Schneider Electric TM2DMM8DRT Modicon M238 Discrete I/O Module

Configured for discrete signal acquisition and relay output switching in Modicon M238 controller architectures, the Schneider Electric TM2DMM8DRT (TM2DMM8DRT Discrete I/O Module) provides 4 x 24 VDC inputs and 4 relay outputs through one removable screw terminal block.

Hardware Specifications

Parameter	Specification
Model	TM2DMM8DRT
Brand	Schneider Electric
Product Type	Discrete I/O Module
Range	Modicon M238 logic controller
Compatibility	Twido, Advantys OTB
Discrete Inputs	4
Input Voltage	24 VDC
Input Voltage Limits	20.4 to 28.8 VDC
Input Logic	Sink or source
Input Current	7 mA
Input Impedance	3.4 kOhm
Discrete Outputs	4
Output Type	Relay, 1 NO per output
Current per Channel	2 A
Maximum Output Common Current	7 A
Minimum Switching Current	0.1 mA at 0.1 VDC
Contact Resistance	45 mOhm
Input Response Time	4 ms for state 0 and state 1
Output Response Time	<= 10 ms from state 0 to state 1; <= 5 ms from state 1 to state 0
Channel Isolation	None
Input to Internal Logic Isolation	500 V for 1 minute
Output to Internal Logic Isolation	2300 V for 1 minute
Input to Output Isolation	1500 V for 1 minute
Output Group Isolation	1500 V for 1 minute
Mechanical Durability	20,000,000 cycles
Electrical Durability	100,000 cycles under specified AC-15, DC-13 and resistive loads
Local Signalling	1 display block
Electrical Connection	1 removable screw terminal block
Mounting	35 mm symmetrical DIN rail
Power Consumption	20 mA at 24 VDC, state 1, all inputs/outputs; 25 mA at 5 VDC, state 1, all inputs/outputs
Weight	0.095 kg
Dimensions	42.9 W x 90 H x 70 D mm

Schneider Electric Modicon I/O Architecture

The TM2DMM8DRT combines four 24 VDC discrete input channels with four normally open relay output channels. The inputs accept either sink or source logic and have a specified 3.4 kOhm input impedance with 7 mA input current.

Each relay output is rated for up to 2 A per channel, with a 7 A maximum current through the output common. The module provides one common point for the input group and one common point for the output group.

The module uses a removable screw terminal block for field wiring and mounts on a 35 mm symmetrical DIN rail. The specified dimensions are 42.9 mm wide, 90 mm high and 70 mm deep.

The electrical isolation structure separates the input and output sections from internal logic and provides 1500 V isolation between the input and output channels. No isolation is provided between individual channels within the respective groups.

The TM2DMM8DRT was discontinued on September 27, 2024. The supplied Schneider Electric data identifies the Modicon TM3 Expansion I/O module range for M221, M241 and M251 logic controllers as the recommended replacement range. Exact replacement selection should be based on the controller architecture and required I/O configuration.

Frequently Asked Questions

Q: Can the TM2DMM8DRT inputs accept both sinking and sourcing configurations?
A: Yes. The specified discrete input logic supports both sink and source configurations. The input voltage range is 20.4 to 28.8 VDC.

Q: Are the individual input and output channels galvanically isolated from each other?
A: No. The specification states that there is no isolation between channels. Isolation is specified between the input and output groups at 1500 V for 1 minute and between the I/O sections and internal logic at the stated test voltages.

Q: What mounting and wiring arrangement does the module use?
A: The module mounts on a 35 mm symmetrical DIN rail and uses one removable screw terminal block for electrical connection.

Field Installation Guidelines

• Mount the module on a 35 mm symmetrical DIN rail with adequate mechanical clearance for terminal access.
• Verify the 24 VDC input supply remains within the specified 20.4 to 28.8 VDC input range.
• Confirm whether each discrete input circuit uses sinking or sourcing logic before field wiring.
• Keep input signal wiring physically separated from high-current relay output wiring where practical.
• Use the removable screw terminal block according to the terminal assignment documented for the specific module installation.
• Observe the 2 A maximum specified current per relay output and the 7 A maximum for the output common.
• Do not treat individual channels as galvanically isolated because the supplied specification states that channel-to-channel isolation is absent.
• For shielded field cables, terminate shields according to the plant grounding scheme and avoid creating unintended ground loops.
• Verify relay load type and switching current against the specified electrical durability conditions before commissioning.
• Confirm controller compatibility before replacing a discontinued TM2DMM8DRT with a TM3 module, since the documented replacement range is designed for Modicon M221, M241 and M251 controllers.

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