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Q: LED Performance/Failure ( Answered 5 out of 5 stars,   0 Comments )
Question  
Subject: LED Performance/Failure
Category: Science > Technology
Asked by: seedy-ga
List Price: $25.00
Posted: 21 Oct 2002 03:54 PDT
Expires: 20 Nov 2002 02:54 PST
Question ID: 85854
A friend of mine who lives in Singapore has a three year old Volvo
with a LED display which is part of rear view mirror. That LED has
leaked and Volvo says it is normal wear and tear. I am looking for
someone who knows LED's and can give an opinion as to whether this
behaviour is expected or unusual. Please provide supporting
documentation.
Answer  
Subject: Re: LED Performance/Failure
Answered By: haversian-ga on 21 Oct 2002 04:29 PDT
Rated:5 out of 5 stars
 
Hello seedy-ga,

I can't claim to know much about cars but I do know a bit about
electronics.  First off, LEDs don't leak.  A LED is a diode (a P-N
junction, where P and N are two different types of silicon) that has
been optimized to glow when electricity is passed through it.  The
actual glowing part is pretty small, usually much less than 1 square
milimeter, though LEDs are packaged in plastic of various sizes to
protect the delicate electronic part and hold the large leads in
place.  When treated properly (voltage kept more or less right (don't
put 12V through a 1.5V LED...), don't hit it with a hammer, etc.) LEDs
should have practically infinite lifetime (100 years or more).

Perhaps you meant a different type of display?  LCDs can leak if they
fracture or break and will cease to function.  Like a sealed lead-acid
battery, an LCD shouldn't leak but can if it is abused.  Keep in mind
that cars are very hostile environments, subject to temperature
variations of 100C or more, jarring and endless vibration, and
fluctuating power.

In either case, after 3 years both LCDs and LEDs should be in fine
shape.

Let me know which you mean via an answer clarification request, and I
will get you the documentation you requested.  Could you let me know
what type of documentation you would like?  Something illustrating how
LEDs are made, such that they do *not* leak; something about the life
expectancy of LCD panels; something specific to the car in question
(let me know the model and such)?

-Haversian

Request for Answer Clarification by seedy-ga on 22 Oct 2002 17:12 PDT
Thank you for your answer to this question about LED's. I passed it on
to my friend in Singapore for clarification but haven't received any
communication as yet from her.  I'd like to leave the question open
for a week or so to see if she clarifies the question if that is OK
with you.

thank you
seedy

Clarification of Answer by haversian-ga on 22 Oct 2002 21:43 PDT
Not a problem.  Best of luck with the car.

Request for Answer Clarification by seedy-ga on 23 Oct 2002 00:34 PDT
Here is a clarification of the question from my friend in Singapore.
It seems quite different from the original question. If you think I
should cancel this question and ask a new one, I'll be glad to do
so....

"The model is Volvo S80 and it is about 2 years and 10 months old. 
Mileage
is 27,365km to date.  The rear view mirror has a feature which is
supposed
to cut the glare of headlights of vehicles behind.

On 1st October 2002, I noticed that there is a ring in the centre of
the
rear view mirror.  The area surrounding the ring has a fuzzy look
whileas
within the ring, the view is as per normal.

When I brought it back to the workshop, I was told that the LED (or
LCD) has
leaked and it was due to the weather in Singapore.    However, when I
challenged them on the suitability of the vehicle for the Singapore
market,
they denied that they had said weather but all electronics will break
down
with wear and tear.   But in my case, my car is hardly used and
constantly
parked under the sheltered car porch at home with the window wind down
to
let in air, so how does one "wear and tear" the rear view mirror?

So, I asked them to explain the cause of the leakage or show me
statistics
to support that the electronics will break down after 2 years (the
warranty
period), they are unable to explain what are the causes.  Their stand
is
that it does not matter what the argument is, I will have to replace
at my
cost.

I would like to have some information that could help me argue that
since
they cannot explain the cause, then, it could  well be a manufacturing
defect for which I should not be penalized.  It should be a fair deal.
 I
had written to Volvo Sweden, and they too cannot explain the cause.

So, can anybody help?"

Thank you if you can help...

seedy

Clarification of Answer by haversian-ga on 23 Oct 2002 10:16 PDT
Anti-glare rear-view mirrors don't have LCD panels, they have EL
(electro-luminescent) panels, just like the backlight on a digital
watch.  You don't see watches dying after 3 years, do you?  They tend
to last about as long as the battery, on the order of 10 years or
more.

I would need to know more about your warranty to know whether you have
a legitimate complaint, but if you have a 3+ year materials and
workmanship warranty, you should be fine - you just need to yell loud
enough.  Volvo pays the mechanic for the work they do on your
under-warranty car, but the mechanic can charge more for non-warranty
repairs, so they tend to argue.  Ask them how many EL panel
replacements they have done after less than 3 years and when they
waffle or admit to "um...not many..." refuse to take no for an answer
and you should be alright.

It's not quite the advice you wanted, so if you would feel more
comfortable assaulting your mechanic with statistics rather than
obstinance, I'll look up numbers and whatnot for you.  If you can find
out from the mechanic what exact panel you have, I can be more
specific.

Request for Answer Clarification by seedy-ga on 25 Oct 2002 03:18 PDT
Haversian:

I need some references to complete this answer. I am ready to rate
answer very favorably but want some references to back up information
already supplied.

Thank you...

seedy

PS:  I would have asked for clarification in the researcher forum but
notice that you are not registered there for a private message...

Clarification of Answer by haversian-ga on 25 Oct 2002 04:03 PDT
There are a variety of EL panels, integrated into a variety of
products (see list below), having an MTBF rating of between 25,000 and
50,000 hours.  That is 3-6 years being used 24 hours a day, 365 days a
year.  Your friend's car doesn't see that kind of usage, so a panel
dying after 3 years isn't right.

A military display using an EL panel (25,000 hours at 60 C):
http://www.gdcanada.com/land/flat_panel_4580el.html

A commercial touch-screen display using an EL panel (50,000 hours):
http://www.centralp.fr/pdf/PC104PANEL500_E.pdf

A bare display using an EL panel (>50,000 hours):
http://www.planar.com/support/pdf/ds_48060.pdf

An embedded systems panel (30,000 hours):
http://www.emjembedded.com/products/eldisplays/lael16080.html

Another display (30,000 hours):
http://www.tridentdisplays.co.uk/home.shtml/?/solutions/industrial_flat_panel/ncs.shtml


For more links, search for "electroluminescent panel MTBF" and you'll
get a long list of products.


It looks like the panel should last a long time, but MTBF isn't a
guarantee, it's an average, which means some people get a long-lived
panel and some people get one that dies a year or three later.

Best of luck with the mechanic.

-Haversian
seedy-ga rated this answer:5 out of 5 stars
Great dialogue....Gives my friend some ammo to work on Volvo
dealership in Singapore....Thanks  seedy

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