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
