Product Overview

The Honeywell 2MLQ-TR4A is a 32-point transistor output module for the MasterLogic-200 PLC system. It uses a sinking (NPN) output configuration to switch DC loads connected to the controller, making it suitable for applications involving solenoid valves, indicator lamps, relay coils, and other low-current control devices.

Unlike relay output modules, which use mechanical contacts, the 2MLQ-TR4A uses semiconductor switching. This allows it to handle frequent switching operations without mechanical contact wear. Its relatively short response time is useful in automated machinery where output commands need to follow PLC logic with minimal delay.

Each output point supports a maximum load current of 0.1 A, while each common terminal supports a maximum combined current of 2 A. The module provides 32 output points arranged around a common connection, allowing multiple field devices to be controlled from one PLC module position.

A typical application would be a packaging machine with several pneumatic valves, machine-status indicators, and auxiliary control circuits. The PLC can use the 2MLQ-TR4A to switch these devices according to sensor feedback and programmed machine sequences.

The sinking output arrangement is an important selection consideration. Connected loads must be wired with the appropriate positive supply and output-side connections. A source-type module such as the 2MLQ-TR4B has a different electrical configuration and should not be treated as a direct substitute.

Technical Specifications

Product Features

1. 32-Point Transistor Output

The module provides 32 independent digital output points for controlling external DC devices. This channel density is useful in machinery with numerous small actuators, indicator circuits, and auxiliary control signals.

2. Sinking Output Configuration

The 2MLQ-TR4A uses a sinking transistor output arrangement. When an output switches ON, the corresponding load circuit is connected toward the common return path. The external load wiring must follow the sinking-output configuration.

3. DC 12/24 V Load Compatibility

The module supports rated load voltages of DC 12 V and DC 24 V, with an allowable load voltage range of DC 10.2–26.4 V. This makes it suitable for common industrial DC control circuits.

4. Photo Coupler Isolation

Photo coupler isolation separates the output signal circuitry from the internal control electronics. This provides electrical isolation between the PLC-side control circuitry and the external output circuits.

5. Fast Switching Response

Both OFF-to-ON and ON-to-OFF response times are specified at 1 ms or less. This is useful for repetitive machine sequences and applications requiring relatively rapid digital output updates.

6. Individual and Common Current Limits

Each output point supports up to 0.1 A, while the common connection supports a maximum of 2 A. Both limits must be considered when assigning loads, especially when multiple outputs operate simultaneously.

7. Integrated Surge Absorption

A Zener diode surge absorber helps suppress voltage transients associated with switching inductive loads. External load protection should still be selected according to the connected device and its electrical characteristics.

8. LED Output Indication

The module provides an output ON LED indication. Maintenance personnel can use the indicator to check switching activity during commissioning and troubleshooting.

9. 40-Pin External Connection

The module uses a 40-pin connector for external wiring. An appropriate connector cable or interface assembly is required to connect the output points to the field wiring arrangement.

Working Principle

The 2MLQ-TR4A receives output commands from the MasterLogic-200 CPU and converts them into transistor switching signals for external DC loads.

Its sinking output arrangement means that the module switches the load circuit toward the common return when the corresponding output point is activated. The external load is typically connected between the positive DC supply and the module’s output terminal.

When the PLC program activates an output, the corresponding transistor conducts and completes the load circuit. When the output command is removed, the transistor switches OFF and interrupts the current path.

The module uses photo coupler isolation between the internal control circuitry and output circuitry. This separates the PLC control signals from the external load-side electrical circuit.

Typical Output Switching Sequence:

1. The PLC program evaluates sensor signals and operating conditions.
2. The CPU determines which output point needs to be activated.
3. The output command is transferred to the 2MLQ-TR4A.
4. The corresponding transistor switching circuit turns ON.
5. Current flows from the external positive DC supply through the connected load and output circuit.
6. When the PLC removes the command, the transistor switches OFF.
7. The connected load returns to its inactive state.

Example: Pneumatic Valve Control

In an automated assembly machine, a PLC may control several pneumatic solenoid valves through the 2MLQ-TR4A. When a sensor confirms that a workpiece is correctly positioned, the PLC activates the assigned output. The corresponding transistor switches the solenoid circuit, energizing the valve coil and initiating the pneumatic movement.

