Emergency Stop Button

[Billy Madison]

     Hi.  I'm trying to figure out how to make an emergency stop button for my VI.  If I click the "Abort Execution" button while my VI is sending an output voltage, the voltage continues to be sent out until I clear it with another program I made that sets all digital I/Os to zero.  This is not good, because this particular output is sent to a $1000 motor that I am testing to see if it can go up in a satellite, and I don't want to break it.  Can someone please help me?

     I've tried many different combinations of event structures, case structures, and local variables, and none of them have worked for me.  From what I can gather, it seems the only way to create a button that will end my VI is if I put the entire VI into a while loop and to have the stop button hooked up to the "Stop If True" box.

     Also, I don't know if this makes a difference, but I want the loop to either only run once, or stop if I press the Emergency Stop button on the front panel.  I just figured that I could set up a comparison test to see if the loop had run more than once, and then to connect that to an "Or" test to see if either the stop button was pressed, or the loop had completed one iteration.

     I'm using a PMD-1608FS digital/analog I/O device.

Thanks very much for any help you can give.

-Billy Madison

P.S. For those of you who think this is an easy problem, and that I sound like a noob, that's because I am.  I taught myself how to use LabVIEW a week ago, from reading the book: "LabVIEW for Everyone."  (By the way, this book did not have very good examples.  It was only an 'okay' book for describing the theory of using different tools in LabVIEW).  My problem is that I only have a few more days at my job before I go back to school.  I want to help them get as far as I can before I leave, so that they will have me back for the summer.

[AnalogKid2DigitalMan]

Billy:

You posted to the Breakpoint, the Social forum. You should probably repost to the LabVIEW forum.

A critical E-Stop should not rely on software or PC operation. If the PC OS or your program 'hangs' you will have no control of the hardware at all.

Use a real E-Stop switch that directly disconnects power or drive signals to the device.

-AK2DM

[Billy Madison]

I wanted to do something like that.  My boss however, is really anal about the way he wants me to do things.  He wants me to put all the controls on the Front Panel for him.  He wont even let me use a fuse as a way to disconnect power to the motor if the current is too high...

[AnalogKid2DigitalMan]

Billy:

Very well, he is the boss, but sometimes the view from the top.......

Seems odd not to provide protective measures for personnell, equipment, and expensive UUT's.

Good Luck and Have Fun!

P.S. -- I'm telling Jim K. 🙂 I have the book, it was quite good in my opinion.

-AK2DM

[smercurio_fc]

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Billy Madison wrote:
I wanted to do something like that.  My boss however, is really anal about the way he wants me to do things.  He wants me to put all the controls on the Front Panel for him.  He wont even let me use a fuse as a way to disconnect power to the motor if the current is too high...

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Frankly, your boss is an idiot. Tell him an engineer said that.

[Billy Madison]

He's an engineer too.  And, he knows more than me so I have to respect him. I think he's just stubborn.

[Billy Madison]

Don't get me wrong, I think the book was really helpful for getting started.  (I skipped the advanced LabVIEW sections).  It just doesn't have any examples that I can use to my advantage for what I'm specifically doing.

[smercurio_fc]

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Billy Madison wrote:
He's an engineer too.  And, he knows more than me so I have to respect him. I think he's just stubborn.

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No, any engineer who doesn't see the need for a hardware emergency button to protect a $1000 piece of equipment (like you wanted to do) is not being "just stubborn", and, in my book, would never get my respect. Perhaps it's my Italian blood, but that's my opinion.

[yenknip]

There's also the health & safety implications of not putting an interlock on a significant piece of moving hardware.

[LV_Pro]

No fuse to protect the equipment, now that is funny! I remember a piece of hardware a number of years ago that had an issue which we refered to as "the microprocessor (I don't remember what type of relatively expensive IC) blows to protect the fuse".  Not having any idea of what this system does, what an E-Stop on it is to protect, but if it has any health safety implications (moving parts, high voltage supplies, Gigawatt laser) depending on WinDoz to be available to stop it is STOOPID. I just fixed a program of mine where a serial port write would hang so badly that it required a Ctl-Alt-Del, kill the app in Windows task manager to stop. And it turned out to be the wrong codec in Windows Media Player being run by my program the last run through. Just what you need when a motor drive starts over reving!!!   I might mention, regarding the health issues, that in many locals (internationally) it is against the law to have the software be the primary means of doing "estop" type functions. If the boss is in one of those areas he isn't being anal, he is being an ...

Not too many engineering schools get to discuss these aspects., so "he's an engineer" may not mean exposure to the issues this brings up.

 Has there been a recent upsurge in LabVIEW questions posted here, or have I not been reading the Breakpoint enough lately?

Message Edited by LV_Pro on 01-22-2009 12:37 PM