Feb 4, 2011

Troubleshooting with PLC Problems

Many a times it happens in the industry that a particular machine is not operating correctly or there is an error in some process. The reason can be numerous for these kind of problems like it is possible that some input is malfunctioning or processor of PLC is giving some problem. In this post we will discuss the general problems encountered.

||How to Troubleshoot PLC Related problems||

To check out the problems whether it is related to PLC for field devices , first of all connect to the the PLC and upload the PLC Program . Now every PLC Programming software have the feature to check the Error Log. Check out the Error Log in PLC and see if there are any errors.
There can be two types of Errors either Fatal or Non fatal , if there is Non-fatal error then simply clear it and if Fatal error is there then note down the code of error and check out the meaning of Error Code in the PLC user Manual.
The Fatal or Non Fatal errors can be easily monitored as every error has its unique code and necessary action can be taken to prevent the error.

The Fatal error is generally comes due to improper I/O allocation in PLC or Memory of the program is more than the PLC memory , due to battery , there can be various reasons , just check out the error code in manual and there you will also find the necessary steps to be taken to remove the error.

But sometimes it happens that a PLC Panel is installed in some machine and suddenly the machine stops to work and we also found that there is no problem in PLC. So in this case definitely there is some problem in the I/O connected with PLC. Yes we can identify that which input or output is malfunctioning.

Upload the PLC Program and monitor online and one by one check all the inputs and find that is there input is coming in PLC and similarly repeat this for the outputs. If some Input or Output device signal is not coming in PLC then definitely there is some problem in that , it can be due to wrong wiring or loose connections.

Also there can be situation that when all inputs and outputs devices signal are coming to PLC but still the machine is not operating , then it may be possible that Interlocking has been done in PLC , so in the PLC Program look out for the Interlock (IL) Instruction and check its condition and rectify the same.Subscribe to Automation-Talk by Email.

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