Implementing Local and Remote Control in LabVIEW for a Test Bench

[Bonapg]

Hi everyone,

I’m an engineering student and a beginner with LabVIEW. I’m currently working on a project where we control a test bench for a mobile HVAC system. We are using NI-DAQ modules to acquire data such as temperature and pressure, and we also control various bench parameters.

Currently, we can manually set parameters via the front panel, but we also need to implement remote control using MQTT communication with another machine and also to read the parameters from a CVS file. Those parts of the project haven’t been developed yet.

Eventually, we will generate an executable for a runtime machine to handle both measurement and control of the bench. One requirement is that the runtime user must be able to select the control mode—either local (manual input and file data) or remote (via MQTT).

Since we are relatively new to LabVIEW, we are looking for guidance on how to structure the software. One challenge we are facing is that our thermocouple module is quite slow. Because of this, I am considering using multithreading with parallel while loops, possibly implementing a producer-consumer architecture with channel wires. Additionally, the code handling remote commands may not be exactly the same as the local control logic with MQTT.

Given these requirements, I have a few questions:

1. What is the best approach in LabVIEW to switch between local and remote control modes at the start of the program?
2. How can we efficiently manage the timing issues caused by the slow thermocouple module?

Any advice, suggestions, or relevant resources would be greatly appreciated!

Thanks in advance!

[ZYOng]

What NI-DAQ modules are you using? What are the model numbers?

[RTSLVU]

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I think the exact method you use kinda depends on the MQTT device and how it appears to LabVIEW. But I believe an Event Driven State Machine would be my first approach. An EDSM can be both local controlled responding to GUI events or remote controlled driven by events generated from MQTT messages. Switching between local and remote control at the start or any time during program operation is pretty simple by enabling or disabling the GUI or MQTT event responses using a Boolean.      

As for your slow thermocouple... Well you are kinda stuck there slow hardware is slow hardware. All you really can do is try to find better faster DAQ. Although some type of multi loop architecture with the slower DAQ in its own loop sending data to another loop using Queues or Channel Wires can help keep your GUI responsive instead of just waiting for each measurement. 

Reading test parameters from a CSV file is easy and there are plenty of examples of this.

[Bonapg]

Hi, 

I forgot to add that, we use 9174 chassis with 9213 thermocouple module and 9205 voltage input.