Photo beam sensors are a mandatory safety feature on most automatic door installations. When they fail, the door becomes unsafe and non-compliant. This guide covers the most common fault patterns and how to diagnose them quickly on site.
Photo beam (also called presence sensors or light curtains) use an infrared beam between a transmitter and receiver. When the beam is broken by a person or object in the doorway, the sensor sends a signal to the door controller to hold the door open or prevent it from closing.
Check both transmitter and receiver units for:
Photo beams must be precisely aligned. Even a few millimetres of misalignment will cause intermittent or complete failure. Most units have an alignment LED that shows solid when aligned correctly. If the LED is flashing or off, adjust the sensor position until it stabilises.
Check the cable run between the sensors and the control panel:
If visual and alignment checks pass, swap the sensor pair with a known-good set. If the problem follows the sensors, replace them. If the problem stays with the door/wiring, the issue is in the cable or control panel.
Photo beams are not always interchangeable between manufacturers. Common types we stock at PDC:
Always verify the sensor output type (NPN, PNP, relay) matches your control panel input requirements before fitting.
If the sensor lens is dirty, cleaning with a soft cloth and isopropyl alcohol may resolve the issue. However, if the sensor has moisture ingress, intermittent operation after cleaning, or physical damage, replace it — don’t risk a safety-critical component failing in service.
Under BS EN 16005, photo beam sensors must be functional on all automatic doors in public access. A door with a failed sensor is non-compliant and should be taken out of automatic operation until repaired. Document any sensor failures in your service report.
PDC stocks photo beams and sensor accessories from Optex, Record, Geze and other manufacturers. Call 01206 591054 for stock availability and same-day dispatch.
