The FX3U-32MT/ESS is Mitsubishi Electric’s 32-point transistor sink output base unit for the MELSEC FX3U compact PLC series, providing 16 digital inputs and 16 high-speed NPN open-collector transistor outputs in a self-contained AC-powered controller — the transistor output equivalent of the FX3U-32MR/ES-A, providing faster output switching, built-in 2-axis pulse output for direct stepper and servo positioning, and unlimited electrical output life for high-cycle 24 VDC load applications. As the most frequently specified transistor output model in the FX3U range for general-purpose machine control, the FX3U-32MT/ESS is the standard specification for packaging machines, assembly automation, and conveyor systems where output switching frequency, pulse generation capability, or output longevity requirements exceed the capabilities of relay output models. In stock at Atlantech Drives. Request your quote within 24-48 hours with worldwide shipping and 12-month warranty.
What Is the FX3U-32MT/ESS?
The FX3U-32MT/ESS is a MELSEC FX3U series compact PLC base unit with transistor sink (NPN open-collector) outputs, providing 16 input points (X0–X17) and 16 transistor output points (Y0–Y17). The «SS» suffix designates the sink output type with AC power supply — the transistor outputs use NPN open-collector topology with a shared positive supply common, requiring the external 24 VDC load supply’s positive terminal to be connected to the output common and the output transistors pulling the load line to 0 V when activated. Designated high-speed output points Y0 and Y1 support pulse generation at up to 100 kHz via the FX3U’s PLSY, DPLSY, PLSR, and DRVI/DRVA positioning instructions — enabling direct 2-axis stepper or servo positioning without additional positioning modules. The FX3U CPU processes programs at 0.065 µs per basic instruction with 64,000-step capacity, identical to all FX3U base unit variants regardless of output type. The transistor output’s 1 ms maximum response time (versus 10 ms for relay output) enables the FX3U-32MT/ESS to handle rapid output switching applications such as high-speed sorting diverters, label applicator triggers, and vision system reject actuators.
Key Technical Specifications
- Model: FX3U-32MT/ESS
- Total I/O Points: 32 (16 inputs + 16 outputs)
- Input Type: 24 VDC sink (X0–X17)
- Output Type: Transistor sink/NPN open-collector (Y0–Y17), 0.5 A per point, 5–30 VDC
- High-Speed Pulse Output: Y0 and Y1 up to 100 kHz; Y2 up to 10 kHz
- Output Common Groups: 1 common for all 16 outputs
- Power Supply: 100–240 VAC, 50/60 Hz
- Program Memory: 64,000 steps
- Execution Speed: 0.065 µs per LD instruction
- Built-in High-Speed Counters: 6 inputs (100 kHz)
- Communication: RS-422 (built-in)
- Real-Time Clock: Built-in
- Battery Backup: Yes
- Expansion: Up to 8 extension units, up to 4 special adapter modules
- Operating Temperature: 0°C to 55°C
- Dimensions (W × H × D): 150 mm × 90 mm × 87 mm
- Weight: Approx. 0.82 kg
Typical Industrial Applications
The FX3U-32MT/ESS is the dominant specification in fast-cycle discrete manufacturing automation where 24 VDC load switching speed and built-in pulse output capability justify the transistor output model over the relay alternative. In secondary packaging machines — case erectors, carton formers, and case packers — the FX3U-32MT/ESS controls pneumatic cylinder solenoid valves, servo-driven belt drives (via Y0/Y1 pulse output), and product detection sensors within a compact controller that fits in a small machine-mounted enclosure. Conveyor sorting systems use the FX3U-32MT/ESS to activate diverter solenoid valves at high speed based on barcode scanner or vision system trigger signals — the transistor output’s 1 ms response time ensures the diverter activates at the correct position for products travelling at high line speeds. In automated assembly systems for electronics and small components, the FX3U-32MT/ESS coordinates multiple pneumatic pick-and-place axes, vacuum generator valves, and conveyor belt drive servos from a single compact controller, with the built-in high-speed counters tracking part counts from photoelectric sensors at rates up to 100 kHz. Textile and printing machinery use the FX3U-32MT/ESS for web tension control and registration mark detection, where the built-in high-speed counter inputs capture encoder pulses from web speed sensors and the Y0/Y1 pulse outputs command dancer position servo drives.
Expert Tips
When using the FX3U-32MT/ESS for 2-axis stepper positioning via Y0 and Y1, note that the DRVI (incremental positioning) and DRVA (absolute positioning) instructions generate trapezoidal speed profiles with configurable acceleration and deceleration times — but the acceleration time parameter in the FX3U-32MT/ESS is defined as the time to reach the target speed from zero, not the time per revolution. For stepper motors with significant load inertia, calculate the required acceleration time using the motor’s torque-speed curve and the load inertia ratio — insufficient acceleration time causes step loss on acceleration, which accumulates as position error that is undetected by the open-loop system. For high-cycle applications where Y0 or Y1 pulse outputs generate thousands of positioning moves per hour, verify that the DRVI or DRVA instruction’s positioning complete flag (M8029 for DRVI, M8029 for DRVA) is confirmed before issuing the next positioning command — issuing a new position command before the previous move completes causes the FX3U to abort the current move and start the new command immediately, potentially causing position overshoot if the mechanical system has not yet decelerated to zero. For applications using the FX3U-32MT/ESS transistor outputs to drive 24 VDC relay coils for panel indication, install a 1N4007 diode across each relay coil with the cathode to +24 V — this is frequently overlooked on the assumption that small relay coils do not generate significant back-EMF, but even small relay coil inductive spikes accumulate damage in transistor output stages over millions of switching cycles.
Frequently Asked Questions
Q: Can the FX3U-32MT/ESS sink output directly drive a stepper motor driver with optocoupler-isolated pulse input?
A: Yes, provided the stepper driver’s pulse input optocoupler forward current matches the FX3U-32MT/ESS output’s drive capability. Most stepper drivers require 7–20 mA through the input optocoupler at 5 VDC, with an internal current-limiting resistor in series with the optocoupler LED. Verify the required pull-up voltage and input current specification from the stepper driver datasheet — if the driver requires a 5 VDC pull-up for the pulse input and the FX3U output provides 24 VDC pull-up via the common terminal, a series resistor of (24 V – 1.2 V) ÷ 10 mA = 2.28 kΩ should be added between the common terminal and the driver’s pulse input to limit the current to 10 mA within the FX3U output’s rated 0.5 A capacity.
Q: What is the difference in output common wiring between the FX3U-32MT/ESS (sink) and the FX3U-32MT/ES (source)?
A: In the FX3U-32MT/ESS (sink/NPN), the output common terminal is connected to the 24 VDC positive supply, and the output transistors pull the load terminal to 0 V (negative) when activated — NPN sensors and devices requiring a sink output are compatible. In the FX3U-32MT/ES (source/PNP), the output common terminal is connected to 0 V (negative), and the output transistors push the load terminal to +24 V when activated — PNP devices and source-input systems are compatible. Select the output type based on the polarity of the field devices connected to the PLC outputs.
Q: Can the FX3U-32MT/ESS be used in a MELSEC iQ Works network project alongside MELSEC-Q modules?
A: The FX3U-32MT/ESS is programmed in GX Works2 or GX Works3 and can be included in an iQ Works project that also contains MELSEC-Q systems, allowing the complete factory automation system to be documented and managed within a single engineering environment. However, the FX3U operates as a standalone controller — it does not connect to MELSEC-Q via the CC-Link IE Controller Network or MELSECNET/H inter-CPU networks. Network communication between the FX3U-32MT/ESS and a MELSEC-Q system is implemented via CC-Link (using a FX3U-16CCL-M option board on the FX3U) or Ethernet (using a FX3U-ENET-ADP adapter).
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