PLC Sinking and Sourcing Module Input Output Connection Diagram

PLC Digital Inputs and Outputs are works in two modes - Sinking Mode and Sourcing Mode. The Sinking Module is also known as NPN Module whereas Sourcing Module is also known as PNP Module. For analog input or analog output, these modes are not applied because, for an analog signal, currents can flow in both directions. But according to the connection technique, NPN and PNP names are used for analog input and analog outputs. The concept of Sinking and Sourcing depends upon the type of PLC input module and how it is connected to the PLC and the whether current flows In or Out from the PLC.

PLC Input Output Connection Diagram

Here, you can see the Input Output Connection Diagram of PLC for Sinking and Sourcing Mode.

Connection Procedure

PLC Sinking type Input Module Connection

In the Sinking Mode of PLC the current flow into the PLC from the external circuit or load. In the above connection diagram, PLC 1 has a sinking input module. You can see the negative terminal from the power supply is connected to the common input terminal of the PLC. And all the input devices(here push button switches) are connected to the positive terminal of the power supply. So when those input devices are activated(here switch is pressed) current will flow from those input devices to the PLC. So, here as the PLC sinks the flow of current from the input devices that is it is known as Sinking Mode.

**It is easy to remember that in the Sinking Mode the Negative terminal of the power supply is connected to the PLC common input**

PLC Sinking type Output Module Connection

In the above wiring diagram, PLC 2 has the Sinking type output connection. It is also known as an NPN output connection. You can see the negative terminal from the power source is connected to the common output terminal of the PLC and all the loads are connected to the positive terminal of the power source. So when the PLC activates the loads the current will flow from the loads to the PLC. So here also the PLC sinks the current.

**Here also I will say in the Sinking Mode the Negative terminal of the power supply is connected to the PLC**

PLC Sourcing type Input Module Connection

In the Sourcing Mode of PLC, the current flows out from the PLC to the external circuit or load. In the above connection diagram, PLC 2 has a Sourcing input module. You can see the positive terminal from the power supply is connected to the common input terminal of the PLC. And all the input devices(here push button switches) are connected to the negative terminal of the power supply. So when those input devices are activated(here switch is pressed) current will flow out from the PLC to those input devices. So, here as the PLC acts as a source of current for those input devices it is known as Sourcing Mode.

**It is easy to remember that in the Sourcing Mode, the Positive terminal of the power supply is connected to the PLC common input**

PLC Sourcing type Output Module Connection

In the above wiring diagram, PLC 1 has the Sourcing type output connection. It is also known as a PNP output connection. You can see the positive terminal from the power source is connected to the common output terminal of the PLC and all the loads are connected to the negative terminal of the power source. So when the PLC activates the loads the current will flow out from the PLC to the loads. So here also the PLC acts as a source of current for the loads or output devices.

**Here also I will say in the Sourcing Mode, the Positive terminal of the power supply is connected to the PLC**

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