LED Bulb dying

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On 09/17/2016 02:26 AM, snipped-for-privacy@hotmail.com wrote:

Most 'new' products today are made from components that have been life tested for years.
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Its true they wont test a new product for 5 or 10 years to get an mtbf numb er before selling it. In the case of an led or ssd drive, its not the firs t one ever made. Manufacturers understand the devices, the physics, the fa ilure modes, and have similar devices that have undergone testing for tens of thousands of hours. That data allows estimates for the next similar dev ice.
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Yet, you can't even spell the acronym correctly.
MTBF - Mean Time Between Failures
"The predicted elapsed time betwen inherent failures of a system during operation".
Of course, in a system that can't be repaired, such as an LED A19 bulb, the proper acronym is MTTF (Mean Time To Failure).
Note that it is incorrect to extrapolate MTBF to give an estimate of the life time of a component, because of the much higher failure rate during end-of-life.
Note also the first term is 'Mean', which implies failures on either side of the computed MTBF can be expected.
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On Mon, 12 Sep 2016 14:04:21 GMT, snipped-for-privacy@slp53.sl.home (Scott Lurndal) wrote:

Actually the highest failure rate per unit time is when the product is new. "infant mortality" is a bigger issue than "old age".
I guess technically you are mabee correct, because just before they fail - at whatever age, they are "approachiung end-of-life"
Predicting "end of life" becomes the issue. We had all kinds of trouble with LED MR16 or GU10 (whichever the 12 volt ones are) so we went back to halogens - these are in a 14-20 foot mceiling. They have been in a month now, and already 3 out of 54? are dead.......
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On Monday, September 12, 2016 at 12:55:37 PM UTC-4, snipped-for-privacy@snyder.on.ca wrote:

If that were true, then there would be a huge scrap bucket at the factory, with most of the product coming off the line failing. Sure there is a higher failure rate in infancy than in the middle of life, but the highest failure rate is at the end of life when they are almost all failing.

IDK what the difference here is between technically correct and just correct.
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On Mon, 12 Sep 2016 12:55:38 -0400, snipped-for-privacy@snyder.on.ca wrote:

All I know is LEDs can't take heat. Halogen bulbs can. Maybe it is hot up there?
Don. www.donwiss.com (e-mail link at home page bottom).
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wrote:

It's a bit warmer up there than at floor level but that doesnt explain why the halogens are letting go even more quickly than the LEDs did - - -
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snipped-for-privacy@snyder.on.ca writes:

because heat rises, and halogens create a lot more of it, particularly base-up.
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On Tue, 13 Sep 2016 13:01:32 GMT, snipped-for-privacy@slp53.sl.home (Scott Lurndal) wrote:

I was replying to "All I know is LEDs can't take heat. Halogen bulbs can. " -- and noting the halogens are dropping like flies - even moreso than the terrible results we had with LEDs.
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On Mon, 12 Sep 2016 23:22:58 -0400, snipped-for-privacy@snyder.on.ca wrote:

Just lost a 4th halogen this morning - - -
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snipped-for-privacy@snyder.on.ca;3623656 Wrote: >

Life expectancy of a halogen in normal service is determined by filament temperature (ie voltage) and hours of operation. Monitor for high voltage or voltage variations that cause intensity to change. If on a properly wired circuit, that bulb should not change intensity even as other major appliances power cycle.
An abnormal event is, for example, traffic on a floor above that bulb. Incandescent bulbs fail pre-maturely with vibrations only when hot (powered).
--
westom


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On Tue, 13 Sep 2016 21:50:33 +0200, westom

50 bulbs on 3 circuits - 2 on each of 2 circuits have failed within less than 6 weeks. No electrical problems - voltage varies less than 5 volts over a typical day. No heavy equipment loads except for the AC - which runs on a different panel. All the fixtures have magnetic transformewrs (not switch mode) It is a single story building built on slab.
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On Tue, 13 Sep 2016 14:54:32 -0700 (PDT), Uncle Monster

ALL MR16 bulbs are rated for base up - it is almost the only way they are EVER used.
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On Tue, 13 Sep 2016 21:19:29 -0700 (PDT), Uncle Monster

Built as a commercial strip plaza, converted at time of construction to high end office space - 7 years old. Has never had incandescent lighting. Has some "U" shaped flourescents - have replaced, if memory serves me correctly, 3 of them There are some incandescents in washrooms and "accent lighting" as well as a Chandelier - I've replaced half of the bulbs excluding the chandelier, and quite a few in the chandelier - havesince relamped it with LEDs - have had a few failures, bur not a high rate They are base down. I don't have the brand of the halogens handy but they were purchaced from my normal electric supply house, Torbram Electric.
The fixtures are mounted in suspended ceiling, vented to the open space above (minimum 4 feet clearance to roof decking)
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On 09/12/2016 09:55 AM, snipped-for-privacy@snyder.on.ca wrote:

Actually they resemble each other. It is called the "bathtub curve". More at Wikipedia:
https://en.wikipedia.org/wiki/Bathtub_curve
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On 09/12/2016 07:04 AM, Scott Lurndal wrote:

And "YOU" never make a typo? Oh pardon me!

