Stop and Start process

There all I am currently having some trouble with a program and I would appreciate some ideas and help.

The main program is based on tank filling process and I have inserted the heating and mixing of the fluid in a sub routine once the tank is filled.

Would you suggest a way I could stop the process upon the pressing of the stop button anywhere during the process and when the start is pressed the problem will continue where it left off?

Somewhat of a pause button situation if you will

Thanks

Iconoclast

iconoclast,

welcome to the forum.

please tell us what plc you are using and post your program.

regards,
james

Would you suggest a way I could stop the process upon the pressing of the stop button anywhere during the process and when the start is pressed the problem will continue where it left off?

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Yes, all you need to do is create a "System Run" relay. Use the Stop and Start Pushbuttons, and also the Auto-Stop flag relay (if you have got to Exercise 3) to control the new System Run relay. Then use this relay in every rung that has an Output (except not for the indicator lights). When System Run is OFF, all your motor Outputs will turn off. When System Run is ON, the process should start and run normally. (See picture).

PS: If you are doing the LogixPro Batch Mix problem, then there are some other steps necessary to make it restart where it left off. For example, use a RTO timer instead of a TON.

Exactly i am trying out the batch mix problem.

I am trying to attach a picture but cannot seem to do so (Maybe i can send an email with the rsl program?)...I have used a subroutine with TONs and their respective TT and DN to produce the desired output.

I did not quite understand what you meant with RTO instead of TON

REALLY appreciate your help guys!

iconoclast said:

Exactly i am trying out the batch mix problem.

I am trying to attach a picture but cannot seem to do so (Maybe i can send an email with the rsl program?)...I have used a subroutine with TONs and their respective TT and DN to produce the desired output.

I did not quite understand what you meant with RTO instead of TON

REALLY appreciate your help guys!

Click to expand...

An RTO timer is different from a TON timer in that the accumulator ACC does not reset should the input go low. It continues to time where it left off from when the input goes back high again. To reset if you can either write directly to the ACC (unusual) or by using a reset coil with the timers address (most common). I am certain you can see just by this description why this timer would be helpful with your application.

Depending on exactly what your process is, you might achieve the same using counters as well. Especially if you are using prox switches or such to count auger revolutions or similar.

I have used a subroutine with TONs and their respective TT and DN to produce the desired output.

Click to expand...

You only need one Retentive Timer On Delay (RTO) to run the mixer for 8 seconds. If you used any other timers for the Batch Mix Exercise 3, your solution is inefficient, and probably does not work very well. You do not need a subroutine for this short program. You should be able to do the entire problem with about 11 rungs of logic (including a Count Up and Count Down counter to record the flowrate from Flowmeter #1 and Flowmeter #3). A subroutine will only complicate the program for no good reason. However I found it useful to use two B3 Step (Flag) relays, one for "Mixing Cycle" and another for "Drain Cycle".

Depending on exactly what your process is, you might achieve the same using counters as well.

Click to expand...

This is a link for the description of the LogixPro Batch Mix Exercise 3 "Continuous Operation".

http://www.thelearningpit.com/plc/psim/doc/batchlab.html