Product Overview

The Schneider Electric TM2DMM24DRF is a 24-point digital mixed I/O expansion module for the Modicon M238 logic controller. It combines 16 digital inputs and 8 electromechanical relay outputs, allowing one module to handle field signal acquisition and external equipment switching.

The input section accepts 24 V DC digital signals from industrial sensors, proximity switches, limit switches, and push buttons. It supports both sink and source wiring configurations, making it compatible with different types of industrial sensor output arrangements.

The output section provides eight normally open relay contacts for switching external electrical loads. Each output supports a maximum switching current of 2 A, while the maximum current per output common line is 7 A. The relay contacts can be used with compatible AC and DC control circuits, making the module suitable for applications involving contactors, solenoid valves, and auxiliary equipment.

The 16 input channels share one common line, while the eight relay outputs are arranged into two groups, each containing four contacts. The designated common connections are electrically separate and must be wired according to the module’s terminal diagram.

Unlike modules equipped with removable screw terminals, the TM2DMM24DRF uses a non-removable spring terminal block. This connection arrangement accommodates direct field wiring and provides a compact interface for the input and output circuits.

One important consideration is the relay output protection. Inductive AC loads require suitable external suppression circuits, and capacitive loads are not supported. Appropriate external fuses must also be installed according to the output current limitations.

For Modicon M238 installations requiring more digital input points and several relay-controlled devices, the TM2DMM24DRF offers a combined I/O solution that reduces the need for separate input and relay output expansion modules.

Technical Specifications

Product Features

• 24-Point Mixed I/O Configuration: Combines 16 digital inputs and eight relay outputs in one expansion module.
• 24 V DC Input Signals: Accepts standard industrial digital signals from compatible sensors and switching devices.
• Sink and Source Input Compatibility: Supports both input wiring configurations for different sensor types.
• Eight Relay Output Channels: Provides eight normally open relay contacts for switching external equipment.
• AC and DC Load Switching: Supports compatible AC and DC circuits within the specified relay contact ratings.
• 2 A Output Capacity: Supports a maximum switching current of 2 A per relay channel.
• Two Output Common Groups: Organizes the eight relay outputs into two groups of four channels.
• Non-Removable Spring Terminals: Provides direct field wiring connections through an integrated spring terminal block.
• Electrical Isolation: Provides isolation between the input circuits, output circuits, and internal logic.
• DIN Rail Installation: Supports installation in industrial control cabinets using a standard 35 mm symmetrical DIN rail.

Product Working Principle

The TM2DMM24DRF combines digital signal acquisition and electromechanical relay switching within one expansion module.

The input section monitors 16 external digital signals. When a connected sensor or switch changes state, the corresponding input circuit detects the voltage condition and transfers the signal status to the Modicon M238 controller.

The module supports both sink and source input wiring. The selected arrangement depends on the output characteristics of the connected sensors and the electrical configuration of the control circuit.

The output section operates through eight normally open relay contacts. When the PLC program activates an output address, the corresponding relay coil is energized, closing the associated contact and completing the external load circuit.

When the controller deactivates the output, the relay coil is de-energized and the contact returns to its normally open state, interrupting the current flow.

For example, in an automated material handling system, the 16 input channels can monitor photoelectric sensors, limit switches, and equipment status signals. The PLC processes these signals and activates the relay outputs to operate contactors, solenoid valves, or auxiliary control circuits.

A simplified signal path is:

Field Sensors → TM2DMM24DRF Digital Inputs → Modicon M238 Controller → TM2DMM24DRF Relay Outputs → External Equipment

The eight relay outputs are divided into two groups of four channels. Each group has its own common connection, allowing the external wiring to be organized according to the electrical requirements of the connected loads.

The relay contacts support compatible resistive and inductive loads, subject to the manufacturer’s power limitations. Capacitive loads are not supported. For inductive AC loads, external protective circuits must be installed to prevent excessive voltage transients and relay contact damage.

