Dave you are 100% right. Your detailed explanation it`s correct conceptually and practically for an industrial application.
Alex Il giorno 08/nov/2014 17:03, "Joe Hildreth" <j...@threerivershospital.com> ha scritto: > Bruce, > > Yeah, I suppose I have been beating the horse to death with the questions. > Sorry. But hey, when you don't know a lot about it you have to start > somewhere, right? Thanks for all the help and clarification. > > After I sent the email, I went off in search of relay logic circuits. > After reading a couple of articles I seen that I had it wron in my head. > > Talking about easy cheap MC's, I loved the PIC, simple to code, implement > and cheap on the wallet. > > I am off to look for circuit examples. Thanks for being so patient. > > Regards, > > Joe > > ----- On Nov 7, 2014, at 11:05 PM, Bruce Layne > linux...@thinkingdevices.com wrote: > > > Joe, > > > > In the words of Roseanne Rosannadanna, you ask a lot of questions! :-) > > > > You don't wire the coils of relays in series for relay logic. The coil > > voltage is selected to match the voltage you want to use to activate > > it... 5VDC, 12VDC, 24VDC, 120VAC, etc. You wire the relay contacts in > > series to implement an AND function (as is the case with your E-stop > > switches and a relay that mirrors the status of the internal LinuxCNC > > E-stop signal, and any other relay controlled signal you want to > > generate an E-stop). You'd wire the contacts from different relays in > > parallel to implement an OR function. > > > > The reason I suggested using relay logic for this application is > > simplicity. You'll need a relay to externalize the internal E-stop > > status anyway, so just wire the contacts in series with any E-stop > > switches you have and you're finished. Why add any discrete logic ICs > > to that? It's needless complexity. > > > > I'm generally a big fan of implementing logic in software or firmware. > > I've replaced a lot of goofy 1950s technology relay logic where relays > > and electromechanical timers were used in the 1990s because someone > > didn't know how to use a PLC or (my favorite) a one dollar RISC > > microcontroller. But if you already have the relay and that's all you > > need, why add an Arduino to drive the relay? > > > > If you search for "E-stop circuit" and look at the images, you'll see > > lots of examples and it'll make sense. > > > > There are also some standard circuits for input power disconnects (I > > don't go to that formality for my small CNC machines) with > > fuses/breakers, ON and OFF pushbutton switches that latch the ON > > condition until the OFF button is pressed, etc. > > > > > > Bruce > > > ------------------------------------------------------------------------------ > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
