HomeLabKits for Introductory Course in Electrical Engineering1

1 This work was supported by the European Union (contract No 2003/005-026.01.02.0020) and Estonian Science Foundation (grant 5614)

Martin Jaanus, Niilo Hein, Vello Kukk, and Anti Sullin Tallinn University of Technology/Faculty of Information Technology, Tallinn, Estonia,

e-mails: martinj@ttu,ee, niilo@ids.ee, vello.kukk@dcc.ttu.ee, emperor@mail.ee

Abstract—Design, implementation, and experience of application of HomeLabKits are described. HomeLabkit is a small box containing everything needed to perform labs in a courses related to introduction into electrical engineering. In addition to the kit, a student needs a computer with internet connection only. Both power supply and data processing is performed over USB-connection. The paper describes content of kit, the labs for which the kit has been designed, software functions and experience of application during one and half year (3 semesters). The different categories of students have used the kit and also different modes of usage were tested. Very positive results have lead us to the decision to base labs on HomeLabKits only.

Keywords— learning systems, laboratories, internet, e-learning, home labs.

I. INTRODUCTION Labs have become the most important part of

technology education because of several reasons. First, the fresh students have much less practical experience from secondary schools than before, particularly because of insufficient equipment in schools. Another reason is caused by technology itself: young people have less and fewer possibilities to get experience as instruments are less available for reassembling, more protected and many operations have become prohibited for security reasons.

Second, lack of experience makes theoretical considerations too abstract and is considered by students as something that has to be learned but have not evident practical value. We cannot expect that a student is able to invent practical application of theoretical constructions if they have very few experiences.

So, we probably have to reverse the paradigm of teaching: instead of illustrating theory in lab, we have to apply theories to explain what has happened in real life, particularly, in the lab experiments.

This has been proved also by questioning students: many of them claim the labs the most useful and interesting part of their studies.

As the conclusion from all these changes during last years we initiated a project that had the following goal: to design HomeLabKits that are compact sets of instruments and devices to be tested, flexible, easily transportable and including everything needed to perform the labs except computer. Certain support for that approach came from the fact that the target course was delivered several years as fully internet-based one. That made integration of home labs into learning environment an easy task.

This action was implemented under learning environment that is being designed for several years [1]. Note that more attention has been paid last years to distant and virtual labs [2, 3] which are obviously less expensive and may promise higher level of cooperation. However, our practice has confirmed that those modes should be applied after newcomers have obtain their, may be the first experience with real equipment, components, measurements, and other instruments. This action is one step towards creating Personal Learning Environment [4].

In this paper, we describe shortly web-based environment, components of the course, design considerations of HomeLabKits, implementation, and experience of their usage, including some statistics.

II. MOTIVATION In addition to aspects described in Introduction there

were several more concerns related to practical work. It is well known that labs are often performed by groups

of students, may be 2-4 students and sometimes they prepare also common report. Even if they have to make personal reports, it appears frequently that the amount of work done by different students is very different. All teachers know that it is not the rare case when practically all has done by one student only and other(s) make simply copies of the report.

When providing university room for practical labs, strict restrictions may be applied for time as the lab must match the general schedule. However, time slots to perform measurements differ up to 4 times depending on student’s background, experience, and simply one’s psychological type. The data demonstrating such differences have been collected over years while labs were organized on the basis of pre-registration. This flexible mode was more efficient than strict scheduling but did not match fully high variety of students’ needs.

Even under flexible registration mode the resources of lab did not enable personalized work. Therefore groups of two non-fixed student groups were used. However, even so small groups were not suitable to set up individuality of assignments.

So, two main reasons were sources for HomeLabKit project: to make laboratory works totally personal and to give students practically unlimited time to perform there work. As a solution, it was decided to design and implement small compact kits covering all labs that could be used anywhere and any time, assuming existing internet connection only. As before, all reports were

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supposed to be formed directly in electronic environment used for all students’ activities in the course.

The project started in February 2005 and was successfully completed in one year. Success here means that HomeLabKits were tested in real learning process and few detected problems were fixed during that time. The experience was so good that it was decided to use only those kits starting from fall semester 2006.

III. LEARNING ENVIRONMENT Learning environment has been developed last 5 years

as a fully web-based one. That means absence of any paper documents and keeping logs of all activities performed by students. All assignments that had to be performed in fixed places (computer class or lab room) have based on pre-registration. From fall semester 2005 all internal deadlines were cancelled and learner could plan his/her activities personally. This increased efficiency evaluated by percentage of positive completion of the course (reached 90%).

Passive learning materials include: videos of lectures, lecture slides in pdf- and pps-formats, links to sources in internet etc. Very popular is ‘learning court’, a structured set of exercises on which about 100 students solve ~40,000 exercises during semester.

Assignments contain three main components: self-tests (12), labs (7), and class-tests (4). Final mark is compiled from results of those items which all must be completed with positive result. The number of attempts in tests is limited only time limit set by university (i.e. end of semester). All assignments have accompanied with prescribed credit units (varying form 0.1 to 0.3) that make together full amount of 3.5cu. Labs have also different workload in the same range.