Role in Schneider Electric Modicon M238 Control Architecture

Within the Modicon M238 control architecture, the TM2DMM24DRF serves as a mixed digital I/O expansion module. It provides the electrical interface between the PLC controller and external field devices.

The 16 input channels acquire discrete signals from sensors and switches, while the eight relay outputs execute switching commands generated by the controller program.

This arrangement is useful in machines where the number of monitored field signals is greater than the number of relay-controlled devices.

A typical control arrangement is:

Proximity Sensors / Limit Switches → TM2DMM24DRF Inputs → Modicon M238 Controller → TM2DMM24DRF Relay Outputs → Contactors / Solenoid Valves

Industrial Applications

The TM2DMM24DRF is suitable for industrial automation systems requiring a relatively high number of digital input signals combined with relay-based output control.

Installation and Maintenance

1. Verify Controller Compatibility: Confirm that the TM2DMM24DRF is supported by the installed Modicon M238 controller and the selected expansion configuration.
2. Inspect the Module: Check the housing, spring terminal connections, and expansion interface for damage before installation.
3. Prepare the Mounting Position: Select a suitable control cabinet location with sufficient clearance for field wiring and terminal access.
4. Install the Module: Secure the module to a compatible 35 mm symmetrical DIN rail and verify that the expansion connection is correctly engaged.
5. Prepare Input Wiring: Identify the 16 digital input channels and determine whether the connected sensors require sink or source wiring.
6. Connect Digital Inputs: Wire the 24 V DC sensors according to the manufacturer’s terminal diagram and the selected input logic arrangement.
7. Connect Relay Outputs: Connect the eight normally open relay contacts to their respective external control circuits, observing the specified voltage and current limits.
8. Check Common Connections: Verify the input common and both output common groups. The COM0, COM1, and COM2 terminals are not internally connected.
9. Install External Protection: Provide appropriate fuses for the relay circuits, ensuring that the current does not exceed 2 A per output or 7 A per output common line.
10. Configure PLC Addresses: Assign the 16 input addresses and eight output addresses correctly in the controller programming environment.
11. Test I/O Operation: Activate each input and relay output individually during commissioning to verify correct signal acquisition and switching.
12. Perform Routine Inspection: Check spring terminal connections, relay contact condition, external fuses, wiring insulation, and inductive-load suppression devices during scheduled maintenance.

When troubleshooting, inspect the sensor supply, input common, and wiring arrangement if input signals are not detected. For relay output problems, check the external load circuit, common connections, fuse condition, and relay contact operation.

Compatible System Components

Recommended Related Models

Key Advantages

• Combines 16 digital inputs and eight relay outputs.
• Supports 24 V DC sink/source input wiring.
• Provides eight normally open relay contacts.
• Supports compatible AC and DC load switching.
• Maximum 2 A switching current per output.
• Two separate relay output common groups.
• Non-removable spring terminal connections.
• Electrical isolation between designated circuits.
• Suitable for Modicon M238 machine automation applications.

Technical FAQs

1. How many input and output channels does the TM2DMM24DRF provide?

The module provides 24 I/O points in total, consisting of 16 digital inputs and eight relay outputs. The inputs operate with 24 V DC signals, while the outputs use normally open electromechanical relay contacts.

2. Can the TM2DMM24DRF accept both NPN and PNP sensor signals?

The digital input section supports both sink and source wiring configurations. This allows the module to interface with compatible NPN and PNP sensor arrangements, provided the common connections and wiring follow the manufacturer’s diagrams.

3. What is the difference between the TM2DMM24DRF and TM2DMM8DRT?

The TM2DMM24DRF provides 16 digital inputs and eight relay outputs, whereas the TM2DMM8DRT provides four digital inputs and four relay outputs. The TM2DMM24DRF is more suitable for applications requiring a larger number of sensor inputs and additional relay switching channels.

4. Can the relay outputs of the TM2DMM24DRF switch capacitive loads?

No. Capacitive loads are not supported by this module. Inductive AC loads also require appropriate external protective circuits to prevent relay contacts from welding closed due to switching transients.