This paper is intended to be included in the category “CDIO Learning Objects”. It describes the design, implementation and results of the second year Basic Engineering Project subject performed by the students of Electronic Engineering degree (EE) and Audiovisual Systems Engineering degree (AV) at Telecom-BCN. Two groups of twenty students complete it every semester working in teams of four members. The students of these two degrees and also those of the other three degrees taught at Telecom-BCN are asked to fulfill the design, implementation and verification of five blocks of a product specified by the faculty. The product in the last three years, with small variations every year, has been a campus-wide announcements distribution system using wireless communications. All students know the requirements and specifications of the whole product and of the interfaces between blocks and the students of each degree are assigned to design, implement and test only one of the blocks. The pedagogical aspects of this subject were already presented in a previous CDIO Conference (at DTU in 2011). In this paper, the design-build projects performed by the EE and AV students, which complement each other and are integrated at the end of the semester, are presented with enough detail to allow other institutions considering its implementation. Additionally to the practical aspects (design guidelines, complexity, components and tools, cost, …), the learning outcomes and students achievements will also be presented. Also the dos and don’ts derived from the experience of three and half years of implementation. The EE students’ assignment is a 2 W class-D audio amplifier, with a bandwidth of 20 Hz to 20 kHz, power efficiency better than 80% and harmonic distortion better than 1% with budget restrictions. They first get a background on audio amplifiers using the puzzle technique and come to the conclusion that the only one that can fulfill the system requirements is the class-D structure. Then they design and simulate the sub-blocks (triangular or sawtooth signal generator, comparator, output stage and output filter, build a first prototype, characterize the blocks and the integrated system and build an improved second prototype on a printed circuit board. They develop the product documentation following our adaptation of the LIPS methodology. The AV students design, implement ant verify a virtual instrument to characterize the performance of the audio amplifier and to correct its frequency response by digital signal processing. This subsystem is developed in Matlab and uses the computer audio card to generate the test signals and record the amplifier output. They first develop a behavioral model of a class-D amplifier (also in Matlab) to simulate their non-idealities and then design and build virtual instruments to measure the amplifier RMS power, its frequency response and its harmonic distortion. They also develop a digital pre-equalizer to correct the frequency response. To test their development, they measure known blocks (filters, a commercial amplifier) and at the end of the semester, those that have succeeded, use their virtual instrument to characterize the amplifiers developed by the EE engineering students.
Proceedings of the 10th International CDIO Conference, Barcelona, Spain, June 15-19 2014