Siemens TXM1.8U Controller Module

Siemens TXM1.8U Controller / I/O Module

 

 

The Siemens TXM1.8U is an 8-channel universal I/O module used in Siemens Desigo PX / TX-I/O building automation systems. It is designed for building control applications (HVAC, room automation, energy management) rather than industrial PLC machine control.

It is often referred to as a “controller module” in listings, but technically it is an I/O expansion module for a main controller.

Key Specifications

• Model: TXM1.8U
• Brand: Siemens
• System: TX-I/O / Desigo PX / Building Automation
• Product Type: Universal I/O Module
• I/O Channels: 8 universal points
• Signal Types (configurable per channel):
  • Digital input (DI)
  • Analog input (AI, 0–10V, sensors)
  • Analog output (AO, 0–10V)
• Communication:
  • TX-I/O bus (connects to Desigo controller)
• Power Supply:
  • 24V DC (typical SELV/PELV system)
• Mounting:
  • DIN rail modular system

What it does (simple explanation)

This module is used to connect field devices to a building automation controller:

Sensors / switches / actuators
↓
TXM1.8U module
↓
Desigo PX controller
↓
HVAC control (fans, valves, dampers, pumps)

So it:

• Reads signals (temperature, switch status)
• Controls outputs (valves, dampers, relays)
• Acts as flexible multi-purpose I/O

Key Features

• 8 fully configurable universal I/O points
• Each channel can be set as:
  • Digital input
  • Analog input (0–10V, sensors)
  • Analog output (0–10V control signal)
• LED status indication per channel
• Modular plug-in design (easy replacement)
• Bus communication to controller (no standalone logic)
• Compact DIN rail installation

System Role

Typical structure:

Sensors → TXM1.8U I/O Module → Desigo Controller → HVAC equipment

So it is:

• ❌ Not a standalone PLC
• ❌ Not a CPU / controller brain
• ✔ A building automation I/O expansion module

Applications

• HVAC systems (heating, ventilation, air conditioning)
• Hotel / commercial building automation
• Room temperature control systems
• Energy management systems
• Fan coil unit control
• Valve and damper control