4 wire proximity sensor to plc input

jeii · Mar 13, 2011

Hi. I'm trying to teach myself PLC's on a mitsubishi FX2N-16MR.
I have connected a 4 wire PNP proximity sensor as NO to my plc but it is not switching the output.

The indicator on the sensor shows that its working when it detects and i have connected the NO wire to my input and the NC wire to my 0V as per a wiring diagram i have.
My program simply has 1 NC input and 1 NO input connected to a respective output.

I feel that maybe i have not specified something in GX developer?

I am using a CQ35-25NPP-KC1 sensor.

Thankyou for your help, please excuse my naivety.

Tharon · Mar 13, 2011

I would not attach the white wire to 0V. While sometimes the white wire is not used, it can be used as a NC output, or sometimes 0-10V or 4-20ma output, etc. Keep the wire taped off and not terminated on any terminal. What happens if you manually switch voltage to the input (using a jumper wire from 24V)?

ibora · Mar 13, 2011

jeii said:
..NC wire to my 0V as per a wiring diagram i have..

You should disconnect NC wire from 0V. You should keep it free or connect to another input.

jeii · Mar 13, 2011

Thanks for the response guys.
I have tried with the NC wire removed, and manualy switching on the input did not work either.
Also, i can see when in monitor mode that the X1 input is not being activated.

Tharon · Mar 13, 2011

Does the indicator for the PLC input turn on?

jeii · Mar 13, 2011

It doesnt.
Is there anything else i need to do to associate the sensor with the ladder program in Gx Developer?

Tharon · Mar 13, 2011

You shouldn't. And I believe the PLC Input indicator should turn on regardless of whether or not it's addressed in the PLC program.

Do you have access to a voltmeter? Can you make sure that 24V is being supplied to the Input terminal?

Your picture shows the RUN indicator on the PLC is off. Is that just because the PLC is powered down when you took the picture?

BTalbot · Mar 13, 2011

For PNP sensors you need to make sure the S/S terminal is connected to the 0V terminal

Tharon · Mar 13, 2011

BTalbot said:
For PNP sensors you need to make sure the S/S terminal is connected to the 0V terminal

Oh. I was wondering where you connected the 24V common for the inputs.

jeii · Mar 14, 2011

Thanks for your help guys, i should of realised this. Hopefully i will have a more complex problem next time..

4 wire proximity sensor to plc input

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