An Easy Way to Remember PNP and NPN Sensor Wiring Here’s a simple way remember how to wire up a 3-wire DC PNP or NPN sensor: PNP = Switched Positive NPN = Switched Negative “Switched” refers to which side of the controlled load (relay, small indicator, PLC input) is being switched electrically. Either the load is connected to Negative and the Positive is switched (PNP), Continue reading "An Easy Way to Remember PNP and NPN Sensor Here’s a Quick Way to Wire NPN and PNP devices | Acc Jan 10, 2015Here’s a Quick Way to Wire NPN and PNP devices. I get asked often on how to wire NPN and PNP devices to the programmable logic controller. This can be confusing at first when looking at the wiring diagrams. I have managed to destroy a few sensors in the process. so let’s get started and I will share my experiences.