I am updating a machine first commissioned in 1998 with a FANUC 90/30 plc
From hours of study, it appears that the original logic documentation is incomplete and in many cases incorrect for this particular process tool. I am beginning to suspect that both the paper copy, and the logic stored in EEPROM is actually a generic package, with a few modifications to suite particulars as needed. I certainly can not fault a manufacturer for such expediency. If there is nothing connected to an input or an output, No harm, no foul. Correct me if I'm wrong.
As a complete tyro to ladder logic programs I can't help but notice some of the logic patterns occur frequently. The diagram below is an extract of one I am struggling with.
|342M 344M 139M 163M 344M
| ------] [-----]/[-----+--]/[-----]/[---------------------------------------------( )-- |
342M 344M |
|------]/[-----] [-----+
In particular, the internal reference %M0344 is used as an open contact, a closed contact, and a coil all in the same rung. Please shed some light on nature of this arrangement of elements. (doubling confusing for me, is that none of these references are connected to anything other than other internal references for several "layers" of logic both forward to an output, and backwards to an input.
I feel that if I can get my head around this "building block" It will allow me to see much more in these pages and pages of ladder diagrams.
I thought I saw a reference explanation of such an arrangement "somewhere on the net". but I did not study the content at the time, and now I can't seem to find the search terms that lead back.
Will someone(s) care to share a simple description of the above contact structure?
All comments welcome
Thanks in advance
Cal
From hours of study, it appears that the original logic documentation is incomplete and in many cases incorrect for this particular process tool. I am beginning to suspect that both the paper copy, and the logic stored in EEPROM is actually a generic package, with a few modifications to suite particulars as needed. I certainly can not fault a manufacturer for such expediency. If there is nothing connected to an input or an output, No harm, no foul. Correct me if I'm wrong.
As a complete tyro to ladder logic programs I can't help but notice some of the logic patterns occur frequently. The diagram below is an extract of one I am struggling with.
|342M 344M 139M 163M 344M
| ------] [-----]/[-----+--]/[-----]/[---------------------------------------------( )-- |
342M 344M |
|------]/[-----] [-----+
In particular, the internal reference %M0344 is used as an open contact, a closed contact, and a coil all in the same rung. Please shed some light on nature of this arrangement of elements. (doubling confusing for me, is that none of these references are connected to anything other than other internal references for several "layers" of logic both forward to an output, and backwards to an input.
I feel that if I can get my head around this "building block" It will allow me to see much more in these pages and pages of ladder diagrams.
I thought I saw a reference explanation of such an arrangement "somewhere on the net". but I did not study the content at the time, and now I can't seem to find the search terms that lead back.
Will someone(s) care to share a simple description of the above contact structure?
All comments welcome
Thanks in advance
Cal