Siemens 6ES7321-1BH10-0AA0 Programmable Logic Controller Module

Siemens 6ES7321-1BH10-0AA0 is a SIMATIC S7-300 digital input module (SM 321) that provides 16 isolated DC 24 V inputs for direct connection to field sensors on an S7-300 backplane. This high-speed input module uses a single 20-pole backplane connector and delivers an input delay of 0.05 ms per channel, enabling rapid state changes to be read by the PLC. Each of the 16 channels accepts a DC signal with a nominal 24 V value and recognizes 0 and 1 per IEC 61131: a logic 0 within -30 to +5 V and a logic 1 within 13 to 30 V; typical input current at the 1 level is about 7 mA. The module draws from the backplane's 5 V supply (up to 110 mA) and has a typical power loss of around 3.8 W, with isolation between the input circuitry and the backplane to protect the controller from field-side transients. Commonly used in automation projects to digitize sensor and switch signals for the S7-300 family, this part is catalogued as an Ersatzteil (spare part) for SIMATIC S7-300 and Siemens lists it as obsolete since October 1, 2023.