[AT] OT LED question

Stephen Offiler soffiler at gmail.com
Sat Nov 5 04:21:08 PDT 2016


I've seen plenty of that too Dan.  Starting noticing it quite a few years
ago, in fact.  (I recall discussing it with my boss while we were
developing an LED worklight... and he passed away several years ago).  I
don't have a technical answer for that, other than to guess it is a
manufacturing defect at the LED emitter level.  The random pattern suggests
it is not a driver circuit issue.  Normally, LED's just dim slowly rather
than go dark.  The hotter they run, the faster they dim.  But of course,
other types of defects will make them go dark.  I do know that when LED
chips are manufactured, they end up with quite a bit of variation, and
there are several testing and sorting steps each and every chip has to
undergo.  In fact it's called "binning" since they essentially sort them
and group them into bins.

SO


On Fri, Nov 4, 2016 at 10:02 PM, Dan Glass <dglass at numail.org> wrote:

> I was driving through town today and noticed that some of the traffic
> lights that have been switched to LED's were about 1/3 to 1/2 burned
> out.   I don't know what they switched from but I never remember seeing
> one of them burned out.  They had about 50 or so LED in each red or
> green light and of those 50 about 20 or 30 random LED were out.
>
> _______________________________________________
> AT mailing list
> http://www.antique-tractor.com/mailman/listinfo/at
>



More information about the AT mailing list