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Sepam 80 Logic Inputs - is there a "noise filter" or "debounce" timer setting to avoid spurious events for a signal that is slow to settle?

In certain situations, it may be useful to add a "debounce filter" to the Logic Inputs of the Sepam.  This could be useful when the relay inputs are connected to circuits that are very noisy, or to circuits having signals that take longer than 10ms to settle upon changing from one logic state to another.

In many cases, Sepam Logic Inputs will be programmed to trigger a Time-Tagged Event or User-Defined Message on the front display.  Especially in these situations, it can be useful to filter out extra transitions of a signal that are recorded only due to electrical noise.

By default, the SFT2841 software (and the associated functions in the Sepam firmware) does not provide a "debounce filter" timer delay setting for the Sepam Logic Inputs.  The Schneider Electric Support Knowledge Base contains other documents which explain the default debounce settings on Logic Inputs for the various Sepam platforms.  This information is not included in this FAQ.

By using custom Logic Equations or a Logipam ladder diagram, it is quite easy to program a debounce filter for a Logic Input.  For the sake of this example, imagine that we want to use the I111 input to trigger a Reset of the Sepam relay, and we want to add a debounce delay to this input of 100 milliseconds.

The screen shot below shows a very simple section of logic that could be added to the ladder logic of the relay to implement this logic.  We simply add a TON timer to the desired input, and then use the output of the timer to trigger the desired function of that input (i.e, in this case, a Reset of the relay).  

Notice that since we are using a custom ladder diagram (or Logic Equations) to add a debounce filter to the input, we can no longer simply choose one of the built-in Assignments for the Logic Inputs in SFT2841.  We will need to directly trigger a variable or function in the Equation Editor or Logipam program.  In addition, as shown in the next image, if a Logipam program is used, the assignment for the relevant Logic Input must be changed in SFT2841 to ensure that the Logipam program will take effect.

Once the Logipam program has been loaded to the Sepam, the Logic Input must also be linked to the program as shown above.  Similar logic could also be used to add a debounce filter for the "ON to OFF" transition for this input.

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