motor control by serial port

[Sunny1290]

Hi GerdW

Got it. I hadn't been defining P,S and M in the LabVIEW program which I had defined in the controller one.

Now it works great with PID control block as well.

'Thank you so much for the help.

[Sunny1290]

Okay now my problem is:-

When I send the command to controller for getting the speed feedback it is giving me almost instantly (0.5ms - 2ms) the number of counts.

But when I interface it with the LabVIEW and I put the delay of 5ms in it, the VI is still not giving me any response(speed reading), its almost 22ms-25ms delay in the VI when the response speed is given back by the LabVIEW.

How can I minimize this delay for getting the response?

[GerdW]

Hi Sunny,

how does your current VI look like?

[Sunny1290]

In your basic VI with comes shipped in LabVIEW examples the default delay given there is 500ms so if that reduced to 5ms I don't get any response.

But if increased to 22ms-25ms the speed count is given.

How can I reduce that delay to 5ms or less?

[Sunny1290]

This is the VI which I am working on.

[Sunny1290]

Ok now when I remove the property of bytes at port and  just give a constant on VISA read of how many bytes do I have to read I am getting the speed response at 2ms also.

Is it the right way?

[GerdW]

Hi Sunny,

yes, that's definitely the way to go. "Bytes at Port" isn't needed for proper serial communication using TermChar...

I removed some of those locals (and race conditions) in your VI. Sequences aren't needed so often. (See attachment.)

You shouldn't use the "STOP" function in your VI. Not at all...

[Sunny1290]

Thanks a lot Sir.

[Deovalente]

Hi

Im a begginer and want to do a PI control on a dc motor speed via avr. I have made a diagram but I think it must have some problems especially with the feedback.

your help really needed.

If there is any problem please tell me.

The other question is that can i send and recieve more than one type of data from one serial port? i mean for e.g having two feedback, one for speed and the other for motor current.

Thanks a lot.

[GerdW]

Hi Deovalente,

using the Simulation toolkit for a simple PI control is surely overkill...

- Do your really need to typecast your PI output to string? What kind of data does your "avr" expect?

- Does the "avr" really send you a DBL casted to a string, so you need to cast it back to DBL?

- Yes, your "avr" might send more than one value per message. It's up to you to decode that message in LabVIEW...

- Why do you close the serial port when you receive a message? You still want to receive further messages...

- Why do you use BytesAtPort when your serial port is set to use termination chars? Simply receive messages that are terminated by that char...