Siemens SIMATIC S7-1200 SM 1221 Digital Input Module, 16 Inputs, 24 V DC, Screw Terminal

The Siemens SIMATIC S7-1200 SM 1221 digital input module is a high-performance expansion module designed for the SIMATIC S7-1200 controller family. It provides 16 digital inputs for 24 V DC signals, offering reliable and fast signal acquisition for industrial automation applications. The module features screw-type terminals for easy wiring and supports both sink and source input wiring configurations. With configurable input delay times and robust isolation, it ensures precise and interference-free signal processing.

Advantages

• 16 digital inputs for 24 V DC – ideal for connecting sensors, switches, and other binary signal sources.
• Configurable input delay from 0.2 ms to 20 ms – adapts to various signal frequencies and noise environments.
• Sink/source input wiring – flexible connection to different sensor types.
• Electrical isolation between channels and backplane bus – enhances system reliability.
• Compact design for DIN rail mounting – saves space in control cabinets.
• Compatible with all SIMATIC S7-1200 CPUs – easy integration into existing systems.

Suitable for

• Industrial automation and control systems
• Machine building and manufacturing
• Process control and monitoring
• Building automation
• Any application requiring reliable digital signal acquisition

Key specifications

• Module type: Digital input module
• Series: SIMATIC S7-1200
• Number of digital inputs: 16
• Input voltage type: DC
• Rated input voltage: 24 V DC
• Input current per channel (typical): 2.5 mA
• Input wiring type: Sink/Source (P-reading/M-reading)
• Isolation: Yes (between channels and backplane bus)
• Input delay time (configurable): 0.2 ms to 20 ms
• Power loss (typical): 2.5 W
• Current consumption from backplane bus: 40 mA
• Permissible ambient temperature (operation): 0 to 60 °C (horizontal), 0 to 50 °C (vertical)
• Mounting type: DIN rail
• Connection type: Screw terminals
• Degree of protection: IP20
• Max. cable length (shielded): 500 m
• Max. cable length (unshielded): 150 m
• Compatibility: SIMATIC S7-1200 CPUs

Recommendations

For optimal performance, use shielded cables in electrically noisy environments. Ensure proper grounding and follow the installation guidelines in the SIMATIC S7-1200 system manual. This module is a direct replacement for the 6ES7221-1BH50-0XB0 and is fully compatible with existing S7-1200 systems.