Proximity switch NPN and PNP how to recognize and PLC wiring - _

by:Coolmay     2020-06-15

how to distinguish the NPN and PNP

proximity switch wiring are brown is blue negative black signal, this is no doubt that they are the difference between the black line, black line 24 v output for PNP proximity switch, instead of NPN, which is judge proximity switch is the basis of NPN and PNP

how and PLC wiring

connection and PLC, you first look at the rules of the PLC to collect digital quantity, that is to ensure that the current flows or flows into the PLC ( That has implications for the source and drain, don't do too much here, to prevent confusion)

PNP proximity switch connection is current flow into the input point, NPN connection is input points out, that is 1 m ( Siemens 1200, for example) The difference on the connection.

PNP proximity switch for 1 m to 24 v, NPN request 1 m by 0 v

how PNP and NPN sensor and PLC controller wiring

sensor is divided into two wire system and three-wire system two kinds, including three wire system distinguish between NPN and PNP two, in the control system of the two kinds of operation modes are opposite, so you must be aware of when wiring.

how to distinguish the NPN and PNP

except will provide positive identification when buy, there are several methods can be used to distinguish the sensor type, sensor switch both NPN and PNP connection methods are brown is blue negative black signal, the power level is 24 VDC commonly, so the difference is that the output of the black line OUT.

brown Vcc, blue GND, the sensors connected to the switch power supply, 24 v +, 0 v, open power supply black line output voltage is measured with a multimeter voltage profile, if in the absence of work condition + 24 v output, working status output is 0, that is NPN low level, if no work in a state of 0 v, the working status output is 24 v +, that is PNP high level, type of sensors and normally open normally closed, don't start speak.

how to connection with PLC controller

drain and source

PLC controller input and output will distinguish between source and drain, the role of the bidirectional diode is used to implement this function, if the S/S access to 24 v, they need from the X input point signal, and then into the S/S, this way is called leakage model, instead of S/S access 0 v, is called the source type.

sensor and PLC connection mode are brown with 24 v +, the blue line connection 0 v, the black line for the output signal lines, connect the input terminal of PLC, form a loop, achieve the goal of control.

NPN connection mode

different PLC connection mode are different, in the image below is mitsubishi PLC3U connection mode, due to the S/S connected with 24 v, so this is leakage model input mode, current flow from S/S, into the X terminal to form a loop, so must connect low-level NPN sensor can work normally.

PNP connection mode

if S/S with 0 v connection, that is the source type connection mode, so the flow of electric current is flowing from X, into the S/S, the sensor is high level PNP, once the source type leakage type decision, all of the PLC input point must choose the same type of sensors, to avoid damage to the power supply.

if only different kinds of sensors, then you need to use the relay switch to connect again, first used for input point.


a lot of content is also need to pay attention to, in the process of PLC connection of NPN and PNP, just remember that when the S/S access 24 v ( Leakage type) , choose NPN, when S/S access 0 v ( The source type) , choose the PNP.

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