Battery backup failure issues

[Walkerok]

I was faced with a problem yesterday on a different PLC brand where certain pieces of data were lost after the unit had been sitting on a shelf as a backup for the customer for too long. This brought me to think about what I need to do for Unitronics products to avoid the same fate at some point in the future.

Lets take an easy scenario. I have a PLC that I am using to monitor different limit inputs on a machine. For each of these limit inputs I have a fixed amount of time I want to wait to avoid nussance shutdowns and alarms. I do not want the user to have access to the delay times so that the times can not be extended from what I have set. I typically block the ability of the useer to get to info mode so that they can not change data in my program through that particular doorway so info mode will not be available to manually re-enter the times to key limit delay timers.

In its simplest form I have a net that says that if I0 is true for 3 seconds then make MB0 true to trigger an alarm or shutdown depending on a decision set that is enterable by the user. When the battery dies (hopefully 7 years into the future and not sooner) I am assuming that this information will be lost with no user ability to re-enter all of the appropriate time delays.

The question is what is my best way to protect key pieces of data even after a battery failure so that only the user enterable variables would need to be re-entered after a battery failure? Flash burned table, loading values into MIs and T variable on first scan every time, other solution? I am looking at this for Jazz, M91, and V series controllers.

[Emil]

First of all - yo have SB8 to prevent you about battery status. So you can prevent situation, where the data will be lost.

If anyway you want to prevent any case of data lost, just idea I performed in some projects:

You can define Data table as Part of Project. The data there will be stored in FLASH memory, whicy is battery independent.

In this data table you can define a list of important parameters with, let's say one column for "Name", another column for Min, another one for Max and the last - for default value.

Then, you can make a power up subroutine, which will read the data from this DT, will compare with the value in relevant register and if it's out of range, load the default value.

Just idea...

[Simon]

The question is what is my best way to protect key pieces of data even after a battery failure so that only the user enterable variables would need to be re-entered after a battery failure? Flash burned table, loading values into MIs and T variable on first scan every time, other solution? I am looking at this for Jazz, M91, and V series controllers.

If it is OK to initailise the values to your defult settings on every power-up, then set them as "power up" values in the required operands.

Note that if you set a timer preset value in the ladder program, that value is retained as part of the project. If the timer preset has been modified online, then the battery dies, the timer preset will revert back to the original value as set in the project file.

Otherwise, if you want to re initialise the values on demand rather than at every power-up, use Emil's suggestion of putting values into a DT as Part of Project.