beginner's question

I just started learning about PLC's and getting confused about the XIC and XIO instructions. Can someone please answer this question?

An NO limit switch is to be programmed to control a solenoid. What determines whether an Examine if Closed or Examine if Open contact instruction is used?

Is this a right answer?

It depends on whether you want to turn on or off the solenoid.
So if i the program wants to turn on the solenoid, you should a XIC or XIO function?

It depends on application.

It can be becouse of sensor type.

One example, simple one.

You have conveyor, you have pnp sensor on start of next conveyor, you want to know its free so you examine if its zero in input image of your plc.

--]/[---( )

Then on other hand you want to know if there is part at that sensor to know when to start second conveyor.

--][--( )

So it depends on application.

Thanks for replying TurpoUrpo

O i almost forgot. Ron Beaufort has made some nice videos, you should look them:

http://www.ronbeaufort.com/sample_lessons.htm

Always remember, plc is programmed with instructions. It does not care how some sensors actual physical state is, it only cares what is stored in plc:s memory. Ron shows that with good examples.

I can vouch that (Phil's) PLC books sold here are worth your time and money.

http://www.plcs.net/store/bookstore.shtml

The first volume is right at your level, useful, affordable, and supports this site.

It depends on whether you want to turn on or off the solenoid.
So if i the program wants to turn on the solenoid, you should a XIC or XIO function?


it would be closer to think of it as it depends on the condition that the senser provides when activated. This can change whether the senser is source or sink, light or dark, or NO NC.