need to debounce a valve output

Hi Group
I have an on/off type steam valve which is set to maintain temperature in a vessel. If the PV drops below setpoint, the valve is energized with a simple OTE placed after a LES instruction which compares the PV with a fixed temperature setpoint.
Actually, forgive me, its not the actual valve output in the OTE instruction, its a dedicated bit which is monitored on the next rung as an XIC which when true will energize the valve output with an OTE.

Issue is, sometimes the valve chatters for a short period of time since the output from the LES instruction is "fluttering" for lack of a better term.
To eliminate the chatter, I want to energize the valve immediately for one full second when the input bit for the valve goes true, even if the input only stays ON for, say 20 milliseconds. Also, if the input stays on for longer than one second, of course I need the valve to stay on too. Anyone have any tips as to how to accomplish this efficiently?

Using Rockwell terminology, the TOF instruction and it's .DN handles this nicely.

As soon as the TOF goes True, the .DN bit will be true.
The .DN bit will remain true until the TOF has been false for the length of the PRE.
If you get blips for less than the preset, the .DN bit will remain True

Works like a charm, thanks so much!

dmroeder said:

Using Rockwell terminology, the TOF instruction and it's .DN handles this nicely.

As soon as the TOF goes True, the .DN bit will be true.
The .DN bit will remain true until the TOF has been false for the length of the PRE.
If you get blips for less than the preset, the .DN bit will remain True

Click to expand...

dmroeder said:

Using Rockwell terminology, the TOF instruction and it's .DN handles this nicely.

As soon as the TOF goes True, the .DN bit will be true.
The .DN bit will remain true until the TOF has been false for the length of the PRE.
If you get blips for less than the preset, the .DN bit will remain True

Click to expand...

dmroeder has a great suggestion. The only thing I would add is if you want the 1 second to start when the input bit goes high try putting an XIO of the timer's done bit inline with the timer (between the input bit and the timer). That way as soon as the input bit goes high, the timer's done but will open the rung (making the rung false) starting the timer. It works just fine without that but the timer won't start until the input bit goes low.

Debouncing it with the timer technically works to prevent chatter, but the more typical way to do it would be to use a deadband controller. Basically you need two LES instructions and a seal in, instead of just one LES as you have now.

That will prevent unnecessarilly firing the steam valve over and over at the set point.