Omron CJ1W-NCF71

The Omron CJ1W-NCF71 is a Position Control Unit (PCU) for the CJ-series PLC. It is a high-performance motion controller that operates via MECHATROLINK-II, a specialized high-speed fieldbus for motion.

Unlike standard position units that use pulse trains (which require massive amounts of wiring), the NCF71 controls up to 16 axes of servos using a single shielded twisted-pair cable.

1. Key Technical Specifications

The “NCF71” is the mid-range model in this series, capable of managing complex multi-axis motion.

2. The MECHATROLINK-II Advantage

Because the NCF71 uses a digital bus, it can do more than just send position commands. It can:

• Read Motor Data: Monitor real-time torque, actual position, and error codes from the servo drive.

• Modify Parameters: Change servo gains or limits directly from the PLC ladder program.

• Reduced Wiring: You only need a short patch cable between each servo drive (daisy-chain), drastically reducing cabinet clutter.

3. Wiring and Connection

The unit features a specific USB-style connector (though it is NOT a standard USB port) for the MECHATROLINK-II cable.

• Terminator: The last servo drive in the daisy-chain network must have a 120-ohm terminator (Omron FNY-W6022) plugged in, or the network will suffer from data reflections and communication errors.

• External Power: The module itself is powered by the CJ1 backplane, but the communication bus power is handled internally.

4. Programming and Software

To use the NCF71, you must use CX-Programmer (part of the CX-One suite) and the CX-Motion-NCF tool.

1. Unit Number: Set the rotary switches on the front of the module (e.g., Unit 0). This determines the memory addresses ($CIO$ and $D$ areas) the PLC uses to talk to the card.

2. Scan List: You must “Register” the connected servo drives in the scan list so the NCF71 knows how many axes to look for.

3. Function Blocks: Omron provides “Smart FB” (Function Blocks) that make it easy to perform tasks like Power On, Home, and Absolute Move without writing complex hex-code logic.

5. Common Status LEDs

• RUN (Green): Module is operating normally.

• ERC (Red): Internal module error.

• ERH (Red): CPU bus error (check the pins on the backplane).

• MLK (Green): Flashing indicates active MECHATROLINK-II communication.

• LNK (Green): Solid indicates a physical link to the servo drives is established.