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Why are LED signs so often seen broken?
July 1, 2009 8:32 PM   Subscribe

Why are LED signs so often seen broken, at least in part?
posted by LSK to Computers & Internet (11 answers total) 1 user marked this as a favorite
 
Do you mean neon signs? I don't really see LED signs very often.
posted by InsanePenguin at 8:48 PM on July 1, 2009


I mean the scrolling signs so often seen near schools, banks, and food stores.
posted by LSK at 8:50 PM on July 1, 2009


Because they're on all the time. Electronic components fail, overheat, etc. I doubt televisions or monitors would do much better if you subjected them to the same treatment. It's not likely that the LEDs themselves fail, though -- when you see a panel that's burnt out or displaying gibberish, it gives you some insight into how the controllers driving the LEDs are arranged.
posted by qxntpqbbbqxl at 8:57 PM on July 1, 2009


1) Because they're on all the time.
2) Confirmation bias.
posted by pompomtom at 9:02 PM on July 1, 2009 [2 favorites]


There are many points of failure but most will not leave the sign totaly unusable, hence repair is not a high priority.
posted by Dr Dracator at 9:31 PM on July 1, 2009


There are many points of failure but most will not leave the sign totaly unusable, hence repair is not a high priority.

This.
posted by InsanePenguin at 9:43 PM on July 1, 2009


LED stoplights suffer partial failures due to busted boards & solder joints. LEDs themselves do go bad but not nearly as often as PCBs crack.
posted by chairface at 11:03 PM on July 1, 2009


qxntpqbbbqxl at 11:57 PM on July 1:
It's not likely that the LEDs themselves fail, though -- when you see a panel that's burnt out or displaying gibberish, it gives you some insight into how the controllers driving the LEDs are arranged.

Not true. It is true that LEDs can have extraordinary useful MTTF (Mean Time To Failure), but only if they are operated well within the moderate range of their power curves. Above a certain point, lifetime decreases nearly exponentially with voltage.

I am an optical engineer, and once interviewed with a company that makes LED lights for plane wing tips (the green and red lights that indicate the plane's direction). During the interview, the manager confessed that they intentionally design these LEDs so they operate in the short-lifetime part of the I-V (current-voltage) curve. The design goal was to produce lighting that outlasted conventional lights (thus, their product was clearly superior, and cheaper in the long run), but still died on a fairly regular basis (insuring a certain level of replacement business).

It's as if dentists seeded cavities in your teeth every 24 months, to ensure their customers needed their services.

Sign manufacturers may do the same, in order to sell spare parts (board segment replacements). Ask almost any manufacturer; the profit is in the service and repair departments.
posted by IAmBroom at 11:21 PM on July 1, 2009 [2 favorites]


There are many points of failure but most will not leave the sign totaly unusable, hence repair is not a high priority.

In other words, the MTBF (mean time before failure) for an LED in a stoplight, say, may be high-- twenty years-- but chances are a couple of them will fail within a few years. Even if the light is still effective, and doesn't need to be replaced until 20 years have passed, it's still quite noticeable.
posted by alexei at 3:32 AM on July 2, 2009


Consider the possibility that it benefits the advertiser to have a broken, but still readable sign. You can ignore something that looks normal. But if the sign is broken, it catches your eye. You take time to try to decipher what it says. Taking that time means the message gets into your head...

(It used to drive me nuts when I'd see a sign that says something like "QPC/C 2 4 $2". How in the world does anyone know what a QPC/C is? Then I realized that there is probably a larger segment of the population that doesn't care what is on sale, just that it is.)
posted by gjc at 6:09 AM on July 2, 2009


My boyfriend (who works for a company which designs and services and provides content for such signs) said that there are a few reasons -- one is that many of the larger signs are outdoors and thus the components are subject to damage from the elements and pollution, etc.

The other reason is that there are simply so many components. A sign in Times Square will have thousands of modules, and each of those modules has hundreds of individual LEDs. The chance of something failing in such a massive sign are pretty high.
posted by peanut_mcgillicuty at 6:25 AM on July 2, 2009


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