New to PLC RS Logix 500 user.

Excuse me if my questions sounds stupid but, I am totally new to PLC, and would like to learn about the type of PLC we use here.

I have done a simple circuit using RS logix 500, one input and one output in series.

Input is an (examine if Open I:0/1) and the output is an (output energise).

Connecting it up practically, I have used a normally closed PB for the input and a lamp for the output.

As it is, I assumed that the lamp should be on but it isnt. Why? I have downoaded to the PLC.

Post your program on here so we can have a look
And we can advise easier

Ok, this is another diagram i did. the normally closed input was connected to a normally clossed push button in the practical. I assumed any normally open contact if pressed should turn on the lamp in the output but it didnt. Did I do it right? All normally open PB were connected to the XIC inputs.

For additional help you may wish to post the specific model of PLC and a wiring diagram.

But Bernie, correct me if I am wrong but the input I:0/5 in my diagram should be connected to a normally closed PB/contact and not a normally open push button/contact.

if your I:0/5 is a NC pushbutton then you will want to use a normally open set of contacts, or XIC.

Yes when I used normally open set of contacts it operated correctly, all my inputs were normally open push buttons.
So was I wrong when assuming that all XIO in the diagrams should be connected to normally closed contacts?

You could relate any NC (Normally Closed) or NO (Normally Open) inputs to any XIO (Examine If Open) or XIC (Examine if Closed) ladder logic instructions; just make sure that the "logic result" is the one intended!

The concept of the type of pushbutton or other 'normal' input condition does not control the type of contacts available in the program.

Essential safe inputs, like a STOP button are often wired Normally Closed to the input pin. The 'Normal' state results in the input circuit being ON. Pressing the pushbutton turns off the input circuit. The input circuit being Off is taken as a command to Stop. This also covers a case if the wires to the Stop pushbutton were accidently cut. This also yields a safe action - stopping.

To help avoid confusion apply internal nicknames. Name the input by the external condition which causes the input circuit to turn ON. You can note in a seperate description the nature (Normally Open / Normally Closed) of the external device. Naming the above mentioned Normally Closed 'Stop' pushbutton can be solved by calling it 'Run Permitted'.

When used with an XIC contact then the logic of the 'normal' state of this pushbutton the logic 'reads' - 'Run permitted' is TRUE. If an XIO contact is used then 'read' the logic as 'Run Permitted' is NOT TRUE.

If you name the inputs as I recommend then you can slowly ignore the wired status of the external device and concentrate on the PLC logic.

Make sure you didn't forget the JSR instruction for the LAD that you create

Whats a 'JSR', kardel?

JSR = Jump to Sub Routine.
You can look up at the instruction help for the detail.
If you didn't set the JSR to the LAD, it won't be executed by the PLC.

in my company, we set the LAD 2 to be the "main routine" where all the JSR instruction placed, so that we can choose which LAD to be executed.

you could try to
- set JSR instruction to execute LAD 3 in LAD 2
- place your program at LAD 3

If your screen shot is of when you think it should be running, it is not scanning that program routine.

1) Is the processor in RUN mode?
2) Is the routine that the rung is in being scanned?

So was I wrong when assuming that all XIO in the diagrams should be connected to normally closed contacts?

Click to expand...

Yes. The type of PLC instruction (XIO or XIC) is not directly locked or linked to the type of physical input device. There are some programmers that require 2 or 3 years to figure that out. You are ahead of the curve now!