Percentage of unsuccessful class tests have been ~23% when 55% threshold has been used. This number seems to be some natural constant as it has been the same both over years and in different courses. The fastest students have completed the course in 10 weeks as some have needed all 20 weeks allowed by official regulations.

IV. HOMELABKIT: SPECIFICATIONS HomeLabkit was designed to support the same works

that existed before. One reason was also assumption that kits would be used in parallel with regular labs. However, real amount of work increased by 20-80%. The list of labs includes:

1. Kirchhoff’s and Ohm’s laws 2. active twopole 3. twoports 4. AC-circuits 5. frequency response 6. transformer 7. periodical waveforms

The kit includes: 1. DC-source 2. AC-source 3. analog and digital multimeters 4. active (autonomous) twopole 5. 2 resistive twoports 6. RC-twoport

7. transformer 8. R-, L-, C-components 9. wires (2 types, 25cm and 50cm ) 10. DVD with lecture videos All components were packed into usual CD-box

23×16×18 cm (Fig. 1, 2) and were implemented using plastic boxes 90×110×35 mm.

Initially, the sources were designed to be powered by batteries. However, first experience showed that their lifetime was too short and this followed by the main and significant change during the project: sources were redesigned to be powered by computer over USB-connection that also served as carrier for information flow in both directions. Further experience showed that that was right decision with only one side-effect: in some experiments laptop had to use AC power as battery could not deliver enough power for USB.

Figure 1. HomeLabKit – external view

Figure 2. HomeLabKit: opened

All DUTs were designed on the base of those that had been used in regular labs and therefore there were almost

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no problems. Of course, low power condition caused some restrictions (combined twoports, transformer, AC-circuit) but design specifications were tested against all possible operations and so practical problems could be avoided. However, in AC-measurements it is recommended to observe signal waveforms and change source level to avoid saturation effects or too low levels that can be detected by improper D/A conversions.

Parameters of signals produced by DC- and AC-sources can be summarized as follows:

1. DC current source: 0..30mA, max voltage 25V 2. DC voltage source: 1..10V, max current 150mA 3. AC source: 0...1Vrms, output resistance 430Ω,

frequency 10Hz...100kHz 4. AC waveforms: sine, square, triangle

Figure 3. DC-source

Figure 4. AC-source-meter

In fall semester 2005, first tests were taken: part of students took the kits to home and performed all labs in places they chose. Part of students was real distant learners, i.e. they had no physical contact with teachers (e-mail, web, and teleconferencing only). Some students took the kit to lab to get more help from teachers (few cases).

There were surprisingly few problems: some minor errors in software and batteries that ran out. Those problems were fixed fast (battery-powered sources replaced by USB-powered ones). In spring semester 2006, only few distant learners used the kits. Another group worked in common computer class. All those tests were so successful that it was decided from fall 2006 to continue with HomeLabKits only, without any other lab resources.

During this semester, 100 students passed the course that made totally 888 labs (some did not complete all).

V. USAGE MODES Initially, it was assumed that kits will be used mainly as

true home labs and not by all students. However, last experience showed that three different modes should be used and combined.

1. True home lab: a student takes the kit and performs his/her labs fully at home. The time needed depends on all activities as assignments are logically dependent. Totally 13 kits were given to this group and one kit was reused by another student. From 14 students, 2 did not complete all labs. Weeks needed to complete all labs were from 12 to 19 (max allowed) distributed almost uniformly.

2. Using kits in lab room. Most of students (about 90) were not confident enough to start with home labs from the beginning and they started visiting lab room. The reason was their need to get help in assembling circuits, getting familiar with meters etc.

3. From about 10th week the third mode became dominant – we called it overnight lending. Students took kits for a night or few days, preferably for weekend.

Finally, the statistics shows that 47 students from 100 did not take kits to home, 9 used lab room only for the first lab, and 12 used kits for ‘true’ home labs.

Note that the learning environment allows using personal scheduling and so, supports flexible using of kits. At he same time, logical order is built-in and therefore one cannot perform labs independently from other activities (self tests, class tests). Namely, self test are prerequisites for labs and the last are prerequisites for class tests. So, one can schedule to perform first all self tests, then labs, and finally all class tests. This has been used by students very rarely. Probably, this is not the best for overall efficiency and different restrictions should be applied to force more harmonic progress in learning tracks.

VI. SOFTWARE During the HomeLabKit project new web-based e-lab

environment was developed. Main design goals were: 1. Build a possibly generic framework that is not

specific only to labs in electrical engineering. 2. Minimize the work needed to create or modify labs. 3. Support automatic validation of data. 4. Permit teacher to interfere giving comments and

hints.

