Omron C500 PLC Installation and Maintenance Guide

The length of the grounding wire should be as short as possible (not exceeding 20m).

The GR terminal (protective grounding) must be grounded. LG terminals (wire grounded) are usually not grounded. If there is severe noise, LG can be short circuited to GR and grounded.

The grounding of PLC must be independent and cannot share the grounding electrode with power equipment (motor, frequency converter), nor can it be connected to building structural metal parts.

All GR terminals of the racks (CPU and expansion rack) should be connected to the same grounding point.

8.2 Noise Suppression Measures

Maintain a distance of at least 300mm between the I/O signal line and the power line.

Use shielded twisted pair cables, with the shielding layer grounded at one end.

For AC inductive loads (contactor coils), parallel RC absorption circuits (typical values: resistance 50 Ω, capacitance 0.47 μ F, withstand voltage 200V) are connected at both ends of the load.

For DC inductive loads, parallel freewheeling diodes (diode withstand voltage ≥ 3 times the load voltage, average current ≥ 1A).

If there are multiple PLCs or frequency converters in the control cabinet, power filters should be installed.

Common fault diagnosis and troubleshooting

9.1 Meaning of LED indicator lights

LED color normal status abnormal meaning

POWER green is always on but not lit: no power supply or internal fuse broken

RUN green constantly on: CPU not running (program error or manual STOP)

ALARM red not flashing: low battery voltage; Always on: CPU hardware failure or memory error

BATT LOW red not shining: low battery voltage

9.2 Common faults and solutions

Possible causes and solutions for the phenomenon

The POWER light is not on and there is no input power supply; Measure the voltage at the power terminal when the internal fuse is blown; Replace the fuse (PS221/222/223 with 3A 250V)

RUN light not on, ALARM light flashing, program syntax error; END instruction is missing and the programmer check is incorrect; Clear errors and rerun

ALARM light constantly on, CPU hardware failure; Poor contact of memory package, power off and reinsert memory package; If it still doesn't work, replace the CPU

BATT LOW light on, battery voltage low, replace battery within one week

The input signal is correct but the PLC does not respond. The response time is set too long; Wiring error check input filtering time (DIP switch or programming); Check the wiring of the S/S terminal

The output point does not operate and the fuse is blown (relay/thyristor output); Check the fuse of the output unit for damage (such as using 5A 250V for OD411/OD217); Replace unit

The expansion rack I/O is not working, and the I/O control unit or I/O interface unit is not installed; Check if II101 and II002 are installed for loose connection cables; Re plug and unplug the connecting cable and lock it securely

When programming, it prompts "I/O VERITY ERROR". The configuration of the I/O unit does not match the actual situation; Check the I/O unit model and slot position for memory packet faults; Reinstall the memory package

9.3 Fuse replacement

Power fuse (located on the side of the power unit, circular knob):

Use a Phillips screwdriver to rotate counterclockwise by about 50 ° and remove the fuse holder.

Replace the fuse with the same specifications (3A 250V for PS22x, 4A 125V for PS213).

Rotate clockwise.

Output unit fuses (such as OD411, OA121, etc.):

The output unit needs to be removed (power off first, remove the terminal block, remove the fixing screws, and pull out the unit).

Open the casing and locate the fuse (usually a 5mm x 20mm glass tube) on the circuit board.

Replace and assemble.