Controlling a multiplexer

[cwillis]

I have several analog devices that need to be converted to a digital signal using a single channel A/D converter that I already have.  I have purchased a multiplexer (Texax Instruments CD4051B) to mux the signal.  This multiplexer requires three inputs.  My question is how to create these three inputs.  Do I need to purchase a digital I/O or can I do this with my computer alone?  Very new to this.  Thanks for any help.

[K C]

Hi,

If you have a parallel port on your computer you can use it to address the MUX.

To keep things neat you only have to add a buffer IC, but for a first try not absolutely necessary.

[cwillis]

Thank you for the reply.  I looked up the pin out for the parallel port.  I assume I will use pins 2 through 7.  Should I move this question over to the LabVIEW help?
Thanks,
Chris

[K C]

Hi Chris,

If you want you can stay here.

Actually it's pin 2 till 9 for the 8 data bits. But is you need more the other I/O signals can also be used.

How far are you (with LV and the Hardware) and what exactly is your application.

Message Edited by K C on 11-08-2007 03:44 PM

[cwillis]

KC,

I am researching crack growth in well holes (about 300ft).  Currently, we have a single LVDT down hole whose signal is digitized down hole with a single channel A/D.  The digital signal is then passed up to the computer at the surface.  We would like to keep using the same A/D with more sensors. (Specifically, another LVDT a compass and a thermometer.)  These analog signals will need to be muxed down hole.

As for my LV experience, I installed it last night.

Thanks,
Chris

[K C]

Normally I would say that the best way is to start with a course basic LV.

If you want to start now in LV then I think I have to make the program for. Not the best way but if you have the time, because I cannot always answer you as quick I do now, we will get a result.

Can you make a frontpanel in LV with the controls and/or indicators that you want ? We can start from there.

I assume that the HW part is no problem for you ?!?

[cwillis]

The HW is no problem.  I need to do all of this so I can change it in the future.  I will make the front panel and get back.  (Or ask a question in the middle.)

Thanks again,
Chris

[cwillis]

Hello,

After getting some help, I made the attached Front Panel.  LVDT1 and LVDT2 are plots.  The compass (orientation) and temp data are fine as numerical values.  Actually, the compass works with two sine waves out of sync but we only need to see the numerical value calculated using the two waves.  Hopefully this can be done in the background.

As I mentioned before, we will have to address the MUX since the A/D is one channel.  (With 1Hz to 5Hz capability)  I don't know how to send the signals to the multiplexer, but I imagine LV will just cycle through each of the sensors.  (The compass will act as two sensors since it is two output voltages.)

The A/D has its own functions that we have gotten to work elsewhere.  I'm not sure if you need this.

I hope this is what you wanted.

Thanks,
Chris

[K C]

Hi Chris,

I cannot read your VI at this moment because I am at home and I only have LV 7.1 installed here     

Have to wait till tomorrow at work where I have 8.5

We talked about addressing the MUX, but how do you read the ADC data ? and if I understand you correctly you will only get data from the ADC through the MUX and no ther data is comming in.

Message Edited by K C on 11-08-2007 09:23 PM

[cwillis]

KC,

I read the ADC data using LV.  And yes, I will only read data that came from the MUX and passed through the ADC.

-Chris