Mitsubishi FX3U-128MR/ES Programmable Logic Controller

The Mitsubishi FX3U-128MR/ES is a high-performance PLC from the FX3U series, featuring 128 built-in I/O points: 64 digital inputs (24V DC, sink/source) and 64 relay outputs (24V DC or 240V AC, 2A per point). The "MR" designation indicates relay outputs, while "ES" denotes the standard model for Europe and Asia (100-240V AC power supply). This controller offers fast processing (0.065 µs per basic instruction), large memory (64K steps), and extensive expansion capabilities, including up to 384 I/O points with additional modules. It is suitable for complex automation tasks in packaging, material handling, and machinery control.

Technical Specifications

Power supply: 100-240 V AC (50/60 Hz), consumption 60 VA. I/O points: 64 inputs (24V DC, sink/source, 7 mA typical), 64 relay outputs (form A, 2A resistive at 240V AC / 30V DC). Program memory: 64K steps (RAM, battery-backed). Basic instruction speed: 0.065 µs. Application instruction speed: 0.5 µs (MOV). Built-in high-speed counters: 8 channels (max 100 kHz). Pulse outputs: 2 channels (max 100 kHz, transistor outputs available on MT model, but MR model has relay outputs, so pulse outputs are not available; check manual). Communication: RS-422 programming port, optional RS-232C/485 adapters. Number of expansion modules: up to 8 (max I/O 384). Dimensions: 130 mm (W) × 86 mm (H) × 86 mm (D). Weight: 0.8 kg. Operating temperature: 0°C to 55°C. Storage: -20°C to 70°C. Protection: IP20.

Key Features

• 64 DC inputs (sink/source), 64 relay outputs (2A)

• 100-240V AC power supply (built-in)

• High-speed processing: 0.065 µs per basic instruction

• 64K steps program memory, battery-backed

• Built-in RS-422 programming port

• High-speed counters (100 kHz) for encoder inputs

• Expandable to 384 I/O with up to 8 modules

• Real-time clock (battery-backed)

• Compatible with GX Works2 / GX Developer

Memory and Expansion

The FX3U-128MR/ES has 64K steps of RAM, backed by a lithium battery (type CR2032, life approx. 5 years). An optional EEPROM or flash memory cassette can be installed for permanent program storage. The CPU can control up to 384 I/O points by adding up to 8 expansion units (e.g., FX2N series I/O modules) and special function modules (analog, positioning, temperature). The built-in high-speed counters (100 kHz, 8 channels) can be used for encoder feedback. However, the MR model does not have high-speed pulse outputs; for pulse train outputs to stepper drives, the MT (transistor) model should be used.

Programming and Software

The FX3U-128MR/ES is programmed using Mitsubishi GX Works2 or GX Developer (IEC 61131-3 languages: Ladder, SFC, ST, FBD). The CPU supports function blocks, structured text, and online editing. The built-in RS-422 port allows connection to a PC via a USB-to-RS422 converter (SC-09 cable). An optional RS-232C or RS-485 board can be added for Modbus RTU communication. The FX3U series also supports Ethernet via an optional module.

Applications

The FX3U-128MR/ES is used in packaging machines (filling, capping), assembly lines, material handling (conveyors), plastic injection molding, and small process control. The relay outputs are ideal for switching AC loads such as contactors, solenoid valves, and indicator lamps. The high-speed inputs allow connection to incremental encoders for position feedback.

Installation and Wiring

Mount the CPU on a DIN rail or directly on a panel. Connect 100-240V AC power to terminals L and N (ground to )। Connect inputs: 24V DC sensors between input terminal (X0-X63) and common (COM). Inputs are sink/source configurable via common wiring. Outputs: relay outputs are form A contacts; connect the load between the output terminal (Y0-Y63) and the power source (AC or DC). Each output group (8 points) has a common terminal; use external fuses. The programming port is an 8-pin mini-DIN. Expansion modules connect via the expansion cable.

Maintenance and Diagnostics

The CPU has LEDs: POWER, RUN, BATTERY, ERROR. A blinking ERROR LED indicates a program or hardware fault. The battery should be replaced every 5 years. The real-time clock can be set via GX Works2. The CPU stores error history in its diagnostics buffer.

Conclusion

The Mitsubishi FX3U-128MR/ES is a powerful, expandable PLC with 128 built-in I/O points. Its relay outputs and high-speed inputs make it suitable for a wide range of industrial automation applications requiring both AC load switching and fast counting.