3119
« on: November 30, 2003, 12:00:16 AM »
Will, I am a little confused. You mentioned that you tried the reset instruction described in this post to no avail. Yet you mentioned that when you went to the site later you found that the PLC is running properly. Does it mean that initially you tried the instruction remotely? How were you able to turn ON DIP Switch and perform the reset if you were not at the site?
If your PLC gets back to running properly after a overnight shutdown without your manual intervention or transfering the program to the PLC, then it is likely that it RAM copies of the PLC CPU has been corrupted by the electrical noise in the system but the EEPROM copy is still intact. So after a power down and reset, the PLC runs the program properly again.
Protecting the supply to the PLC is important. Power to the microprocessor electronics is like life blood to human being. The PLC I/O circuit already filtered most of the noise coming from the I/O but the power supply noise goes directly to CPU.
Diesel/gas power generator are pretty noisy fellow. However, most power surge filter on the market are for AC circuit. You may want to try to search for a DC power filter to improve the reliability of your system.