OMRON NX502 CPU Unit Hardware Installation and Maintenance Guide

Design points for NX bus power supply:

The maximum total current is 10A, and the voltage drop per unit is proportional to the total current (for example, when the total current is 3A, the voltage drop per unit is 0.06V).

Ensure that the voltage of the farthest unit still meets the specifications (usually 21.6-26.4VDC).

If there are different voltage levels (such as 24V and 12V) in the same rack, additional I/O power supply units need to be inserted for isolation.

Calculation example: The total current is 3A, passing through 4 units (including itself) from the additional I/O power supply unit to the farthest unit. The voltage drop is 0.06V × 4=0.24V. If the power output is 24.00V and the remote voltage is 23.76V, it is still within the allowable range.

3.3 Selection of protective devices

Unit power supply side: Use circuit breakers or fuses, and their breaking time should meet the following requirements: 6A ≤ 1min, 12A ≤ 15s, 21A ≤ 5s, 30A ≤ 2.5s.

I/O power side: Select the corresponding protection curve based on the terminal capacity (10A or 4A).

Wiring and Grounding

4.1 Unit power wiring

Terminal block (model NX-TBC082, 8-bit, including functional grounding terminal):

A1/B1:24VDC positive pole

A3/B3：0VDC

Two 24V terminals and two 0V terminals are connected in parallel internally and can be used for wiring to downstream devices (such as additional NX unit power supply).

4.2 Terminal Wiring Method

Recommend using tube terminals with insulated rings (Phoenix Contact AI series) or tinned stranded wires.

When the current is greater than 2A, tin plated wire or tubular terminals must be used.

Connection steps: Insert a straight screwdriver into the release hole at an angle of 10-15 °, feel the spring resistance and maintain pressure. Insert the wire or terminal into the circular hole, and then remove the screwdriver.

High current (>2A and bare stranded wire) requires zip ties to secure the wire harness to the binding holes of the terminal block.

4.3 Grounding

The functional grounding terminal (A7/B7) must be grounded (resistance ≤ 100 Ω), with a grounding wire of ≥ 2.0mm ² and a length ≤ 20m.

DIN rails should also be grounded. If the surface of the guide rail is insulated (such as anodized aluminum), a DIN rail isolation gasket (NX-AUX01) should be used.

EtherCAT/EtherNet/IP communication cables are recommended to use equipotential bonding systems or star grounding, with shielding layers at both ends connected to the connector housing.

Indicator light status diagnosis

The NX502 front indicator light provides rich operational status information.

5.1 CPU status indicator light

Meaning of indicator light color and status

POWER green light, normal power supply

RUN green light, RUN mode running

Blinking at 2-second intervals (later converted to 0.5 seconds), starting up

2 seconds flashing continuously for ≥ 30 seconds, system initialization error

Extinguish Program mode or major malfunction

ERROR red light indicates a major fault or CPU error

Partial fault level or minor fault flashing at 1-second intervals

Eliminate normal or monitoring information

BUSY yellow flashing non-volatile memory access in progress

SD PWR green, SD card powered on

Flashing backup/restore/compare in progress

SD BUSY yellow flashing SD card access in progress

Important: Do not turn off the power when the BUSY indicator light is flashing, otherwise it may cause damage to the user's program or settings, and result in major malfunctions during the next power on.

5.2 EtherNet/IP port indicator light (NET RUN/NET ERR)

NET RUN green light: normal; Flashing: Communication is in progress (such as establishing a tag data link); Extinguish: Unable to communicate.

NET ERR red light: unrecoverable error; Flashing: Recoverable errors (such as IP address conflicts, label settings errors).

5.3 EtherCAT Port Indicator Light (NET RUN/NET ERR/LINK/ACT)

NET RUN green light: Process data communication is running; Flashing: message only communication or input only; Extinguish: Communication has stopped.

NET ERR red: Hardware error or unrecoverable error; Flashing: Recoverable error.

If the ERROR light is on or flashing, the event log should be viewed through Sysmac Studio. Common initial faults include "power off detection" (voltage briefly below 20.4V) and "unit configuration verification error" (actual installation does not match software configuration).

Battery and clock maintenance

The NX502 factory does not have a battery installed. If you need to maintain the clock during long-term power outages (beyond the capacitor retention time), you can choose to purchase CJ1W-BAT01 battery (with a lifespan of 5 years).

Installation steps:

The controller should be powered on for at least 5 minutes (to charge the capacitor).

Power off (or operate without electricity after releasing static electricity).

Open the left SD card cover, insert the battery connector into the CPU battery interface, place the battery into the slot, organize the wiring harness, and close the cover.

Power on again, set "Battery related Error Detection" to "Usage" in Sysmac Studio, and calibrate the clock.

Battery error handling: