The FX2N-16EX is Mitsubishi Electric’s 16-point digital input extension module for the MELSEC FX2N compact PLC series, providing 16 additional 24 VDC sink input points to expand the FX2N base unit’s input capacity — the standard I/O expansion unit for FX2N systems requiring more input points than the base unit provides, widely used in active FX2N installations for conveyor sensor arrays, multi-position limit switch monitoring, and comprehensive machine status input coverage. As a right-side extension unit connecting directly to the FX2N base unit’s extension bus, the FX2N-16EX adds input capacity without consuming any special function module slots or option board positions. In stock at Atlantech Drives. Request your quote within 24-48 hours with worldwide shipping and 12-month warranty.
What Is the FX2N-16EX?
The FX2N-16EX is a MELSEC FX2N series extension I/O unit providing 16 digital input points (X addresses assigned sequentially from the last input address used by the preceding module in the extension chain) with 24 VDC sink input circuits compatible with NPN-output 3-wire proximity sensors, photoelectric sensors, limit switches, and push buttons. The module connects to the FX2N base unit’s right-side extension bus connector via the supplied extension cable, with subsequent FX2N-16EX or other extension modules cascaded in sequence. Each of the 16 input points is individually optically isolated from the FX2N internal bus, providing galvanic isolation between the field sensor circuits and the PLC logic circuitry. The module draws its power from the FX2N base unit’s internal power supply without requiring an external 24 VDC supply — though the sensor supply current for 3-wire sensors connected to the input terminals draws from the FX2N base unit’s internal 24 VDC sensor supply output, which has a limited current capacity (typically 460 mA for the FX2N-32MR/ESS) that must be verified against the total sensor current draw when many sensors are connected. The FX2N-16EX has no output capability — it is a pure input expansion unit, distinct from the FX2N-32ER combined input/output extension unit.
Key Technical Specifications
- Model: FX2N-16EX
- Extension Type: Digital input only
- Input Points: 16
- Input Type: 24 VDC sink (NPN-compatible, source current ≥4 mA)
- Input Voltage Range: 20.4–28.8 VDC (signal ON), ≤6 VDC (signal OFF)
- Input Current: 5 mA typical at 24 VDC
- Response Time: 10 ms standard (adjustable in FX2N program)
- Isolation: Optical, per input point
- Extension Bus Connection: Right-side FX2N extension bus (cable connection)
- Power Supply: From FX2N base unit internal bus (no external supply)
- Extension Cable: FX-16E-500CAB-S (supplied)
- Operating Temperature: 0°C to 55°C
- Dimensions (W × H × D): 55 mm × 90 mm × 87 mm
- Weight: Approx. 0.25 kg
Compatibility & System Integration
The FX2N-16EX is compatible with all FX2N base units and connects in cascaded sequence with other FX2N extension modules (FX2N-8EX, FX2N-8EYR, FX2N-8EYT, FX2N-16EYR, FX2N-16EYT, FX2N-32ER, and FX2N special function modules) up to the FX2N platform’s 256-point total I/O maximum. Input addresses are assigned sequentially — if the FX2N base unit uses X0–X17 (octal) for its 16 inputs, the first FX2N-16EX in the extension chain receives X20–X37, the second FX2N-16EX receives X40–X57, and so on. This automatic sequential address assignment is managed by the FX2N system’s I/O configuration — no software configuration is required to assign addresses, as they are determined by the physical position of each module in the extension chain. The FX2N-16EX is also compatible with FX3U base units via the FX3U-CNV-BD conversion adapter, enabling existing FX2N-16EX input expansion hardware to be reused when upgrading an FX2N base unit to FX3U without replacing the extension modules. This compatibility makes the FX2N-16EX a cost-preserving component in FX2N-to-FX3U migration scenarios where the field wiring and sensor infrastructure connected to the FX2N-16EX does not need to be changed.
Troubleshooting Guide
If the FX2N-16EX inputs are not responding — all 16 inputs showing OFF in GX Works2 device monitor regardless of sensor state — verify the extension cable connection at both the FX2N base unit connector and the FX2N-16EX connector. The FX2N extension bus uses a flat ribbon cable with edge connectors that can appear seated but be slightly misaligned — press both connectors firmly inward until a positive click is felt and confirm the connector locking latches are engaged. A partially seated extension cable causes total loss of all input data from the affected module and all downstream modules in the extension chain, without any FX2N CPU fault indication. For individual inputs showing permanent ON or permanent OFF states that do not respond to changes in the connected sensor state, disconnect the sensor from the affected input terminal and short the input terminal to +24 VDC (for a sink input) directly with a test lead — if the input activates under direct drive but not from the sensor, the sensor, its power supply, or the connecting cable is faulty rather than the FX2N-16EX module. Verify the sensor’s output signal meets the FX2N-16EX’s 4 mA minimum source current requirement — a sensor with marginal output drive current (such as a low-quality proximity sensor with deteriorated output stage) may produce a voltage within the undefined range (6–20 VDC) that the FX2N-16EX input does not reliably detect as either ON or OFF.
Frequently Asked Questions
Q: Can the FX2N-16EX be used with PNP-output (source) sensors, or is it limited to NPN-output (sink) sensors?
A: The FX2N-16EX uses sink input circuitry — the input activates when the input terminal is pulled to approximately 0 VDC by the sensor (NPN transistor output). PNP-output sensors (which source +24 VDC to the input terminal) are not directly compatible with the FX2N-16EX’s sink input. For PNP sensor compatibility, an inline NPN-to-PNP conversion relay or transistor can be used per input channel, or the FX2N-16EX-ES/UL (source input variant, if the specific application requires it) should be specified instead.
Q: How many FX2N-16EX modules can be connected to a single FX2N base unit?
A: The maximum number of FX2N-16EX modules is limited by the FX2N platform’s 256-point total I/O constraint — a FX2N-64MR base unit with 32 inputs already uses 32 input addresses, leaving 224 points (or approximately 14 additional FX2N-16EX modules worth of addresses) before the 256-point limit is reached. In practice, the FX2N hardware manual limits the total extension module count to 8 special function modules maximum, and the physical extension chain length also imposes practical constraints on the number of cascaded modules.
Q: Does the FX2N-16EX require any GX Works2 configuration, or is it automatically recognised?
A: The FX2N-16EX is automatically recognised by the FX2N system without any GX Works2 configuration — the module’s input addresses are assigned sequentially at power-up based on its physical position in the extension chain. No hardware configuration, I/O assignment, or parameter settings are required in GX Works2 for the FX2N-16EX to operate. The assigned input addresses are determined by the physical module order and can be verified in GX Works2’s PLC system information after connecting online to the FX2N.
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