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I have been watching LED technology make great advances lately. One item not solved to my knowledge is a little known issue of Lumen Maintenance. What this means is as LED's age, the Lumen output degrades. Most consumers are not aware of this issue. Now that a large number of TV's and laptops come with a LED lit LCD display, I worry about the lifespan of the light. From what I have been able to tell, the life is much shorter than the common cold cathode lamps of old.
Consumers are assuming that solid state LED lights are rock solid and are unlikely to fail. Since I have first read about Lumen Maintenance, I have looked into the issue and running some tests of my own.
The first test was with LED Christmas lights. We put some up two years ago and were impressed. One of the strings had high failure rates of the Green LED's. Last year we bought some more LED lights. My daughter really liked some of the blue ones I got. So she put up two strings in her room. One was completely dead in less than 6 months. The other was dim with many barely lit at the same time. It was about this time I heard of Lumen Maintenance.
To run the experiment, I picked up a package of LED bulbs from Costco. It was a package of 3 bulbs. One was placed in service in a bathroom with no windows to serve as a night light. It was on 24/7. Another bulb was placed in the headboard of my bed for occasional use, and the 3rd was placed with my camp stuff for low power battery inverter use while camping. Below are the photos of the direct comparison of two of the bulbs. One is from the bathroom and the other is from my headboard.
To prevent the camera from hiding the result by changing settings, the camera was set to Manual exposure to use the same exposure for both photos. Two pairs of photos were combined into the composite photo below. Two pairs of photos are of the bulbs in use with the bathroom lights on and two of a paper on the wall lit only by the LED's.
Anyone else having problems with LED life?
Last edited by Technician1002 on Fri Sep 23, 2011 9:46 am, edited 1 time in total.
I own two strings of white LED Christmas lights, had one for two years now, the other for three. No bulb failures AT ALL. I don't know where you're getting yours...
It sounds horrible, but after reading some of the Wikipedia article, it seems like the degredation of that LED bulb is your fault. The article says white LEDs are often made by coating a blue LED with phosphor, so that much of the blue light undergoes a stokes shift, and lengthens the wavelength. The extra energy is dissipated into the LED (I think) as heat. So you pretty much fried the LED by leaving it on all the time and not letting it cool.
Don't leave them on all the time and they should be fine.
This is what Google found
http://gizmodo.com/5151865/led-bulb-lif ... -they-seem
so yeah it seems they have limited lifespan
Children are the future
unless we stop them now
But your LEDs probably have less total run time than his.
My concern is if you use a computer or TV with LED lighting 8 hours a day 5 days a week, it could have faded as much as my example in under 3 years. The bottom two photos could easily represent the screen brightness of a TV or monitor that is used daily for work shift after only 3 years of use.
In photography one F stop change or one shutter speed change will double or half the exposure. Without making any change, it is easy to see that my fade was way more than 1 f-stop. This lamp has faded well below 1/4 output in under a year. The blue Christmas lights in my daughters room did the same thing. My concern is they are now using these in TV's and Laptops.
Last edited by Technician1002 on Wed Sep 28, 2011 7:37 pm, edited 2 times in total.
I have both a led and a plasma tv, and to be honest I think the plasmas picture is 100 times better.
No offense, but if you're watching 8 hours of TV 5 days a week... I'd have other concerns.
Do you have any numbers to calculate energy savings? If you're really on the fence, you could just use that to decide.
If used 3 hrs a day, they claim a warranty for 3 years. The yearly estimated cost to run is about 30 cents since these are only 1.5 watts. The real cost is the bulbs. A package of 3 is about $20. In your laptop or TV the energy savings won't pay a shop to re-lamp it in 2 years because it is dim.
I don't watch that much TV. I do however have a family. It includes a full time homemaker wife, kids, etc. Between them and the shows I do watch, the TV easly gets 6-8 hrs/day. Between Netflix, news, and Wii games, it adds up.
I have had my plasma for almost 2 years. It runs at least 12 hours a day. Have not had 1 problem yet. I actually bought another of the same exact tv 6 months ago and got the 3 year warranty fot the extra 50 bucks. If it does shitt the bed, which I think it wont, I am covered. I would go with a plasma if I were you. In my opinion, they come in better and will last longer. Especially if your a sports fan, because plasmas have a higher HZ I believe its called. On mine, its 800 to 1, where on a led, its only like 60 to 1.
