Siemens 6ES7 131-1BL11-0XB0 SM321 Digital Input Module for S7-300 PLC

Product Overview

The Siemens 6ES7 131-1BL11-0XB0 is a digital input module from the SIMATIC S7-300 series, designated as SM321. It provides 32 digital input channels with a common potential for each group of 16 inputs. The module is used to connect 24 V DC field devices such as pushbuttons, limit switches, proximity sensors, and encoders to the PLC. It is designed for use with the S7-300 backplane bus and communicates directly with the CPU without requiring additional adapters. The module is ideal for applications requiring a high density of digital inputs in a compact footprint.

Key Features of SM321 DI32x24V DC

The module features 32 inputs organized in two groups of 16, each with a common terminal. Inputs are opto-isolated from the backplane bus. The rated voltage is 24 V DC (20.4-28.8 V), with a input current of 7 mA typical at 24 V. The input delay is adjustable (0.1 to 25 ms) via programming. The module includes a removable front connector (screw or spring type, depending on order) for easy wiring. LED indicators on the front show the status of each channel. The module also has a power supply (L+) and ground (M) connections for the field power.

The SM321 is compatible with all S7-300 CPUs and can be placed in any slot of the rack. It supports hot swapping (with appropriate active backplane). The module is isolated between channels and the backplane (500 V DC). It operates in temperature range 0 to 60°C. The current consumption from backplane is 25 mA (5 V DC), and from field power is 80 mA (24 V DC). Dimensions are 125 mm x 40 mm x 120 mm (HxWxD). The module is certified for CE, UL, and CSA.

Technical Specifications

• Manufacturer: Siemens AG

• Part Number: 6ES7 131-1BL11-0XB0

• Series: SIMATIC S7-300

• Product Type: SM321 Digital Input Module

• Number of Inputs: 32 (24 V DC)

• Input Voltage Range: 20.4-28.8 V DC (rated 24 V)

• Input Current: 7 mA typical at 24 V

• Input Delay (programmable): 0.1 / 0.5 / 3 / 5 / 10 / 25 ms

• Isolation: Opto-isolated, 500 V DC

• Backplane Current: 25 mA (5 V DC)

• Field Power Current: 80 mA (24 V DC)

• Indicators: Green LED per channel (input state)

• Front Connector: 40-pin, screw or spring type (sold separately)

• Operating Temperature: 0 to +60 °C

• Storage Temperature: -40 to +70 °C

• Dimensions (W x H x D): 40 mm x 125 mm x 120 mm

• Certifications: CE, UL, CSA, FM

Functional Description

Each input channel reads the voltage level from a field device. If the voltage is above 15 V, the input is recognized as "1" (true); below 5 V, it is "0". The input delay prevents false triggering from contact bounce. The module transmits the input states to the CPU via the backplane bus during each I/O scan. The module can be programmed to trigger hardware interrupts on rising or falling edges. The removable front connector allows the module to be replaced without rewiring.

Applications

The 6ES7 131-1BL11-0XB0 is used in S7-300 PLC systems for high-density input applications such as packaging machines, assembly lines, and material handling systems. It is a replacement module for existing S7-300 digital input racks.