Re: Anybody Seen a Simple LED "Fail-Over" Circuit ?

Subject	Re: Anybody Seen a Simple LED "Fail-Over" Circuit ?
Newsgroups	comp.os.linux.misc
References	<ywWdnVFGrNEA6tj6nZ2dnZfqnPSdnZ2d@earthlink.com> <lqlh20F6uqU1@mid.individual.net>
From	"186282@ud0s4.net" <186283@ud0s4.net>
Organization	wokiesux
Date	2024-11-27 00:20 -0500
Message-ID	<8mSdnRRCUbWkMdv6nZ2dnZfqnPSdnZ2d@earthlink.com> (permalink)

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On 11/26/24 4:00 AM, Bernd Froehlich wrote:
> On 26. Nov 2024 at 08:24:12 CET, "186283@ud0s4.net" <186283@ud0s4.net>
> wrote:
> 
>> LEDs are great, but never "forever". They DO
>> fail - but for some safety apps you can't
>> just HAVE things go black.
> 
> Hmm, just a thought:
> If I understood the problem correctly, you want the LED to show some
> failstate, right?
> 
> What if you switch the LED on when everything is fine and off would signal
> a fail?
> 
> If the LED is off then you know it´s either a fail or the LED is broken.
> Either way you have to do something.

   The fail state can (usually) be detected just past the
   current-limiting resistor. If the voltage there suddenly
   equals the supply voltage then the LED is not conducting.
   Again though, more electronics.

   COULD use that elevated voltage to trip a 'relay' trans
   connected to LED-2 however.

   For some apps, you may just be able to look and SEE which
   LED is illuminated. If you normally light the right-side
   one, but peeking in shows the left-side one lit, then
   you have a problem.

   The original LED traffic lights used a cluster of LEDs,
   divided into individually-driven segments. If one failed
   then only a segment went dark, but MOST of them would
   keep working. It was always the greens that went bad.
   TODAY, not sure - I fear they use some more monolithic
   device that'll die all at once.

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Anybody Seen a Simple LED "Fail-Over" Circuit ? "186282@ud0s4.net" <186283@ud0s4.net> - 2024-11-26 02:24 -0500
  Re: Anybody Seen a Simple LED "Fail-Over" Circuit ? rbowman <bowman@montana.com> - 2024-11-26 08:40 +0000
    Re: Anybody Seen a Simple LED "Fail-Over" Circuit ? "186282@ud0s4.net" <186283@ud0s4.net> - 2024-11-27 00:05 -0500
  Re: Anybody Seen a Simple LED "Fail-Over" Circuit ? Bernd Froehlich <befr@eaglesoft.de> - 2024-11-26 09:00 +0000
    Re: Anybody Seen a Simple LED "Fail-Over" Circuit ? "186282@ud0s4.net" <186283@ud0s4.net> - 2024-11-27 00:20 -0500
  Re: Anybody Seen a Simple LED "Fail-Over" Circuit ? Rich <rich@example.invalid> - 2024-11-26 13:34 +0000
    Re: Anybody Seen a Simple LED "Fail-Over" Circuit ? not@telling.you.invalid (Computer Nerd Kev) - 2024-11-27 08:21 +1000
      Re: Anybody Seen a Simple LED "Fail-Over" Circuit ? Rich <rich@example.invalid> - 2024-11-27 01:26 +0000
        Re: Anybody Seen a Simple LED "Fail-Over" Circuit ? Computer Nerd Kev <not@telling.you.invalid> - 2024-11-27 15:12 +1000
          Re: Anybody Seen a Simple LED "Fail-Over" Circuit ? "186282@ud0s4.net" <186283@ud0s4.net> - 2024-11-28 03:11 -0500
            Re: Anybody Seen a Simple LED "Fail-Over" Circuit ? not@telling.you.invalid (Computer Nerd Kev) - 2024-11-29 07:06 +1000
              Re: Anybody Seen a Simple LED "Fail-Over" Circuit ? "186282@ud0s4.net" <186283@ud0s4.net> - 2024-11-29 05:53 -0500
    Re: Anybody Seen a Simple LED "Fail-Over" Circuit ? "186282@ud0s4.net" <186283@ud0s4.net> - 2024-11-27 00:36 -0500
      Re: Anybody Seen a Simple LED "Fail-Over" Circuit ? Rich <rich@example.invalid> - 2024-11-27 06:47 +0000
        Re: Anybody Seen a Simple LED "Fail-Over" Circuit ? "186282@ud0s4.net" <186283@ud0s4.net> - 2024-11-27 23:47 -0500

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