Keyence GL-R Light Curtain — Lockout & Error Codes

Keyence · intermediate · 20 min

A Keyence GL-R safety light curtain in lockout shows a code on its 7-segment display that points straight at the cause. Learn to read the indicator colors, look up the code, and work through the common causes — ambient light, sync wiring, mutual interference and OSSD faults.

ℹ️ The GL-R's 7-segment display shows an error code when it detects a fault — that's the whole point of the display, to cut diagnosis time. Read the code and the indicator colour (clear / interrupted / lockout) first; don't just power-cycle blindly.

Read the indicators before anything else

A Keyence GL-R safety light curtain tells you its state through its indicators, and this is always the first thing to check:

• The status indicators change colour to show whether the beams are clear, interrupted (something is in the field), or in a lockout condition.
• When the curtain detects an error, the 7-segment display shows a code identifying the cause — Keyence designed this specifically so you can take corrective action quickly instead of guessing.

So: note the indicator colour, then read the 7-segment code and look it up in the GL-R error-code table in the instruction manual.

A lockout is protective — find the cause

A lockout (the ESPE has put its OSSD outputs to the OFF/safe state and latched) is the light curtain refusing to allow the machine to run because something isn't right. Work through the documented common causes:

• Ambient light / interference on the receiver. Strong ambient or reflected light can disturb the receiver — shield the receiver from ambient light and check for reflective surfaces in the field.
• Mutual interference between adjacent curtains — two systems seeing each other's light. Re-orient or separate them, or set the interference-prevention configuration.
• Sync wiring. Check the wiring of the synchronization wire between emitter and receiver.
• Sub-unit installation direction. Verify the direction of the sub-unit installation — a curtain installed the wrong way round won't sync.
• Setting switch / configuration. Check the setting-switch configuration, and if it's wrong, upload the configuration again with the Keyence Safety Device Configurator.
• OSSD wiring fault. A short or overcurrent on the OSSD outputs will fault the device — inspect the output wiring.

Step-by-step

1. Read the indicator colour — clear, interrupted, or lockout.
2. Read the 7-segment error code and look it up in the GL-R manual's error-code table.
3. Clear a simple beam interruption — remove the object from the sensing field; the curtain returns to the clear state.
4. For a lockout, work the cause list: ambient light/reflections, mutual interference, sync-wire wiring, sub-unit direction, setting-switch/config, and OSSD wiring.
5. Reset — with the cause removed, reset the light curtain (a power-off/on will clear it once the fault condition is gone).
6. Re-validate the protective function (alignment and response) after any wiring or configuration change.

Alignment matters

Many "random" lockouts and unstable states are really poor alignment — the emitter and receiver not squared to each other, so beams drop in and out. Use the GL-R's alignment indicators to peak the signal before you conclude the unit is faulty.

Never do this

Never bypass, blank, or muting-defeat a light curtain to clear a lockout — the lockout is the safety function working. Never wire around the OSSD outputs or force the machine to run with the curtain faulted. Find and fix the real cause, then reset, then re-validate the safety function per your risk assessment.