Joaquim Oliveira, José Salvado - IATED · PDF fileJoaquim Oliveira, José Salvado...

Joaquim Oliveira, José Salvado

Thursday, June 19, 2014

International Conference on Education and New Learning Technologies,

July, Barcelona/Spain

Outline

• Introduction and Objectives

• The importance of instructional laboratories

• Teaching Methodology

• Examples of Simulation/Experimental Works

• Results and Discussion

• Conclusions

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July, Barcelona/Spain Thursday, June 19, 2014

Engineering problem solvers are individuals who find the best-fit solutions, from a specifications;

The engineering graduation programmes aspire that students acquire a set of skills that will be of great value in the professional role and invest time and efforts to create engineering problem solvers and to develop critical thinking minds;

The shortening on courses and the technological evolution, demand a strong focus on basis and the fundamentals of technology and a balance on theory and practice while emphasizing practical and critical thinking skills by using a “learning by doing” basis;

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The new typical students with diverse technical skills and background, demands new solutions to the new classroom challenges allowing the appearing of new platforms and environments of teaching;

Simulation software, remote control of instruments, data acquisition and rapid data analysis and presentation changed the traditional laboratory instruction but to better consolidate knowledge a focus on real instructional laboratories is required;

The importance and benefits of experimental based learning and laboratory instruction must be pointed out, starting from the entry level.

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This paper presents a prospective approach to teaching electronics and telecommunication subjects to engineering graduation students, at different levels and courses, with a strong focus on experiments and the use of laboratory equipment to enhance their technical skills and background.

Goal: prepare graduates with the ability and the skills

to apply knowledge and technology to design and develop products, solutions or systems in an effective way despite the effects on course reduction and the fast technological evolution.

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To become true problem solvers, students need to develop creative thinking processes which requires good training in problem analysis, hours of practice and exposure to good and creative solutions, helpful team work and flexibility in the approaches;

Training good engineer professionals demands a very effective hard work both from students and educators;

The importance of experimental based learning, the laboratory instruction, the team work and personal engagement must be continuously pointed out, especially for freshmen.

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6



Analytical formulation and Resolution;

Discuss with colleagues

Knowledge is satisfactory?

Simulation;Compare results with

analysis Discussi with colleagues

NoYes

Knowledge is satisfactory?

No

End

Experimental test;Evaluate and compare

results with simulation and analytical formulation;

discuss with colleagues

Yes

Knowledge is satisfactory?No

Yes

BeginStudent gets work

assignement

Write final report and send it for Assessment

Work assignement

Technical Report

The methodology adopted comprises three different phases: analytical formulation and resolution of the proposed problems or experiments, the circuits simulation and the implement an experimental setup;

The three phases are interconnected and the results of each phase are analyzed and discussed with colleagues;

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From the author’s experience, the third phase is the most critical phase to the overall students´ success and performance and also the one where most students can become despondent. Breadboard misconnections, wrong measurement procedures or deficient adjustments on instruments are the most frequent issues, all caused by a lack on technical skills on laboratory equipment usage;

To save time, to avoid stalls during the Lab sessions, and to facilitate the learning process, the experimental setup uses the Analog System Lab kit Pro (ASLK-Pro) from TI as a base for all experiments;

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The simulation tool used is the TINA-TI software which is an easy-to-use Spice based simulator and includes several virtual Lab instruments. It allows students to work as if they were in a virtual lab which diminishes the lack of confidence and facilitates their performance with real equipment;

The curricular units involved are: Electronics I (ELE-1), Electronics II (ELE-2), Propagation (Propag) and Applied Electronics (AE). The first three are part of the electrical and telecommunications engineering course. The last one at pos-secondary specialized courses in electronics and telecommunications.

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ELE-1 / AE ELE-2 Propag

Syllabus

Basic electronic devices (Op-Amp, Diode, BJT, MOSFET) Op-Amp circuits; Rectifier and clamping circuits; BJT and MOSFET based amplifiers. Logic circuits with BJT/MOSFET

BJT/MOSFET current sources; BJT/MOSFET differential amplifier; Frequency response of amplifiers; Analog active filters; Oscillators and signal generators;

Transmission Lines; Time-domain reflectometry principle and analysis; Smith Chart and matching networks; Waveguides; Fiber Optics.

