ShaunR

Name: Windows API Submitter: ShaunR Submitted: 09 Sep 2010 File Updated: 03 Jan 2011 Category: General LabVIEW Version: 2009 License Type: Other (included with download) Windows API Utilities. An eclectic set of wrapper VIs around some windows API functions. I wrote these many years ago (1998? wow!) but have used them to some extent in virtually all my windows programs. I've included all the original functions (accidentally re-compiled under LV 9.0) and just wrapped them up in a project and added the LAVA required stuff so your getting them "warts 'n all". Many functions have been superseded by LabView functions and I expect many people already have their own. But there are still some gems I couldn't do without and maybe someone will find them useful. Installation: Unzip to a directory of your choice. Required Packages: Labview 9.0 or greater Windows XP or greater (may work on earlier versions) Known Issues. None. Versioning: Current version 1.0. Contact: PM ShaunR on lavag.org (http://www.lavag.org) Click here to download this file

I wonder why NI pulled the LabView Player? That would have solved Cats code review problems at least.

Fantastic. Very talented guy. But a very expensive way to record a song

Once again in the minority. Its good to be back Afraid? Hardly (that's almost funny ). Can't argue with that I think you mean most people that program in Linux or Unix. When I write text programs in windows and I need a quick "tool" I write something in LabView On the rare occasions I am required to do something in Linux, I probaly still wouldn't use those utilities for task automation unless there was no other way. On windows the analogy would be using the cmd.exe do tasks which I think (personally) is a bit icky, But I recognise it is a standard method on Linux/Unix.. Now pearl I would use to write a script to automate a task after all it is a "scripting" language (if only i could understand my own code 3 weeks later ). I find the project manager is sufficient. Although perhaps you could elaborate? Hmmm. One of the areas I definitely wouldn't use scripting is data population. I would prefer a run-time solution so that I only have to replace the document not re-hash/re-compile my code every time there is a spec change.. We have a similar implementation where the design engineers create a spec, which I deploy as part of the distribution and is parsed by the software. The document comes under document control and i've offloaded the responsibility of keeping it up to date onto a technician. As for system documentation. Shouldn't this be generated from the requirements spec? Maybe so. But my time and budget aren't. There has to be a very strong reason for doing something that is not easily equatable to tangible benefit (damned accountants ). Should I spend 2 days writing a script that can only be used to make my life as a programmer easier? Or should I spend that time to write a piece of code, that I can deposit on the clients site,and means I save travelling expenses, board/logging and corporate face?. If it was deployable I could do both Tool developers don't have this dilemma since they can monetise scripting directly. Perhaps we should start another thread since we are now way off topic. Or maybe we're getting to the point where there we just admit there are 2 camps (ok one of them isn't really a camp, more of a sole resident )

What crossrulz. means (I think) is that events are more efficient for user selection than a state machine. Assuming that the goal is to make a selection based on user input. Although it is not a state machine in the classical sense, since the the next state is not dictated by the previous one. Note that I have changed the mechanical action of the booleans too.

I'm sure (as we've seen) people that create product will use scripting (the same way that a programmer will use more memory if more is available). But as it cannot be deployed it remains a feature that I (not being a tool developer) could have, quite happily, lived without . Tool developers, however, love it to death because it is the only way they can exist. It has opened up a 3rd party business where previously there was none and, previously, non-NI add-ons and tools were petty much free (this being a cultural change rather than a technological one) .I just find it really hard to get excited about scripting:P I can't comment on your LV 2010 (or indeed web-services) only to say that in LV2009 an executable, DLL, and .NETs build number is included and indexable and maybe the lack of one on a web service is an oversight that should have been reported. But you didn't need scripting to do that,. The useful feature (and I do think this is really useful AND in benefits all of us) is the additionof the pre and post vi's without wihich, even scripting couldn't help and you would have had to use your previous method (which was probably a vi you run after the build, manually)

I think that depends on your point of view. I have used "lazy" instruments before.But generally my design philosophy involves hardware several layers below the user interface, modularised and loosely coupled. This enables me (amongst other things) to bolt on different user interfaces to the same back-end Peculiarities of a device are handled by the modules and/or driver. I re-use many of the modules and wouldn't want to keep putting instrument specific code in to the user interface.

Why do you need to do that? Are you porting to LV?