Oh no you misspelled "between"! Oh My Gosh!!!! A TYPO, A TYPO, A TYPO !!! You must have gone to the same publik skool I went to! AAAAAAHHHHHHHH !!!!!
You also gave a superficial definition. The full definition is Mean time between failures (MTBF). The total functioning life of a population of an item divided by the total number of failures within the population during the measurement interval. The definition holds for time, cycles, miles, events, or other measures of life units. --DOD-HDBK-791, page 215
You missed the "measurement interval". It is one hour. I have done this professionally for the military. There is much more to it than the superficial definition you gave. And it does lead to a lot of misunderstandings, like yours. The general public does not realize the tables you use to look these things up (also published by the miliary) are all based on one hour. You are relying on the work of others to come up with your predictions. Intervals other than an hour would require all kinds of math manipulations to combine it with MTBF of other parts analyzed in your prediction. You are not just analyzing one part by itself, you can just look that up.

It is improper to interpolate Mean Time To Failure (MTTF) with with MTBF do to the way MTBF is calculated.
And, I do not mean to poke the condescending in the eye, but infant Mortality and Old Age Failure (Wear Out Failure) match each other (one is the inverse of the other). It is called the Bathtub curve.
https://en.wikipedia.org/wiki/Bathtub_curve
Now you can go back happily condescending about all our typos, not yours, of course.
And yes, I had to study all the above shit.
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On Wednesday, September 14, 2016 at 6:46:41 PM UTC-4, T wrote:

It's sure odd that you made the same "typo" four times in a row in the same post and never once got it right. What are the odds of that?

What a buffoon. The measurement interval is exactly that, how long the system if being measured for failures. You have a jet engine being tested, you clock how long it is before a failure occurs. Typically it's measured in hours, but it's not "one hour", it as long as the test goes on, which is typically tens of thousands of hours. And your own reference says it can be measured in miles, cycles, etc. How does that translate to your "one hour"? So, even your own cite says you don't know what you're talking about.
I have

That's scary.
There is much more to

ROFL
Intervals other than an hour would require

So we can only test light bulbs, LEDs, jet engines for a measurement interval of one hour? Good grief

Sadly you didn't even learn the basics.
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trader_4 has brought this to us :

It's not really an acronym.

Use the MWBT (Mean Words Between Typos) formula [See Appendix E], just add up all of the words in intervals between the starting typo and between subsequent typos and divide by the number of typo events recorded excluding the starting typo. It comes to about 14.33 WPT (Words Per Typo) I think.
Be advised, small data sets may give suboptimum results and excluding the 'warm-up' period and the 'past bedtime' period is recommended for the best results.

Not just "how long the system if[sic] being measured for failures", but where. The idea is to exclude the outliers of 'infant failure' and 'system age wearout' by getting the data set from the steady rate of midlife operation from the nearly flat bottom of the bathtub curve.

It would certainly speed up the process, and marketing would just love the great looking numbers. No need to test them for *two* hours when you get such good results from one hour.
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> trader_4 has brought this to us : > <snip> quoted Left Wing drivel </snip>
On 09/15/2016 12:27 PM, FromTheRafters wrote:

Hi Rafters,
I once asked how the military came up with the numbers. I don't remember exactly what I got back, but the term "Fudge Factor" had to apply. I do believe they did things like speed up aging by heating the guys and then used formulas to extrapolate the numbers back to room temperature. Different types of parts had different formulas. Iron versus silicon, for instance. Or something like that.
Here is a good example of where MTBF means nothing:
https://www-ssl.intel.com/content/dam/www/public/us/en/documents/product-briefs/ssd-530-brief.pdf
"Life Expectancy: 1.2 million hours Mean Time Between Failures (MTBF)"
Does anyone actually think that the average lifespan is 137 YEARS? Oh brother. The metal would corrode by then. The silicone in the transistors would start dripping and turning back into glass.
The real "Life Expectancy" would be the warranty, which is five years. And five years is good for such drives. But 137 years does sound a lot better to the marketing weasels.
-T
Hmmm. I wonder if I made any typos. AAAAAHHHHHHH !!!!
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After serious thinking T wrote :

http://www.reliasoft.com/newsletter/v9i1/prediction_methods.htm
https://www.quanterion.com/reliability-predictions-parts-count-part-stress-pseudo-stress-and-dormant/
It's about using the right tool for the right job and not confusing mathematical predictions with actual empirical measurements.
Marketing can use engineering numbers to confuse and confound end users who think units were actually tested for 274 years on a test bench and half-life used as a conservative measure of life expectancy.
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