Motor Run PLC Logix

[Ones_Zeros]

Hello
I was needing some guidance on how to incorporate a high flow value of 14000 into the logic below to start the second motor.

What I have is the following
1. A run permissive bit (B9:1/0) at a flow of 2000
2. Then the logix compares the run hours to determine which motor has the lowest hours to run.
3. Once its determined which motor to start by the 2000 flow and smallest run hours. Then I'd like to add to the logix to where if the same flow gets to 14000 I'd like to start the second motor.

how would i add this logix to the attached screen shot?

I appreciate the help
thanks,

 

[ValeoBill]

Have another rung : If F8:0 > 14000, then B9:3 . Have B9:3 start both motors. B9:3 programmed parallel to B9:1 and B9:2 in motor enable rung. This would start both without regard to which is running. ....off the top of my head...

 

[drbitboy]

Have another rung : If F8:0 > 14000, then B9:3 . Have B9:3 start both motors. B9:3 programmed parallel to B9:1 and B9:2 in motor enable rung. This would start both without regard to which is running. ....off the top of my head...

+1. The point is that each branch in parallel is equivalent to a logical OR: the combined output of parallel branches will be True if any (at least 1) of the individual branches are True. So the logic is

IF (motor A should run) OR (both motors should run) THEN (run motor A)

​

and the same for motor B.

Rung 0002 in the image in Post #1 is a second destructive on B9:1/0 and should be removed.

Having a double-destructive - two OTEs writing to the same bit - is a "feature" many of us have implemented while we were on our learning curve: there's a club; we're having jackets made up; the logic on your double-destructives is identical, so you can be the president.
_

 

[drbitboy]

General comments:

Note that the LEQs on run hours will run both motors when their run hours are equal. Also, because they will both be running together after that, their run hours will remain equal going forward so they will rung together forever (although perhaps there is a per-minute accumulator incrementing the individual run counters, so there may be times when the integral hours differ).

Changing them both to LESs is an even worse approach, as then neither motor will run when the run hours are equal, so the run hours will never change.

At least one correct fix is not obvious - until you see it.

Also, someone with experience might chime in about the disadvantage of evening out the run hours like this.