Mitsubishi FX3U-128MR/ESS – 128-Point Relay Output PLC Main Unit | MELSEC FX3U Series
Engineering Background
The MELSEC FX3U is Mitsubishi Electric’s flagship third-generation compact PLC platform, engineered for high-speed, high-density discrete control in demanding industrial environments. The FX3U-128MR/ESS is the 128-point relay output variant with a built-in Ethernet port (ESS suffix), enabling direct network integration without an additional communication module.
Product Positioning
Designed for procurement engineers and system integrators who require a proven, high-I/O-density controller with native Ethernet connectivity. The FX3U-128MR/ESS serves as the central processing unit in mid-to-large automation cells, replacing legacy FX2N installations or anchoring new greenfield projects where relay output robustness and network transparency are non-negotiable.
Complete Technical Specifications
- Model / SKU: FX3U-128MR/ESS
- Series / Platform: MELSEC FX3U
- Manufacturer: Mitsubishi Electric Corporation
- Country of Origin: Japan
- I/O Configuration: 128 points total — 64 inputs (DC 24V sink/source) / 64 outputs (relay)
- Output Type: Relay (2A per point, 8A per common)
- Max Output Current: 2 A / point; 8 A / common
- Program Memory: 64,000 steps (with memory cassette)
- Processing Speed: 0.065 µs / basic instruction
- Built-in Communication: Ethernet (10BASE-T/100BASE-TX), RS-422 (programming port)
- Ethernet Protocol Support: MELSOFT connection, MC protocol, CC-Link IE Field Basic
- Expansion Capability: Up to 8 extension modules; max 256 I/O points
- Power Supply: AC 100–240 V, 50/60 Hz
- Power Consumption: 65 VA (max)
- Internal Power Supply Output: DC 24V / 600 mA (for sensor supply)
- Operating Temperature: 0 °C to +55 °C
- Storage Temperature: −25 °C to +75 °C
- Humidity: 5% to 95% RH (non-condensing)
- Vibration Resistance: 10–57 Hz: 0.075 mm; 57–150 Hz: 9.8 m/s²
- Shock Resistance: 147 m/s² (3 times each direction)
- Protection Rating: IP20 (panel-mount)
- Dimensions (W × H × D): 285 mm × 90 mm × 87 mm
- Weight: Approx. 1,580 g
- Certifications: CE, UL, cUL, KC
- Programming Software: GX Works2 / GX Works3 (FX3U compatible)
- RoHS Compliant: Yes
Proven Application Environments
- Automotive Assembly Lines — High-cycle relay switching for fixture clamping, part presence detection, and conveyor sequencing.
- Food & Beverage Packaging — Relay outputs tolerate inductive loads from solenoid valves and motor starters without additional isolation.
- HVAC & Building Automation — Ethernet connectivity enables BACnet/IP gateway integration via third-party middleware.
- Semiconductor & Electronics Manufacturing — Precise high-speed scan cycle supports tight process timing requirements.
- Water Treatment & Utilities — Robust relay contacts handle pump and valve control in wet environments (panel-enclosed).
- Machine Tool Control — Replaces aging FX2N-128MR installations with backward-compatible ladder logic migration.
Engineering Advantages
- Native Ethernet (ESS): Eliminates the FX3U-ENET-ADP adapter cost and DIN-rail space — Ethernet is built in at the CPU level.
- Relay Output Durability: Mechanical relay contacts rated for 200,000 operations at rated load; ideal for inductive and resistive loads without external snubbers.
- High-Speed Counters: 6 built-in high-speed counter channels up to 100 kHz for encoder feedback without expansion.
- Interrupt Inputs: 6 interrupt input channels for sub-millisecond event response.
- Analog Expansion Ready: Supports FX3U-4AD, FX3U-4DA, and temperature modules for mixed discrete/analog architectures.
- CC-Link IE Field Basic: Enables distributed I/O over standard Ethernet infrastructure — no proprietary cabling required.
- GX Works2/3 Compatibility: Full structured text, ladder, and SFC programming with online monitoring and simulation.
System Architecture & Signal Flow
The FX3U-128MR/ESS operates as the master CPU node in a star or daisy-chain Ethernet topology. Field devices connect to the 64 DC24V sink/source inputs via terminal block wiring. The CPU executes the scan cycle (input refresh → program execution → output refresh) at 0.065 µs/step. Relay output contacts switch field loads (solenoids, contactors, indicator lamps) directly. The built-in Ethernet port communicates upstream to SCADA/HMI systems via MC Protocol or to peer PLCs via CC-Link IE Field Basic. Extension modules attach to the right-side bus connector, expanding I/O up to 256 points across up to 8 modules. Optional FX3U-232ADP or FX3U-485ADP adapters add serial communication for legacy device integration.
Sourcing & Quality Verification
- Authenticity: All units sourced through verified Mitsubishi Electric authorized distribution channels. Each unit ships with original Mitsubishi packaging, holographic authenticity label, and factory test documentation.
- Inspection Protocol: Pre-shipment functional test — power-on self-test (POST), I/O point verification, Ethernet link confirmation, and firmware version check.
- Warranty: 12-month Konmask warranty covering manufacturing defects. Mitsubishi OEM warranty terms apply where applicable.
- Traceability: Serial number and date code recorded at dispatch for full supply chain traceability.
- Counterfeit Risk Mitigation: Units are never sourced from gray-market brokers. Provenance documentation available on request.
Procurement Process
- Confirm Specification: Verify FX3U-128MR/ESS matches your I/O count, output type (relay vs. transistor), and Ethernet requirement. Contact our engineers if unsure.
- Request Quote: Submit your BOM or single-line item via [email protected] or the on-site inquiry form for volume pricing.
- Lead Time: In-stock units ship within 1–3 business days. ETA confirmation provided at order placement.
- Export Compliance: HS Code 8537.10 applies. Export documentation (commercial invoice, packing list, COO) provided for international shipments.
- Payment Terms: T/T, PayPal, and trade credit available for qualified accounts.
- After-Sales Support: Application engineering support available post-delivery for commissioning assistance.
Technical FAQ
Q: What is the difference between FX3U-128MR/ES and FX3U-128MR/ESS?
A: The /ESS suffix denotes the built-in Ethernet port. The /ES variant requires an external FX3U-ENET-ADP for Ethernet connectivity. The /ESS is the recommended choice for new installations.
Q: Can FX3U-128MR/ESS replace an FX2N-128MR?
A: Yes. The FX3U is backward compatible with FX2N ladder programs with minor modifications. GX Works2 includes a migration wizard for FX2N-to-FX3U conversion.
Q: What is the maximum expansion I/O?
A: Up to 8 extension modules, reaching a maximum of 256 I/O points (including the base unit’s 128 points).
Q: Is the relay output suitable for AC loads?
A: Yes. Relay contacts are rated for both AC and DC loads. Maximum switching capacity is 240 VAC / 2 A or 30 VDC / 2 A per point.
Q: Does the unit support MODBUS TCP?
A: Not natively. MODBUS TCP requires a third-party gateway or a custom MC Protocol-to-MODBUS TCP converter. Contact us for recommended solutions.
Q: What programming software is required?
A: GX Works2 (version 1.570T or later) or GX Works3. GX Developer is not recommended for new FX3U projects.
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