Product Overview

The Honeywell 2MLQ-TR8A is a 64-point transistor output module in the MasterLogic-200 PLC family. It uses a sinking (NPN) output configuration to control external DC loads, including solenoid valves, indicator circuits, auxiliary relays, and other low-current industrial devices.

Compared with the 32-point 2MLQ-TR4A, the TR8A offers twice the number of output channels. This makes it particularly useful in production equipment where a large number of discrete control signals must be handled without allocating additional PLC output module positions.

The module supports DC 12 V and DC 24 V loads, with a maximum current of 0.1 A per output point and 2 A per COM. Its semiconductor switching arrangement avoids mechanical contact movement, making it suitable for applications involving frequent output switching.

A typical application is an automated production line with multiple pneumatic actuators, machine-status indicators, and auxiliary control circuits. The PLC can use the 64 output points to coordinate these devices according to sensor feedback, machine sequences, and programmed interlocks.

The 2MLQ-TR8A uses two 40-pin external connectors. Its output wiring must follow the sinking-output arrangement, and the load distribution must account for both individual channel current and common-group current limits.

Technical Specifications

Product Features

1. 64-Point Transistor Output

The 2MLQ-TR8A provides 64 digital output points in one module. This high channel count is useful for machinery with numerous independently controlled DC devices, reducing the need for multiple lower-density output modules.

2. Sinking (NPN) Output Configuration

The module uses sinking transistor outputs. When an output is activated, its switching circuit provides a current path toward the common return. External loads must be wired according to the NPN 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 operating load voltage range of DC 10.2–26.4 V. This accommodates common industrial DC control circuits.

4. Photo Coupler Isolation

Photo coupler isolation separates the output signal circuitry from the internal PLC control circuitry. This helps limit the direct transfer of electrical disturbances between the control and field sides.

5. Fast Switching Response

The OFF-to-ON and ON-to-OFF response times are both specified at 1 ms or less under the applicable conditions. This supports repetitive machine operations and applications requiring relatively fast discrete output switching.

6. Defined Channel and Common Current Limits

Each output point supports a maximum load current of 0.1 A, while each COM supports up to 2 A. The module uses a 16-point-per-COM arrangement, making load distribution an important part of the wiring design.

7. Integrated Zener Diode Protection

A Zener diode surge absorber helps suppress voltage transients associated with switching loads. The characteristics of inductive devices should still be checked when selecting external load protection.

8. Dual 40-Pin Connections

Two 40-pin connectors provide the external connection interface for the 64 output points. This arrangement supports the module’s higher channel density and organized field wiring.

9. LED Output Indication

Output ON LED indicators allow maintenance personnel to identify active channels during commissioning and troubleshooting.

Working Principle

The 2MLQ-TR8A receives digital output commands from the MasterLogic-200 CPU and converts them into transistor switching operations for connected field devices.

Its sinking output configuration uses NPN transistor switching. In a typical circuit, the external load is connected between the positive DC supply and the module output. When the PLC activates an output point, the corresponding transistor conducts and completes the current path toward the common return.

When the PLC removes the output command, the transistor switches OFF and interrupts the load current.

Photo coupler isolation separates the internal control signal from the output-side switching circuit. This allows the module to interface the PLC logic with external DC loads while maintaining the specified electrical isolation arrangement.

Typical Output Switching Sequence:

1. Field sensors provide operating information to the MasterLogic-200 CPU.
2. The CPU evaluates the PLC program and determines the required output states.
3. Output commands are transferred to the 2MLQ-TR8A.
4. The corresponding transistor channels switch ON.
5. Current flows through the connected DC loads.
6. The module’s output indicators show the active switching channels.
7. When the PLC removes the commands, the corresponding transistor channels switch OFF.

Example: Multi-Station Pneumatic Control

Consider an automated assembly line containing several pneumatic stations. Each station has solenoid valves for clamping, positioning, and releasing workpieces.

The 2MLQ-TR8A can control compatible valve circuits across multiple stations. When the PLC receives confirmation from a position sensor, it activates the assigned output channel. The transistor completes the solenoid circuit, allowing the pneumatic actuator to perform its programmed movement. The same process is repeated across the remaining output channels.

Role in MasterLogic-200 Control Architecture

Within the MasterLogic-200 architecture, the 2MLQ-TR8A acts as a high-density digital output interface between the PLC controller and external DC equipment.

The CPU handles program execution, sequence decisions, and interlock logic. The TR8A performs the actual switching operations according to the output commands received from the controller.

Its 64-point configuration is particularly useful in applications where output signals are distributed across multiple machine sections. Two external connectors provide the wiring interface, while the 16-point-per-COM arrangement allows the field circuits to be organized into separate common groups.

The module belongs to the MasterLogic-200 transistor output family, which also includes lower-channel-count models and sourcing-output alternatives.

Industrial Applications

Installation and Maintenance

1. Verify Output Configuration: Confirm that the installed module is 2MLQ-TR8A with sinking outputs, rather than the sourcing-output 2MLQ-TR8B.
2. Check Load Voltage: Ensure that connected equipment operates within the DC 10.2–26.4 V load voltage range.
3. Observe Individual Current Limits: Keep each output point within the maximum load current of 0.1 A.
4. Check Common Current Distribution: Ensure that the combined load current for each COM does not exceed 2 A.
5. Verify NPN Wiring: Connect external loads according to the sinking-output circuit arrangement, checking positive supply and common return connections.
6. Inspect Both Connectors: Check the two 40-pin connectors for secure engagement, damaged contacts, and correct cable routing.
7. Use Appropriate Wiring: Follow the recommended 0.3 mm² cable specification when preparing external connections.
8. Check External Power Quality: Verify that the DC 12/24 V supply meets the specified voltage tolerance and ripple requirements.
9. Review Load Characteristics: Check the inrush current and inductive characteristics of solenoid valves, relay coils, and other connected devices.
10. Monitor Output Indicators: Observe the LED indications during commissioning to identify active channels and assist with output diagnosis.
11. Investigate Channel Faults: If an output does not switch correctly, inspect the PLC command, external supply, wiring, load condition, and common connections.
12. Maintain Channel Records: Keep an updated wiring schedule showing all 64 output addresses, connected devices, and COM group assignments.

Compatible System Components

Recommended Related Models

Key Advantages

• 64 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 under rated resistive load conditions.
• Integrated Zener diode surge absorber.
• Two 40-pin external connectors.
• LED output operation indication.
• Integration with the MasterLogic-200 PLC architecture.

Technical FAQs

How does the 2MLQ-TR8A differ from the 2MLQ-TR4A?

The main difference is the number of output points. The 2MLQ-TR8A provides 64 sinking transistor outputs, whereas the 2MLQ-TR4A provides 32. Both support a maximum load current of 0.1 A per point and use the same general sinking-output principle.

How are the 64 output points divided between the common terminals?

The module uses a 16-point-per-COM arrangement. Each common group has a maximum current limit of 2 A. Load allocation should therefore consider both the number of active channels and the combined current of each group.

Can the 2MLQ-TR8A switch AC loads?

No. The module is specified for DC 12/24 V loads. AC switching applications require an appropriate output module, such as a compatible relay output module or triac output module, depending on the load characteristics.

Why does the 2MLQ-TR8A have two 40-pin connectors?

The two connectors provide the external wiring interfaces for its 64 output points. They allow the field connections to be organized across the module’s output channels and associated common groups.