slc 500

Dear all,


Is there an instruction or a code that can make the PLC go to a fault state after a certain time period and the fault can only be reset thro a laptop and only if online with the processor. This is important because somehow people have started ignoring the warnings.

thanks'

kanwar

This should do the trick, assuming you haven't modified the math overflow status bits.

But it shouldn't really be necessary to "fault" the PLC. If you want to create a condition that requires online program access to fix, just latch an internal bit without a corresponding unlatch. That bit could then be used to disable the necessary rungs. The latched bit could easily be reset by going online and toggling it in the B3 data table.

Remind me to NOT HIRE YOU, either as an employee or as an integrator!!

If you were to put a time-bomb in one of my machines, for whatever reason, that would be the last thing you would do for me or my company!

It sounds like you have a management problem, not a technology problem.

OZEE said:

Remind me to NOT HIRE YOU, either as an employee or as an integrator!!

If you were to put a time-bomb in one of my machines, for whatever reason, that would be the last thing you would do for me or my company!

It sounds like you have a management problem, not a technology problem.

Click to expand...

I worked on equipment that had these "Time Bombs" in them, after eliminating them we had less Service Calls and things ran a lot smoother.

If people are ignoring the warnings then maybe some operator training would be a good option? Perhaps some security if an HMI is used in this application. Installing 'malicious' code that requires a programmer, and only a programmer, to go online and clear a fault is not the solution and will not end with good results for anyone.

I've heard of this prcatice used for call outs on weekends, in order to increase overtime. Needless to say these people end up looking for new jobs when the 'wrong' person is called out and discovers the real reason for such a callout.

I have to agree, the Company that programmed the Service Calls into the machines was all too willing to do a program revision once they where found out. They had a good product but someone screwed up in the programming. I guess there is more money in Service than selling Machines??

Looking at the original poster's other thread I think he has a PLC which is faulting. He doesn't know why. Has just been resetting it via laptop. And is looking for suggestions as to why the fault is occurring. I don't think he is implying deliberately placing a fault causing code into the program. Though possibly he is asking if someone might have done that.

To urvinder_pal: the next time it faults and you go online make screen shots of the fault message. If your company allows please post the RSS file, especially if you can do a seperate upload in its faulted state before clearing the fault, that would really help.

Faulting PLC

thanks everyone. I will work on the system backwards and then post the result. Hopefully with all the help I will find out what is happening.

thanks once again

kanwar

look under the SLC 500 instruction set I can post the link on Monday if you cannot find it. You can get it at AB website. Look under fault finding routines. There are status bits you can set I believe S:21 but could be mistaken to show where the fault occurs.