# teaching hours per week 5 / 4 5 5

% of Lab per week 60 / 50 60 60

Students’ average workload 7 / 5 7 7

ECTS 6 / 5 6 6

Lab Experiments Proposed (*) Biasing and transient analysis of a CE BJT

amplifier; Precision rectifier Circuits

Frequency response of a CE BJT amplifier;

Analog Active RC Filters; Sinusoidal and relaxation

oscillators

VSWR and reflectrometry on simulated

transmission line

(*) refers to experiments or practical works developed on the TINA-TI simulator and experimentally evaluated in the ASLK-Pro, as an integrated LAB environment and test setup.

Biasing and Transient response of a Common Emitter (CE) BJT amplifier

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In ELE-1 and AE students apply the analysis methods from circuit theory, the importance of stabilizing the bias point and the need of using coupling capacitors.

Objective: design from the scratch the amplifier and the switching inverter circuits, stable bias circuits, read and interpret the device datasheet, choosing the bias point analytically, simulation the design and finally test experimentally.

Q

2 8 5→ ( . , )Q mA V

Frequency Response of the CE amplifier

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In ELE-2 class students evaluate the CE amplifier designed previously in ELE-1 class using circuit analysis and the BJT π−hybrid models.

Objective: evaluate the frequency response of the BJT based amplifier, determine the lower and upper cutoff frequencies influenced by coupling and bypass capacitors and the limitations due to the internal capacities of the BJT.

Transient Response of the ideal Miller Integrator

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In ELE-1 and AE, Op-Amp are part of the subjects studied and the Miller integrator are among the op-amp based circuits with significant application to electronics used in circuits for telecommunications.

Objective: study either, the ideal and the practical configurations of the Miller integrator in terms of its transient time domain response but also for its response in the frequency domain.

+

– 2

3

6TL081

+10V

– 10V

7

4

v0

viR1

C1

VSWR and reflectrometry on transmission line model

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In Propag the observation of the stationary wave pattern and reflection pulses of the real transmission line is difficult in the laboratory.

Objective: use standard laboratory equipment to analyze the electrical phenomena mentioned using a transmission line model of LC lumped elements.

V-

V+

C1 1

0n

L1 1m

C2 1

0n

L2 1m

C3 1

0n

L3 1m

C4 1

0n

L4 1m

C5 1

0n

L5 1m

C6 1

0n

L6 1m

C7 1

0n

L7 1m

C8 1

0n

L8 1m

C9 1

0n

L9 1m

C10

10n

L10 1m

RL

R1

R2

+

VG

TP3TP2

C11

4.7n

Rgen

TP1

-

+ +3

2

6

74

OP1

This methodology was performed for only one academic year and the number of students enrolled is relatively low to consider the data representative for evaluation. Nevertheless some objective data is available and can be used for discussion;

The success rates obtained from the assessment on each course taught does not deviate significantly from those of earlier years, when this methodology was not implemented. However, the misconnections of the circuits were reduced and consequently as well the time of carrying out experiments;

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At the beginning students tend to become anxious about the method and workload compared to colleagues of the previous years where we did not use this methodology. However, after the first few weeks those who dedicated have emphasized the benefits on a “learning by doing” approach and the use of the simulator/kit rather the use of a breadboard assembly;

Regardless the difficulty there is a general acceptance that this methodology reinforces their knowledge and understanding about the topics taught. Moreover, the use of simulators facilitates the preparation of each laboratory session and helps to take conclusions as students have prior and supported knowledge on what they can expect from the experiments.

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A balanced simulation/experimental methodology with focus on hands-on laboratory skills used and implemented at a Polytechnic School, was presented; The aim is to minimize and compensate the minor emphasis on practical skills and critical thinking in engineering students due to the reduction on course time and the heterogeneous of the classroom; This methodology keeps emphasis on practical skills, and gives students the opportunity to become well rounded, highly trained and multi faceted engineering professionals recognized by employers;

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Student's interviews denote a good overall reception although some complaints on the extra workload; This methodology is still considered at an early stage, both in terms of experience to implement as the insufficiency of data to support its suitability for other engineering disciplines. Further work is undergoing to evaluate these issues in particular.

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For any questions please contact us to:

[email protected] [email protected]

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