Type 4 Safety Light Curtain Receiver with PROFIsafe
The Siemens 3SF7844-8BD17-0SS1 is a Type 4 safety light curtain receiver from the SIMATIC FS420i family, with 30 mm resolution and a 1200 mm protective height, covering a range of 0 to 18 m. The 30 mm resolution means it detects fingers or hand-sized objects entering the hazard zone — finger-protection class per IEC 61496-1 — so it suits guarding around assembly stations, robotic cells, and packaging lines where operator access to pinch points must be interrupted. The 1200 mm height covers a typical standing operator's reach zone without stacking multiple units. The receiver communicates over PROFIsafe bus connection, integrating directly into a SIMATIC FS420i safety controller. That means no separate safety relay or interface module for the safety loop — the light curtain's status is read over the PROFIsafe telegram, and the safety PLC handles the logic and stop commands. This reduces panel wiring and simplifies the safety validation documentation.
Integration Notes
The receiver includes blanking capability (0 to 18 m range), which allows fixed or floating blanking zones to pass through objects like workpiece carriers or conveyor belts without tripping the safety output. This is configured via the PROFIsafe parameter assignment in the safety PLC engineering tool — no physical DIP switches or jumper wires. Mount the receiver opposite its matching emitter (same series, same resolution and height) on a rigid surface. The optical axis alignment tolerance is tight — use the built-in alignment aid or a laser tool during commissioning. The PROFIsafe address is set via the bus connector or the safety PLC configuration; verify the F-target address matches the safety program.