Abstract:

This article focuses on the development of an experimental electronic model for remote access to a laboratory exercise in the discipline "Electrical Engineering", which is designed to study the amplitude-frequency and phase-frequency characteristics of RC and LC filters. The present research is inspired by the transition from face-to-face to distance learning because of Covid-19 pandemic.The developed electronic circuit is based on an electronic module created by a team from Plovdiv University, which is used successfully for one year in conducting remote access to laboratory exercises in the discipline "Fundamentals of Telecommunications". Thanks to the unification of the hardware used in the laboratory models of various engineering disciplines, a significant simplification of the maintenance of the developed system for remote access, as well as a significant reduction of the costs necessary for its construction are achieved.

When performing the laboratory exercises, students can set the frequency and shape of the input signal of the filter. For this purpose, a DDS generator realized with the integrated circuit ADS9833 is used. The change of the signal amplitude is performed by a digital potentiometer MCP42010. These two specialized integrated circuits are controlled by the Arduino Uno via a common digital bus with a serial SPI interface. For students to remotely control this model and to set the necessary parameters of the generated signal, the Arduino Uno board is connected to a laboratory server via a USB interface.

The input and output signals of the filter are measured by a laboratory two-channel oscilloscope GWInstek GSD-2000A. After measuring the parameters of the two signals at different frequencies, students determine the change in the amplitude of the output signal, as well as the phase difference occurring between both signals. The obtained results are recorded in a table and then used by the students to draw the graphs needed to analyse the characteristics of the studied filter.

The filters are implemented as separate hardware modules that can be connected to the main board of the laboratory model. This ensures freedom of the teacher to change the type and scheme of the filter, which creates an opportunity to make a variety of research tasks.

Remote access to the individual modules of the laboratory system (measuring instruments, laboratory models) is carried out through developed specialized user software with WEB interface. For this purpose, the software is installed on a laboratory server and the communication between the software, the laboratory model and the oscilloscope is carried out via USB interfaces.

The methodology for performing the laboratory exercise in the discipline "Electrical Engineering" contains simulation of an electronic circuit of the studied filter using a software electronic simulator, study of the filter parameters of a real laboratory model in a remote laboratory by conducting real measurements and comparing the results from simulation and from actual measurements. The results from the distance training of engineering students in this laboratory exercise so far show a good understanding of the operation of the filters and the ability of students to work with both software simulators and real laboratory measuring instruments.

Keywords:

Remote laboratory, electrical engineering, distance training, engineering disciplines.