Allen Bradley Slot numbering

[Jerther]

Hi!

I need to add a contact to an existing AB system and I'm getting WAY too confused with the setup I have here. The PLC is a Allen Bradley ControlLogix5561. The current I/O Configuration shows 16 modules with slot numbers from 1 to 16.

This is where I get lost. The rack doesn't even have 16 slots. The input module I'm using is the 4th from the left and the I/O Configuration shows no input modules until slot 12!

I've been reading for many hours in AB docs, forums, tutorials and I'm about to go nuts. This can't be that complicated, I'm sure I'm missing something way too obvious to be documented.

Any help, clue, anything please!

 

[sthompson]

Hi!

I need to add a contact to an existing AB system and I'm getting WAY too confused with the setup I have here. The PLC is a Allen Bradley ControlLogix5561. The current I/O Configuration shows 16 modules with slot numbers from 1 to 16.

This is where I get lost. The rack doesn't even have 16 slots. The input module I'm using is the 4th from the left and the I/O Configuration shows no input modules until slot 12!

I've been reading for many hours in AB docs, forums, tutorials and I'm about to go nuts. This can't be that complicated, I'm sure I'm missing something way too obvious to be documented.

Any help, clue, anything please!

The best thing would be to post your PLC Program File (Zip it first) so we can have a look at it, and try and sort it out for you.

Stu....

 

[Jerther]

Never mind... It's obvious that I don't know AB very well. I wasn't even looking at the PLC, I was looking at one of it's remote racks. I had to find the PLC and then everything made sens.

I had to ask here to find the solution 10 minutes later. This happens too often. Oh well, the absence of any documentation on the system what so ever didn't help either.

Thanks for the quick reply though

 

[Ken Roach]

In the local 1756 chassis, the slots are numbered starting from 0 on the left. While it is very common to put the controller in Slot 0, it can go into any slot.

If you're using legacy PLC-5 I/O racks, the numbering system does get complicated; you have to start thinking in base 8, and reflecting on the wonders of 1975's technology.

Post the *.ACD file or a screenshot of the I/O tree (and a description of the tags) and there's a wealth of knowledge here on the Forum.

 

[Jerther]

I'll post a screenshot of the IO tree tomorrow. No problem with octal, I've used GE plcs in the past and yeah, it's quite a pain. There might be a rack like that here. I haven't found all the wonders yet. What are they like?

 

[Jerther]

There it is. In blue is the module I was looking for.