Siemens 6ES7221-1BH50-0XB0 SIMATIC S7-1200 SM 1221 16DI 24V DC PLC I/O Module

The Siemens 6ES7221-1BH50-0XB0 SM 1221 is a digital input module for the SIMATIC S7-1200 that adds 16 DC digital inputs rated 24 V DC, wired in groups of four. Input delay is parameterizable from 0.2 ms to 12.8 ms per group. The module draws its logic power from the backplane bus, drawing 90 mA max, and carries IP20 protection.

Technical Specifications

Certifications & Standards

• CE
• UL
• cULus
• RCM
• KC

Selection Notes

16 DI in groups of four covers larger field-input counts than the CPU's onboard channels without adding a second module - each group of four shares one input-delay setting, so wire similar sensor types (dry contacts vs. proximity switches) together within a group to keep the delay setting appropriate for all of them. Sink/source wiring on every channel means the module accepts both PNP and NPN field devices without rewiring. Choose this 16 DI module over an 8 DI variant when expansion-slot count is limited and the full 16 channels are needed in one card.

Applications

Expands digital input capacity on SIMATIC S7-1200 stations for pushbuttons, limit switches, proximity sensors, and other 24 V DC dry-contact or transistor-output field devices where onboard CPU inputs are insufficient.