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Noob question:  How can I turn on a bit for 1 min?  

In all of my attempts, the timer starts counting down again when it reaches 0 and the bit stays high.  

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Which of the 3 types of timers are you using? Look in the Help file under Timers (T) and you'll find a very clear and detailed description of how each timer works.

If you want a bit to stay on for 1 minute, one way is to use a TE timer set for 1 minute. You will need to reset it before using it again, however. Another method is to use a TD timer and Set the bit you want on for 1 min and Reset the bit when the timer expires.

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I need to turn on an MB216 for 1 minute and then turn off MB216.  

This particular project has a function that is activated when the pressure gets too high.  The existing code assumes that the function will release the pressure.  If it does not it runs forever and makes a mess.  Also, if this happens more than three times in an hour I need to alarm.  If I turn up the pressure it stays high and only counts as one event.  

 

My attempts so far, either do not turn on MB216 or it never turns off.  I am sure it is easy and I am probably overlooking something.  

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You cannot do what you want as long as a Direct Contact for MB 1004 is in Rung 7. You either need to remove it or change it from a Direct Contact to a Positive Transition Contact.

Change the MB 216 Direct Coil to a Set Coil in Rung 7, remove the contact for TE 21, and remove the contact for MB 216.

Change Run 9 to:

MB216      TD21

---| |---------( )---

Add after Rung 9:

TD21      MB216

---|P|-------(R)---

Note that the above requires you to change the Timer from a TE to a TD.

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No, if the pressure stays high, MB216 stays on and the timer continues to reset.  

Which doesn't make since because of the rising edges.  

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