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Digital I/O modules

Siemens digital I/O modules provide the field-level signal interface between automation controllers and connected sensors, actuators, and devices in industrial installations. This collection covers two distinct product families: SIMATIC ET 200AL distributed I/O modules for PROFINET-connected systems and AS-i compact modules for Actuator-Sensor Interface networks, both rated at IP67 for direct machine and field mounting.
We supply Siemens digital I/O modules for customers maintaining existing SIMATIC and AS-i installations and sourcing replacement signal interface hardware across the ET 200AL and 3RK series.

Where Siemens Digital I/O Modules Are Used

Digital I/O modules sit at the edge of every automated system, and a failed or unavailable module affects the controller's ability to read inputs or drive outputs for the entire connected segment. In distributed architectures where modules are mounted close to the machine or field device, IP67-rated housings are required to withstand the wash-down, dust, and moisture conditions of the installation environment. Sourcing a like-for-like replacement with the correct channel count, connector type, and protocol support is essential to restoring normal operation without reconfiguring the upstream controller.

Facilities and systems that depend on Siemens digital I/O modules include:

Automotive manufacturing lines using PROFINET-connected distributed I/O
Food and beverage processing equipment with IP67-rated field mounting requirements
Assembly and material handling systems running AS-i sensor/actuator networks
Packaging machinery using distributed I/O at the machine level.
Industrial conveyor systems with field-mounted input and output modules
Machine tool and robotics installations requiring compact, high-density I/O

When an installed module needs replacing, matching the channel configuration, output current rating, and connector type to the original ensures the replacement drops in without control system changes.

Siemens Digital I/O Modules Products

This collection covers two confirmed product families: SIMATIC ET 200AL modules for PROFINET-based distributed I/O and AS-i compact modules for field-level sensor/actuator networks. All product families and part numbers below are confirmed on the live PLC Direct collection page.

Product Families

SIMATIC ET 200AL — Distributed Digital I/O Modules: The ET 200AL is a distributed I/O system for PROFINET networks, designed for direct machine mounting at IP67 protection. Modules in this collection cover digital input, digital output, and combined digital I/O configurations with M8 and M12 connector interfaces. Confirmed variants include:
1. DI 16x 24 V DC, 8x M12, IP67 (6ES7141-5AH00-0BA0)
2. DI 8x 24 V DC, 8x M8, IP67 (6ES7141-5BF00-0BA0)
3. DQ 8x 24 V DC/2 A, 8x M12, IP67 (6ES7142-5AF00-0BA0)
4. DIQ 16x 24 V DC/0.5 A, 8x M12, IP67 (6ES7143-5AH00-0BA0)
5. DIQ 4 DI + DQ 4x 24 V DC/0.5 A, 8x M8, IP67 (6ES7143-5BF00-0BA0)
AS-i Compact Modules — K20, K45, and K60 Form Factors: AS-i (Actuator-Sensor Interface) compact modules provide digital I/O connectivity for AS-i network-based field installations at IP67. The collection covers three housing form factors, K20, K45, and K60, with varying channel counts and connector configurations across the 3RK1 and 3RK2 series.
K20 modules: Compact form factor with M8 connectors, covering 2 DI/2 DQ and 4 DI/4 DQ configurations at 1 A output ratings. Confirmed part numbers: 3RK2400-1BQ30-0AA3, 3RK2400-1CT30-0AA3, 3RK1400-1CT30-0AA3.
K45 modules: Mid-size form factor with M8 and M12 connectors, covering 4 DI, 4 DQ, 3 DQ, and 4x (1 DI/1 DQ) configurations. Output ratings of 1 A per channel, up to 3 A aggregate. Confirmed part numbers: 3RK1200-0CT20-0AA3, 3RK1100-1CQ20-0AA3, 3RK2100-1EQ20-0AA3, 3RK2200-0DQ20-0AA3, 3RK2400-1GQ20-1AA3.
K60 modules: Standard form factor with M12 connectors and Y-II assignment, covering 4 DQ, 8 DI, 4 DI/4 DQ, and 4 DI/3 DQ configurations at output ratings of 1–2 A per channel. Mounting plate (3RK1901-0CA00) ordered separately. Confirmed part numbers: 3RK1100-1CQ00-0AA3, 3RK1400-1CQ00-0AA3, 3RK1400-1DQ00-0AA3, 3RK1400-1DQ01-0AA3, 3RK1400-1DQ03-0AA3, 3RK2100-1CQ00-0AA3, 3RK2200-0DQ00-0AA3, 3RK2200-1DQ00-1AA3, 3RK2400-1DQ00-0AA3, 3RK2400-1DQ00-1AA3, 3RK2400-1FQ03-0AA3.

