I have error following error with Concept quantam PLC. "Controller failed to start" Controller's stop code is 0004 hex"
Any one can define reason and solution.
Thanks in advance.
It is "Logic Checksum Error".
Calculated user logic checksum does not agree with stored checksum. Can be caused by an illegal change of memory or bad RAM. This may also be caused by a defective power supply.
1. Reload program into CPU and start controller.
If PLC will not run, replace the CPU and try again.
2. If controller continues to fail, replace the power supply.
Gloria is correct when she writes:
>It is "Logic Checksum Error".
>Calculated user logic checksum does not agree with stored checksum. Can
be caused by an illegal change of memory or bad RAM. This may also be
caused by a defective
>power supply. <
If this error occurred from a normally running PLC program (not recently modified), then the program has become corrupt.
>1. Reload program into CPU and start controller.
>If PLC will not run, replace the CPU and try again.
>2. If controller continues to fail, replace the power supply.
This is probably the most prudent action.
However, beyond the two items Gloria wrote, I've seen a third problem from time to time: fluctuations of the power feeding the PLC's power supply.
(rant - but not to anyone in particular) While hoping not to drift too far OT, as controllers, "smart"/wireless instruments, etc. get smaller and faster, their power specifications (power quality) grow increasingly tighter. Many are either unaware that such power quality issues exist, or they (especially those writing the checks) ignore this issue beyond paying for some very rudimentary checks. Some refuse to believe there are power quality problems... until the lights are completely out.
While understandable, it's unfortunate that those with knowledge beyond such the basics (power industry) aren't interested in power quality issues that would effect the sensitive controls used in manufacturing down to the 480vac/120vac. Their focus is loss of transmission of voltages at the 115KVA and above, i.e. loss = $$.
I've noticed in recent years the newer technologies being installed on older distributed power infrastructure... they're failing from time to time with error messages that are vague or point to power issues. While UPSes are useful, they may not be fast enough to keep a PLC program from corrupting, or even able to be located in the desired space. If you have large motors, etc. (480vac) feeding the PLC's power supplies (120vac), the likelihood of increased failures such as "Logic Checksum Error" occurs... and will continue to do so for the near future.