The FX3U-1PG is Mitsubishi Electric’s 1-axis pulse output positioning special adapter for the MELSEC FX3U compact PLC series, providing a dedicated high-speed pulse output channel at up to 100 kHz for stepper motor or servo drive positioning — supplementing the FX3U base unit’s built-in Y0/Y1 pulse outputs with an additional independent positioning axis on the left-side special adapter interface, enabling up to 3 simultaneous positioning axes from a single FX3U system without requiring a separate positioning module. As a left-side special adapter, the FX3U-1PG connects to the FX3U base unit without consuming any extension bus capacity or base unit slot, preserving all 8 extension unit positions for I/O expansion. Atlantech Drives holds stock of the FX3U-1PG. Contact us for fast worldwide delivery and competitive pricing.
What Is the FX3U-1PG?
The FX3U-1PG is a MELSEC FX3U series special function adapter module providing one channel of open-collector pulse output for stepper or servo axis positioning control. It connects to the dedicated left-side special adapter bus interface of any FX3U base unit (left of the base unit housing) alongside up to three other special adapter modules — analogue, temperature, or additional pulse adapter modules — without using the right-side extension bus. The FX3U-1PG provides all the positioning functions required for single-axis applications: preset position, home return, JOG operation, and speed control, with up to 600 positioning patterns stored in the adapter’s internal memory for execution by the FX3U CPU program via FROM/TO buffer memory instructions. The adapter generates step/direction or CW/CCW pulse output at up to 100 kHz, matching the performance of the FX3U base unit’s built-in Y0/Y1 high-speed outputs, and provides external signal inputs for near-point DOG, upper/lower limit switches, and manual pulse generator (handwheel) connection on the adapter’s dedicated input terminals — separate from the FX3U base unit’s X input terminals, preserving all 8/16/40/64 base unit input points for field I/O.
Key Technical Specifications
- Model: FX3U-1PG
- Controlled Axes: 1
- Connection Interface: FX3U left-side special adapter bus
- Output Type: Open-collector transistor, step/direction or CW/CCW
- Maximum Output Pulse Frequency: 100 kHz
- Positioning Patterns: 600 (stored in adapter memory)
- Position Data Range: -2,147,483,648 to +2,147,483,647 pulses
- Speed Range: 1 to 100,000 pps
- Acceleration/Deceleration: Trapezoidal (configurable)
- Manual Pulse Generator Input: Supported (×1, ×10, ×100 magnification)
- External Signals: Near-point DOG, upper/lower limit switches (dedicated input terminals)
- Current Consumption (from FX3U base unit adapter bus): 0.09 A at 5 VDC
- Operating Temperature: 0°C to 55°C
- Weight: Approx. 0.12 kg
Series Comparison & Selection Guide
The FX3U pulse positioning adapter range offers two models: the FX3U-1PG (single axis, 100 kHz) and the FX3U-2PG (two axes, 100 kHz per axis). Both adapters connect to the FX3U left-side special adapter interface and operate identically in terms of positioning functions, speed, and pattern storage. The FX3U-1PG is the correct choice when one additional positioning axis beyond the FX3U base unit’s built-in Y0/Y1 pulse outputs is required — for example, a system using Y0 for X-axis positioning and requiring one additional axis for Z-axis control can use a single FX3U-1PG for the Z-axis without occupying a base unit extension slot. The FX3U-2PG provides two additional axes in a single adapter, appropriate when two extra axes are needed beyond the base unit’s built-in outputs. Comparing the FX3U-1PG adapter architecture to the MELSEC-Q QD75P4N positioning module: the FX3U-1PG provides simpler positioning functionality (no S-curve acceleration, no linear interpolation between axes) but at significantly lower cost and without requiring a MELSEC-Q base unit — the FX3U-1PG is the right choice for FX3U-based systems requiring basic single-axis positioning, while the QD75P4N is appropriate for MELSEC-Q systems requiring advanced 4-axis coordinated positioning.
Expert Tips
When using the FX3U-1PG alongside the FX3U base unit’s built-in Y0 and Y1 pulse outputs for multi-axis positioning, ensure that the axis addressing in the FX3U program clearly distinguishes between the built-in pulse outputs (addressed via DRVI/DRVA/PLSY instructions referencing Y0, Y1) and the FX3U-1PG (addressed via FROM/TO instructions referencing the adapter’s buffer memory). A common commissioning error is using the wrong instruction set for the FX3U-1PG — attempting to control the FX3U-1PG using DRVI instructions (which address the built-in pulse output hardware) rather than the FROM/TO buffer memory interface will result in no movement on the FX3U-1PG axis. For systems using the FX3U-1PG’s manual pulse generator input for handwheel jogging, set the MPG magnification factor (×1, ×10, or ×100) based on the required manual positioning resolution: for precision fine positioning (sub-mm), use ×1 magnification; for rapid coarse positioning, use ×100. The magnification factor can be changed via a buffer memory write from the FLC program, enabling the operator to select the appropriate jog resolution from the HMI without requiring PLC program modification. When connecting multiple FX3U special adapters (analogue + temperature + pulse) to the same FX3U base unit, verify that the total current draw of all adapters from the 5 VDC adapter bus does not exceed the FX3U base unit’s adapter bus current capacity — the FX3U hardware manual specifies the maximum total adapter current allowance, which varies by base unit model.
Frequently Asked Questions
Q: Can the FX3U-1PG operate a servo drive equipped with RS-422A differential pulse input rather than open-collector input?
A: No. The FX3U-1PG provides open-collector transistor pulse output only — it does not generate differential RS-422A line driver signals. For servo drives requiring differential pulse input (such as Mitsubishi MR-J4 servo amplifiers in pulse train input mode), the FX3U-20SSC-H special adapter or an external single-ended-to-differential converter must be used. The FX3U-1PG is appropriate for stepper motor drivers and servo drives with open-collector or optocoupler-isolated pulse input, which covers the majority of mid-range servo systems.
Q: Does the FX3U-1PG’s positioning pattern storage retain data when the FX3U base unit is powered off?
A: Yes. The FX3U-1PG stores positioning pattern data (target positions, speeds, acceleration times) in non-volatile flash memory within the adapter — positioning data is retained indefinitely without power and without battery backup. The positioning data is loaded into the adapter’s flash memory via GX Works2’s special adapter parameter editor and is retained through power cycling, FX3U program changes, and battery replacement, ensuring that positioning parameters are not lost during routine maintenance activities.
Q: Can the FX3U-1PG be installed on any position in the left-side adapter chain, or must it be in a specific position?
A: The FX3U-1PG can be installed in any of the four left-side adapter positions (positions 1–4, counting from the base unit outward). The adapter position number determines the buffer memory base address offset used in the FROM/TO instructions in the FX3U program — adapters in position 1 use one address range, position 2 uses another, and so on, as documented in the FX3U-1PG user manual’s buffer memory map section. GX Works2’s special adapter configuration tool automatically calculates the correct buffer memory addresses based on the configured adapter installation position, eliminating manual address calculation errors.
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