DC-Power Supply Simulator: a scenario-based educational tool to enhance student learning
King Fahd University of Petroleum & Minerals (KFUPM),
31261, Dhahran, Saudi Arabia
Abstract
Simulation-based educational products are excellent illustrative tools that proffer features like visualization of the dynamic behavior of a real system etc. Such products have great efficacy in education and are known to be one of the first-rate student centered learning methodologies. These products allow students to practice skills such as critical thinking and decision-making. In this paper, a case is presented where a scenario-based e-learning product namely ‘DC Power Supply Simulator’ is developed at KFUPM for an introductory technology course. The product simulates a DC power supply – an electronics circuit consisting of various components. The product strongly supports the visualization of the dynamics of these circuits while a user manipulates its parameters. The voltage waveforms at different places in the circuit are dynamically plotted in real-time as in an oscilloscope, a strong feature of this product. The product was put to test during three semesters and results of the survey conducted by the instructors and the students are presented. The results clearly suggest the benefits of using such a tool in enhancing student learning.
Keywords: Scenario-based e-Learning; Teaching/learning strategies; Interactive learning environments; Active learning; DC power supply, diode rectifier, virtual oscilloscope.
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* Corresponding Author.
1. Introduction
Simulation-based educational products are excellent “illustrative tools”, used exceedingly in student centered learning methodologies. It is an active learning technique, which stimulates users’ diverse cognitive skills and insight into a system by instantly staging the consequences of their actions and strategies. Such actions and strategies can be tested without the apprehension of failures or reprisal. Such products allow a user to increase his understanding of a system in a short span of time. As compared to real world experience, this accelerated learning is one of the unequaled advantages of such products.
These simulation-based educational products provide a unique way to reinforce the theory discussed in the classrooms. As a student/user becomes deeply involved in the scenario, a sense of competition and a desire to perform well is most likely to develop. Consequently, the teaching effectiveness of these products is exceptionally high. These products render a great opportunity for the students to visualize and experience a practical scenario of what they learn in their coursework.
An elating facet of these products is the inherent concentration of a user on decision making. It is this intensity that gives these simulation-based educational products its richness and effectiveness. Even though these interactive approaches are not considered to be a substitute of more formal approaches in teaching, it effectively complements these methods. Using Bloom’s taxonomy, the first three levels of knowledge, comprehension, and application, in most cases, are fully served. The fourth level of analysis could be present fully or partially depending upon the type of the tool or product and the use of it by the instructor.
The tool or product presented in this paper is developed in an academic project at King Fahd University of Petroleum & Minerals (KFUPM). The motivation behind this project came from a workshop on increasing teaching effectiveness (Ellington, 2002) and an undergraduate course that the authors are teaching. The course is an introductory technology course namely ‘Electronics-I’ which is a compulsory course taken by the undergraduate students in three departments; Electrical Engineering, Computer Engineering, and Systems Engineering and as an optional in various other departments at KFUPM and its community colleges.
The objective of the course is to develop the basic understandings of the electronics components such as diodes and rectifiers which are being used in various areas of electrical and electronics technology. To increase the effectiveness of the course, three different scenarios of DC power supply simulation based product were developed in this project. According to taxonomy presented in Randall (2002) this product can be categorized as a scenario-based e-learning products referred to as SBELP in this paper. As the course is compulsory in three departments, average enrollment per semester is essentially high.
In section 2, literature review is presented. Section 3 explains the experimental setup and section 4 elaborates on the features of the SBELP. Section 5 provides an overview of development. Feedbacks from the instructors, who have taught this course, are presented in section 6. Section 7 shows the outcomes when the SBELP was tested with the students. Finally, conclusions are presented in section 8.
2. Literature Review
Simulation-based educational products in academics are becoming wide spread and ample literature is available on this area. These products are categorized as scenario-, simulation-, and game-based e-Learning (Randall, 2002). The realization of the efficacy of these products is growing (Carlson, 2003). Using new media and information technology in the classroom can not only make studying more attractive to the students, but might also make teaching much easier. In engineering classes complex technical problems have to be presented in a way which is easy to follow and understand. Learning on-line is one of the fastest-moving trends in higher education, as engineers and executives in technology industries are discovering (Ubell, 2000).
