SV0380 LED Error (Separate Detector) fault in Fanuc drive

SV0380 LED Error (Separate Detector) fault in Fanuc drive

Description

SV0380 is the "LED Error" (Broken Glass/Light source) for an external scale, distinguishing it from SV0365 which is for the motor's built-in encoder. This applies to machines using Heidenhain, Fagor, or Magnescale linear scales for high-precision feedback. The "LED Error" signal is generated by the scale's own internal diagnostics and passed to the Fanuc drive. It indicates the analog signal amplitude from the scale reading head has dropped below the usable threshold.

Cause

Contamination is the primary culprit.

• Dirty Scale: Coolant mist, oil, or fine dust has entered the scale housing and coated the glass ruler. The light cannot penetrate the dirt, so the sensor sees darkness.
• Alignment: The gap between the reading head and the scale body is incorrect due to a loose bracket or machine crash.
• Head Failure: The electronics inside the scale reader head have failed.
• Cable Voltage: The 5V supply to the scale is sagging due to a poor connection.

Solution

1. Clean the Scale: If the scale is air-purged, ensure the air pressure is correct. For glass scales, you may need to disassemble and clean the glass with isopropyl alcohol and a lint-free cloth (Consult scale manufacturer manuals first).
2. Disable Scale (Temporary): To get the machine running, you can disable the external scale in Parameter 1815 (Bit 1 OPT = 0) and revert to motor encoder feedback. Note: Accuracy will decrease.
3. Check Voltage: Ensure the scale is receiving a solid 5V. Voltage drops cause the LED to dim.