Adapting PNP Sensor for NPN PLC Configuration

[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 …