Adapting PNP Sensor for NPN PLC Configuration

[acone]

I’m looking into using the Panasonic HG-C1100L3-P sensor as a much more precise alternative to the Keyence LR-X series. My PLC needs the I/O link capability of this particular HG-C model, but is currently set up to accept NPN signals; this I/O link-compatible HG-C only comes in PNP configuration, so it’s incompatible as things stand.

It’s my understanding that the PLC can be reprogrammed to look for the opposite signal, thus accepting the PNP signal, but that it may be designed for NPN with failsafe conditions in mind. Can anyone recommend any method of converting PNP to NPN, maybe via transistor or similar component integration? Any suggestions are appreciated!

Thanks,
ACone

[APDahlen]

Hello Acone,

Welcome to the DigiKey forum.

This is a common problem with industrial controls. Physically, a single resistor should do the trick.

You may be interested in this piece I wrote for using NPN sensors with a PNP (default PLC) - link below.

I suspect you can reverse the polarity suggested in this diagram. Be sure to test for sensor activation with a voltmeter before connecting the PLC.

Please let us know if you were successful.

Best Wishes,

APDahlen

PLC Connections: Comparing PNP and the Challenging NPN Type Sensors

Return to the Industrial Control and Automation Index This post presents the “how to” and the “why” for connecting type PNP and NPN industrial sensors to a typical Programmable Logic Controller (PLC). We will concentrate on PLCs with 24 VDC digital inputs. We will also assume that the PLC features digital positive-logic thresholds defined as: voltages less than 5 VDC are considered logic-zero voltages greater than 15 VDC are considered logic-one Finally, we will assume each of the PLC’s I/O …

[shawn_adams]

We do carry some NPN options that may work for your application. Please review the datasheets to see if one will work for you.

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