Product Overview

The Honeywell 2MLQ-TR4B is a 32-point transistor output module for the MasterLogic-200 PLC system. It uses a sourcing (PNP) output configuration to switch external DC loads, making it suitable for industrial control circuits involving solenoid valves, indicator lamps, auxiliary relays, and other compatible field devices.

An important distinction between the 2MLQ-TR4B and the closely related 2MLQ-TR4A is the output polarity. The TR4B supplies current from the positive DC side when an output is activated, whereas the TR4A uses a sinking configuration. This difference directly affects field wiring and load compatibility, so the two models should not be treated as electrically interchangeable.

The module provides 32 output points, with a maximum load current of 0.1 A per point and 2 A per common connection. Its transistor switching architecture is suitable for repetitive DC switching operations where mechanical relay contacts are unnecessary.

In a packaging machine, for example, the TR4B can operate compatible pneumatic valve circuits and machine-status indicators. The PLC activates individual channels according to sensor feedback and programmed operating sequences, allowing multiple field devices to be coordinated through one output module.

The 2MLQ-TR4B is particularly relevant to installations using PNP-compatible field wiring. Correct selection requires checking the load voltage, output polarity, individual channel current, and common-group current before connecting field equipment.

Technical Specifications

Product Features

1. 32-Point Digital Output

The module provides 32 transistor output channels for controlling external DC equipment. This channel count is suitable for machinery requiring multiple independently controlled devices without occupying additional PLC output module positions.

2. Sourcing PNP Output Configuration

The 2MLQ-TR4B uses sourcing transistor outputs. When a channel switches ON, the output supplies positive voltage to the connected load. The external circuit must be arranged with the appropriate return connection for PNP switching.

3. DC 12/24 V Load Support

The module supports DC 12 V and DC 24 V rated loads, with an allowable operating 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 control circuitry from the internal PLC signal circuitry. This helps limit the direct transfer of electrical disturbances between the controller and external load circuits.

5. Fast Transistor Switching

The specified OFF-to-ON and ON-to-OFF response times are 1 ms or less under the applicable conditions. This is useful for repetitive switching sequences and automated equipment requiring rapid output changes.

6. Defined Current Capacity

Each output point supports a maximum load current of 0.1 A, while the common connection supports up to 2 A. Both limits must be considered when distributing connected loads.

7. Integrated Zener Diode Surge Absorber

The output circuit incorporates a Zener diode surge absorber to help suppress voltage transients associated with switching operations. Additional protection should be evaluated according to the connected load characteristics.

8. 40-Pin External Connection

A 40-pin connector provides the external wiring interface for the module’s 32 output channels. This arrangement supports organized field wiring in modular PLC installations.

9. LED Output Indication

The output status indicators allow technicians to identify active channels during commissioning and maintenance. They are useful when checking whether the module is responding to PLC output commands.

Working Principle

The 2MLQ-TR4B receives digital output commands from the MasterLogic-200 CPU and converts them into transistor switching signals for external DC loads.

Its sourcing output arrangement uses PNP transistor switching. In a typical circuit, the load is connected between the module’s output and the negative DC return. When the PLC activates a channel, the corresponding transistor conducts and supplies positive voltage to the load.

When the output command is removed, the transistor switches OFF and interrupts the current supplied to the connected device.

The module’s photo coupler isolation separates the internal control signal from the external output circuit. This allows the PLC to operate field devices through the transistor output interface while maintaining the specified electrical isolation.

Typical Output Switching Sequence:

1. Field sensors send operating information to the MasterLogic-200 CPU.
2. The CPU evaluates the application program and determines the required output state.
3. The output command is transferred to the 2MLQ-TR4B.
4. The corresponding PNP transistor channel switches ON.
5. Positive DC voltage is supplied to the connected field load.
6. The connected device operates according to the output command.
7. When the command is removed, the transistor switches OFF and the load circuit becomes inactive.

