Jerry Hatfield, David Scott, David Szmyd
Northern Arizona University
The foundation of the first course is built upon the use of Ohm's and Kirchhoff's laws to deal with electrical voltage, current, resistance, inductance, capacitance, and power. This is no different than the traditional course; however, we strive to treat these issues within a context that uses real applications that are relevant to the several different majors in the course. For example, transducers and operational amplifiers are introduced very early and are used to show how electrical principles apply to measurement and control in mechanical, thermal, chemical, and computational systems. The study of circuit analysis methods takes on a new meaning when applied to real world circuits rather than the artificial and somewhat random combination of electrical elements frequently found in the traditional textbook.
The laboratory associated with this course has been totally redesigned to be consistent with the theme of ``real and relevant.'' A National Science Foundation Instrumentation and Laboratory Improvement grant supported implementation of a modern laboratory with high quality computer interfaced test equipment. The laboratory serves as a learning resource center in which the students not only perform formal lab assignments, but also have the opportunity to use the equipment and computers to strengthen their understanding of the concepts presented in the lecture section. A computer on each bench can be used for instrument control and data acquisition, data processing and plotting, report preparation, and circuit simulation. The lab assignments deal with practical applications of electrical engineering and include subject areas such as residential and commercial electrical wiring, DC systems and measurements, AC systems and measurements, components (R, L, C, diodes), AC/DC power supplies, amplifiers, transducers, data acquisition systems, and a design project.
This paper describes the structure, content, equipment, computer tools, and teaching methods used in both the lecture and laboratory sections of the course.
Our first course in electrical engineering serves two purposes. First, it is intended to build a foundation that prepares electrical engineering students for the remainder of their major studies. A second, and equally important, function of this course is to equip the other engineering majors in the college (mechanical, civil, environmental, and computer science) with the electrical engineering knowledge and tools needed to support their fields of study. Historically, this course had been only marginally adequate in satisfying these goals, and a major remodeling was needed for both the lecture and the laboratory.
The following objectives were established as guidelines for the changes:
The lecture section was modified extensively, starting with selection of a new text, Electrical Engineering for All Engineers. [1] The content, and even the title, was exactly what we were looking for, providing an excellent structure to support the lectures and class discussions. The subject areas addressed and the number of 50 minute sessions allocated to each are shown in Table 1.
The circuit analysis technique stressed in this course is the repeated application of Ohm's and Kirchhoff's laws. Most real, or practical circuits, can be analyzed with nothing more than these simple tools. Roadstrum and Wolaver call this ``intuitive circuit analysis.'' [1] True, many of the circuits found in textbooks, such as the example in Figure 1, require more complex methods; but, I have seen very few circuits in the real world that look anything like this!
Analysis tools such as Thevenin and Norton equivalent circuits are used to simplify more complex circuits during analysis and to help develop an understanding of input and output impedance and an appreciation of circuit loading effects. Mesh and nodal analysis techniques are introduced so that students know that they exist, but they are not used to any extent in this course.
Rather than ``do nothing'' circuits, as shown in Figure 1, we strive to use examples of real applications when teaching circuit analysis techniques. However, old habits are hard to kill. A zener diode voltage regulator circuit provides an excellent opportunity to demonstrate circuit analysis, address variations of operating conditions, and provide a limited exposure to design. However, zener voltage regulator circuits have been mostly replaced by integrated circuit voltage regulators or voltage references; it looks like we have some lecture notes to update.
Two adjoining rooms were combined into one large laboratory that accommodates 16 student work benches, one teaching station, and tables and seating for twenty four students. The tables provide large flat workspaces for projects and special demonstrations, and also allows the lab to serve as a mini-classroom for lectures and discussions related to the laboratory.
As a result of recent expenditures by the College and receipt of an NSF Instrumentation and Laboratory Improvement (ILI) grant, this laboratory is very well equipped. [2]
Each of the 16 benches and the teaching station are equipped with modern test equipment and instrumentation:
The digital storage oscilloscopes and digital multimeters are interfaced to Macintosh computers for data acquisition and instrument control using software developed by NAU. The arbitrary waveform generators also have a computer interface and we plan to link these instruments to the computer within the next year. The high power DC power supplies are quite versatile, operating in either constant voltage or constant current modes. Protoboards with internal power supplies support labs using discrete and integrated circuit electronics.
Two Philips PM6303 RLC meters are available for measurement of component characteristics.
In addition to data acquisition, the computer on each bench provides capabilities for data analysis and plotting, circuit simulation, and report writing. A laser printer provides high quality printouts.
Several types of software are available on the lab computers:
The LabSoft software has extensive capabilities for data acquisition and analysis. This package was developed by Northern Arizona University for instrument control and data acquisition, initially in our advanced electronics laboratory. [3,4] This software now assists the students in our Electrical Engineering I course with their lab work and provides a first introduction to data acquisition methods. Signal information, once captured by the software via the oscilloscope or the multimeter, can be processed and examined in detail in the time domain using the signal workbench within LabSoft. Up to ten signals can be worked with simultaneously, allowing addition, subtraction, or multiplication of two signals; calculation of average or RMS values; one signal can be plotted against another in an X-Y plot; and any waveform can be magnified, inverted, or shifted in time. Any of the modified waveforms can be saved as a new waveform, printed, or exported as a graphic or tabular data file. The LabSoft software, through Fast Fourier Transforms, is able to serve as a spectrum analyzer on data collected by the oscilloscope, ultra low frequency data from the digital multimeter, or data from any external source contained in a disk file. Data captured in the laboratory can be exported to several different analysis, plotting, graphics, or document processing programs on either the Macintosh or PC/Windows computers.
The laboratory activities were structured using five guiding principles.
A key element of the learning process in this course is the hands-on experience gained in the laboratory. This experience is provided through ten formal lab assignments plus a design project:
The laboratory assignments include the traditional activities to help the students learn what the instruments do and how to use them for testing and measurement. In addition, they are introduced to a number of electrical and electronic components and their application:
The design project provides an opportunity for the students to integrate several different circuit elements studied in the course and perform some useful function of their own choosing. The projects have included: LED voltage level indicators, emergency lighting systems, a motion detector, turn signal and emergency flasher circuits, water level detectors and alarms, audio crossover networks, sound amplifiers, sound activated switches, and a solid state message recorder. The students report that the design project is one of the more interesting activities in the course.
We have been teaching this course in accordance with its new design for about one year. The students have been at the sophomore level or higher, but the course has been designed as a second semester freshman course, and we will see our first freshmen in this course in the Fall 1995 semester. We believe there are several advantages to making this course available to students earlier in their programs of study. With the strong emphasis on application of electrical principles to all the fields of engineering, this course helps build a better understanding of the inter-relationships between each of the engineering disciplines and develops a foundation for an interdisciplinary engineering design sequence that is being developed concurrently.
Student response to the course has been very favorable, but the real test is how well these students perform in later courses. It is still too early to tell.
One very promising opportunity that the new laboratory presents is the possibility of using the computer and the instruments linked to it to develop interactive computer driven tutorials on instrument operation and on test and measurement techniques.
Faculty are very excited about the nature of the changes that have been implemented in what used to be a very stodgy old course and are interested in applying some of the same philosophies to other courses.
