Timed VI

[joelkangs911]

Hi,

I am working on an application that requires me to execute a certain task (turn a motor) every 1 hour for 1 minutes.

Though I am getting my code to run correctly, I can only get it to run once for some reasons.

Can someone help me make it a continuous VI until the user decides to stop it, please?

I am using dummy variables to check if it works (1hr -> 30 s, 1 min -> 10 s and the motors are replaced by LED)

Thanks

[GerdW]

Hi Joel,

build a statemachine with some states:

1. wait for x seconds

2. switch on motor

3. switch off motor

Then it will become easy to fulfill your requirements…

I can only get it to run once for some reasons.

- Well, you compare the elapsed time with some set value: the elapsed time is counting up all the time while your value is fixed. There is only one opportunity to have both equal…

- Comparing floating point numbers for equality often gives unexpected results. There are a lot of threads here on this very topic - read them! (Search for "floating point accuracy".)

- Your outer loop is running as fast as it can: that's the reason why that floating point comparison is working so far. But do you really want to burn a CPU core just to wait for some amount of time?

[joelkangs911]

I came across a solution later today.

It does what I want it to do, but I want to make sure that it is a viable and robust enough solution for the application.

Could you look at it? Meanwhile, I will look into statemachines, get familiar with it and come up with something for it.

Thank you for the suggestion.

[RavensFan]

It's not a great solution.

Suppose you set up for a 1 hour loop iteration.  Then you decide to stop the VI.  It might take up to 2 hours after you hit the stop button, for the VI to actually come to a stop.  Not a robust solution.

A state machine can execute much more quickly and can respond to a stop command quickly.

[joelkangs911]

I see. I will work on coming up with a state machine and post any concern along the process.

Thank you