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Path: ...!Xl.tags.giganews.com!local-3.nntp.ord.giganews.com!nntp.earthlink.com!news.earthlink.com.POSTED!not-for-mail NNTP-Posting-Date: Wed, 27 Nov 2024 05:20:57 +0000 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: Wed, 27 Nov 2024 00:20:56 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <lqlh20F6uqU1@mid.individual.net> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Message-ID: <8mSdnRRCUbWkMdv6nZ2dnZfqnPSdnZ2d@earthlink.com> Lines: 37 X-Usenet-Provider: http://www.giganews.com NNTP-Posting-Host: 99.101.150.97 X-Trace: sv3-1owOu2+UTxDjNdJwcq5HhXC+gajQeoRQ0uuovNtPliuzFrubDmQ/KGGvJDa9RTRCnWAen5E22zmlla+!a8tMGI/MjL3BqzdfyW/zdT96QYvYRlE0e2KQ2pQdtkE4a842PUqZ/IfkHDCgrF90SU9k4oIVggee!xV7FOyi1KrvOTqJOdT9O X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly X-Postfilter: 1.3.40 Bytes: 2692 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.