There are a lot of engineering web-based courses, in which practical sessions are often condensed into relatively shorter period near the end of the course. This has a negative effect of not permitting the students to experiment step by step with the concepts. Romano (1998) has developed an analog cathode ray oscilloscope simulator to permit students to practice with a good simulator.
Crutchfield (1998) presented a Java applet that performs graphical convolution of continuous-time signals on the screen to aid in teaching, where a student can select from provided signals or draw a signal with mouse. A combination of Java Script, RealAudio, and technical presentation on the screen, and Java applets to complement classroom lectures.
Poole (1994) discussed the application of simulators in teaching digital electronics. Some examples of practical exercises used with students are presented. The advantages and disadvantages of the simulator approach are compared with conventional courses.
Ponce (2001) presented an educational tool for the analysis of some parameters in wireless communication. This tool is especially interesting for telecommunications students since it provides an easier way to understand the characterization of radio channels. The graphical visualization of the results allows students to identify the path followed by each ray from its origin at the transmitter antenna to the receiver after reflection, diffraction, etc. It also allows students to see its contribution to path loss, the power delay profile, and the direction of arrival.
Drofenik (2002) introduced the Interactive Power Electronics Seminar - iPES - a new software for teaching a basic course on power electronic circuits and systems. iPES is constituted by web-based with Java-applets for interactive animation, circuit design and simulation and visualization of electromagnetic fields and does comprise an easy-to-use self-explaining graphical user interface.
Ferre (2002) discussed about Macromedia Flash to develop animations for web-based learning in undergraduate electrical engineering course in circuits and systems. Some key concepts such as time scale, time reversal and convolution are developed to allow students to better visualize these ideas. Some problem solving exercises are also developed to allow students for input and get immediate feedback.
Higashi (2003) presented an educational simulator (e-SCAT) for switched-mode power converter which has new algorithm and user-friendly interface to encourage students to learn more concerning the field of Switched-mode power converter.
Hantsaridou (2005) presented a multimedia module for climate-simulation- experiments. The application was based on the energy balance model. The proposed method was free from numerical or algebraic computations. The fundamental principles of the subject are taught in an active learning environment.
Viliam (2005) presented an overview of the current state of development of e-Learning in Electrical Engineering with a special attention to the fields of Electrical Drives and Power Electronics. Two examples are presented in this paper; the first example is from field of electrical drives that shows time courses of AC drive typical variables – phase voltage of the motor, stator current, electrical torque and speed course. Another example for illustration is from field power electronics. The animations are developed using Macromedia Director.
Canesin (2005) presented Java applet programs for a web-based multimedia course in basic power electronics circuits. These tools make use of the benefits of Java language to provide a dynamic and interactive approach to simulate steady-state idealized rectifiers to assist the teaching of basics rectifier power electronics circuits.
Due to ever-increasing scope and scale of work in this area, formulating development standards are becoming important. Shareable Content Object Reference Model (SCORM) is “a collection of standards and specifications for web-based e-learning. It delineates communications between client side content and a host (generally part of a learning management system)” (ADL, 2007, Wikipedia-SCORM 2007). SCORM is an e-learning standard in which the goal is to have learning objects reusable, accessible, interoperable and durable, abbreviated as ‘RAID’ (Li and Lin, 2005). Li and Lin (2005) proposed a hybrid scheme, for SCORM compliant courses, composed of an XML binding model and a WAP based directory service in which complex metadata could be dealt efficiently. Content Object Repository Discovery and Registration Architecture (CORDRA) is another standard which is “open, standards-based model on how to design and implement software systems for the purposes of discovery, sharing and reuse of learning content through the establishment of interoperable federations of learning content repositories” (cordra.net, 2007, ADL2, 2007).
3. Experimental Set
The DC power supply converts the standard 120V /220V, AC available at wall outlets into a constant DC voltage (usually in the range of 5 to 20 V). One of the most common electronic circuits to produce DC voltage which is used to power all types of electronics circuits, such as televisions, satellite receivers, computers, mobiles, stereo systems, VCRs, CD players, voltage converters and stabilizers, and most laboratory equipments. A basic block diagram of a complete power supply is shown in figure 1.