Available at PLC Direct

SIMATIC ET 200AL DI modules, 8- and 16-channel, 24 V DC, M8 and M12, IP67
SIMATIC ET 200AL DQ modules, 8-channel, 24 V DC/2 A, M12, IP67
SIMATIC ET 200AL DIQ combined modules, M8 and M12 connector variants, IP67
AS-i K20 compact modules, 2 DI/2 DQ and 4 DI/4 DQ, M8, IP67
AS-i K45 compact modules, DI, DQ, and mixed configurations, M8 and M12, IP67
AS-i K60 compact modules, DI-only, DQ-only, and mixed 4 DI/4 DQ configurations, M12, IP67
3RK1 and 3RK2 series AS-i modules across standard and A/B slave variants

What to Know Before You Buy Siemens Digital I/O Modules

Replacing a digital I/O module requires matching several parameters to the installed unit. Channel count, output current rating, connector type, and protocol are all non-negotiable; a module with the right channel count but the wrong connector or network type won't restore operation.

Hardware condition options: We supply Siemens digital I/O modules as surplus sealed, refurbished, and used hardware. For field-mounted modules in harsh environments, confirming the condition grade is worthwhile; surplus sealed units are factory-sealed stock, while refurbished units have been tested and verified for functionality.

Compatibility considerations: ET 200AL modules connect to PROFINET networks and are not compatible with AS-i installations, and vice versa. Within the AS-i range, K20, K45, and K60 modules use different mounting plates and connector configurations. The mounting plate for K60 modules (3RK1901-0CA00) must be ordered separately and is not included with the module. For K45 modules, the required mounting plate is either 3RK1901-2EA00 or 3RK1901-2DA00. Always confirm the mounting plate requirement before finalising an order.

Part identification: For ET 200AL modules, the part number prefix 6ES7141 indicates digital input, 6ES7142 indicates digital output, and 6ES7143 indicates combined DIQ modules. For AS-i compact modules, the form factor (K20, K45, K60) is specified in the product description, and the channel configuration (DI, DQ, or mixed) is specified in the module description. Confirm both before ordering to ensure the replacement matches the installed unit.

Warranty: All Siemens digital I/O modules purchased from PLC Direct include a standard 1-year warranty covering defects and functionality, applicable to surplus sealed, refurbished, and used products.

Frequently Asked Questions

SIMATIC ET 200AL modules are distributed I/O devices that connect to PROFINET networks and are configured through a SIMATIC controller. AS-i compact modules connect to AS-i (Actuator-Sensor Interface) networks, which operate on a separate two-wire bus designed specifically for field-level sensor and actuator connectivity. The two systems are not interchangeable; the correct module type depends entirely on the installed system's network infrastructure.

ET 200AL modules use M8 or M12 circular connectors, depending on the specific module variant: M8 on the -5BF variants and M12 on the -5AH variants. AS-i K20 modules use M8 connectors, while K45 and K60 modules use M12 connectors. The connector type must match the installed field wiring to ensure a direct replacement.

We carry SIMATIC ET 200AL digital input, output, and combined DIQ modules at IP67 across M8 and M12 connector variants, plus AS-i compact modules in K20, K45, and K60 form factors covering DI-only, DQ-only, and mixed channel configurations across the 3RK1 and 3RK2 series. Contact us with your part number to check current availability.

The mounting plate for AS-i K60 compact modules (3RK1901-0CA00) must be ordered separately; it is not included with the module. For K45 modules, the required mounting plate is either 3RK1901-2EA00 or 3RK1901-2DA00, depending on the installation. If you are replacing an installed module where the mounting plate is already in place, the module body alone is sufficient. Contact us if you need to source the mounting plate alongside the module.

As an independent supplier, we source Siemens AS-i compact modules outside standard OEM channels, giving us access to stock of older 3RK1 and 3RK2 series variants that may be difficult to find through regular distribution. Contact us with your part number, and we will check current inventory and sourcing options.