Zelio Ladder Programming Question

[kallileo]

I have created a washing sequence of five cycles for a storage tank which is located on a farm. As soon as a selection switch is turns turned on the program starts running until the washing program is finished. The problem is that this specific farm has problems with mains voltage so some times while the program is running or even finished the voltage is cut off and then it is back it starts from the very first cycle.
The client isn't going to invest into fixing his mains so I want to find a way to fix it though Zelio.
Activating "Latching" in all the coils and timers of the program will make the program to continue from where it was before the power was cut off.
The problem is that if the washing sequence was already completed and the selection switch is used to start the cooling process (turning off Zelio) then washing is selected again it will not run because the "Latching".
It could be easily avoided by adding a push button to start the washing sequence after turning on the Zelio but I would like to solve using only software.

How to distinguish fast voltage drops from selection switch turning ON and OFF?

 

[shooter]

if switch is not in off position while plc starts up do not start the sequence.

 

[Lancie1]

The problem is that if the washing sequence was already completed and the selection switch is used to start the cooling process (turning off Zelio) then washing is selected again it will not run because the "Latching".

The last step in the washing sequence should reset all latches and step relays to the beginning positions. If your washing sequence completes, then when washing is selected again, it should run as if it was the first time ever. If your Zelio program does not work like this, then you have some logic errors.

It is best not to use a mechanicaly-held selector switch to start a machine, but rather a pushbutton. Then use the pushbutton to latch on a relay for the first step, which then starts Step 2, which then start the next step, until the last step, which unlatches all relays before quitting. If power is lost, the machine continues at the last latched step until done.

Could you or the client add a pushbutton to the existing control panel, so that the selector must be in "WASH" and then the Pushbutton pressed to start the cycle?

 

[alhughes]

Are you using FBD or ladder?

 

[kallileo]

The control panel and the program were not designed by myself. I'm just trying to fix the problem by creating a new program with some modifications. By adding a push button to start the washing cycle the problem is solved and this will probably be the final solution. I think there is nothing else to be done.
I'm using Ladder.