After the programmed operation is completed, the CPU removes the output command and the transistor switches OFF. This sequence can be repeated across multiple stations using the module’s available output points.

Role in MasterLogic-200 Control Architecture

Within the MasterLogic-200 PLC system, the 2MLQ-TR4A functions as the digital output interface between the controller and external DC field devices.

The CPU executes the application program and determines the required output states. The 2MLQ-TR4A then performs the physical switching operations based on those commands.

Its 32-point configuration is particularly useful when several low-current devices need to be controlled from one output module. Instead of installing numerous individual relay interfaces, an automation system can use the transistor outputs for compatible DC switching applications.

The module belongs to the MasterLogic-200 digital output family, which also includes relay, source-type transistor, and other transistor output configurations.

Industrial Applications

Installation and Maintenance

1. Verify Output Type: Confirm that the module is the sinking-output 2MLQ-TR4A rather than the sourcing-output 2MLQ-TR4B.
2. Check Load Voltage: Ensure that connected devices operate within the specified DC 10.2–26.4 V load voltage range.
3. Observe Current Limits: Keep the current of each output point within 0.1 A and the total current of each COM within 2 A.
4. Check Load Compatibility: Confirm that the connected devices are suitable for transistor switching rather than assuming that every relay-controlled load can be connected directly.
5. Verify Wiring Polarity: Follow the sinking-output wiring arrangement and check the positive supply and common return connections.
6. Inspect the 40-Pin Connector: Check the connector contacts, cable assembly, and locking arrangement for secure mechanical and electrical connections.
7. Use Appropriate Cable: Follow the specified 0.3 mm² cable recommendation when preparing the external connection.
8. Check Inductive Loads: For solenoid valves and relay coils, verify that the load’s transient characteristics are compatible with the module’s output protection arrangement.
9. Review Output Allocation: Organize the 32 output points according to the PLC program and external device wiring diagram.
10. Monitor LED Indication: Check the output ON indicators during operation to identify switching activity and assist fault diagnosis.
11. Investigate Unexpected Switching: If an output remains active or fails to operate, inspect the PLC logic, external power supply, wiring, and connected load.
12. Document Output Connections: Maintain an updated point-to-device list showing output addresses, connected loads, supply voltage, and common-group allocation.

Compatible System Components

Recommended Related Models

Key Advantages

• 32 transistor output points in one module.
• Sinking (NPN) output configuration.
• Supports DC 12 V and DC 24 V loads.
• Maximum load current of 0.1 A per point.
• Maximum common current of 2 A per COM.
• Photo coupler isolation.
• OFF-to-ON response time of 1 ms or less.
• ON-to-OFF response time of 1 ms or less.
• Integrated Zener diode surge absorber.
• 40-pin external connection.
• LED output operation indication.
• Integration with the MasterLogic-200 PLC architecture.

Technical FAQs

What is the difference between the 2MLQ-TR4A and 2MLQ-TR4B?

Both modules provide 32 transistor output points, but their output configurations differ. The 2MLQ-TR4A uses sinking (NPN) outputs, while the 2MLQ-TR4B uses sourcing (PNP) outputs. The correct model depends on the external load wiring and control circuit design.

Can the 2MLQ-TR4A directly control a 24 V DC solenoid valve?

It can control a compatible 24 V DC solenoid valve provided that the coil current does not exceed 0.1 A per output and the common-group current remains within 2 A. The coil’s inrush and inductive characteristics should also be checked before connecting it.

How should the 32 output points be loaded?

The module supports a maximum of 0.1 A per point and 2 A per COM. These are separate limits. Even when every individual load is below 0.1 A, the combined current of the common group must not exceed 2 A.

Why does the 2MLQ-TR4A use transistor outputs instead of relay contacts?

Transistor outputs provide semiconductor switching without mechanical contacts. This makes them suitable for frequent switching of compatible DC loads and applications requiring short response times. However, they are not a universal replacement for relay outputs, particularly where AC loads or higher switching currents are involved.