Emerson Exchange 365

• Not Answered

Signal Intermittently

Hello,

I need to activate a signal intermittently (DO), how can I program this?

Thank you very much.

Kind regards

RAguilar

• 6 Oct 2022 11:20 AM
• Cancel

5 Replies

• SANAND

  

  • 6 Oct 2022 11:48 AM

  Open a new control module, add Reset override (RS flipflop). Connect out of RS flipflop to In of On delay block and set timer for after how many seconds the DO should be On. Connect out of On delay block to In of Off delay block and set required time to keep the DO in On condition. Connect out of Off delay block to Output parameter, change the parameter type to IO and link the parameter to required DO channel. Also connect the output of Off delay to Reset input of RS flipflop. Keep the Set value always on in offline so that it remains 1 even after downloading the module. Save and assign the control module to the controller which is having this DO channel and download the control module.

  • Cancel
• RAguilar

  

  • 6 Oct 2022 11:54 AM

  In reply to SANAND:

  Hello SANAND,
  
  Thank you very much, could you send me a picture of the control studio, please.
  
  Thank you very much.
  
  Kind regards

  • Cancel
• SANAND

  

  • 6 Oct 2022 12:07 PM

  In reply to RAguilar:

  Hello Raguilar,
  
  Sorry. Currently i am not working with DeltaV and shared you this logic based on my past experience.

  • Cancel
• Bryce Elliott

  

  • 6 Oct 2022 2:03 PM

  Can you describe your application a little more? I think you may want something like what Bruce Greenwald details here, but I'm not certain: acmebiotech.blogspot.com/.../
  It requires the I/O point itself to be configured a certain way and for the module to be set up in a fashion complimentary to that.

  - Bryce H. Elliott, P.E.

  • Cancel
• Andre Dicaire

  

  • 6 Oct 2022 3:21 PM

  You've not given us much detail on what "intermittently" means. Or what IO hardware you are using.
  
  The DO channels on DeltaV can be configured as Momentary, Continuous pulse or Latched.
  
  Normal or latched output follows the state of the logic set in the module.
  
  Momentary allows you to set a time duration for how long the DO will stay energized on a positive transition of the module signal. This would allow a 1 second module to generate a short pulse, turning off before the module executes again. The Module would have logic to determine when the DO is energized. The module has to execute a second time to clear the channel before another pulse can be generated.
  
  The Continuous Pulse provides a duty cycle where the DO channel will effectively generate a square wave, well, rather a rectangle wave. The period of the wave is set on the channel and the On Time of the DO is set as an analog % value. This allows an AO block to drive the DO channel.
  
  Depending on what your application is, you might want to consider one of these options for the DO channel and configure the control module accordingly. For instance, if you want to intermitently drive the DO channel for a short 100 ms pulse, that occurs infrequently, or on demand, the Momentary DO setting would allow you to do so with a 1 second module, provided you never need a second pulse within 2 seconds. The module would drive the DO with a one scan positive transition and reset on the next scan.
  
  But if your intermittent output is expected to be ON for several seconds or for a variable amount of time, you would want to use logic in the control module to have control of those varying times.
  
  To offer a solution, we would need to know more about the behavior of the output, in terms of what triggers it, how often that is likely to happen and how long the output stays ON. There will likely be multiple approaches to solving the problem, but finding the "right" solution means understanding the problem.

  Andre Dicaire

  • Cancel