Quad Encoder output in Labview Help

[Josh@bpe]

Hello All,

I am having some trouble setting up an encoder in labview and getting an output.  My labview skills are weak at best.  I have a PCI-6259 and a quad encoder wired into the counter 0 terminals of the SCB.  I set up some Boolean indicators on the channels to make sure I am getting my pulses (which I am).  I tried using the DAQmx VIs like I saw in some examples but kept getting errors.  I tried using the DAQ Assistant to set it for angular postion but I wasn't getting any output when I ran it.

[kosist90]

I'm not sure, that this is the problem source, but you have Acquisition Mode set to 1 Sample. Try to change it to multisampling...

[Josh@bpe]

I did try that, but it errors out because it needs some sort of clock input to use as a reference.  I tried to create one but I couldn't get that to function properly.

[Alexander_Sobolev]

Try to read very basics of DAQmx, try to open LabVIEW examples (search quadrature encoder). 

Right now you are saying "my program gives some errors. I have tried some examples, they do not work".

By a screenshot of the block diagram with express VIs I can only say that you are probably trying to read from the same lines simultaneously and getting conflict.

PS. If you use ALT+ printscreen, it will capture only one window. If you use command Edit -> Create VI snippet from selection on blockdiagram, we will be able to open this snippet and see how everything is configured. Guess what is more informative? 

[Josh@bpe]

I had to work on some other projects, but I am back on this now.

I managed to get the encoder setup and reading correctly. 

The only thing I can't figure out now is how to reset the counter to zero with the software.

Using the z-channel would not work for my application.

It seems like I am going to have to stop and then re-start that portion of the program unless there is another way?

[cbutcher]

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Josh@bpe wrote:

I managed to get the encoder setup and reading correctly. 

The only thing I can't figure out now is how to reset the counter to zero with the software.

Using the z-channel would not work for my application.

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Why won't the z-channel work? Do you mean you can't get LabVIEW to recognise it, or that the z-channel is unsuitable for some physical reason? (As a possible side note, are you sure X1 is the right decoding type?)

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It seems like I am going to have to stop and then re-start that portion of the program unless there is another way?

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It seems extremely unlikely that that will be your only choice. LabVIEW is pretty flexible (sometimes too much, and encoders seem to be a pain...)

[Josh@bpe]

Channel Z works fine.  When I enable it, the encoder will reset to zero when it passes that point.  However, the application I am using it for has technicians installing it onto various valves to measure the opening angles.  Using the Z channel would not be practical for this application.  But I was able to solve my dilemma yesterday.  Here is a pic of the code.  I basically use a couple local variables, one to store the position of the encoder when the reset button is pressed and one of the position of the encoder and then subtract the 2 values.

[GerdW]

Hi Josh,

I basically use a couple local variables, one to store the position of the encoder when the reset button is pressed and one of the position of the encoder and then subtract the 2 values.

Why don't you use a shift register to store the position (on reset button)?

Why don't you get rid of the other one and use a simple wire instead?

THINK DATAFLOW!

[Josh@bpe]

The thought had crossed my mind but I don't have much experience with shift registers and don't have a lot of time to 'play' with Labview at the moment.  I will look into it more when I get some time free'd up.  Thanks.