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What did it do for scripting? Scripting is only useful for tool developers. Those of us that create product have zero use for scripting. Except perhaps the occasional need to automate a few tedious tasks if we find ourselves in a lax minute or 2.. OK just re-read you post...lol. Missed the "we" bit . Yes "you" (as in tool developers) did get it published by NI, but my original point still stands.

In fact. thinking about it..... You don't even need the replace element.

And your reply is that they shouldn't be using un-trained operators But I see what your after. I think you will just have to filter the changes. Although I had a quick look at the slider example you referenced and I certainly wouldn't have done it that way One thing you could do is build an array of the controls that are clicked and the latest value for that control and put that in the on change event case (the same on-change would be used for all controls). You would need to look up the control reference on each click and if it doesn't exist, add it. This is fairly trivial. Then, in the time-out case (set it to a few seconds for example) unwind the array using a for loop and read the control(s) that have changed and send the value to the the instrument(s). If nothing has been clicked, then the for loop won't execute when the time out expires. If some controls have been clicked (the timeout will be reset every click automagicaly) , then they will have an entry and the for loop will iterate through them. Well. That's one way at least. You could also use Cats previous method and start a timer when the user clicks on a control. Then, if the timer times-out,, activate a really annoying sounder (add flashing lights too) and a dialogue box saying "Press The GO Button Idiot". Finally, send an e-mail to the logged in users supervisor telling him that the operator needs scheduling for re-training as he cannot follow simple on screen instructions. I guarantee you will only be called out once late at night

It's a bit like asking "what's a LabView Wire" equivalent in C/C++

Amen!

HI Cat. Hows tricks? If I understand correctly (which is quite rare) could you use the "mouse leave"event case so that your "send to instrument" function only fires when they move outside the control (i.e stopped clicking and gone elsewhere). The advantage of that is you can attach all your controls to a single event case and use the events control ref to wheedle out the control and value.

Sorry for the delay. Had my own projects that weren't falling and needed kicking into place No need to apologise. I was just trying to let you know that you need to understand what you are doing OK. So you have a 12 digitally controlled motor. That's your design decision Nothing wrong with that, after all we need to keep within budget don't we? I'm assuming you have seen the NI PID Examples and seen that they get a lovely smooth control curve. Right?. Just change the sampling time from 50m to, say 500 m. Does it still look like a nice well controlled curve? What do you see? Remember we haven't changed any PID parameters, or the load we are controlling. Just how often we sample the PV. What do you think is happening here?

Name: Dispatcher Submitter: ShaunR Submitted: 07 Sep 2010 File Updated: 03 Jan 2011 Category: Remote Control, Monitoring and the Internet LabVIEW Version: 2009 License Type: Other (included with download) This is a Publisher/Subscriber implementation of network communications. The package is comprised of two main parts. 1. A Dispatcher that handles connection requests. 2. An API for interacting with the Dispatcher. Overview. Most people are probably familiar with RSS feeds. An RSS feed is an example of a publisher/subscriber implementation, where information is "published" onto the internet and people may "subscribe" to updates using their browser or some other client. A single published service may have millions on subscribers and publish its data every few hours as data changes or periodically, maybe once or twice a day. This package contains a similar implementation where a client "subscribes" to a "publisher", however, it is geared towards high bandwidth data streaming across a local network. So, unlike its internet counterpart, it is not attempting to service millions of clients who require an update once or twice a day. But service a few (maybe 1-10) clients every few seconds or even milliseconds. Detail: The main focus of this package is the Dispatcher which facilitates the publisher/subscriber environment. The implementation can support many network topologies that suit the developers requirements. For example: A single dispatcher may be located on a remote machine and all publishers and subscribers are remote and communicate through it (centralised). Alternatively, there may be many dispatchers on different machines, each with their own cluster of local services and the subscriber connects to the machine that contains the publisher of interest (decentralised). Or even a mixture of both. The implementation is not rigid and allows for the developer to choose the topology simply by installing once or more dispatchers and initiating a connection. An API is provided to enable interaction with the Dispatcher to query its services, request a connection and send/receive data. Additional Features: Supports data-stream encryption (blowfish). Installation: Unzip to a directory of your choice. Required Packages: Labview 9.0 or greater. Transport.lvlib (Included) Queue.vi (Included) Position Form.vi (Included) Stop.vi (Included) Elapsed Time.vi (Included) Known Issues. None. Versioning: Current version 1.0. See changelog.txt. Contact: PM ShaunR on lavag.org (http://www.lavag.org) Click here to download this file

