forcing bits on and off Logix 5000

[TConnolly]

 

[daba]

 

[showshocka]

You need to find the tag Local:3:I.Data.11 assuming its your 11th input on your card just guessing it is from where your cursor was in the screen shot, then it should allow you to force it

WOW....why would they make this so confusing. seems like RSL500 is click heaven compared to this. thanks a million guys. even though i can run now with the force installed my line is still stopping, this time with no fault because my fault bit never goes true due to the force. can this stopping possibly be because of that second problem i was unaware of at first, the 1756 DHRIO, maybe?

 

[bernie_carlton]

In the SLC500 the inputs have fixed system names (I:1/5 for example). But if, at the start of the program the whole group of inputs were copied to, let's say, a B register's word, you would have the same problem in trying to 'force' one of the 'B' bits. You would have to go back to the actual 'I' input bit to force it.

The problem lies in the understanding of the structure. Once you understand that 'Local ... etc' is the pre-assigned system name for the input and it was being copied to another memory register you would realise that you couldn't force that second register, you can only force the pre-assigned name.

But (to add to the confusion) the Controllogix family adds the idea of an 'alias' which is a whole seperate tag but can be DIRECTLY tied to the input bit. It is SO directly tied that you can 'force' the alias and it is exactly the same as forcing the 'Local' bit. This does not have a similar idea in the SLC500/Micrologix world. But we weren't dealing with the 'alias' in this case.

 

[TConnolly]

In this case the "they" you speak of is not the designers of RSLogix5000 but whoever converted a SLC PLC program to CLX and decided to follow legacy conventions. Its one of many reasons why I prefer to rewrite the programs to take advantage of the features of the ControlLogix platform.

 

[rdrast]

The DHRIO card will always show a fault if it is included in the IO tree, with no connections under it. I normally ignore that one.

 

[OkiePC]

can this stopping possibly be because of that second problem i was unaware of at first, the 1756 DHRIO, maybe?

Highly unlikely. see rdrast post above.

More likely in no particular order:
1) You mis understood what is triggering the fault, and have forced one of two or more input devices (haven't looked at your alarm code) that must be forced.
2) You caused another fault that doesn't like the fact that the photo cell now never changes states.
3) The photocell is hardwired to more than just the PLC input and stops the line electrically via external control wiring or other logic.

 

[showshocka]

1) You mis understood what is triggering the fault, and have forced one of two or more input devices (haven't looked at your alarm code) that must be forced.
2) You caused another fault that doesn't like the fact that the photo cell now never changes states.

i found that fault on the DHRIO card before i even learned how to do forces....but if i don't need to worry about that fault i won't...with my force installed the line is running find for now. ThankS for all your help.

 

[showshocka]

The problem lies in the understanding of the structure. Once you understand that 'Local ... etc' is the pre-assigned system name for the input

now that we're on the subject of "local", i looked through my training course notes and found exactly what you're talking about...thanks

 

[ruellaurio]

Basically, that was my temporary solution... only good for short logic sequence... though... thanks anyways...