IMEJ main Wake Forest University Homepage Search articles Archived volumes Table of Content of this issue

1. Introduction
2. Design Philosophy of Interactive Lab
3. Implementation/ Functional Description of Interactive Lab
4. A Guided Tour through Interactive Lab
5. Measurement of Teaching Advantages of Interactive Lab
6. Conclusions
7. References
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Interactive Lab: A System for Teaching Electronics using an Interface to PSpice
Julio J. González, State University of New York at New Paltz
Laurence Reitman, State University of New York at New Paltz

We have developed and implemented Interactive Lab, a computer-assisted tool for teaching electronics. This tool has been under development and improvement for several years and is currently utilized to teach electronics in the Department of Electrical and Computer Engineering of SUNY New Paltz.

About the authors...

1. Introduction
A general interactive system for teaching electronics is depicted in Figure 1. In this system, there are two interactions, one professor/student and the other student/computer. The incorporation of the latter interaction has undoubtedly enhanced the way electronics is taught. In fact, circuit simulation through powerful programs such as PSpice has the following teaching advantages. a) The student's role turns from passive to active, which improves student attention. b) The student can visualize all circuit waveforms at once and relate cause and effect, which helps in the acquisition of concepts. c) Any voltage or current can be readily measured without the need for actually inserting measurement instruments, and d) the student can easily change a parameter value and investigate its effect on the circuit's behavior.

Figure 2 illustration

Figure 1. Diagram of general interactive system.

Unfortunately, there are four main teaching drawbacks to circuit simulation.

1) Lack of didactic environment: Circuit simulators are, of course, created to simulate circuits, not to teach, and therefore, they do not provide a didactic environment to address specific circuits of design interest.

2) Class time allocated to teach computer programming: The student needs to learn how to code the simulator language, which consumes a significant portion of the available teaching time. The feature, programming by drawing the circuit ("clicking and dragging"), offered by modern simulators, is often mentioned as an easy way to overcome this problem. However, industrial job opportunities will favor graduates who possess the ability to write code, as a circuit schematic unnecessarily takes a considerable amount of computer memory. Furthermore, writing code is a more robust approach than drawing the circuit schematics, as an additional program is needed to translate circuit schematics into code. This program, according to the author's experience, often introduces errors of its own, of which the user is completely unaware.

3) Programming difficulties divert student's attention: Even if the student is proficient at writing code, programming subtleties can easily divert his/her attention from the main objective of computer simulation (which is to understand the circuit's operation). A typical example is the PSpice dysfunction that occurs when the programmer inadvertently leaves an extra space after the END command.

4) False sense of completion: Oftentimes inputting incorrect data yields a wrong simulation outcome. However, students who have not learned to develop a theoretical expectation for the result will feel completely satisfied with this wrong simulation outcome.

It is apparent that a teaching method is needed which will preserve the advantages of simulation while eliminating its disadvantages. With this idea in mind we developed Interactive Lab.

2. Design Philosophy of Interactive Lab
Figure 2 depicts our interactive system for teaching electronics, which we have developed and improved for several years [1] [2]. In this system, our program Interactive Lab carries on the interaction student/computer. Notice that the student does not interact directly with the computer simulator PSpice. Instead, Interactive Lab offers an easy-to-use, graphical interface written in Visual Basic (VB) that eliminates the disadvantages of computer simulation while preserving its advantages.

Figure 2 illustration

Figure 2. Diagram of developed educational system.

In the following text we will explain how Interactive Lab overcomes the drawbacks of computer simulation mentioned in the previous section.

1) Didactic environment: Our laboratory system comprises a set of selected circuits for analysis and design. For each circuit Interactive Lab provides a complete description, consisting of circuit schematics, data, analysis questions, design specifications, and even design hints.

2) No need to allocate class time to teach computer programming: For each circuit, Interactive Lab utilizes a customized pre-written PSpice code, which is to be completed from component values entered by the student. Thus, time is not needed to teach PSpice coding during class. However, after class, once having designed and simulated the circuit, the student can peek at the code and attempt to relate it to the circuit's schematics and operation. By playing this detective game, the student, strongly driven by previous success, will be able to grasp PSpice by him/herself. It is our experience that, by repeating this procedure over time for each circuit under study, the student will progressively learn PSpice up to the point of becoming proficient in this language.

3) No programming difficulties to divert student's attention: Since the student does not have to write code in class, he/she can fully concentrate on the circuit under study.

4) No false sense of completion: Interactive Lab provides a "knowledge as a password" feature. This means that a student must enter reasonable values for the designed circuit components or else he/she will not be able to obtain any simulation outcome. This feature prevents a clueless student from obtaining simulation results that would be completely meaningless to him/her. Although technology can help significantly, it cannot and should not attempt to replace the mental effort needed in the learning process.

3. Implementation/ Functional Description of Interactive Lab
Implementation-wise, Interactive Lab is an application program (written in Visual Basic for the Microsoft Windows environment) that serves as an interface between the user and the PSpice simulator. Except for the Microsoft Windows environment, no other computer knowledge is needed, which allows the student to concentrate on analysis and design. The idea of interfacing with PSpice has been extended to other environments such as HTML [3] [4], turning a multimedia application into a hypermedia one.

Functionally, Interactive Lab consists of two sets of laboratories: theoretical and practical, which can be selected from a Lab menu. For the theoretical laboratories, the student is expected to analyze a given circuit and determine some theoretical characteristics, such as gain, bandwidth, input and output resistance, etc. For the practical laboratories, the student needs to calculate component values of a given circuit to meet given design specifications.

