R. B. Foist, J. Butler, G. Fleming
Jun 22, 2020
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Abstract
Laboratory projects can be strategically used to improve the Electrical and Computer Engineering (ECE) curriculum across all four years, according to National Science Foundation (NSF) research in which we participated. In this “spiral model” approach, lab component themes are introduced in the freshman year and revisited with increased sophistication and interconnection in the following years. Labs are thus used as a “cohesive framework” that connects and integrates individual courses. Three themes were used in the research: video (and image), sound, and touch sensors. In this paper, we present a new lab project within the video/image theme—a 10-component printed circuit board (PCB) design, based on a 555 timer chip, that alternately flashes two light emitting diodes (LEDs). Based on prior experience, and for ease of soldering, this project uses only through-hole (and not surface mount) components— hence the name “big” blinky. The main contribution of this paper is to integrate together the spiral model concept (by providing a flashing LEDs lab project) with a useful, how-to PCB tutorial that should help students (and professors) to make future circuits for labs and research. Specifically, we provide a two-part, detailed, easy-to-follow tutorial which teaches the student how to use the popular industry PCB software, Altium Designer 2018 (AD18), and then to submit the project to a PCB maker’s website to manufacture big_blinky. A three-day introductory AD18 course taken by one of the faculty authors did not show how to do a simple design from start-to-finish. In contrast, the big_blinky tutorial provides a simple, interesting, start-to-finish, guaranteed-to-work ECE project for professors and students who want to learn PCB design using world-class software. At the same time, this paper provides a relatively simple circuit design that fits nicely within the video/image theme of the spiral model for ECE curriculum improvement—the control of LEDs. Proposed upgrades of the project, which show “increased sophistication and interconnection” for later years of the curriculum, are also provided. This project has been successfully used in our first year “Introduction to Engineering” course, but has also been used effectively as an IEEE club project that included freshmen through seniors (and graduate students). Student feedback through formal surveys has been very positive. The project was also successfully converted to CircuitMaker (the free version of Altium Designer). The tutorial documents (PDFs) and AD18 (plus CircuitMaker) project code (and bill of materials for ordering components) will be available for downloading online, via the Wixsite web-hosting service: https://cbuece.wixsite.com/repositories. Introduction—Educational Research Using Labs Laboratory projects can be strategically used to improve the Electrical and Computer Engineering (ECE) curriculum across all four years, according to National Science Foundation (NSF) research done by Chu [1]. The aim is to enhance student learning and better prepare graduates for new challenges. Chu’s viewpoint is that a good engineer must not only become knowledgeable in certain content areas (components, learned in individual courses), but also be able to apply and integrate that content to solve complex, real-world problems. Motivation for Chu’s work came from an earlier 5-year study of engineering education [2]. That study found a deficiency in the curricula—subjects were taught in isolation, did not have proper context, and did not adequately prepare students to integrate knowledge across courses. Furthermore, labs were not used effectively. The study recommended a so-called “spiral model” and effective use of labs (by basing them on design projects): “... the ideal learning trajectory is a spiral, with all components revisited at increasing levels of sophistication and interconnection. Learning in one area supports learning in another.” [1]-[2] A digest version of the study is available online. It compares a “linear components” model (of a curriculum) to their proposed “spiral model”—using two helpful diagrams [3]. Chu’s approach applies the spiral model by introducing certain lab component themes (for freshman labs) and then maps out a plan to revisit them with increased sophistication and interconnection in the following years. In addition, he emphasizes design-oriented projects— because they can effectively “approximate professional practice”, enhance knowledge synthesis, build teamwork, and even encourage student persistence. Thus, within a spiral model approach, labs are used as a “cohesive framework” that connects and integrates individual courses. The three themes employed in Chu’s research are focused on video (and image), sound, and touch sensors. It is interesting to note that these are the main interface subsystems used in contemporary hand-held devices (like smart phones). One of the faculty authors (of this current paper), and a colleague, participated in Chu’s work as external collaborators. Some new lab projects were implemented and tested within three existing courses over a two-year period—a second-year digital logic design course, a third-year microcontrollers course, and a senior course in advanced digital design. In addition, some of this work has been used in our Institute of Electrical and Electronic Engineers (IEEE) student club. Students were surveyed at the end of the courses to assess the impact of the labs on their learning. Results seemed quite positive. Consequently, we were inspired by seeing the benefits of creating lab projects which can be useful across the ECE curriculum to provide a cohesive framework (for our courses) and thereby enhance learning. For example, our students are exposed to lab projects using visual feedback (LEDs and LCDs) in all four years—but with more “sophistication and interconnection” introduced in each year. This inspiration led to the development of two lab projects as contributions within the spiral model, in previous work [4], [5]. This paper’s contribution In this paper, we present our own design of a new (first-year) lab project within the video/image theme—a 10-component PCB design, based on a 555 timer chip, that alternately flashes two LEDs. Based on prior experience, and for ease of soldering, this project uses only through-hole (and not surface mount) components. Hence the name “big” blinky. The main contribution of this paper is to integrate together the spiral model concept (by providing a flashing LEDs lab project) with a useful, how-to PCB tutorial that should help students (and professors) to make many more circuits for labs and research. Specifically, we provide a two-part, detailed, easy-to-follow tutorial which teaches the student how to use the popular industry PCB software, Altium Designer 2018 (AD18), and then to submit the project to a PCB maker’s website to manufacture big_blinky. A three-day introductory AD18 course taken by one of the faculty authors did not show how to do a simple design from start-to-finish. In contrast, the big_blinky tutorial provides a simple, interesting, start-to-finish, guaranteed-to-work ECE project for professors and students who want to learn PCB design using world-class software. Recently, we were able to convert the entire design into CircuitMaker (the “free” version of Altium Designer), and also create versions of our tutorial documents based on that software. At the same time, this paper provides a relatively simple circuit design that fits nicely within the video/image theme of the spiral model for ECE curriculum improvement—the control of LEDs. Proposed upgrades of the project, which show “increased sophistication and interconnection” for later years of the curriculum, are also provided later. For assessment, we adapted surveys from Chu’s NSF work and applied them to the current work. Results are presented below. Overall, (and consistent with our previous work [4], [5]), we found that students really enjoyed creating hands-on lab projects that implement real-world electronic circuits, and learning something of how the (PCB) design software works to create the desired functionality (a simplified timer flashing LEDs, in this case). In addition, we consistently find that students have a lot of interest in learning and practicing soldering skills—as they assemble the finished circuit. A final point of introduction is that the spiral model approach, more broadly, is also consistent with the growing interest in hands-on (or project-based) learning that is becoming widespread in engineering education. As an example, The STEM Lab Report stated [6]: “Throughout higher education in engineering, colleges are requiring students to pull their gaze from a text-book to perform real-world, hands-on, team-based project learning. In short, they are teaching students to become engineers by having them work as engineers.” And in a previous work [7], we concluded: “...the key benefits of hands-on approaches for students are better outcomes, seeing the relevance of math (and engineering) with real-world examples, deeper understanding, more enjoyment, and persistence in engineering.” The 555 Timer Circuit (to be implemented in the PCB) At the heart of the big_blinky design is an integrated circuit (IC) chip known as a 555 Timer, which provides the timing at which the LEDs flash. 555 timers have been popular for decades in electronics, are known as “the classic timer chip”, and are discussed in detail in the well-known electronics textbook by Horowitz and Hill [8]. A good online tutorial for doing 555 Timer designs—showing how to choose component values to create the timing you want—is found here [9]. The big_blinky PCB Project I. Learning Objectives The key learning objectives for this learn-by-doing project are: To understand and implement control of LEDs using analog circuitry (as opposed to digital control) To understand the function of a basic 555 timer circuit—and s