 Watts of electricity is also available online from Home depot for the same price.

markviii wrote:I am still running Mercury Vapor outside lights because I can't stand the pukey orange light of high pressure sodium. Metal Halide looks like the best alternative, but the 100,000 hr advertised bulb life of the light in the link above has my attention.

The "banning" of mercury vapor lamps and ballasts is another steaming pant load dropped on the public by the enviro-Nazi's. We all know CFL lamps contain mercury, and all other fluorescent lamps do as well - they have to otherwise they wouldn't work. But HID (high intensity discharge) lamps also contain mercury (besides the obvious mercury vapor lamps). A 175 watt mercury lamp contains about 34mg of mercury. A 175 watt pulse start metail halide lamp contains about 30mg of mercury. Even a 150 watt high pressure sodium lamp contains 17mg of mercury.

Now, mercury vapor is the least efficient of the 3 HID lamp types, so one could blither on about CO2 and mercury emissions from coal fired power plants. But on the flip side, it is well documented that mercury vapor street light fixtures (specifically 175 watt lamps) installed in the late 50's through early 60's still have the original lamps installed!!! If you do the math, that equates to 175,000 hours or more of operation. Mercury lamps really don't "burn out", but just gradually fade in output. Even still, these high-hour lamps are still producing useful amounts of illumination. The "Big Three" lamp makers (Sylvania, GE, and Westinghouse) soon figured they were making lamps "too good", and soon after started making lamps that would last the rated (24,000 hour) lifetime.

Traditional metal halide lamps have very poor lumen maintenance, although the latest ceramic metal halide lamps are much better, and are available in sizes as small as 20 watts. I've been running a 35 watt lamp on an electronic ballast behind my house for 7 years now averaging about 6 hours per night in an antique "gumball" streetlight fixture and it's still going strong. The lamp is a 3000K color temperature, so it looks similar to an incandescent lamp which would have been originally installed.

High pressure sodium lamps (that wonderful puke pinkish-orange color) and the associated fixtures in which they are installed are typically very prone to ballast and/or ignitor failure and lamp cycling. HPS lamps maintain lumen output very well, but as they approach end of life, they "cycle". As the lamp ages, the voltage required to keep the arc struck increases beyond what the ballast can supply, and the lamp goes out. As it cools, the ballast and ignitor are busily trying to restrike the arc which causes the ballast to overheat and the ignitors to fail. I've seen many new HPS streetlighting installations that have dead fixtures and cycling lamps within a year. Junk.

I find it a real treat to visit my parents in New Jersey as many areas are still lit with incandescent streetlights. Most are fixtures installed in the 50's that are little more than the typical "NEMA" yard light head with a simple stamped aluminum reflector shaped in a half-moon or "admiral's hat" look. Slowly they are being replaced, but many still exist. 205 watt "multiple"* lamps are used, rated 12,000 hours, producing 2500 lumens. Yes, they are inefficient, but cheap to maintain with only a photocell and a bulb. Since they use electricity during off-peak times, the consumption isn't a big deal. However, they produce a very nice ambiance at night that in stark contrast to the prison yard look of HPS lighting. Besides, the street in front of my last house was lit with 200 watt HPS lamps (in a 25mph dead-end subdivision!!! ) so the electricity use was the same but it was so bright you could perform brain surgery on the sidewalk....but I digress.

LED technology is really starting to mature as of late. The light color choices have grown to match fluorescents (warm, cool, etc.) and outputs are well over 100 lumens/watt. I can even replace the 250 watt landing light bulb on my '46 Cessna with an FAA approved LED PAR-46 lamp. Takes current draw from 20A down to about 3 amps and produces more light.

The trick to LEDs is keeping the chip die cool and driving them within their ratings. Overdriving and/or overheating will cause a much more rapid drop in lumen output over time, even losing over 50% in less than 5,000 hours.

