Continuation of the Program when there is a power failure

U_69aebab7-d7cb-4fb2-a632-44421d2e0cdf

Thanks.

In my program I have 6 processes.

1 - Serving;

2 - Pasteurize and Serve (1);

3 - Pasteurize and Serve (2);

4 - Pasteurize and Cool (3);

5 - Pasteurize and Cool (4);

6 - Cool down.

I needed it to save the process that was on so that when it restarts due to a voltage drop, it continues.

Knowing these steps is not really helpful. The types of instructions used and the structure of the program is of bigger importance. Consider making a sample program that you can share with the forum.

Roughly said some of the instructions have a retain function. To give you an idea a picture is shown below (click to enlarge). The attribute of the set-reset-latch is shown.

Saving timers can be a little bit more involved. You may find that you need a time pulse counter instead of a TON, for example. The time pulse counter is not a standard instruction.

Luckily we have the possibility to test what happens after a power outage. There is a power interruption button in the simulator. See the picture below.

Do keep in mind that a too long interruption may not have you continue the process where it left off. So consider making a option to restart or even dump product if that is needed.

Are these introductory notes already of value to you?
What are your thoughts?

[snip]

Follow the link of the program!

Looking at your LAD program, it is not immediately apparent to me how the process moves from one stage to the next. I do see that you are using --( ) coils with a self retaining contact.

Consider making some changes as to accommodate some SR-latches. Think about having a bit that sets when a stage is active. (A stage may have many sub steps.) The SR-latches can be set to retain while the memory bit (like M1) cannot be retained by itself.

What are your thoughts?

Off-topic: If it was my project, I would avoid LAD and code the program in FBD language. The natural language for the LOGO! is FBD. We have seen forum members that had software bugs when using the LAD language. This is not a recommendation to change your program.

Roni Gass

Do you have a tutorial on how to set this up?

The program works perfectly, there is only this case that if the power goes out, until the generator comes back, it would continue with the execution. If you were going to put a UPS on the Logo line, would you be able to pause the program with an input, for example?

Please be specific. Of what do you want a tutorial? My guessing gives the attachment.

Siemens sells a 24V UPS. The PLC does not need to see any switch-over if you use this. From the UPS you can wire a signal that says if you are running from the backup battery which you can use to pause the process.

@Roni: Is the original program your creation?

Roni Gass

This only works if it is an entry with the button in position, it would have to be with the memories. It worked, but for this application it doesn't work.

Procedure:

It has a three-position button that selects three processes, which are: pasteurize, cool and serve.

When the function is selected, to start the process, you need to press the start button and the stop button to stop.

I do not follow your thoughts. What works that does not work for the application? Why is it not possible to route through an SR-latch before the wire reach the memory bit?

Retro fitting the latch for your already designed program is not convenient but it is possible. See the attached animation.