Can you please explain PLC PNP and NPN Wiring?

Can you please explain what’s going on here in the PLC wiring diagram below?

In PLCs, sinking and sourcing refer to the way electrical current flows between devices (like sensors or actuators) and the PLC inputs and outputs:

  1. Sinking:
  • The device (sensor/actuator) provides a path to ground for the current.
  • The current flows into the PLC input.
  • Commonly used in NPN transistor configurations.
  1. Sourcing:
  • The device supplies voltage to the PLC input.
  • The current flows out of the PLC output to the device.
  • Typically associated with PNP transistor configurations.

Key Points:

  • Sinking (NPN): Current flows from the device to ground (negative).
  • Sourcing (PNP): Current flows from the positive supply to the device.

Choosing between sinking and sourcing depends on the PLC and field device compatibility and wiring preferences.

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