Pulse

The Plc Kid · May 18, 2011

I need to make 15 1 second pulses in a clogix. Is there a sysytem value or something like in slc that triggers every second that i could use vs using timer and counter.

Just looking for a cleaner way to do it.

The Plc Kid · May 18, 2011

This will be acting on a local ac output for a clippard valve.

cwal61 · May 18, 2011

only thing that comes to mind is the WallClock with GSV Instruction. One Shot current time to storage and compare Last to current with a bit for pulse. Maybe Flash timer and Counter would be cleaner.

curlyandshemp · May 18, 2011

The Plc Kid said:
I need to make 15 1 second pulses in a clogix. Is there a sysytem value or something like in slc that triggers every second that i could use vs using timer and counter.

Just looking for a cleaner way to do it.

You could create a timed task that is executed every 500ms, and place this rung. First call Timer_Pulse is TRUE, next call 500ms later next call Timer_Pulse is FALSE

TConnolly · May 18, 2011

Create a task with a period of one second.

Place a rung similar to this



  Pulse  Counter.DN     Pulse

---]/[---]/[-------------( )-



Program a counter right below it.

  PULSE

---] [-----------+CTU--------+

                 |PRE      15|

                 |ACC       0|

                 +-----------+

If they don't have to be exactly one second, i.e., if 1024 milliseconds is OK you could program a free running timer and use the Timer.ACC.10 bit, then set the preset to whatever is needed to get however many pulses you want.

edit: I see curlyandshemp has made a similar suggestion.

rdrast · May 19, 2011

Check out also, the POSP (Position Proportional) instruction in Logix5000. Note, it is FBD/ST only, not LAD, but it might be applicable to your application.

daba · May 19, 2011

There are many ways to generate your pulses, but you need to be more specific in your requirements....

e.g.
Do all the pulses drive the same output ?
What delay is required between pulses ?
Does the delay need to be variable ?
Will it always be 15 pulses ?
What version of ControlLogix are you using ?
What language do you want it (LAD, FB, ST, SFC) ?
etc.

the more information you give the better responses you will get....

The Plc Kid · May 19, 2011

Daba

this will always be driving the same output. No delays needed between pulses.

It is driving a clippard valve to back blow/ clean a filter. Right now it blows for 15 seconds solid and the oem has recommended we do pulses like this.

Pulse

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