Cause : Encoder communication error comes when no communication between the encoder and driver, the detective function for broken en- coder wires is activated.

"alarm 21" in panasonic servo drive indicate " Encoder communication" error. This means an issue with the communication between the servo drive and the encoder. This error suggests that the drive is either not receiving a proper signal from the encoder or there is a problem in the communication interface.

Troubleshooting Steps:

1. Check Encoder Connections:

• Inspect the wiring and connectors between the encoder and the servo drive. Ensure all connections are secure, correctly wired, and free of damage.
• Look for loose, bent, or corroded pins in the connectors that could disrupt communication.

2. Inspect the Encoder:

• Check the physical condition of the encoder for any signs of damage or wear.
• Ensure that the encoder is properly mounted and securely fastened to avoid any mechanical issues that might affect signal transmission.

3. Inspect the Communication Cables:

• Verify that the communication cables between the encoder and the servo drive are in good condition and of the appropriate type.
• Replace the cables if there is any visible damage or if you suspect a fault.

4. Check for Interference:

• Ensure that the encoder cables are not routed near sources of electrical noise, such as power lines, high-frequency equipment, or motors, which could interfere with the signals.
• If possible, use shielded cables to reduce the likelihood of interference.

5. Parameter Settings:

• Review the servo drive’s parameters related to encoder communication. Ensure they match the specifications and settings required by the encoder.
• Verify that the communication protocol and baud rate (if applicable) are correctly configured.

6. Test the Encoder:

• If possible, test the encoder on another drive or system to determine if the issue is with the encoder or the servo drive.
• If the encoder works on another system, the issue may lie within the servo drive or its configuration.

7. Inspect the Servo Drive:

• Check the servo drive for any signs of internal issues, such as component failure, that might be affecting encoder communication.
• Perform any available diagnostic tests to ensure the drive’s communication interfaces are functioning correctly.