Safety light curtain receiver for point-of-operation guarding
The Siemens 3SF7844-6TD11-0SS1 is a Type 4 safety light curtain receiver with 30 mm resolution and a 750 mm protected height, designed for cycle control applications where operator access to a hazard zone must be reliably detected. Sensing range is 0 to 18 m. Detects objects of 30 mm or larger. Communication is via the ASISAFE bus connection, integrating into a SIMATIC FS440I safety system without additional interface modules; the bus carries both safety signals and diagnostic data back to the safety CPU.
For BOM-line commitment, the key fit parameters are the 30 mm resolution (determines what size object the curtain detects), the 750 mm protected height (must cover the full hazard opening), and the ASISAFE bus protocol (must match the existing safety controller).
Integration into a safety circuit
Mount the receiver opposite the emitter across the hazard zone, aligned so the optical axis is unobstructed. The 0 to 18 m range covers most machine cells; for longer spans a different curtain family would be needed. The ASISAFE bus connection replaces point-to-point OSSD wiring — the safety signals and configuration data travel on the same two-wire bus cable back to the FS440I controller, reducing panel wiring and simplifying diagnostics. Type 4 per IEC 61496-1 means the curtain is rated for the highest safety integrity (SIL 3 / PL e) and can be used for point-of-operation guarding where a hand or finger entering the field must stop the machine before contact.