Hmmm. I think maybe I have failed miserably to explain the key concepts. The previous example was to show how you can add a very simple PWM (there is more than 1 type) to an on/off controller that controls a single digital output Cutting and pasting my example and wiring up controls with the same name won't cut it since you want to use a PID controller and not an on/off controller. I'm not doing your project for you, merely trying to show, with he use of examples, how to go about it. The example demonstrates how you can vary a digital output to react a a certain stimulus and since it was available, I used Neds on/off controller . You could, for example, replace the PID VI in the NI example "PID simulator" with the vi I supplied, but you would still have to figure out a method of calculating the duty-cycle on each iteration in relation to the input (which you haven't). You could, however, replace it with Neds example (no mods needed) and see what the difference is to the PID one. I would suggest taking the time to view all the PID examples shipped with the PID toolkit (assuming you have it) and understand the theory. I would even be tempted to rip out the process simulator into another vi and use it to create the step response graph and log the results. Then do my ZN analysis on it to see if I came close to the ones in the example. Then change the process values and repeat. From your project supervisors comment, I think he is expecting an analogue output (or a PWM simulation of an analogue voltage which isn't the type of PWM I used). Is the pump analogue controlled? If it is. What is the reason for using a digital output when your USB device has analogue outputs (And there are many tutorials on Youtube of PID with an analogue output. using LabView) One further point. If your posting VIs that uses sub-vis. Can you put the all vis into a single directory and zip up the entire directory so that all the sub-vis are included. I don't have "On-Off Controller-PWM.vi" or "Simple PID- ViFormyproject.vi". I can guess at what they probably are but its always best to be looking at the same code.

Oppps. Just noticed a feature (bug..it is the wee hours is my excuse) The over set-point check is inverted (sorry about that). This is what it should be

Unfortunately. You have the software, but not the hardware. You need FPGA hardware to run the FPGA stuff on. I only mentioned it to illustrate that NI also have a digital solution. But all is not lost. If you remember back to my example, I said we just need a way to open the valve for a period the PID algo tells us. This seems to be the bit you are having problems with. For the digital output. You already Have an on/off controller example supplied by Ned. But what we really want is a PWM On/Off Controller then it would give us the opportunity to vary the on/off outside the dead-band. PWM always sounds complicated. It really isn't and to demonstrate I've modified Neds example. The bottom half of the loop is Neds on/off controller. I've just modified it a bit so it isn't reliant on the previous iteration of the loop. It's functionally identical. The top half is a timed gate which allows the signal from the on/off controller through for a specified period of time. So now we have an on off controller that we can vary the pulse width in the time domain. And that's PWM. Generally we wouldn't have it all in the same VI and the PWM would run asynchronously to the controller. But for our purposes its actually a bonus. If we set the duty cycle to 100% (note I've used duty cycle and made it a percentage) then it will behave as Neds On/Off controller) then we have our on/off controller back again. If only we could figure out a way to turn the error between the setpoint and the process value into a percentage...... It's unfortunate your hardware doesn't have a configurable counter/timer output otherwise you could have used that.

There are several examples shipped with labview . Use the NI example finder and you will find them under: >Building User Interfaces > Listboxes and Tables

Who? The Prof? Or your colleague? What I meant was that there are certain processes that on/off controllers simply cannot control. They become unstable and oscillate. As an example of an asymmetric system (just to clarify after all.....aren't they all?). I once had an environmental chamber that was convection heated but nitrogen cooled. So. To ramp up (say) 5 °C would take 15 mins at 100% output, but with a 2 second injection of liquid nitrogen the temp would drop by 5°C in about 10 seconds. Especially since some dork had designed the thing with the temperature probe near the injector. What you have to bear in mind is that PID isn't 1 algorithm. Its 3 algorithms cascaded. And you can choose which benefits from the 3 you want to include. You could (for example) use only the P and I terms or the P and D or just the P. Its the flexibility that makes it attractive since there is no "one size fits all" solution for every system. If maths is your forte then I would suggest reading P, PI, PID Control. If (like me) you only want the bullet points and prefer practical examples then try PID Tutorial is

It also gives you the option of running them in different priorities and execution systems.

We should have a jokes/humour section