About DAQ Assistant

[Sidney Nogueira]

I am studing this tollkit - Part Number: 778940-03 - at first time.

Then, I woud go to try to improve one Project using the steps indicated into its Help.

My problem is that I don't get to achieve the NI DAQmx Generator Step.

Otherwise this Step is clearly indicated within the steps to follow, in the example showed on      " Getting Around the Express Workbench " , subfolder " Using  Hardware ",   another subfolder " NI DAQmx " and the sublevel  " Generating a DC Signal with NI-DAQmx Devices ".

My objective is to Create a Signal type DC, and using de NI DAQmx Generator Step, and send this signal to the DAQmx device       ( PCI 6221 ) installed on my system.

I woud like to know if this probem occurs because my version ( V 2.0 ) of this Software doesn't have this Step Function, or if I am doing some mistake ! I don't know !

I will wait your brief response.

Best Regards

Sidney Nogueira

[lrallen]

Sidney,

First of all, are you using LabVIEW or SignalExpress?  The steps that you have described sound like SignalExpress.  If you are using LabVIEW, then I can see why you would be having a problem.  If you want to generate a DC signal in LabVIEW, you want to use the DAQ Assistant Express VI.  This can be found in your DAQmx pallette in LabVIEW.  This will walk you through setting up a DC output signal. 

Regards,

Lon

[Sidney Nogueira]

Mr. Irallen;

Thank you very much, about your attention on my problem / difficult.

I think that I found where was the error. Really, I don't have installed in my computer, the "SignalExpress Software".

However,  I thought that using only the "Control Design Toolkit V-2.0"  plus the "LabVIEW 7.1",  I could simulate any example there are into the Help of the first Software ( Control Design Toolkit ).

Sorry may mistake !

Regards

Sidney Nogueira

[Sidney Nogueira]

I made a block diagram using LabVIEW 7.1 and DAQmx PCI 6221.

On it, with the DAQ Assistant,  I configured one Analog Input Signal  AI0 ( -10 to +10 Vcc ) and two Digital Output Signals: P0.0 and P0.1 of the devise above indicated.

Using one Sate Machine Architecture, I want turn on the output P0.0 ( if the condition is TRUE and the amplitude of the analog input is POSITIVE  ),  or turn on PO.1 ( if the condition is FALSE, and the amplitude of the analog signal is NEGATIVE ).

The arrow of the program is not broken ! Therefore I think that all of the code is correct.

However, when I run this VI, occurrs that : if the analog input is POSITIVE, then the TRUE case is selected and the Digital Output P0.0 turn on.

Otherwise, when the analog input ( AI0 ) is NEGATIVE, looking with the highlight activeted, I see  each cases being changed, but the only the led of the first digital port ( P0.0 ) remains ON STATE, and the second digital port ( P0.1 ) is not turn on .

Coud you please informe me where is the problem ?

[lrallen]

Sidney,

It is very difficult to know what could be wrong.  Can you possibly post a simplified version of you VI that exhibits the same behavior.  That way I can take a look at it and try to diagnose or explain the problem.  Thanks!

Regards,

LA

[Sidney Nogueira]

Mr. Irallen good morning !

Sorry the long time, but I have been very busy lately.

My intention is, using LabVIEW 7.1,  make one VI that produces one PWM Signal from one Digital Output of my board PCI 6221, for example the bit P0.0 of this device. I need to chagne  the frequency and the duty cycle of this output, during the run mode. The range of the frequency is 10 Hz up to 1 KHz.

Then I thought to use one Signal Generator Express VI configurated to Square Signal wiht amplitude 0 to +1, to create the internal signal and send it to that output ( P0.0 ) throught the DAQ Assistant.

With this solution, then I wil duplicate it to the second outuput, for example the bit P0.1 .

Using one internal trigger by software ( only ) I want to alternate when the output P0.0 is ativated, the another ( P0.1 ) is inative during a certain time, and vice-versa.

The trigger signal wil be received from hardware, using one Analogue Input ( for example  AI0 ) and one potenciometer varying its voltage between -10 and +10 Vcc.

Using one logic code in the Block Diagram, I can trigger the output P0.0 if the Analogue Input is int the positive range or, the another output (P0.1) if the signal wil be in the negative range.

These Digital Output with PWM Control, wil be used to turn on / off two Directional Pnaumatic Valves type ON-OFF.

I hope that my description above, was clear to pass the idea of this VI that I need to create.

Best Regards

Sidney

[Justin_M]

Hi Sidney,

Have you seen any of the examples that come with the DAQmx drivers?  It is often a good idea to start with an example, then build your program up from that.  Take a look through the VIs in the NI Example Finder (start LabVIEW, go to Help -> Find Examples... to launch the Example Finder).  If you go to the search tab, you can search for the different programs you are interested in, such as "pulse generation" or "PWM".  Or, go to the Browse tab and search under Hardware Input and Output -> DAQmx.

Have a great day!

Justin M
National Instruments

[Sidney Nogueira]

Mr. Justin M. , thank you about your idea.

Have a great day !

Sidney

[Sidney Nogueira]

Please, I need to create one VI using LabVIEW 7.1 to generate one Digital Signal Output with amplitude from -1 to +1 ( for example ), and the period ( or frequency ) must have one randomic distribution. Some people denominate this kind of Signal like : PRBS ( PSEUDO RANDOMIC BINARY SIGNAL ).

To perform one VI to get a Digital Signal like above mencioned, I don't have any problem. But I ask: how can I produce several frequencys?

Using one While Loop Structure and the randomic number in the entry of the Wait Until Next ms Multiple, will be possible to change the moment for each iteration and consequently the frequency obtained ?

Thanks  about your attention, and I will wait your brief answer about this subject.

Best regards.

Sidney Nogueira

[Sidney Nogueira]

Dear Sirs;

I am waiting for any answer about this new message : RANDOMIC BINARY SIGNAL

This type of signal is simillar the White Noise. The unique difference between then is that the Randomic Binary Signal we have only the frequency changing and the amplitude is constant ( -1 and +1 in this case ). Otherwise, the White Noise both the amplitude and the frequency are changed during the time.

Please, help me sending any suggestion / idea.

Thank you very much.

Sidney Nogueira