Just, pull the selector switch on the CPU down to STOP position. Wait a couple of seconds. Then push it back to RUN position.

There is not many major effect of this procedure on the CPU itself. It would go through its boot-up routines, and user-define boot-up tasks (if programmed). Depending on the user defined boot-up tasks, the rebooting may be a bit stressful for the machine it controls.


Please note that, your problem is a bit fishy. Are you sure it is a problem from the program? Any cards bad? Any field device mal-functioning? Do you have the PLC source code? What you are suggesting is not acceptable as an operation procedure.

the PLC control two motor (primary and secondary)
the tow motor is same function
the first motor receive the command from PLC to run at certain period and then deactivate
but the second motor continually receive the command without stop ,I've checked the all connection and switches all is correct
I replaced the PLC card but nothing new,
if the problem from PLC program ,what can I do??

If the program ever ran correctly it would be VERY odd for it to change to something with a problem that still runs at all.

What this means is that you have a switch or wire or something external that is causing the problem. You say, "I've checked all the connect and switches all is correct", but it's not clear to me that you've checked their actual function and continuity right up to the PLC terminal screws. Have you used a meter and traced the actual signals?

If you're ABSOLUTELY sure the wiring is flawless and you've swapped in a new PLC, you'll need someone who understands the PLC and the development tool to work with it.

Keith Cress
kcress - http://www.flaminsystems.com

It would be helpful to know what the PLC is controlling, reversing contactor or a ac/dc drive and if any work was done on these devices. Most PLC I/O cards have integral indicators showing the active output/inputs...is the "run command" active in the PLC? if not you have a hardware or field wiring problem.