Work in Progress: Simple software solution for accessing remote lab on mobile devices Dag A. H. Samuelsen, Joakim Bjørk, Olaf H. Graven Kongsberg Institute for Engineering Buskerud and Vestfold University College Kongsberg, Norway
[email protected],
[email protected],
[email protected] Abstract— In this paper we describe some of the work taking place in a system to create an affordable setup for a remote laboratory. The system utilizes HTML5 and JavaScript to make the user interface accessible on various platforms, including mobile devises and computers, without any additional software installation. The system comprises a remote laboratory for configuring and analyzing a simple power supply for electrical engineering students. Practical testing on the separate components shows the feasibility of the proposed solution. Previous versions of the remote laboratory has proven to be a valuable addition to the exercise program the students need to complete in order to fulfill the learning objectives in various modules run as part of an electrical engineering education. (Abstract) Keywords— remote lab; mobile devices; HTML5; engineering education (key words)
I.
INTRODUCTION
In engineering education, laboratories play a vital role in completing the learning objectives given for the students. In the last two decades, remote laboratories have evolved a lot. Remote laboratories have now become a mature technology for accessing physical laboratories from a remote location, and many aspects of the creation of remote laboratories has been investigated thoroughly in a large number of publications. In [1] laboratories are grouped into four types, named “hands-onlab”, “remote lab”, “local simulation”, and “virtual lab”. A simple definition of a remote laboratory is a physical laboratory that can be remote controlled by the user. Focus in this paper is on the “remote lab”, but will applicable to the “virtual lab” as well. Remote laboratories can be accessed from any place where there is an internet connection. This means that any institution setting up their own remote laboratory will be able to share this facility with any other institution or users. This has led to the organization of projects and consortiums for making this sharing process simpler and more standardized. The iLab project [2] is a system which consists of lab clients, a service broker and lab servers, as well as a lab resource scheduling service which allows for batch run of pre-configured experiments and for experiments that require interactive control from the user during the experiment. Another example is The Global Online Laboratory Consortium (GOLC) (http://www.online-lab.org/) which has been created to facilitate the creation and distribution of shared remote
laboratories. The organisation carries the statement "The mission of the consortium is the creation of sharable, online experimental environments which increase the educational and scientific value of learning which may not be accessible, scalable or efficient through traditional methods". One of the outcomes of the latter is the Labshare (http://www.labshare.edu.au/) which have developed a resource kit reported on in [3] “to facilitate the engagement of academics”. The creation and implementation of remote laboratories involves a number of steps that are necessary to complete, involving both hardware and software, but also topics such as pedagogics and assessment are important. The front-end of the remote laboratory is discussed in publications such as [4] where much effort is put into mimicking the real world physical instruments, and in [5] where the frontend is much more simplified allowing the users to focus more on the contents of the experiment. This topic is also discussed in [6]. The hardware as a basis for the physical part of the experiment is discussed in [7] as a low cost variant as opposed to the more expensive VISIR [4]. Remote laboratory and pedagogy is among others discussed in [8]. Only recently, focus of publications has been set on how to access remote laboratories on mobile devices. In [9] the ability to use e-portfolios in combination with accessing remote laboratories through mobile devices is discussed, while [10] talks about using apps on smart devices to access remote laboratories. However, the main motivation for the authors of this paper is the development of a more platform independent solution. The authors have implemented a number of remote laboratory installations and have gained much experience from using these on students. Many of the installations created required the use of remote panels from the National Instruments LabVIEW software. Although the run-time version of the software is free, requiring students to install a large software package on their computer showed to be difficult when part-time students used computers that were centrally administered, meaning that installation of any software were prohibited. For those students who were able to install the software, the actual access to the remote panels were hindered by crash between the software and certain anti-virus software already installed on their computers. The authors therefor desire to use pure web programming to give access to the remote laboratory, both on the own
978-1-4799-7672-0/14/$31.00 ©2014 IEEE 08-10 December 2014, Wellington, New Zealand 2014 International Conference of Teaching, Assessment and Learning (TALE) Page 69
computers as well as from their mobile devices. An implementation using HTML5allowing real time interaction is presented in [11], but the main focus of that paper is the usability of the user interface, while the focus of this paper is on how to create a user interface accessible on a variety of mobile and computer platforms.
Fig. 1. Interface for selecting power supply configuration when selecting single diode and a lamp as load.
the circuit in the remote laboratory. In this way, they can play with the circuit as much as they like, in order to gain an intuitive understanding for the behavior under different conditions and configurations. The other parts of the learning objectives of the syllabus, such as doing connections on a breadboard, structured troubleshooting and understanding of circuit diagrams is left to other exercises. A. The hardware of the experiment In order to keep the implementation cost at a minimum, a simplified setup has been chosen. The experiment setup consists of the components shown in the diagram of figure 1, plus the mains connected transformer. Standard relays are used to shift in and out the different components as they are chosen by the user via the user interface. In figure 2 the pull-down menu for choosing the different values of the filter capacitor is shown. The relays are controlled by an Arduino board, and the voltages and currents are measured using the integrated ADC of the microcontroller on the same Arduino board. Due to the problems associated with the relatively high input capacitance of the ADC under fast switching of the analogue mux before the sample-and-hold circuit of the DAC, buffer circuits in the form of op-amps are installed on all inputs to the ADC. Current measurements are also done via the internal ADC of the Arduino, using low-ohm resistors placed in the circuit where desired with instrumentation amplifiers before the DAC. Although this solution is not optimal, the result is considered sufficient for this application. Configuration data for the experiment setup and experiment measurements are transferred through an Arduino compatible network interface card connected to the Arduino. The Arduino itself can hold a limited amount of data, so the measurement data from running the experiment are transferred via network to a MySQL-server.
Fig. 2. Interface for selecting power supply configuration when selecting the diode bridge and a LED as load. Also showing pull-down menu for selecting capacitor size.
I.
THE LABORATORY
The laboratory presented in this paper is a simple setup of a power supply using a diode rectifier, a filter capacitor and a load represented by an incandescent lamp (approximately resistive load) and/or an LED light source (non-linear load). Although this might seem simple, doing these connections in a hands-on lab causes many problems, such as the need to use an isolated transformer to avoid deadly voltages from the mains, short circuit protection of the transformer to avoid fire, a large amount of burnt components due to wrong connections, and broken instruments. In addition the authors of this paper appreciate that the students can do the lab without spending too much time troubleshooting the connections, reading circuit diagrams and connecting the different measurement instruments correctly. Instead, they can focus their attention on the relationship between the theory they learned in class and what is happening in practice when they do different choices in
The Arduino needs to perform a number of tasks to complete an experiment. Setting the configuration of the experiment is done prior to the sampling phase, and do not impose any limit on the performance of the system. The critical phase is the sampling phase, as failure to complete all tasks within specific time limits will result in invalid data from the experiment. The tasks to be performed during the sampling phase include reading the ADC on all selected channels at given sampling steps, collecting data to be sent to the MySQLserver, and transferring the data to the MySQL-server. Practical testing of the system shows that it is possible to do this using the Arduino board. This is a result of the low sampling rate requirements of this particular experiment as the power supply operates off the mains frequency of 50Hz (in Europe), and hence, fast sampling rates and rapid data transfer are not needed. B. Experiment configuration The server frontend is installed on a Linux virtual machine running on an ESXi server (free version). The web page of the experiment is using HTML5 and JavaScript to present the graphics of the experiment. Once the configuration has been updated in the webpage, and the start-button is pressed, the configuration data is transferred to the Arduino, which sets the corresponding relays to connect the desired components and, and after that to connect the transformer feeding the circuit.
978-1-4799-7672-0/14/$31.00 ©2014 IEEE 08-10 December 2014, Wellington, New Zealand 2014 International Conference of Teaching, Assessment and Learning (TALE) Page 70
The measurement is started just before the transformer is connected, giving the user the chance to see the resting phase before the transient phase of the power supply. The measurement lasts long enough to show the stationary phase as well. During measurement, all signals are sampled, regardless of what the user intends to see. This is done in order for the user to change his or her mind as to which graphs to present, without running the experiment over again. C. Presentation of measurement data Measurement data is presented using HTML5 and JavaScript with the Dygraphs library (http://dygraph.com) to create charts. This system allows for very simple zooming and panning on mobile devices, as well as desktops or laptops. The system runs on all major web-browsers without any extra installations, allowing the user to access the remote laboratory freely from any computer or mobile device. As shown in figure 3, any measurement series can be selected or deselected after the experiment has been run, which allows the user to investigate thoroughly how the circuit performs, without rerunning the experiment.
In figure 4 the AC voltages has been deselected, and the graph is zoomed in on the two first pulses of the 100Hz signal from the diode bridge. Here, the nonlinear behavior of the circuit can be seen clearly by the non-sinusoidal shape of the current graph and the characteristic wave pattern of the DCvoltage over the capacitor. It is also shown that when moving the mouse over the graph, the instantaneous values are shown at the top of the graph, making it easy to find accurate measurement values when desired.
