What exactly is a DSC module?

[belae1ka]

I am trying to determine what would be the best way to design the control system for my project. I am in charge of designing the control system for a shock dynamometer.

Components of the control system;

-load cell

-temp sensor

-data acquisition device (DAQ)

-3 phase motor

-variable frequency drive (VFD) 

**I am using ModBus to communicate to the VFD using a USB-RS485 adapter**

At the moment I am having difficulty communicating to the VFD through ModBus. I finally understand how ModBus works but the problem is trying to implement that through Labview. I see many people online doing this using a DSC module. 

My question is, would using a DSC module be the right idea for what I am trying to do in my project?

First, we are to run the motor until the Temp sensor reaches a desired temperature (sensor is attached to shock being tested). Next, the user inputs a frequency reference for the motor to run at. Once the motor is running at a constant frequency, a graph is to be plotted. This will be a plot of Force (from load cell) vs Speed (frequency of motor). Once enough data points are plotted, the motor will turn off.

Thank you.

-Kevin

[belae1ka]

@RavensFan Perhaps a DSC module can be used for my project? When you had asked me before I thought a DSC module was a physical device.

[pincpanter]

What troubles in communications did you run into? Did you try the MODBUS library for LabVIEW ?

I used it some years ago to interface a special printer. I found it easy to use.

On the linked page you will find references to other options, too.

The DSC module, however, features much more functionality and may be suitable for you application if, e.g., you need historical data storage.

[belae1ka]

Hi pincpanter,

Thank you for the response. 

I did download the library but it is a bit confusing to me, perhaps I need more experience with Labview. If I am trying to start small and do something simple such as turn the motor on would I use a VI such as "MB Serial Master Query Write Single Coil (poly).vi"? What does the poly mean?

Also, In what case would I use VI's such as "MB Serial Master Query.vi" and "MB Serial Init.vi"?

Last question, can the DSC module be downloaded anywhere for free? I am running Labview 15.0.1

Thank you.

-Kevin

[RavensFan]

The DSC module is not free.  I do not know if you can download it and run it in an evaluation made for a limited amount of time.

The module is software.  It has a few aspects to it.  1.  It provides an historian that will log values you assign in the background so that you can review data later on.  2.  It provides alarming functions.  So if you assign a parameter an expected range of values, it will go into an alarm mode.  Flash an indicator, log the event.  3.  It provides other interface protocols like OPC and Modbus that lets you said up communication without having to explicitly program it.  4.  It provides some control elements like pipes, tanks, valves, and motors that you can put on your front panel so it can give you a schematic of an operating plant.  It is designed to give you the means to more easily create an operator control station if you are are trying to control an industrial process.

"Poly" is short for polymorphic.  You can drop down a VI, then change the selector to pick among specific types of that VI.  Same way a DAQmx function lets you choose among different types of sensors and whether it is 1 channel or many, 1 sample or many.

[belae1ka]

is there any way to use an I/O server without a DSC module or real time?

[RavensFan]

No.  They are a part of the DSC module.

[Jacobson-ni]

Going back to having trouble with Modbus, which API are you using to do that? Just from the name, it sounds like you are using the old Modbus API. There is a Modbus Library on VIPM which is pretty straightforward and what I will usually recommend for most applications.

[Hooovahh]

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@Jacobson-ni wrote:

Just from the name, it sounds like you are using the old Modbus API. There is a Modbus Library on VIPM which is pretty straightforward and what I will usually recommend for most applications.

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I was under the impression the ones recommended by NI are the one that ship and install with the base LabVIEW under Data Communication >> Modbus.  I've downloaded and tried several and I thought these were the most complete and cleanly written.  I'm unsure if this is the API OP is talking about.

[Jacobson-ni]

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@Hooovahh wrote:

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@Jacobson-ni wrote:

Just from the name, it sounds like you are using the old Modbus API. There is a Modbus Library on VIPM which is pretty straightforward and what I will usually recommend for most applications.

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I was under the impression the ones recommended by NI are the one that ship and install with the base LabVIEW under Data Communication >> Modbus.  I've downloaded and tried several and I thought these were the most complete and cleanly written.  I'm unsure if this is the API OP is talking about.

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It gets kind of confusing here because there is a Modbus folder under Data Communications that does ship with the RT and DSC Module. It's good if you have one of those modules but to my understanding they do not ship with base LabVIEW. The API I am talking about is the "NI Modbus Library" on the VI Package Manager which is one built by Systems Engineering and I think will also put a "Modbus Library" folder in Data Communications as well as Addons. It has basically the same API calls and looks to be constructed very similarly (at least until locked VIs, I don't know what's different under the hood).

Both seem to work pretty well and the difference I usually bring up is that the one shipped in the RT and DSC modules is supported by our R&D team while the VIPM one is not. I'm always willing to help troubleshoot problems with the VIPM API but I let people know from the start that I'll be getting very little help from our R&D team (which is totally understandable). I'll go ahead and backpedal to say I make sure people understand the options available to them and they can decide what is best for their project.