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Server-side software is developed on Microsoft's ASP.NET platform using Microsoft SQL Server as database backend. Internal design of software was somewhat inspired by Adaptive Object-Model Architectural Style [5] where programs object model is constructed during startup phase of server software using metadata stored in separate XML files (one per lab). The metadata of a lab specifies:

1. Lab-level constants and constant parameters of components included in kit, used for verification of measurements and calculations. Concrete kit-specific constant values are stored in database.

2. Data items to be entered by the student e.g. results of measurement and calculations. Supported data types are floating point and complex numbers, vectors, and matrices. Also are supported simple arithmetic formulas and text comments. Each data item can have validator(s) to test correctness of input and show errors, warnings and hints to student or teacher. Validation algorithm can be specified in a JavaScript script associated with a validator and there can be validators that run in student mode, in teacher mode or in both modes.

3. Derived values that are calculated from constants, parameters of measured components, measurements, calculations and other derived values. Derived values are calculated using bound JavaScript script. Use of derived values enables simplifies the creation of validator.

4. Lab-level validator that are not bound directly to any user enterable data item.

5. Common functions to be used in several scripts. JavaScript scripts used in validator and in calculation of

derived values are dynamically evaluated on server. Because all HTML is dynamically generated by the

server software, each lab has an additional layout model (stored in XML format) to specify visual appearance and structure of the web page(s) and the workflow rules.

Experience gathered in the HomeLabKit project has shown the need for modularization of so far monolithic lab definitions into smaller parts that can be reusable in different labs.

On the client side, besides HTML, JavaScript is used to paint graphics and to communicate with server software. Communication is based on Asynchronous JavaScript and XML (AJAX). The use of AJAX technology enables instant saving and validation of entered data, thus eliminating the need for web page reloading each time the user requests a change, minimizing risk of data loss and giving opportunities to warn and guide the user during data entry.

VII. ANALYSIS AND CONCLUSIONS HomeLabKits appeared to be more efficient and

suitable to expand students’ possibilities to get familiar with electrical measurements, analyze the results, and understand relationships between theory and reality. This model gives students better conditions to invest his/her resources, first of all time, into learning.

On the base of HomeLabkit and related software it is easy to create different versions of labs. The underlying idea of learning environment is compiling courses from a large field of components (incl. static materials, tests,

home and class works, labs), HomeLabKits has helped to implement this idea in area of practical works.

Logical structure of the lab was built as series of steps (measurements, calculations, reporting) without possibility to return to previous steps. For example, after completion of measurements this action was closed and one could continue with related calculations and commenting only. This was caused by previous experience: when reactions to incorrect measurement or calculation results were highlighted, students started to ‘adjust’ measured values to get ‘correct’ highlighting. So, when a student recognized errors in home labs he/she was recommended to comment this but there was no possibility to repeat measurements. Such restrictions appeared to be not appropriate in case of home labs, particularly because of increased time resources and also because of higher responsibility obtained by student. This restriction was decided to change.

All actions in lab are accompanied with comment boxes which must be filled to get to the next step. However, most of students appeared not to be able to write acceptable explanations or comments. The decision for future is to collect comments from students’ reports and to give them possibility to select (parts) of comments in database (including wrong or inappropriate ones). There is no experience with such approach so far.

Teacher mode allows to se the status of work at every moment and this was used for sending hints to student and changing the state, for example, to switch back to measurements. This was sometimes asked by student who recognized the errors. Some special communication was needed for such actions and probably it should be automated i.e. sending message to the teacher automatically if something is going wrong.

The main conclusion is that the use of HomeLabKits should be extended to more courses and become part of labs even when distant and in-site labs are applied because of restricted cost, weight and complexity of equipment.

Second important conclusion is that labs should be integrated into learning environment along with other components that means more and smaller experiments embedded into logical structure of assignments. It follows that instead of 0.1…0.3cu that are now assigned to labs, experiments will be evaluated together with other activities, and as in tests, unsuccessful experiments are to be repeated until correct results will be obtained.

REFERENCES [1] V.Kukk, "Analysis of Experience: Fully Web Based

Introductory Course in Electrical Engineering“. Proceedings of the 1st International Workshop on e-learning and Virtual and Remote Laboratories, Setubal, Portugal, August 24-25, 2004. pp. 111-118

[2] G.S.Ferreira and W.B.Zapelini, “Analysis and comparison of educational resources in an undergraduate course in electronics”, ICL2006, Villach, Austria, September 27-29, 13 p.

[3] J.Machotka and Z.Nedic, “Remote experiments in engineering undergraduate programs”, ICL2006, Villach, Austria, September 27-29, 13 p.

[4] G.Attwell, “Personal Learning Environments - the future of eLearning?”, eLearning Papers, www.elearningpapers.eu,Vol 2, Nº 1, January 2007,ISSN 1887-1542

[5] Joseph W. Yoder & Ralph Johnson, „The Adaptive Object-Model Architectural Style“ (2007, Feb.). [Online]. Available: http://www.adaptiveobjectmodel.com/WICSA3/ArchitectureOfAOMsWICSA3.pdf

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