Add "Fail Softly" to your conditions. When the result of a failure leads to continued but degraded operation. Example: when your car computer cannot manage closed loop but allows the engine to continue in open loop rather than leaving you stranded. John Ferrell W8CCW "My Competition is not my enemy" http://DixieNC.US ----- Original Message ----- From: "James Newton, Host" To: "'Microcontroller discussion list - Public.'" Sent: Thursday, November 02, 2006 7:00 PM Subject: RE: [EE] Failsafe vs. Redundant, was Automobile LED headlights > > >> -----Original Message----- >> From: piclist-bounces@mit.edu >> [mailto:piclist-bounces@mit.edu] On Behalf Of Mike Hord >> Sent: 2006 Nov 02, Thu 07:09 >> To: Microcontroller discussion list - Public. >> Subject: [EE] Failsafe vs. Redundant, was Automobile LED headlights >> >> As Russell points out, many people don't know what the >> difference between "fail safe" and "redundant" is. >> >> Perhaps as engineers we really should. I've heard engineers >> misuse the terms before. It's an important distinction. >> http://en.wikipedia.org/wiki/Failsafe is a poor explanation >> of the concept. Wikipedia DOESN'T know everything. >> >> Anyone want to take a crack at it? > > Fail safe means that a failure is possible and even expected, but that > when > it happens, it will do so in a way that is the least likely to do damage. > The device "Fails" in a "Safe" way. > > Redundant means that there is more than one system for the function > required > and some means of switching from one to the other when a failure is > detected. > > > Some (rather bad) examples include: > > Redundant is an electric fuel pump behind a mechanical one with a switch > to > turn it on if the main pump fails. > > Fail safe is when there is a shroud under the fuel pump that directs > leaking > gasoline away from the exhaust headers. > > > Redundant is when the engine has both air and water cooling. > > Fail safe is when the thermostat spring is engineered to corrode away long > before the actuator causing it to fail in the open position rather than > closed. > > > Redundant is capacitors in series. > > Fail safe is capacitors in series with a fuse. > > > I'm sure someone can improve on that... > > --- > James. > > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist