If you de-energize the main circuit power supply, the Digital Input Option terminals will not operate, even when you connect the external 24 V power supply to terminals PS-AC. When you set N.O. functions to F3-xx [Terminal Dx Function Selection], the input terminals on the digital input option always deactivate. When you set N.C. functions, the input terminals on the digital input option always activate. Connect the external 24 V power supply to the Input signal common terminal (SC).
Figure 1. Wiring Digital Input Option (DI-A3)
- External power supply
- Photocoupler
- Signal processor