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Watchdog Issues
How do I continuously loop inside a program without getting a watchdog error?

I am running a process involving solar power. To determine the startup of the system in the morning I want to continuously run through a startup program throughout the night.

To do this I am checking the PV voltage, and if it is not a min value I am jumping back to the top of my program. Is it possible to do this without getting the watchdog error or is there a better way to do loops like this using different programs?

The reason I am doing it this way is that I don't want to turn on other equipment until the power is high enough to run said equipment.

I am using a Micro850 controller if that makes any difference.

Simply move the watchdog timer logic to the start of the program so that it always runs and is not skipped by your voltage check. Or call it before the voltage check is called.

good luck

I don't know how to do that. The watchdog timer is something that seems to be hardwired into the program. I haven't created anything for it to happen.

I think I got around it though by writing my programs differently. Thanks for your response.

By Bob Peterson on 9 February, 2018 - 7:24 pm

It appears that you have a poor understanding of how this kind of controller is programmed. There's no need for a jump statement to wait, just program it not to do anything until you want it to.

If it's an AB MicroLogix 850, then get rid of the loop. If your "run" command is an output from the controller, just put the voltage check as a condition to turn on that output. If your program is complicated and you want to interrupt the sequence (or whatever...), it will likely be more complicated than what I just described.

The watchdog timer in these is built in to the processor and makes sure you don't have any endless loops. The time-out value can usually be adjusted but not long enough to last overnight (nor should it be since that isn't the right way to do this).