Plasma TV's are well known for a fade known as sputter etching. A plasma in the vicinity of the phosphor etches it away over time. Google it.
Contrast ratios and speed have vastly improved on LCD screens.
There was a test on light bulbs regarding their efficiency and life. An issue with both conventional and worse with CF bulbs is they do not last if they are cycled on and off often. On the converse LED bulbs fade if left on constantly. With this in mind I just changed out the bulbs in my small bathroom with LED bulbs. The ceiling light was 60 watts. The three bulbs over the sink were 40 watts each. To make a long story short, I replaced 180 watts of bulbs with 4 2.5 watt LED bulbs. It is not quite as bright as before, but will work fine for my use. I don't spend 3 hours a day in the bathroom, so this should work fine for the relatively frequent operation of the lights.
Too be fair the camera did some great color correction on that photo. The bulbs are listed as warm white. With the camera flash, you can see they do a decent job looking like an incandescent.
I am not ready to replace lights in the other rooms yet until I see better LED life.
Last edited by Technician1002 on Fri Sep 23, 2011 9:49 am, edited 1 time in total.
One thing to consider is the fact that heat has a SEVERE effect on LED life. If you want to do a true test, try this.
Buy a single, high quality LED. Something along the lines of a CREE XP-G.
Then use some thermal compound to attach it to a large heatsink (An old CPU heatsink would be ideal). Set up an LED driver to drive it at it's rated power or slightly below, and measure the brightness. Leave it on 24/7, and see if the output drops considerably over time.
My understanding is that drop-in LED bulbs don't last long because they need to fit a lot of LEDs in a small housing with very little heatsinking. Plus, the LEDs they use arn't always of the greatest quality.
I wonder how much deeper the ocean would be without sponges.
Right now I'm having amnesia and deja vu at the same time. I think I've forgotten this before.
Add me on msn!!! email@example.com
I like a quality picture no matter what. By far the best picture I've ever seen on a TV is the Samsung 3D LED with Backlight. Stop by any store that sells them and check them out, incredible!
The one I watched was in BestBuy, I thought they were going to tell me to buy it or move along...
When life gives you lemons...throw them back they suck!
Tech, sputter etching and power consumption are some of the reasons I would never buy a plasma, not to mention I can't stand overly contrasty screens.
Thanks for bringing it to my attention, I'm still using a 10 year old 51cm CRT that's still going strong, but I'll be feeling the back of the TVs in the store for heat when I do (eventually) upgrade.
This is the TV I have in my media room, MITSUBISHI WD-73840
It is awsome!!!
Yes it has a bulb in the back that has to be replaced, I can get the bulbs for under $100 and they last about 5yrs. No LED fade.
You made me look that one up. It is a DLP for those who didn't look up the MITSUBISHI WD-73840. I found as a general rule the pixels on a DLP are relatively huge compared to their counterparts. It is one of the few models that consumer replaceable lamp. I was hoping some of the LED models would have replaceable modules, but none I have seen so far contain this.
I have a DLP projector for Power Point and other presentations. I do agree they provide a bright high contrast picture, have a replaceable lamp, and look good from a distance. Unfortunately DLP still needs to use a projector, so they are not flat panel TV's you hang on the wall or use in your laptop screen, which puts them outside of this thread. Thanks for the input.
To be fair, HID lifetimes are most often in the 2,000 to 4,500 hour life, which is why they are consumer replaceable. Look up the bulb life for your TV. HID bulb failure is often hard to start bulbs, a glass break, or arc wander on worn electrodes causing flicker and a wandering hot spot in the screen brightness. A 5 year life on a 2,000 hour bulb is about 1.5 hours a day average use.
I have considerable experience with HID bulbs in both projectors and stage lighting. Their color temperature can't be beat. They are a fantastic light source.
All modern movie theaters use them. A typical projector uses a 2,000 watt high pressure Xenon HID projector lamp. Typical use is 2,000 hours. For 2 feature films per night the life is about 1 year.
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