Figure 1. DC Power Supply Block Diagram
The first block in a DC power supply is the power transformer. The diode rectifier can be either a half-wave rectifier or a full-wave rectifier (center-tapped and bridge). The variation in the magnitude of the rectifier output is considerably reduced by the RC filter block.
In electronics course, students are taught diode rectifiers and DC-power supply circuits, and students realize these circuits in the electronics lab using various components, oscilloscope and multi-meter as shown in the figure 2.
Figure 2. Experiment Set for DC-power supply
There are various drawbacks noticeable with this physical set as compared to the virtual setup. A common happening, while using physical setup, is that the students burn components such as transformers, capacitors, resulting in their weakening poise and ease of handling. This leads to a more defensive or even ‘better not try’ approach in experimenting with their ideas. Another disadvantage that emanate from the physical setup is that the students are unable to visualize the voltage waveforms at different points; especially right after the rectifier circuit, since RC filter meets at that point and produce cumulative effect, to produce DC output voltage.
4. The SBELP: ‘DC Power Supply Simulator’
The SBELP is named as ‘DC power supply simulator’ as it tries to emulate the electrical power supply conversion from AC to DC. This product reacquaints students with the fundamentals of AC (alternating current) and DC (direct current) voltages as well as introduces students to the basics of AC to DC conversion through the use of diode rectifiers.
Electronic circuits are harder to understand where voltages and currents are not directly visible and must be measured indirectly with meters and oscilloscopes. This lack of visibility impedes learning about circuits in many ways. Thus one of the key objectives of this SBELP is to assist the students to visualize the dynamics to various circuits and test the effects of various decisions they can make on the outcome of their circuits.
The general objectives of this SBELP are listed as follows:
§ Enhance student motivation and learning by providing them a hands on experience in a virtual environment.
§ Provide an interactive way of understanding and experiencing the effects of various decisions making skills.
§ Supplement the class material and concepts used in various electronics courses.
§ Augment the application, analysis and decision-making skills of the students.
§ Encourage students to practice without the fear of burning components.
Electronic circuits are harder to understand where voltages and currents are not directly visible and must be measured indirectly with meters and oscilloscopes. This lack of visibility impedes learning about circuits in many ways. Thus one of the key objectives of this SBELP is to assist the students to visualize the dynamics to various circuits and test the effects of various decisions they can make on the outcome of their circuits.
The highlighted SBELP features, including SBELP development, user interface, text guides, various scenarios, are presented below:
5. SBELP Development
The SBELP is developed in Macromedia Flash 8. The programming is done in Flash ActionScript 2. The suite was selected because of its excellent animation and graphical abilities along with the programming capabilities provided by scripting language known as ActionScript.
5.1 SBELP User Interface
One of the aspects, in which the SBELP varies with other similar kinds of electronics simulators, is the virtual oscilloscope display of waveforms during the course of the task. In real environment, a user usually connects one oscilloscope at a time, while in this SBELP, a user observes the virtual display of all signals at each point of the circuit. This SBELP has a fully interactive and dynamic interface, and all output results displays such as waveforms and voltages in real-time, rendering detailed dynamics of the circuit.
SBELP has been developed in such a way that every time the user logins, a new input voltage is given randomly to provide him a new challenge every time; this will enhance user’s learning for different supply input.
The transformer primary winding turns has been fixed to 230 and secondary turns are under user control to achieve step down voltage transformer. The transformer is completely interactive, where user controls and visualizes the variation of secondary turns as well as the output secondary voltage in the virtual digital meter. This output secondary voltage is then fed into the rectifier circuit. All three types of rectifiers are developed in this SBELP to provide complete and practical understanding to the user; half-wave, center-taped full-wave and bridge full-wave rectifier circuits. These three scenarios are explained in the later section. The rectified voltage is then passed through RC filter, where user has full control on it to achieve his objectives by minimizing ripples with clear visualization in the oscilloscope.