Fig. 4. Measurement graph showing the current flowing in the leg between the diode bridge and the capacitor (green), and the DC voltage over the capacitor (purple).
CONCLUSIONS AND FURTHER WORK In this paper, a simple setup for a remote laboratory capable of running on mobile devices as well as normal computers is shown. Due to the use of HTML5, the experiment is possible to run without installing any extra software components, and fits all normal screen sizes from small mobile devices to large screens on desktop computers. The use of free software and low cost components make the installation affordable. Only parts of the system have been completed at this stage. The main functionality of the web interface has been implemented and tested. The experiment setup and the Arduino hardware component are implemented and tested separately, but has to be assembled into one working unit. The communication from web interface to the Arduino, from the Arduino to the MySQL server, and from the MySQL server to the web interface has been partly tested, but not fully implemented. The authors do not see any major obstacles in finishing the complete setup. Practical testing on initial versions of the setup demonstrates the usability of the laboratory in terms of easy access and as a valuable contribution to the completion of the learning objectives for the students. Fig. 3. Screen capture of a mobile phone showing the interface for selecting power supply configuration when selecting diode bridge and both a LED and a lamp as load.
978-1-4799-7672-0/14/$31.00 ©2014 IEEE 08-10 December 2014, Wellington, New Zealand 2014 International Conference of Teaching, Assessment and Learning (TALE) Page 71
REFERENCES [1]
[2]
[3]
[4]
[5]
[6] [7]
[8]
[9]
[10]
[11]
D. G. Zutin, M. E. Auer, C. Maier, and M. Niederstatter, "Lab2go — A repository to locate educational online laboratories," in Education Engineering (EDUCON), 2010 IEEE, 2010, pp. 1741-1746. J. L. Hardison, K. DeLong, P. H. Bailey, and V. J. Harward, "Deploying interactive remote labs using the iLab Shared Architecture," in Frontiers in Education Conference, 2008. FIE 2008. 38th Annual, 2008, pp. S2A-1-S2A-6. E. Lindsay, S. Murray, and B. D. Stumpers, "A toolkit for remote laboratory design & development," in Global Online Laboratory Consortium Remote Laboratories Workshop (GOLC), 2011 First, 2011, pp. 1-7. M. Tawfik, E. Sancristobal, S. Martin, R. Gil, G. Diaz, A. Colmenar, et al., "Virtual Instrument Systems in Reality (VISIR) for Remote Wiring and Measurement of Electronic Circuits on Breadboard," Learning Technologies, IEEE Transactions on, vol. 6, pp. 60-72, 2013. D. A. H. Samuelsen and O. H. Graven, "Remote lab for experiments on a small-signal bipolar-junction transistor amplifier," in Global Engineering Education Conference (EDUCON), 2011 IEEE, 2011, pp. 721-725. N. E. Cagiltay, E. Aydin, and A. Kara, "Principles for the design of a remote laboratory: A case study on ERRL," in Education Engineering (EDUCON), 2010 IEEE, 2010, pp. 879-884. D. A. Samuelsen and O. H. Graven, "Design of a general purpose platform for easy setup of low-cost remote laboratories in electronics," in Remote Engineering and Virtual Instrumentation (REV), 2013 10th International Conference on, 2013, pp. 1-6. O. H. Graven and D. A. Samuelsen, "Remote laboratories with automated support for learning," in Remote Engineering and Virtual Instrumentation (REV), 2013 10th International Conference on, 2013, pp. 1-5. D. May, C. Terkowsky, T. Haertel, and C. Pleul, "The laboratory in your hand Making remote laboratories accesible through mobile devices," in Global Engineering Education Conference (EDUCON), 2013 IEEE, 2013, pp. 335-344. M. Latorre Garcia, G. Carro Fernandez, E. Sancristobal Ruiz, A. Pesquera Martin, and M. Castro Gil, "Rethinking remote laboratories: Widgets and smart devices," in Frontiers in Education Conference, 2013 IEEE, 2013, pp. 782-788. J. P. C. de Lima, W. Rochadel, A. M. Silva, J. P. S. Simao, J. B. da Silva, and J. B. M. Alves, "Application of remote experiments in basic education through mobile devices," in Global Engineering Education Conference (EDUCON), 2014 IEEE, 2014, pp. 10931096.
978-1-4799-7672-0/14/$31.00 ©2014 IEEE 08-10 December 2014, Wellington, New Zealand 2014 International Conference of Teaching, Assessment and Learning (TALE) Page 72
