Help me with valve opening cycle

[Sergey(PSU)]

About a week ago I have posted similar question (http://forums.ni.com/ni/board/message?board.id=170&message.id=167412)but it had too complicate VI that nobody could understand it.

I have created simplified VI for the problem I have:

Lets call this Vi valve opening program (that's what I am going to use it for).

This program should have two mode of  operations: manual and automatic.

In manual (constant) mode it just opens valve (BIG GREEN LED) periodically for some period of time. You can try it changing switch from Auto to Constant mode. It works as I would like it to be.

Now Auto mode: It should start valve opening procedure when pressure is above some limit, again you can try it by changing switch from Constant to  Auto mode and adjusting either pressure knob or "BF start level". This part of the program does not work as I need.

Because it is feedback, in real life the pressure coud rise above the START level and then drop back during valve opening, it means that Valve opening procedure stops to work (you can check it by changing pressure from level above start level to level below it at the moment when LED is lit). I need it to continue to work in the same manner as in a constant mode: when it starts valve opening cycle it should finish it no matter what the pressure is and it should repeat itself after that cycle only if the pressure is still high.

Thanks. Sergey.

[Rashid]

Sorry, I'm not proposing solution but while
looking at your VI I had to re-arrange it as it's very difficult to get where inputs & outputs on your block diagram.

Hope this helps to others.

See attached for the same VI but more readable.

Best regards,
Rashid.

[Sergey(PSU)]

Thanks Rashid,

for the suggestion. Unfortunately I can not open your file. Which Labview version it  is? Could you, please, save it as Labview 7.1 or just as a image file for me.

Thanks.

[nyc_(is_out_of_here)]

see if the following will work

[johnsold]

sergey,

I have put together a simple state machine which will implement your specified functions. I changed the names of some of the controls to more accurately reflect the way I used them, specifically Open and Closed representing the minimum time duration that the valve will stay open or closed after a transition.

Lynn

[Sergey(PSU)]

Lynn,

thanks for the sample.

But I am not sure that it works as I need.

In "constant" mode it works just as mine and it is OK, but in auto mode it just opens and stays opened while the Pressure value is higher than a limit. I would like it to work as it does in "constant" mode, open and close.

May be I missed something.

Sergey.

[nyc_(is_out_of_here)]

Did you try programming a VI as shown in simple.jpg?

I think that will work for you.

[Sergey(PSU)]

I did take a look and it looks like it is the same algoritm as in my program.

I'll try to make VI or can you post your VI(compatible with LabView7.1).

[johnsold]

Sergey,

I think I may have misunderstood your requirement in the Auto mode. Is this what you want?

Auto mode:
If Pressure > setpoint
Then Open valve
Wait minimum open time
Close valve
Wait minumum close time

Repeat If...

The attached VI does this. Also note that an error exists in the previous version. It does not properly set the timeout times.

Lynn

[Sergey(PSU)]

Thanks a lot Lynn,

looks like it works properly now.

I'll try ti understand how ot works. Any way I can us it as it is already.

Thanks again.

Sergey.