LG PLC, do I use PNP or NPN proximity switch for input

[Peter LG]

I have been given the task to buy a LG PLC, about 20 I/O, I need to wire some proximity switches up to the inputs, I need to use the inbuilt 24v dc 200ma supply, do I by PNP or NPN proximity switches to hook up to these inputs, I believe they will switch at 19.5 volts

 

[Paul B]

Depends on the inputs to the plc. Will they do sink/source on the fly?

To explain, I will use a GE module IC693MDL645 as an example. With this module I can put +24vdc supply to the module and then use NPN sensors that switch the negative to turn the input on.

-Or-
I could wire the 0 vdc to the module and then use PNP sensors to switch the positive to turn the input on.

So the deal is it depends on whether your LG plc will do this. Consult the specs and let us know what you find.

 

[Peter LG]

If you have a look down the bottom of the page of this link
http://www.who-sells-it.com/images/catalogs/4136/20291/ct/inductive-proximity-sensors-000001.jpg
there are 4 diagrams, the 1st (top left PNP),I presume I wire negative to the "common" input terminal of the PLC as well as to terminal No.3 of the proxy sw, positive of the power supply goes to terminal 1 of the proxy sw, and terminal 4 goes to the PLC input. I presume the drawing to the right of the connecter point(small rectangular box) shows the "load" or resistance, which I interpret as my PLC input, therefore when the proxy switches I get positive on terminal 4.

 

[ArikBY]

You correct.
I would use external power supply (stabilized)(short cut might damage your PLC,in the worst case you will have to replace power supply)
I use always positive as an input and positive as an output
I also ground the negative of the power supply.

 

[Peter LG]

Thanks folks,
I found a manual online, and info from another forum, they will sink/source on the fly, I just need to find some PNP proxys if I can, otherwise I will go with NPN and positive to common and negative switch.