Limit Switch Connection to Micrologix PLC

Brown of limit sensor to +24V,

Blue of limit sensor to Micrologix input,

Common of Micrologix input to 0V.

Job done.

(If the common of your Micrologix inputs is already connected to +24V,

connect Brown of sensor to the Micrologix input, and Blue of sensor to 0V).

May have to re-think that!

Please give the manufacturer and part number of your sensor.

Check out this link: http://www.tektron.ie/namur1.htm

You're answering the implied question and not the actual question. The OP will have to use more wire and preferably a few keyed connectors to connect the sensor and the PLC together. It would be helpful to locate a multiconductor cable that has an identical color collection as the sensor's wires to keep the color coding the same. Since this is just a limit switch, I do not see a need for shielded wire, but if you have it you can use it.

Have you looked into Namur type sensors? I'm pretty sure it's not just a wiring problem! Too tired to check it out tonight.

Yes I have looked into NAMUR limit switches and found that the NAMUR designation makes the switch suitable for a harsh chemical environment, but does not specify any particular electrical condition. (You'll notice my switch has different signal options than your citation.) So a two wire sensor will probably just be a switch contact but it could actually be any electrical signal characteristic known to somebody. While this remains unknown, no further help can be given. Regardless of what it is, one will still connect this directly or indirectly to the PLC using a combination of electrically conductive and non-conductive material known as wire.

Now if the OP wishes more help than this, they will have to produce more information about the proximity limit switch, like a model number and manufacturer.

Good morning, guys.

If you would indulge me, I would treat this as an educational opportunity for the Doorman as well.

I am unfamiliar with this type of sensor, and as I research the varied sites available it appears the digital interface (input in OP) module (mentioned in the OP) needs to be compatible with the sensor (sites reviewed indicate they should be the same brand. Were I the manufacturer, that is what I would tell someone as well.). Is this perhaps the trouble: incompatible components?

Here is one site that seems to have some good info. Am I being steered in the wrong direction?

It is possible that the proximity switch you have is not compatible with the input of the PLC. You may have a NPN proximity switch and your plc inputs may be wired for PNP. Check the Com 1 terminal of the PLC if it has +24vdc going to it your PLC inputs are wired for sinking inputs. If it has 0vdc going to it your PLC inputs are wired for sourcing inputs. You then have to make sure that your Proximity switch is compatible. Banner makes an excellent test box to determine this, (part #DBQ5) if you don't have the proximity switches manufacturers information.

The NUMAR switch operates at a lower voltage than some digital inputs on PLC's. I know it seems old school, but I just used a separate low voltage to power the prox switch and fed it to a low voltage relay to power the digital input. ...FrankenPLC :)

This link may help.

www.tektron.ie/namur1.htm

Good luck

An active converter/adapter is needed.

Namur is designed for I/S operation. It requires 8.3V but is current activated, so you need a converter to run on 24Vdc.

The link to Tektron shows a typical converter. Pepperl & Fuchs and Phoenix Contact have "NAMUR switch amplifiers" that convert the Namur change of state into PNP/NPN active or passive. I'm sure other vendors do as well.

An interposing relay would do it.