labview valve control

[brapp321]

Hello,

I am trying to write a program in Labview to automatically control two valves with a pressure transducer inbetween measuring oil pressure.  I am very new to Labview and have been reading a lot about state machines, but do not know how to implement them.  I have tried following an example, but it does not seem to work.  I would appreciate some help with my project.  I want to be able to automatically open and close the two valves after a 60 second time period for when the pressure reaches and hold 3500PSI or shut off if it does not reach it.

a) open first vavle with second closed and increase pressure to 3500PSI

b) close first valve and hold pressure for 60 seconds

            b1) if pressure does not reach 3500 PSI after 60 seconds, open second vavle and close first valve

            b2) if pressure does not hold 3500PSI for 60 secs and drops below 3400PSI, open second vavle and close first valve

c) open second vavle releasing the oil pressure to a supply tank

[Bob_Schor]

Did you notice the "Broken Arrow" in place of the Run button?  It means that your VI has errors.  Have you tried to fix them?  They are basic LabVIEW "mistakes" that you should be able to understand and fix by yourself.  If you cannot, then you need to learn about Boolean Controls, Case Statements, other very basic stuff like that, all of which should be covered in any of the "Beginning LabVIEW" tutorials that you can find, for example, by looking at the Forum's "Home Page" (upper right).

A comment on your Front Panel design -- you should never almost never have more than one Stop button, and it should (almost) always do only one thing, namely stop the program.  Use push buttons or toggle switches to open or close controls (note that with a Push Button, you can either treat it as a "command", namely "Start Opening the Gate", in which case it should be a "momentary" switch as you're only issuing the command, or a "command + status" switch, meaning "Open the Gate and remind me that it is open, or opening".  The first case requires two switches, one to give the Open command, the other to give the Close command, while the latter can be done with a single switch (Push "On" to open, Push "Off" to close).  Again, it's your (design) choice, but you need to think about programming the switch actions.

I really recommend that you review the Tutorial material.

Bob Schor