Lifetime of High Intensity LEDs

On 12 Jan 2007 14:13:44 -0800, "James Arthur" wrote: [snip]

Sounds like "Da Bomb" for this topic.. Imagine that design job...The pressure due to public safety and lawyers swimming around big companies like sharks. Big driving forces to do it right.. So that's AlInGaP... Very interesting to hear that night time dimming is done..

In addition to my curiousity of tail lights, I'm also learning about LED lifetime to evaluate devices such as:

• Luxeon emitters

• Osram thin film LEDs (Will be researching shortly.)

• other competitive LED's D from BC

Well I don't know. The marketplace strategy seems screwed up to me. I thought (hoped) real science like electronics might be held aloft, or kept to our moral compass better than those other guys (pharmaceutical companies, psychologists, land developers, wall street, et al).

Philosophically, Realistically:

Wall street rules. Even if you have the best idea ever, and nurture it along for decades, eventually, you or your heirs will sell it to a capital venture company, who will make it an IPO, then discard it faster than garbage to a landfill . . . that's the way money "is made" (transferred from the people that do work to people that don't) They call it Capitalism - and revere the word like "God." You criticize the process and you are a "communist." (and just seeing that in print, if you grew up in my generation, makes you mad - because we were brainwashed)

The sad fact of the matter is that Humans were designed to work in a tribe no greater than about 50 people - that works. Civilization is trying to make tribes of millions/billions of people. We are unlikely to adapt fast enough to the environment we created. That's one irony.

The real irony is religion. Save China, who through greed, kept religion at bay. We, the US and Israel (who are NOT our allies) who believe in the "prophet" Abraham are killing each other in the name of religion! To keep others who also worship Abraham (before Muhammad)

I don't know where civilization is heading. I do know it can't be good (from this perspective).

Further off topic: or major rant coming on here:

I found a pod of dolphins on my way to a wreck to fish. 20 miles off shore - no sight of land. Those dolphin have been there 20 years that I know of. I jumped in the water and pretended to be floating. They bumped me to the surface (five times! couldn't hold my breath longer) like they were saving me. When I "recovered" they were all over me making passes to hoist me up and touch me.

Those dolphins are always there and always greet me. They behave like humans would if they could. They play with shells off the bottom or flotsam, they have sex (and really seem to enjoy it) for pleasure, they nurture the young like a commune - un till it comes to feeding time then Mom takes front and center. They are more advanced than Humans in my opinion - they don't cause pollution, have awareness, don't kill each other - - - what do you need? Color TV? that's better somehow? Internet?

If one lives in harmony with nature - all the rest is smoke and mirrors.

Wall street hype - - work at the jobs we allow, so that you might raise us above the masses (where we don't "belong') We will grant you easy living (well sort of - - -compared to where we told you - you would be) and many accolades in return for raising our standard of living. (like I really can't live without imported marble and solid gold dinner ware) That makes you feel good?

The US and world is overdue for revolution - so some other scum suckers can take over.

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Burn out...fade...burn out...fade... At least I have evidence of 2 failure behaviors :) D from BC

How would you know. geezer? Those that do die, know.

As you said "dying at an early age is highly overrated" One might also say college is over rated.

As we age we learn we are mortal. Better young, dumb and dead, IMHO

You really think all that cannon fodder in Iraqi is dying to preserve your/our way of life? They die to preserve their buddies. That is the group/tribe imperative from millions of years or evolution. I went through boot camp and leaned the dogma.

They care about Bush? I'll bet every one of the photo ops was carefully scanned for weapons. Had I been there with a loaded weapon inches from his magot head . . .

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[snip]

Philips' K2s are pretty impressive. The 130-lumen model is rated for 50,000 hours to 70% "lumen maintenance".

[snip]

HTH... -f

Well, the folks here (Neanderthals dragging their knuckles against the ground - FIGURTIVELY SPEAKING - I'd rather a good heart and numb brain for my friends - like Forest Gump)

These DOTTies can't get anything right - to think there might be intelligence back at home base (hive)?

HP was the WORD. But that was decades ago?

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IIRC I got the K2 auto email from Lumileds sometime ago.. It's really cool stuff... I sometimes wear sunglasses when testing LED arrays...and it only gets better. D from BC

I've seen the same in green clusters -- I suspect bond wire failures becoming intermittent, leading to relaxation oscillations as the dice heat. Solid-state blinker bulbs. That suggests abuse; wear-out presents as gradually declining brightness.

James

[snip]

Crappy LED Christmas lights failing this way would look pretty :) D from BC

That is what I see here - east coast Poedunk.

The LEDs are out in defined regions suggesting that it is bias reactance/resistor failure or an interconnect problem.

That isn't the LEDs themselves going bad - just the series string like solder connections.

And given that televison makers got it right two decades ago - - - why can't traffic lights do the same? Trying to replace light bulbs with LEDs and start-ups jumping in with more hype than ability?

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Any Enlightenment is Enlightenment - we receive what we're open to. :-)

Good Luck! Rich

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My LED bedside clock is >7 years old and the red led display shows no detectable to my eye degradation. I suspect it is driven a whole lot more gently than your blinker.

Ed

I've noticed the same thing here in the Fort Worth/Arlington/Dallas area: LED traffic lights with chunks missing. I assumed this was a failure of internal connections because there is no noticeable difference in brightness of individual LEDs; either they're on or they're off.

I've never seen an actual LED traffic light close-up; are they all sealed into one unit, so the grunt doing the installing can just screw the whole thing in like a regular incandescent bulb? Is this "patchwork" failure repairable?

A common circuit topology used in such devices is a number of series strings in parallel. What you're seeing is the failure of an individual series string.

Look at the Avago notes on emitter life -- companies such as HP and Lumileds worked hard to get solid numbers for the assemblies used in traffic lights. The biggest problem with those LED luminaires is they don't get hot enough to melt snow, so the enclosures have to be redesigned slightly.

From what I remember, migration issues aren't the big problem anymore. Phosphor life is still an issue.

--
Namaste--

[snip] [snip]

More reports of failed traffic signal lights!!??? I haven't noticed this yet in British Columbia...but it doesn't mean LED's are being used and working without failure. I have to wonder if there are lens that make it indistinguishable. Only turn on/off time is a clue. I have seen crosswalk signs that are LED. Maybe the city is trying that out first before it dares to change the car traffic lights. :) D from BC

They seem to have switched the railway level crossing lights to LEDs around here. Of course the duty cycle is much lower for that application.

Best regards, Spehro Pefhany

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Embedded software/hardware/analog  Info for designers:  http://www.speff.com

Right. The sparkling / 2Hz-flickering strings suggest a single-point wiring failure aggravated by heat.

Yep, I linked to the Avago app notes a little earlier in this thread.

Any info on that? AFAIK, degradation still proceeds as the time-integral of current through the LED. AlInGaP reds might reasonably be expected to be a more mature process than GaN--I've had some chinese blue units fade to half brightness in a shockingly short time ... a couple weeks or so, at 20mA.

No phosphors in traffic lights though, only in the Walk/Don't Walk thingies. Traffic lights here are clusters of oodles of plain old monochromatic 5mm LEDs.

Apparently they're getting the snot driven out of them. Either that, or assembly practices that snap the die bonds during manufacturing might explain what we see. Vendors warn against mechanical loads on the leads during lead-forming and insertion, for fear of shearing those bond wires.

Best, James Arthur

Do you have traffic lights in British Columbia?

John

Mostly to prevent cars and polar bears from crashing :) D from BC