The example is properly described. The example shows a normally closed contact and then two parallel contacts next which are normally open. The output coil drives one of the parallel contacts so the logic line is basically a start/stop logic rung with a seal in contact.
In the old PLC training books they used some terminology to help new users understand ladder logic. The normally open contact (NO contact) was said to be an "examine for on" instruction and the normally closed contact (NC contact) was said to be an "examine for off" instruction. The use of the term "instruction" made people realize that that ladder logic was really a programming language rather than actual contacts and relays which made ladder logic training a lot simpler. So reading the rung from left to right... the first instruction is an "examine for off" - so if bit B0 is off that instruction will be true. The next instructions to the right are logically ANDED with the first instruction. So examine B1 for on OR examine Q0 for on .. Then take the logical AND result and write it to the output coil Q0. Dave On 3/23/2015 7:52 AM, Rick wrote: > I managed to get lost in this thread, what ladder component is in > question here? > > I rely heavily on Classicladder in my machines, averaging over 200 rungs > per machine, and am curious as to what may be possibly wrong. > > Thanks > > Rick > > > > On 3/23/2015 8:33 AM, Mark Wendt wrote: >> On Mon, Mar 23, 2015 at 8:09 AM, Erik Christiansen <dva...@internode.on.net> >> wrote: >> >>> On 23.03.15 07:30, Mark Wendt wrote: >>>> On Mon, Mar 23, 2015 at 7:17 AM, Erik Christiansen > wrote: >>>>> Try it as I describe, and the diagram and text should align without any >>>>> clashing of mental gears. >>>> The logic still doesn't match up with the simple switch diagram. >>> And yet you show yourself that it does, and your subconscious >>> understands the logic: >>> >>>> B1 has to be activated for current to flow to the coil, to close the >>>> contact on Q0. >>> Yep, that's the green button on a commercial or homebuilt NVR. >>> It's momentary, NO. Press it for the NVR to latch on. >>> (And activated == "on", so NO -> closed, both for switch and relay.) >>> >>>> B0 has to be in it's normal state. >>> Yep, that's the red button on a NVR, as on my lathe. >>> It's momentary, NC. Press it to reset the NVR latch. >>> (normal state == inactivated == "off" == NC is closed, NO is open ) >>> >>>> If you "activate" B0, you cut off the current and the contacts on Q0 >>>> open. >>> Yup, that's the mechanics of the relay logic implementation. >>> (activated == "on" => NC->open, NO->closed, possibly both on the same >>> switch or relay, and maybe six of each on the one relay, if there is >>> output to many other ladder rungs.) >>> >>> See, the logic _is_ coherent. :-)) >>> >>> Erik >>> >> So, following that logic, "off" is "on," and "on" is "off." ;-) >> >> Mark >> ------------------------------------------------------------------------------ >> Dive into the World of Parallel Programming The Go Parallel Website, >> sponsored >> by Intel and developed in partnership with Slashdot Media, is your hub for >> all >> things parallel software development, from weekly thought leadership blogs to >> news, videos, case studies, tutorials and more. Take a look and join the >> conversation now. http://goparallel.sourceforge.net/ >> _______________________________________________ >> Emc-users mailing list >> Emc-users@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/emc-users --- This email has been checked for viruses by Avast antivirus software. http://www.avast.com ------------------------------------------------------------------------------ Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
