03-04-2011 07:17 AM
Hello People,
I am currently enrolled in a course (mechanical measurements) which requires a project from us.
Unfortunately, we decided to go with a relatively 'over our level' project instead of the recommended ones and even though the professor and t.a. were very excited about our project, we have recieved no help till now.
Our project is very similar to this one:
http://decibel.ni.com/content/docs/DOC-12243
Ofc our project is not exactly the same - we are just solely focusing on the force (the above one also has % body weight etc. which we don't need).
Where can I find the VI for the above project? If not, where should I begin?
Basically we have two sensors and the circuit we've configured, and we now need to begin on the VI. I must mention that we will use a wireless DAQ.
So in that case, what should I do?
03-04-2011 07:54 AM - edited 03-04-2011 07:56 AM
First install LabVIEW and the needed drivers (NIDAQmx for a starter, which should be installed when you install LabVIEW). This should also result in the installation of the National Instruments Measurement and Automation Explorer, referred to colloquially as MAX on these forums. This tool is VERY helpful when you are beginning a hardware project as it can allow you to talk to a lot of hardware before writing a bit of code (in any language), which allows you to troubleshoot hardware setups and connections separately from debugging your program. You mention a wireless DAQ, is it a National Instruments one? If so that is good, because MAX doesn't "play" with other companies' DAQ hardware, with the exception of those that are talked to through VISA (a driver abstraction that allows communications with serial, GPIB,TCP based instruments), but a non-NI wireless DAQ probably won't fall into this later categories. If it isn't a National Instruments DAQ all isn't lost, it will just be more difficult. You say the circuit you have configured. Do you mean designed, or have you connected and "configured" this, gotten information out of it? As to where the VI for the example you refereed to, probably on one of the author's laptops, or a CD in some professor's desk. The PDF diagram shows the entire vi, it would be mildly educational to replicate it from scratch, but I say mildly because it will have removed much of the thought process from solving the problem, will only be showing someone how to find the various components, which isn't very educational.
Look at your force sensors, see what their outputs are, voltage, resistance, whatever. Then try and determine how to take what is probably a small signal, which would be prone to picking up environmental electrical noise, and figure how to amplify the signal to a useable level. You determine what would be a useable level by looking at the requirements of the DAQ units inputs. Are the signals big enough? Do they change value at a rate/frequency that is compatible with the DAQ's inputs. You then build a basic VI to capture these signals, maybe display them (if the DAQ is compatible with MAX you can check out the hardware connections using that, which can also show you what kind of issues of electrical noise, etc., you may have.) Then once you have the basic VI working and successfully acquiring data you can start focusing on what to do with the data, what kind of "signal processing" you may have to perform to "clean up" the data to get at the underlying information.
But just copying someone else's work may get you the grade, but really won't help you when you actually have to do this from scratch in the real world. Make your mistakes in school, they are more forgiven, there usually are more resources to turn to for help, it is the place to make them. Not that you won't make mistakes once you are in the "real world", but it is usually better to do it in the "nest" of academia.
03-04-2011 10:47 AM
We have LabView already available on our servers from the University.
The thing is, the projects which other students have used, the prof has given them the VI to work with. Our project is mainly related to getting values and not creating the VI which is why I was wondering whether I can find that VI online.
The DAQ we have been given is a NI Wireless DAQ so that step is gone out of the way.
We have already purchased the same sensors used in the above project. What is their output? One of my partners is in charge of the VI while I will be in charge of using the program to get results. The third will do the write-up.
I'll briefly discuss what we have:
- We've built the breadboard circuit and will connect the wireless DAQ and connect the sensors to that. We used a very similar setup to the thread I've linked before.
If our purpose is to basically show the force on the heel and foot, what should I use on the VI?
I was wondering whether I have to include anything from the sensors or should I just place the DAQ on the block diagram - amplify and filter that, then display them on a graph? Or is there something I'm missing? Because the block diagram in the linked thread is WAY beyond our level and way more than what we want. This is a freshman/sophomore course so that should explain our simple-mindedness at the moment.
Thanks for the quick reply and hoping for more.
03-04-2011 11:56 AM
I don't think any one is just going to hand you a VI with out you making any effort. What you want to do should be pretty simple. Take a few hours and study one of the FREE labVIEW lessons on the NI web site. OR search the help in LabVIEW for how to use DaqAssist. That is what is being used in the example you site above. You will need to know what the sensors out put is and as LVpro advised the specs of your DAQ. For instance you may need to build an OP Amp circuit like in your example or maybe not. If your sensor puts out a linear voltage VS foot pressure you again can probably just shove that output into one of your Analog inputs on the DAQ, then again, you will need to know if the DAQ has any Analog in's. If you are feeling really lazy, just drop a DAQAssist on the block diagram and open the HELP\SHOW CONTEXT help dialog box and hover over the ICON then chose the detailed help. If you want more than one measurment at a time you will need a While loop also. The FREE 3hr or 6 HR course should get you started though. After that you will probably know more about LV than anyone in the class.
Alan