comprare controllogix offline and online project

[wilsonzhu]

Thank you, gmferg, you are so helpful.

 

[Ron Beaufort]

just a little clarification ... in Allen-Bradley processors, (PLC-5, SLC-500, ControlLogix, etc.) when you FORCE an OUTPUT, the value in the bit/box does NOT change in response to the force operation ... specifically, you can make an output device in the field go ON or OFF by forcing an output ... BUT ... the status/value (ONE or ZERO) in the bit/box (memory location) is NOT changed ...

incidentally, this turns out to be one of the topics discussed in my latest "Email PLC Quiz" if you're interested in following up on the subject in more detail ...

 

[Ron Beaufort]

this dog DOES bite ...

and while we're on the subject ...

in RSLogix5000, the "Find All Forces" button will find forces ONLY (I repeat ONLY) in the Routines (programming code) ...

specifically, if a force has been applied to a memory location (in the tag listings) and that input or output has NOT yet been "entered in" to the programming code, then the "Find All Forces" button will NOT (I repeat NOT) find that "memory only" force for you ...

this "issue" usually pops up when someone is commissioning a new field device - and doesn't have the logic to control the device entered into the "program" (routines) yet ...

worse case scenario: a technician hits the "Find All Forces Button" and the search comes up empty ... so - no forces are involved - right? ... next the technician installs "his" force for "his" field device - and then "Enables" the forces ... ooops! ... the force for the brand new (as yet unprogrammed) Hydraulic_Ram suddenly takes effect - because someone left a Force installed in the tag listing ... bummer! ...

NOTE: I haven't checked this "issue" out with RSLogix5000 version 16 yet ... if anyone has time to try this with the "latest and greatest", I'd appreciate knowing if it works the same as previous versions ...

 

[wilsonzhu]

thanks

 

[gmferg]

The Forces tab area will tell you if forces are installed and you can remove all forces here even if not found in a search. The I/O Forces LED will flash yellow when forces are installed and not enabled.

 

[Ron Beaufort]

The Forces tab area will tell you if forces are installed and you can remove all forces here even if not found in a search.

yes, you are certainly correct ... but a problem could come up when a “less-than-adequately-trained” technician hits the “Find All Forces” button - and expects it to automatically “Find All Forces” ... if there are “some” forces that he doesn’t find, then that could lead to a problem ...

The I/O Forces LED will flash yellow when forces are installed and not enabled.

usually this is correct ... but ... the smaller/older L1 type ControlLogix processors don’t even have a “Force” LED on the front ...



just in case you’ve somehow misunderstood, I’m NOT arguing with anything that you’ve said ... I’m just trying to add more detail to the discussion ...

PS Edit ... possible exception ... it's hard to tell from the thread so far, but if you think that entering a value into the "Force Mask" of an OUTPUT is going to change the value/status stored in the output's memory location, then we need to go a little bit further with the discussion ...