Comparing the cost to operate a 60 Watt equivalent LED lightbulb to 60 Watt incandescant bulbs, considering 24 hour a day operation:

1) Standard 60 Watt bulb, life = 2,000 hours, electricity cost = $0.11 per KWH:

Cost of bulb $0.50
25,000 hours /2,000 hrs = ~12 bulbs needed to last 25,000 hours. 12 bulbs = $6.00
60 Watts x 25,000 hours = 1,500,000 Watt hours = 1,500 KWH
1,500 KWH x $0.11/KWH = $165 in electiricity cost for 25,000 hours
total 25,000 hour cost = $6 + $165 = $171

2) LED light bulb, 60 equivalent Watts, 25,000 hour life, electricity at $0.11 per KWH:

Cost of bulb = $37.50 (taking the average)
12.75 Watts consumption (also taking the average)
25,000 hours x 12.75 Watts = 318,750 Watt hours = 318.75 KWH
318.75 KWH x $0.11/KWH = $35 in electricity cost over 25,000 hours
Total 25,000 hour cost = $37.50 + $35 = $72.50

Chris, I read the same information about the mercury in the HID lamps. I wonder they banned the fixtures because "Mercury" was in the name...even if they don't contain much more Hg than competing bulbs.

I actually bought two mercury vapor dust to dawn lights on ebay just recently. $60 for two (with bulbs!), shipped to the door. I mounted one on a pole next to the driveway, and the other will be replacing my last HPS light out by the shop. I can't believe how much more "useful light" the Mercury vapor lights produce than the HPS fixtures. Objects far away from the light will still stand out with MV, not so with HPS.

By the way, I like your "retro" fixture.

Freddy wrote:I do think that CFL's are a temporary thing. As Yanche says, new LED's are on the way & I think once they get it figured out they will be the thing to have.

African communication went from the jungle drum to the cell phone, without the expensive intermediate step of land-line phones. It has been pointed out that, absent government "encouragement", we might have gone directly and more quickly from incandescent bulbs to LEDs, without the intermediate step of CFLs.

A few months back I can remember reading about the northern states where they changed over to LED traffic signals they were having trouble with ice buildup on them because they weren't warm enough to melt the ice & snow off.

Here's a link with "tear downs" of LED lamps.

http://www.edn.com/blog/PowerSource/405 ... art_II.php

Lots of good photos and it will give you an idea of how complex these Edison base bulbs are. Also realize all these parts have to all work for the lamp to function. That's a lot of series failure points and all individual parts have to be very, very, very reliable to meet the claimed overall reliability. If you read the warranty fine print carefully the reliability could be inferred to be only on the LED light emitter itself not the entire bulb.

samhill wrote:A few months back I can remember reading about the northern states where they changed over to LED traffic signals they were having trouble with ice buildup on them because they weren't warm enough to melt the ice & snow off.

Technological growing pains.

LED's are upcomming because of their energy savings. The situation is that they require DC voltage to operate. To run them on AC a driver (power supply) is required.

The automotive industry is a natural for low power, DC voltage lighting. Plus there is safety in the redundancy of mutiple LED's in one light. Traffic lights were the next natural progression as they are very costly to change out bulbs. The next big area that is occuring is outdoor lighting, mainly street/parking lighting as maintenance of these type of fixtures is very expensive. The added cost of the LED is offset in the long term by maintenance savings.

Outdoor building lighting is gaining in favor but has a long ways to go in terms of cost. Indoor lighting is available but is very expensive and the industry is still developing standards on how to rate the units. Without these standards, the claims of super high efficiency are tough to verify. As the industry develops, these standards will be firmed up.

You will see more and more LED lighting as time goes on. Personally, I am not jumping on the bandwagon just yet but will consider LED's on a job by job basis.

rberq wrote:

Freddy wrote:I do think that CFL's are a temporary thing. As Yanche says, new LED's are on the way & I think once they get it figured out they will be the thing to have.

African communication went from the jungle drum to the cell phone, without the expensive intermediate step of land-line phones. It has been pointed out that, absent government "encouragement", we might have gone directly and more quickly from incandescent bulbs to LEDs, without the intermediate step of CFLs.

It's highly unlikely the US government's encouragement of CFL bulbs delayed the development of LED base bulbs. The technology of the basic florescent bulb has been known for decades. On the other hand the LED emitter, i.e. changing electrons into photons is still very much in it's infancy. If fact what's made LED emitter based bulbs possible was discoveries by Japanese researchers at a Japanese chemical company. Their discover greatly improved the conversion efficiency. Certainly, Japanese researchers don't march to the tune of the US government or our domestic politics. Without the basic efficiency improvement there wouldn't be any LED based bulbs and CFL's would be the only game in town.