Many engineers often ask manufacturers whether NPN or PNP proximity switches can be connected to the digital input points (DI points) of a PLC, or how to connect two-wire/three-wire/four-wire proximity switches to the PLC's DI points. This week, we'll briefly share some insights on these two questions.
First, let's talk about proximity switches, which are components that have the ability to "sense" objects that approach them. These types of sensors do not need to contact the object being detected. When an object moves toward the sensor and gets close to a certain distance, the sensor can "sense" it. This distance is usually called the "detection distance". A switch made using the sensor's sensitivity to approaching objects is a proximity switch. Proximity switches are divided into two-wire, three-wire, and four-wire systems.
1. Two-wire proximity switch
(1) There are two lines
(2) It needs to be connected in series in the circuit.
(3) It is equivalent to a normal switch, with positive and negative terminals.
2. Three-wire proximity switch
(1) There are three lines
(2) Requires a separate power supply to work
(3) One output, two output forms: NPN/PNP
3. Four-wire proximity switch
(1) There are four lines
(2) Requires a separate power supply to work
(3) Two outputs, NC/NO
(4) Output format: NPN/PNP
We have briefly introduced three types of proximity switches above. So how do you connect proximity switches to PLC digital inputs in practical applications? Below, we will use the EVE UN 214-1BD23-0XB8 CPU as an example to illustrate.
1. Connect the two-wire proximity switch to UN 214-1BD23-0XB8 DI.
2. Connection of three-wire NPN proximity switch to UN 214-1BD23-0XB8 DI
3. Connection of three-wire PNP type proximity switch with UN 214-1BD23-0XB8 DI
This week's reflections:
We've shared how to connect two-wire and three-wire proximity switches to PLC digital input points. Now, what is the wiring diagram for a four-wire proximity switch (one NC, NPN type; one NO, PNP type) to the UN 214-1BD23-0XB8? You can reply with your answer through our official WeChat account, and we'll share it with you next week!
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