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Train i n g Kit O peratio n Manua l

6-4

6.2 Basic Inspection of a PLC and Troubleshooting

The malfunctions which commonly occur in a PLC and troubleshooting are described in the tables

below.

1. System malfunction

Symptom Troubleshooting and Corrective Actions

All LEDs are OFF

1. Check the power supply wiring.

2. Check whether the power supplied to the PLC control units is in

the range of the rating.

3. Be sure to check the fluctuation in the power supply.

4. Disconnect the power supply wiring to the other devices if the

power supplied to the PLC control unit is shared with them.

If the LEDs on the PLC control unit are turned ON at this

moment, the capacity of the power supply is not enough to

control other devices as well. Prepare another power supply for

other devices or increase the capacity of the power supply.

5. If the POWER LED still does not light up when the power is ON

after the above corrective actions, the PLC should be sent back

to the dealer or the distributor whom you purchased the product

from.

ERROR LED is

flashing

1. If the ERROR LED is flashing, the problem may be an invalid

commands, communication error, invalid operation, or missing

instructions, error indication is given by self-checking function

and corresponding error code and error step are stored in

special registers. The corresponding error codes can be read

from the WPLSoft or HPP. Error codes and error steps are stored

in the following special registers.

Error code: D1004

Error step: D1137

2. If the connections between the PLCs fail and the LED flashes

rapidly, this indicates the DC 24 V power supply is down. Please

check for possible DC 24 V overload.

3. The LED will be steady if the program loop execution time is over

the preset time (set in D1000), check the programs or the WDT

(Watch Dog Timer). If the LED remains steady, download user

program again and then power up to see if the LED will be OFF.

If not, please check whether there is any noise interference or

any foreign object in the PLC.

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Delta Electronics Ethernet Extension Module DOP Specifiche Pagina 145