Building a Remote Learning Lab with LabVIEW and Data Acquisition

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"We chose the Web Publishing Tool in LabVIEW to quickly develop a remote laboratory for the course. The tool provided a clean solution without having to develop sophisticated applications."

- Professor Dan Lascu, Politehnica University Timişoara, Faculty of Electronics and Telecommunications, Department of Applied Electronics

The Challenge:
Teaching the technology of uncontrolled rectifiers via real-world experiments to students at 12 universities across Europe.

The Solution:
Developing a remote E-learning lab with NI LabVIEW software and data acquisition hardware that can be accessed, controlled, and monitored by students and faculty at all times.

Author(s):
Professor Dan Lascu - Politehnica University Timişoara, Faculty of Electronics and Telecommunications, Department of Applied Electronics
Associate Professor Mihaela Lascu - Politehnica University Timişoara, Faculty of Electronics and Telecommunications, Applied Electronics Department

The faculty of Electronics and Telecommunications at the Politechnica University in Timişoara, Romania, aimed to incorporate a blended approach for teaching uncontrolled rectifiers concepts in the Leonardo da Vinci E-learning Distance Interactive Practical Education (EDIPE) program framework.

We wanted to allow eight types of uncontrolled rectifiers to be investigated in the course material, and each is comprised of single-phase and three-phase structures with resistive, inductive, and capacitive loads, and with or without a freewheel diode. Table 1 displays a complete list of remote experiments.

 

Experiment

Title

1

Single-phase, half-wave rectifier with inductive and capacitive load

2

Half-wave rectifier with inductive load and freewheel diode

3

Center-tapped full-wave rectifier with inductive load

4

Single-phase bridge with capacitive and with inductive load

5

Voltage doubler

6

Three-phase rectifier with inductive and capacitive load

7

Three-phase bridge rectifier with inductive and capacitive load

8

Six-phase rectifier with inductive and capacitive load

Table 1. Uncontrolled Rectifiers Included in the Remote Lab

We chose the Web Publishing Tool in LabVIEW to quickly develop a remote laboratory for the course. The tool provided a clean solution without having to develop sophisticated applications.

Using LabVIEW in the EDIPE-Power Electronics project allowed our team to carry out the following tasks:

  •  Access, control, interface, and monitor practical experiments remotely
  •  Acquire and measure the representative rectifier waveforms
  •  Book under the LabVIEW Web Publishing Tool using an easy Moodle-based tool
  •  Configure rectifier topologies with a switching board interface
  •  Monitor user connection states and circuit protection

With the LabVIEW Web Publishing Tool, we could manage interfacing and remote control of the experiments. In addition, we selected the NI PCI-MIO-16E-1 DAQ board and the NI SCB-68 shielded I/O connector block for data acquisition and measurements.

LabVIEW controls the switching board interface (SBI), which configures the desired rectifier topology and signal acquisition. The switching board consists of a 32-bit shift register followed by the buffers that switch a relay matrix on and off, allowing for safe operation. Sequential writing of 32-bit words takes place in the shift register to ensure proper order.

Figure 1 demonstrates the remote laboratory architecture for the experiments. Figure 2 outlines the hardware architecture for one of the modules.


Figure 1.Structure of the Distance Laboratory for E-Learning Practical Teaching of Uncontrolled Rectifiers

Figure 2. Hardware Architecture of the “Single-Phase and Three-Phase Rectifier Circuits” Module

When a student accesses the application online to perform an experiment, he or she can access two front panels: the Selection Front Panel (SFP) for selecting the desired experiment, and the Measurement Front Panel (MFP) for visualizing waveforms and measurements.

The main LabVIEW VI permanently monitors the student’s connection state. If the student closes the remote panel window without properly exiting the program, the experiment automatically closes and a warning message displays. This function protects the power circuit from a permanent connection, which can be dangerous. In addition, as long as the power circuit configuration is established, no control is available to the user. The same happens when a student completes one experiment and moves to another one.

Each of the rectifier experiments has its own DAQ Assistant built according to the signals that need to be analyzed in the corresponding rectifier experiment. We also customized the signal list, waveform graph, and spectrum analyzer for each rectifier.

Because simultaneous signal display is an important concept in studying rectifiers, any signal in the application can be displayed, inhibited, and analyzed separately or with any other signal. At any time during the connection, the student can stop the acquisition and use cursors to perform measurements on the displayed waveforms. Parameters including time, amplitude, phase, the root mean square (RMS) of harmonics, overall RMS values, and power factor or total harmonic distortion (THD) are available.

Figure 3 demonstrates the measurement front panel for a half-wave rectifier with inductive load and without a freewheel diode.

PosterREDRnet

Figure 3. Measurement Front Panel Window

LabVIEW and NI data acquisition hardware are powerful, flexible, and easy-to-use tools for creating, monitoring, and controlling remote experiments and acquiring, analyzing, and displaying different signals. Future work on this project will focus on remotely controlled, high-frequency experiments such as DC/DC converters and PWM inverters to build a complete power electronics remote laboratory based on LabVIEW.

Acknowledgement

This work was performed within the project EDIPE. The project was supported by the European Community within the framework of the Leonardo da Vinci II Program (project No CZ/06/B/F/PP-168022). The opinions expressed by the authors do not necessarily reflect the position of the European community, nor does it involve any responsibility on its part.

Author Information:
Professor Dan Lascu
Politehnica University Timişoara, Faculty of Electronics and Telecommunications, Department of Applied Electronics
Bd. V. Pârvan 2
Timişoara 300223
Romania
Tel: +40-256-403343
Fax: +40-256-403295
dan.lascu@etc.upt.ro

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