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Camera to PLC Communication Fails

This page explains how to troubleshoot when the OV20i camera fails to communicate with a PLC. You can integrate via:

  1. EtherNet/IP (network-based communication using EDS files)
  2. Hardwired Digital I/O (DO/DI signals)

Option 1: EtherNet/IP (Network Integration)​

How It Works​

  • The OV20i functions as an EtherNet/IP adapter
  • Your PLC acts as the scanner/master, reading/writing I/O assemblies cyclically
  • Use EDS file to configure the camera in your PLC's engineering environment

Setup Steps​

  1. Assign static IP to OV20i and ensure it's on the same subnet as the PLC
  2. Enable EtherNet/IP Mode in the camera UI under
  3. Download and import the OV20i_EDS file into your PLC tool
  4. Add the camera as a device, configure Input/Output assembly instances, and set the RPI (Requested Packet Interval)
  5. Map assembly I/O tags to PLC variables and verify real-time data exchange

What You Get​

  • Input Assembly includes status bits (Online, Trigger Ack, Result Available), Recipe ID, ROI results, etc.
  • Output Assembly allows PLC to send commands like hardware trigger or recipe switch

Troubleshooting EtherNet/IP​

  • Check PLC I/O connection status in your PLC tool
  • Ping the camera's IP to ensure network reachability
  • Ensure RPI is set within supported cycle time (20–10,000 ms)
  • Confirm Inspection Completed and ROI data bits are toggling correctly in I/O

Option 2: Digital I/O (Physical Wiring)​

warning

The camera’s digital outputs (DO0 / DO1) are NPN open‑collector, sinking only. They pull to GND when active, and cannot source +24 V. For proper operation, your PLC input or load must include a pull-up or supply to +24 V.

  • Use Digital Output (DO1) to signal results
  • Use Trigger Input for PLC-initiated capture
  • DO/DI lines are NPN sinking (pull-down to GND)

Wiring Overview​

  1. Connect DO GND to PLC GND
  2. Wire DO1, Trigger IN, or other I/O to corresponding PLC input/output
  3. PLC is configured for active-low detection since DO1 sinks to GND

When to Use a Relay​

A relay is required when:

  • PLC expects PNP/sourcing signals
  • Load exceeds 100 mA (max DO current)
  • Isolation is needed between systems

Relay wiring example:

nginx
CopyEdit
DO1 ──⟶ Relay Coil ──+24 V
│
DIO GND ──────────┘

  • Relay's contacts then deliver a clean signal to PLC without drawing current from DO1

Troubleshooting Digital I/O​

  • Measure DO1 voltage toggling from 24 V → 0 V when active
  • Ensure DIO GND shared with PLC
  • Verify PLC input is configured for NPN/active-low logic

Final Checklist​

CheckpointEtherNet/IPDigital I/O
OV20i on same subnet as PLC✅n/a
Static IP configured✅n/a
EDS file imported✅n/a
EtherNet/IP I/O assembly mapped✅n/a
DIO GND wired to PLC GNDOptional✅
DO1 wired to PLC input or relayOptional✅
Relay used when required for sourcing/voltageOptional✅
PLC reads valid inspection result✅✅

🔗 See Also​