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Troubleshooting of PLC SCADA system
Prior to beginning a system start up procedure, it is important to check and verify that PLC system has been installed according to the manufacturers specifications and that the installation meets local, state and national codes. Special attention should be given to system grounding.
Before applying power to the PLC controller, following is to be ensured:
Check all power and communication cables to ensure that connector pins are straight and not bent or pulled out.
Connect all cables making sure that connectors are fully inserted into their sockets. Secure connectors as applicable.
Ensure that all modules are securely held in the I/O rack.
Place PLC System processor key switch to a safe position.
Apply power and observe processor indicator light for proper indication. When power is applied and safety switch is closed, the power supply should provide the necessary DC voltage for the processor and I/O rack. If the proper voltage is present, the input indicator LEDs of the input modules will function. Any input device that is closed or ON will have an illuminated LED.
Testing PLC Inputs PLC input module should illuminate. Failure of a LED TO illuminate indicates:
Improper input device operation
Incomplete or incorrect wiring; check to be sure that the input device is wired to the correct input module and proper channel.
Loss of power to the PLC input device
Defective LED or input module
Testing PLC outputs before testing output devices, it must be determined which devices can safely be activated and which devices should be disconnected.
The second method uses the force function of the PLC system to energize outputs, one at a time. This allows the user to turn an output device ON and OFF without using a push button or other contacts.
For final system checkout, the following steps should apply:
Place the processor in the program mode
Clear the memory of any previous rung used for testing.
Using a programming device, enter the program (ladder diagram) into memory.
Place the processor in the test or disable output mode, depending on the PLC system and verify correctness of program.
Once the circuit operation has been verified in the test or disable output mode, the PLC processor can be placed in the run mode for final verification.
Make changes to the program as required (timer setting, counter presets etc.)
Once the circuit is in final form and the machine or process is running correctly it is recommended that a copy of the program be made.
Systematic approach towards PLC troubleshooting should consist of the following steps:
Symptom recognition
Isolate the problem
Corrective action
The status lights of a typical PLC system with built-in power supply indicate:
DC Power ON if this LED is not lit, there is a fault in the DC power supply. Check the power supply fuse or incoming power.
Mode indicates which operating mode the processor is in (Run, test, program etc.). The fault may simply be that the key switch is in the wrong position.
Processor fault when this status light is on
Memory fault this status light illuminates when a parity error exists in transmission of data between the processor module and memory module. Replace only one module at a time.
I/O Fault this light indicates a communication error between the processor and the I/O rack.
Some PLC manufacturers offer deluxe output modules that have two indicator LEDs. One indicates that the logic from the PLC processor has been received to turn on the output: the second LED comes on when the triac or power transistor has been turned ON. Similar to the deluxe output modules, there are also input modules that have two indicating LEDs. The first LED indicates that the input device has closed and a voltage signal has been received by the input module; the second LED indicates that the status of the input device ON has been communicated to the processor.
For more, visit at Troubleshooting of PLC SCADA system
Prior to beginning a system start up procedure, it is important to check and verify that PLC system has been installed according to the manufacturers specifications and that the installation meets local, state and national codes. Special attention should be given to system grounding.
Before applying power to the PLC controller, following is to be ensured:
Check all power and communication cables to ensure that connector pins are straight and not bent or pulled out.
Connect all cables making sure that connectors are fully inserted into their sockets. Secure connectors as applicable.
Ensure that all modules are securely held in the I/O rack.
Place PLC System processor key switch to a safe position.
Apply power and observe processor indicator light for proper indication. When power is applied and safety switch is closed, the power supply should provide the necessary DC voltage for the processor and I/O rack. If the proper voltage is present, the input indicator LEDs of the input modules will function. Any input device that is closed or ON will have an illuminated LED.
Testing PLC Inputs PLC input module should illuminate. Failure of a LED TO illuminate indicates:
Improper input device operation
Incomplete or incorrect wiring; check to be sure that the input device is wired to the correct input module and proper channel.
Loss of power to the PLC input device
Defective LED or input module
Testing PLC outputs before testing output devices, it must be determined which devices can safely be activated and which devices should be disconnected.
The second method uses the force function of the PLC system to energize outputs, one at a time. This allows the user to turn an output device ON and OFF without using a push button or other contacts.
For final system checkout, the following steps should apply:
Place the processor in the program mode
Clear the memory of any previous rung used for testing.
Using a programming device, enter the program (ladder diagram) into memory.
Place the processor in the test or disable output mode, depending on the PLC system and verify correctness of program.
Once the circuit operation has been verified in the test or disable output mode, the PLC processor can be placed in the run mode for final verification.
Make changes to the program as required (timer setting, counter presets etc.)
Once the circuit is in final form and the machine or process is running correctly it is recommended that a copy of the program be made.
Systematic approach towards PLC troubleshooting should consist of the following steps:
Symptom recognition
Isolate the problem
Corrective action
The status lights of a typical PLC system with built-in power supply indicate:
DC Power ON if this LED is not lit, there is a fault in the DC power supply. Check the power supply fuse or incoming power.
Mode indicates which operating mode the processor is in (Run, test, program etc.). The fault may simply be that the key switch is in the wrong position.
Processor fault when this status light is on
Memory fault this status light illuminates when a parity error exists in transmission of data between the processor module and memory module. Replace only one module at a time.
I/O Fault this light indicates a communication error between the processor and the I/O rack.
Some PLC manufacturers offer deluxe output modules that have two indicator LEDs. One indicates that the logic from the PLC processor has been received to turn on the output: the second LED comes on when the triac or power transistor has been turned ON. Similar to the deluxe output modules, there are also input modules that have two indicating LEDs. The first LED indicates that the input device has closed and a voltage signal has been received by the input module; the second LED indicates that the status of the input device ON has been communicated to the processor.
For more, visit at https://aristautomation.com/
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