5 mm slot, NPN Light-ON — panel-fit sensor for flag detection
The Omron EE-SX871A is a through-beam photomicrosensor with a 5 mm sensing slot, designed for object presence, edge counting, and position verification in industrial control panels and automation equipment. Its NPN open-collector output, configured Light-ON, sinks up to 35 mA when the beam is uninterrupted — a direct interface to PLC digital inputs or relay coils without an external amplifier. The 5 V supply rail is fixed, so the panel's sensor power bus must already provide 5 V, or a dedicated regulator is needed.
Mounting and environment — cabinet duty, not outdoor
Chassis mount with M3 screws; the housing accepts standard M3 hardware through its slots. Verify the bracket hole pattern and screw length — over-torquing or bottoming out in the plastic can crack the housing. Storage temperature exceeds the operating range, but the sensor should not be run outside the -25°C to 55°C window.
Output type and load budget
The NPN open-collector Light-ON output means the transistor turns on (sinks current) when the beam is made. The maximum switching current is 35 mA — enough for a PLC input, small relay, or LED indicator, but not for a contactor coil or solenoid directly. A pull-up resistor to the load's supply is required if the receiving logic expects a voltage-high signal. The Dark-ON variant (EE-SPX305-W2A) is the complementary logic choice for the same 5 mm slot.