Help with Modbus and a CAL 3300 Temperature controller needed!!

[Sundown]

Hi all,

So I have a Cal Tech model cal3300 temperature controller that I am trying to control remotely using labview. I have found that it either uses modbus rtu or ASCII (I'm not really sure which).

I have used ASCII in the past for another instrument, but using that same code did not work, and I have not been able to get anything else to either. I have seen the labview modbus library, but this didn't help me as I'm, again, new to modbus and it didn't really make much sense to me.

I tried a simple write/read code sequence, but either I didn't have the write buffer correct or this is just not the way to go about this.

I was able to find some description of the code required here (hex addresses etc.):

http://www.thermoelectric.com/2010/manuals/pdf/TC-3300-modbus.pdf

but I don't know how to implement it and the addresses are pretty confusing.

Also here is the generic manual:

http://www.advindsys.com/Manuals/CALManuals/Cal3300.pdf

Any help that anyone might have would be greatly appreciated!!

If anyone can post generic code and help show me how to fill in the addresses or something like that, you would be a lifesaver!!

Thanks,

Luke

[Sundown]

Also if it helps, I'm just trying to read the setpoint that it's at and change it to a different value.

Thanks

[Ben-N]

Hi Sundown,

You mentioned that you were having problems communicating with your device.  When you did try, what happened?  Did an error occur or did nothing occur at all?  Are you familiar with the Modbus protocol?  We have a Developer Zone that goes into the addressing and some of the other caveats of the Modbus protocol.  You should be able to get a better handle of the addressing and implementation of the protocol after you look through that document.

Additionally, our Datalogging and Supervisory Control Module has a very clean interface to do Modbus communication.  There is another white paper on using this software, but it does focus on communicating with PLCs.  Take a look at it and let us know if you have questions.

[Sundown]

Hi,

I've been looking over the different things that labview offers to help with modbus, but I'm still having difficulty. I have this pdf from the company, but I really just need help figuring out how to put this form into labview. all I want to do is read the current setpoint and then change it once.

Any help, guidance, or examples would be helpful!!

[Sundown]

I don't mean to make this more complicated than it needs to be, I just need to figure out how to get any response from this instrument.

It is very time sensitive, and I'm kind of getting desperate. Any help at all would be appreciated!!

Thanks,

Luke

[Ben-N]

Hey Luke,

What do you have so far?  What are you trying to use to send these commands?  Are you using a specific library or the Datalogging and Supervisory Control Module (DSC)?  What have you tried so far?  Do you have any code you could post that we could take a look at? 

DSC gives you an interface to manually configure all of this through an I/O Server as part of a project.  The interface looks like the following.  You do have to choose whether this is a serial or ethernet interface.  Other than that though, you should be mostly good to go.

 
Let us know where you are at so we can work through this.

[Sundown]

No, at the moment we don't have the dsc module. I've tried a number of different things, from visa to the modbus library with no effect. So I really don't have any semi-functioning code to post... I wasn't able to see the picture you posted for some reason, but do you think this would be significantly easier if we bought the dsc? At this point, it might be better than dealing with a work around.

Thank you!

[Ben-N]

Hey Luke,

Using the DSC Module will make connecting to your devices through the Modbus protocol much easier than trying to build the protocol through VISA or otherwise.  There is a section in the LabVIEW Help file provides a fair amount of information on configuring our IO Server as a Modbus Server.  Additionally, there is an example for you to look at that gets installed as part of the DSC Module to do this exact sort of communication.  If you were curious, I would suggest downloading the evaluation software and checking out the example.

[unclebump]

Download the NI modbus library. Most of the work is already done for you.

http://sine.ni.com/nips/cds/view/p/lang/en/nid/201711

[Rhys_CKTC]

'Sundown', did you get anywhere with writing a VI for this?