[time-nuts] LED reliability

Magnus Danielson magnus at rubidium.dyndns.org
Wed Apr 30 13:37:44 EDT 2008

From: "Poul-Henning Kamp" <phk at phk.freebsd.dk>
Subject: Re: [time-nuts] LED reliability
Date: Wed, 30 Apr 2008 17:12:56 +0000
Message-ID: <34736.1209575576 at critter.freebsd.dk>

> In message <20080430165656.3C300BE3B at ip-64-139-1-69.sjc.megapath.net>, Hal Murr
> ay writes:
> >> LEDs been viable since at least the early 70's?  Talk about planned
> >> obsolescence... 
> >
> >How reliable were the early LEDs?  When did they start to get used in high 
> >reliability applications?
> Many of them are still happily emitting their faint red or green light.

If you do not drive your LEDs too hard, they will surely survive longer.

> >The best reliability story I heard (many years ago) was about installing 
> >another trans-Atlantic telephone cable.  They used tubes long after 
> >transistors were out.  They knew how long the tubes would last.  They didn't 
> >have much data on transistors yet.
> Actually, that's not entirely correct:  They had reliability info
> on transistors and they sucked.

Konrad Zuse stayed with relays for quite some time, since it took time for the
much faster tubes to become reliable enought. However, he used his relays
wisely, since they always changed state with the contactors carrying no
current. The commutator driven by a synchronous motor took that heat. One place
to service.


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