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U3-HV labjack


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11 replies to this topic

#1 vipin valsan

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Posted 01 August 2012 - 11:41 PM

hi friends, I am working on a test bench project for a brushless dc motor (BLDC) testing. Here, various parameters of the BLDC has to be tested for its reliability. The main parameters to account for are: 1. Torque (Nm) 2. Speed (in rpm) 3. Temperature of the pcb and the motor (including windings) 4. Output power of motor at different load conditions 5. Battery current and battery voltage As such, am assigned to come up with an interface to read all these parameter via Labview. I hav Labview 7.1 and Labjack U3-HV. But am entirely new to this software and don't have any idea about it as of now. I have to start off from the scratch. I don't even know how these are interfaced with hardware or how the corresponding program is dumped in the Labjack. So it would be of great help help if someone could guide me through and help me out with it from the basics itself. I would like to go start from the Labview and Labjack basics and go step by step to accomplish this project as its going to be a learning experience also for me. looking forward for a positive response from all of you. Thank you

#2 LabJack Support

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Posted 03 August 2012 - 12:08 PM

Sounds similar to this topic:

https://forums.labja...?showtopic=5894

Anyway, first start by going through the quickstart for the U3:

http://labjack.com/support/u3

Then, try to connect your own signals to the U3 and view those signals using the test panel in LJControlPanel. Do you have sensors for all the things you want to measure? If you are stuck at this step, post links to technical details for your sensors for further help.

#3 vipin valsan

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Posted 04 August 2012 - 05:21 AM

Thank you for the response sir. well, i have already gone through the Labjack U3-HV basics from the link you have provided here. I do have an idea about its pin configuration, typical connections and such things from the manual provided. But all my knowledge is limited to theoretical approach. So as such, as a begining, i tried to connect a 10k pot to the analog inputs of the Labjack and was able to read those values in the Control panel interface of labjack. I varied the pot and corresponding change in the voltage was also reflected in the control panel interface of labjack. and ya, we do have sensors for all these parameters except for power, which i was informed that we have to calculate from the current and voltage readings. All the sensor output availabe lies in 0-5V range.I would like to read the values into Labview from Labjack and process that data. So it would be highly appreciated if you could help me out by providing information about the interfacing tools to be used for the same.

#4 LabJack Support

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Posted 05 August 2012 - 12:52 PM

LabVIEW is an excellent programming language for data acquisition. If you search labjack.com using the term "labview", you will find the following page:

http://labjack.com/s...xamples/labview

Follow steps 1-5 on this page.

#5 vipin valsan

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Posted 10 August 2012 - 12:34 AM

well, i have already gone through those examples. But in the Labjack manual, section 4, various high level driver functions are given. As such, I just want to know where does these functions come into play while interfacing with Labview? Do we have to program the Labjack? Pls do reply for the same in detail. Thank you

#6 LabJack Support

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Posted 10 August 2012 - 04:11 AM

THe LabView examples use the constants and functions described in section 4. For instance, if you look at the "U3 Single IO Example" it calls two driver functions OpenS and eGetS. If you look into those two LabView VIs you can view the actual library calls to .dll functions of the same name. The OpenS call takes constants from section 4 to open a devices. It needs both the desired device type and the interface over which to search for that device type. The eGetS function takes an IO type, which informs the function of what operation you wish to perform, such as LJ_ioGET_AIN and a channel number to tell it which line to perform the desired operation on.

#7 vipin valsan

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Posted 12 August 2012 - 09:41 PM

oh..k..that was really informative. Thanks. so now as an initial step, how should i start off my project? what should be my first approach now? Pls do guide me with the same Thank you

#8 LabJack Support

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Posted 13 August 2012 - 09:19 AM

First of all, are you experienced with LabVIEW? LabVIEW is a programming language similar to C, except graphical, so if you are new to LabVIEW you need to go through the tutorials provided by National Instruments about LabVIEW programming/development. As for your U3 project, seems like you want to read analog inputs, so I would suggest you start by looking at the example "U3 eAIN Example.vi". Then after you have a good understanding of that VI, check out "U3 Efunction Loop Example.vi", except that rather than the different e-function calls you probably just want multiple eAIN calls to get your different channels.

#9 vipin valsan

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Posted 17 August 2012 - 02:52 AM

well, am totally new to Labview. I jst started using it a month before only. And I started off with the tutorial examples only first. I carried out all the basic examples and am confident of all the examples discussed. And i will definitely look into the examples u mentioned right away and hope i will understand something about it. As you mentioned, we will be reading analog voltage values from each sensors. But my main hurdle is to take these analog voltage values from labjack and process the same in Labview for the corresponding parameter readings. So it would be of great help if you could tell me how that can be done using this U3. Thank you

#10 LabJack Support

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Posted 17 August 2012 - 08:33 AM

But my main hurdle is to take these analog voltage values from labjack ...

This is what is discussed in general in Section 4 of the U3 User's Guide, and specifically demonstrated in "U3 eAIN Example.vi".

If you have further questions about this step, let us know what you need help with.

... and process the same in Labview for the corresponding parameter readings.

This just sounds like LabVIEW programming, and nothing specific to the U3. The example above shows you how to get a voltage reading into LabVIEW. At that point, it is up to you what processing you want to do with the voltage and how you want to do that in LabVIEW. It is just standard LabVIEW programming.

If you need further help with this step, I would start with standard LabVIEW tutorials and documentation. If that does not solve your problem, ask NI for help, or post on the LabVIEW forums at NI.com. This step has nothing to do with the hardware, so phrase the question that way and you will get clearer help. For example, you could post a question as follows:

"I have a voltage value from 0.0 to 5.0 in a DOUBLE control. I would like to apply the following formula to that value: Torque = (100*Voltage) + 25. Then I want to write that torque to file. Please help."

#11 vipin valsan

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Posted 22 August 2012 - 09:28 PM

Thanks for your replies.
well..now I am successful in my first stage. I was able to interface the torque sensor and was able to read the corresponding values from the test bench. I could also get the waveforms corresponding to the same and enter the values into excel sheet for future references.

But now I have been asked to CONTROL the test bench set up using my labjack and vary the speed of the test motor from his Labjack. So my first question is, Can we really control a system using this labjack? If yes, how can that be done? How should i approach for the same?
Awaiting for your reply ASAP. Thank you

#12 LabJack Support

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Posted 23 August 2012 - 07:52 AM

Yes, you can do control with the U3. Your measurements generally use inputs. For control you generally use outputs. The U3 has various outputs: analog outputs, digital outputs, and timer outputs. How do you control the speed of your motor? Do you have a motor controller or motor driver? What sort of control signals does the controller/driver want?


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