To describe the program functionality, let us assume the student selects a practical laboratory dealing with the design of a circuit. After selecting the practical laboratory, the student is presented with an operational window that contains the circuit schematic, circuit data, design specifications and a set of empty text boxes. These boxes are to be filled by the student with parameter values resulting from his/her design.

The student transfers the values resulting from his/her design to the text boxes one at a time. If a value entered is within an acceptable range, the student will be able to access the next text box. However, if the value is incorrect, the program displays the message "value out of range" and prevents the student from accessing subsequent text boxes until he/she enters a suitable value. This program feature, which we call "knowledge as a password," develops the student's habit of reviewing calculations and avoids the false sense of completion produced by quickly obtained, wrong simulation results. To facilitate design and design review, the application has a "hint" feature. By placing the cursor on a component, the student gets a design hint corresponding to that component.

Once all the correct values have been entered, the program allows the student to press the button Start Lab in the operational window. Upon activation of this button, the application generates PSpice code (a .cir file) created from a customized template and completed by the values that the student entered. The application next invokes PSpice to execute the code and perform the simulation.

Finally, the application places the student in the PSpice environment so that he/she can examine the simulation results. By using the PSpice "probe" window, the student can obtain a graphical representation of the circuit waveforms and compare them to his/her theoretical expectation. Finally, by pressing the "View Code" button in the operational window, the student can access the PSpice code. Relating this code to the circuit schematic and simulation output makes it possible for the student to become progressively familiar with PSpice commands and syntax.

4. A Guided Tour through Interactive Lab

An interactive demo (50 KB) of the Interactive Lab.
Require Shockwave plugin.

5. Measurement of Teaching Advantages of Interactive Lab 
The task of evaluating the efficiency of multimedia-assisted education is so complex that it has become a research topic in itself [5]. Nevertheless, we have made an attempt to quantify the teaching improvement provided by Interactive Lab. Table 1 shows the average grade obtained by students taking the courses Electronics 1 (E1) and Electronics 2 (E2) at the Department of Electric and Computer Engineering at SUNY New Paltz. The professor in all these courses was the first author of this paper, which ensures that the grading criteria were consistent.

Semester Course Avg.Grade NumberStudents
Fall 1994 E1 64.2 14
Spring 1995 E2 64.9 11
Fall 1996 E1 63.7 12
Spring 1997 E2 72.7 11
Spring 1998 E1 69.6 12
Fall 1998 E2 69.4 14
Fall 1999 E1 67.0 10
Spring 2000 E2 68.1 15

Table 1. Average course grades for students of the first author in Electronics 1 (E1) and Electronics 2 (E2). The system was first implemented in the spring 1997 semester.

To investigate whether or not Interactive Lab had a positive effect in the students' understanding of electronics, we examined the students' overall grades. We looked at 10 students who had taken both E1 in the fall of 1994 and E2 in the spring of 1995. These students showed an average grade decrease from E1 to E2 of about one point. ( xbar =-0.73, s =4.96 ). Interactive Lab was first implemented in the spring 1997 semester in E2. In order to study the impact of Interactive Lab we looked at the 8 students who took E1 in the fall of 1996 and E2 in the spring of 1997. These students showed an average increase from E1 to E2 of almost 5 points ( xbar = +4.96, s = 8.47).

With the idea of further quantifying the benefits of our teaching method, we incorporated the question "Was Interactive Lab helpful to learn electronics?" into the SUNY New Paltz Student Evaluation of Instruction (SEI) corresponding to E1 taught in the spring of 2001 by the first author. The answers were as follows. Strongly agree: 93%, Agree: 5%, Disagree: 2%, Strongly disagree: 0%.

6. Conclusions
Over many years of work, we have developed and refined an interactive system for teaching electronics. The system has proven beneficial to students, as it can be quantified by their grade increase and by their instruction evaluation.

Interactive Lab has many features of teaching value that result from its carefully thought-out design. For example, the View Code feature allows the student to learn PSpice by him/herself in a progressive and efficient manner, without consuming class time. The feature "knowledge as a password" encourages the student to generate a theoretical expectation for the result, reinforcing the concept that simulation by itself cannot replace mental effort.

7. References
[1] González, J.J. and Mandado, E. (1998). An Interactive Electronics Course using PSpice, Second European Workshop on Microelectronics Education, May 14-15 1998, Noorwijkerhout, The Netherlands, 43-45.

[2] González, J.J. (1997) Toward an Optimized Computer Assisted Electronics Laboratory, 1997 IEEE Computer Society International Conference on Microelectronic Systems Education, July 21-23 1997, Arlington, Virginia, 55-56.

[3] Valdés, M.D., Tarrío, J.A., Moure, M.J., Mandado E. and González J.J. (2000). Electronics Education System, ED-MEDIA 2000 World Conference on Educational Multimedia, Hypermedia and Telecommunications, June 26-July 1, 2000, Association for the Advancement of Computing in Education, Montreal, Canada (CD-ROM, in file edm.pdf, 1095-1099).

[4] Salaverría, A., Moure, M.J., Valdés, M.D., Mandado E., and González J.J. (2000). Memphis, a Hypermedia System for Learning Microelectronics, EWME 2000 3rd European Workshop on Microelectronics Education, May 18-19, 2000, Fuveau, France, 143-146.

[5] Belfer K. (2000). Assessing the Use of Technology to Enhance Learning in Higher Education, ED-MEDIA 2000 World Conference on Educational Multimedia, Hypermedia and Telecommunications, June26-July 1, 2000, Montreal, Canada (CD-ROM, in file edm.pdf, 1226-1229).

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IMEJ multimedia team member assigned to this paper Yue-Ling Wong