How to Connect Inductive Proximity Sensors to PLC

Inductive proximity sensors are essential in modern automation and monitoring systems. These non-contact sensors detect metal objects using electromagnetic induction, offering advantages like high reliability, fast response, and durability. In this article, we will explore how to connect Bedook inductive proximity sensors to PLCs, ensuring precise and efficient control in various applications.

If you are interested, you can also take a look at this article (https://www.bedooksensors.com/npn-and-pnp-proximity-sensor/), which is about how to wire NPN and PNP types

Introduction to Inductive Proximity Sensors

Inductive proximity sensors are non-contact sensors based on the principle of electromagnetic induction.

They detect the presence of metal objects. When a metal object approaches the sensor, the electromagnetic field generated by the sensor coil changes, triggering the sensor’s output.

These sensors offer advantages such as simple structure, fast response, and easy implementation of non-contact measurement.

Applications of Inductive Proximity Sensors

due to their non-contact detection, high reliability, and long lifespan, Inductive proximity sensors, can achieve more precise and efficient control when combined with various control systems.

They are widely used in both industrial automation and daily life:

Automation Control: Used for detecting object positions to enable precise operation of automated equipment.

Safety Monitoring: Monitors the status of doors to ensure operational safety.

Counting Applications: Used for automatic counting of product passes.

Level Detection: Works with float or magnetic float to achieve automatic detection and control of liquid levels.

Metal Detection: Detects the presence of metal objects, such as in scrap recycling or metal detectors.

Categories of Inductive Proximity Sensors

Inductive proximity sensors from Bedook are categorized based on their internal structure into NPN and PNP types; based on output type into NO, NC, and NO+NC dual-output types; and based on power supply form into DC2-wire, DC3-wire, DC4-wire, AC2-wire, and AC/DC2-wire types.

NPN Type: Outputs a low voltage (close to 0V) when a metal object is detected.

PNP Type: Outputs a high voltage (close to the power supply voltage) when a metal object is detected.

NO Type: Normally open, the output is open when no object is detected.

NC Type: Normally closed, the output is closed when no object is detected.

You can see here how to connect DC3-wire proximity sensors with relays/PLC.

Connect Inductive Proximity Sensors to PLC

Taking the Bedook DC3-wire inductive proximity sensor as an example, connecting it to a PLC involves the following steps:

• Determine Sensor Type: First, identify whether the sensor is NPN or PNP type, and whether it is NO or NC type.

Note: Choose the inductive proximity sensor based on whether the PLC is NPN or PNP to avoid damage to the sensor due to incorrect selection or wiring.

• Connect Power: Determine the required power supply voltage and connect the sensor’s power wires to the appropriate power source.
• Connect Signal Wires: Connect the sensor’s signal wires to the PLC’s INPUT port.
  • For NPN type, connect the signal wires to the PLC’s INPUT port, and the PLC’s COM port to the positive terminal.
  • For PNP type, connect the signal wires to the PLC’s INPUT port, and the PLC’s COM port to the negative terminal.
• Configure PLC: Configure the corresponding input port in the PLC’s program to correctly read the sensor’s status.

 

By following these steps, the inductive proximity sensor can be effectively connected to the PLC, enabling automation control and monitoring functions.

In practical applications, adjustments and configurations should be made according to the specific PLC model and relay specifications.

 

Inductive proximity sensors can also be directly connected to and drive intermediate relays.

It is necessary to select an appropriate intermediate relay whose coil current and voltage requirements match the sensor’s output.

The relay’s coil should be connected to the sensor’s output terminal.