Example: Solenoid Valve Operation

In an automated material handling system, the PLC controls several pneumatic solenoid valves through the 2MLQ-TR4B. When a position sensor confirms that a component has reached the required location, the PLC activates the corresponding output channel.

The transistor supplies positive DC voltage to the compatible valve coil, causing the pneumatic valve to change state. Once the programmed movement is complete, the CPU removes the output command and the channel switches OFF.

This arrangement allows multiple pneumatic functions to be coordinated through the module’s 32 output channels.

Role in MasterLogic-200 Control Architecture

Within the MasterLogic-200 architecture, the 2MLQ-TR4B functions as the physical output interface between the PLC CPU and external DC field devices.

The CPU executes the application program and determines when individual outputs should operate. The TR4B performs the corresponding transistor switching operations using its sourcing output circuits.

Its PNP configuration is particularly relevant when the field devices and wiring arrangement are designed for positive-side switching. This makes it important to distinguish the TR4B from the TR4A, even though both modules provide 32 output points and have similar current ratings.

The module can be incorporated into compatible MasterLogic-200 I/O configurations alongside digital input modules, analog modules, CPU units, and system power supplies.

Industrial Applications

Installation and Maintenance

1. Verify the Output Type: Confirm that the module is 2MLQ-TR4B with sourcing PNP outputs rather than the sinking-output 2MLQ-TR4A.
2. Check Load Voltage: Ensure that connected devices operate within the specified DC 10.2–26.4 V load voltage range.
3. Confirm Output Polarity: Verify that the external load circuit is compatible with positive-side sourcing switching.
4. Observe Individual Current Limits: Keep each output channel within the maximum load current of 0.1 A.
5. Check Common Current: Ensure that the combined load current does not exceed 2 A for the common connection.
6. Inspect External Wiring: Check the positive supply, load connections, and negative return wiring against the PNP output circuit diagram.
7. Check the 40-Pin Connector: Inspect the connector contacts and cable assembly for damage, contamination, or loose connections.
8. Use Appropriate Cable: Follow the specified 0.3 mm² cable recommendation when preparing external connections.
9. Review Inductive Loads: Check the electrical characteristics of solenoid coils and relay coils before connecting them to the transistor outputs.
10. Monitor LED Indication: Observe the output status indicators during commissioning to confirm channel switching activity.
11. Investigate Abnormal Outputs: If a channel fails to operate, check the PLC command, external power supply, output wiring, and connected load.
12. Maintain Channel Documentation: Keep an updated record of the 32 output addresses, connected devices, supply voltage, and field wiring arrangement.

Compatible System Components

Recommended Related Models

Key Advantages

• 32 transistor output points in one module.
• Sourcing (PNP) 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.
• Photo coupler isolation.
• OFF-to-ON response time of 1 ms or less.
• ON-to-OFF response time of 1 ms or less under rated resistive load conditions.
• 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 main electrical difference between the 2MLQ-TR4B and 2MLQ-TR4A?

The TR4B uses sourcing PNP transistor outputs, while the TR4A uses sinking NPN transistor outputs. The difference determines how positive voltage and the load return are connected in the external circuit. The correct model must match the field device wiring arrangement.

Can the 2MLQ-TR4B control a DC 24 V relay coil?

It can control a compatible DC 24 V relay coil if the coil current remains within the 0.1 A per-point limit and the common current limit is respected. The coil’s inrush characteristics and inductive switching requirements should also be evaluated.

What happens if the connected load requires more than 0.1 A?

A load exceeding the specified per-point current should not be connected directly to the output. An appropriately rated external interface relay or switching device can be used so that the PLC output controls the interface rather than carrying the full load current.

Does the 2MLQ-TR4B support both PNP and NPN field wiring?

No. The TR4B is a sourcing-output module. It should be used with compatible PNP switching circuits. For NPN sinking applications, the corresponding 2MLQ-TR4A is the relevant alternative.