The Siemens 6ES7221-1BH32-0XB0 is a SIMATIC S7-1200 SM 1221 digital input module that provides 16 digital inputs for 24 V DC signals, allowing you to easily expand the on-board I/O of S7‑1200 CPUs in compact control panels. Each channel is designed as a sink/source (IEC Type 1 sink) input, so the module can flexibly interface with a wide range of field devices such as sensors, switches, and pushbuttons in modern machine and process automation systems.
The module operates at a rated voltage of 24 V DC with an input current of around 4 mA per channel, and permits a voltage range of approximately 20.4…28.8 V DC, with continuous permissible voltage up to 30 V DC and surge up to about 35 V DC for short durations. It offers typical switching thresholds of about ≥15 V for logic “1” and ≤5 V for logic “0”, as well as selectable input filter times (for example 0.2 to 12.8 ms in groups) to balance noise immunity and response speed. Internally, the module is isolated between field side and logic at approximately 707 V DC (type test), arranged in four isolation groups, improving robustness in industrial environments.
With compact dimensions of 45 × 100 × 75 mm and a weight of about 210 g, the 6ES7221‑1BH32‑0XB0 mounts directly on 35 mm DIN rail alongside the S7‑1200 CPU, using screw terminal connections for reliable wiring. Power dissipation is around 2.5 W, with current consumption of about 130 mA from the S7‑1200 module bus, and the number of simultaneously active inputs is the full 16 channels. The module is rated IP20 for installation in control cabinets and supports typical industrial ambient conditions, roughly −20 to +60 °C and up to about 95% non‑condensing humidity, making it well-suited to small machines, building automation, and OEM control panels.
