LXI Technologies for Remote Labs: An Extension of the VISIR Project

Abstract

Several remote labs to support analog circuits are presented in this work. They are analyzed from the software and the hardware point of view. VISIR remote lab is one of these labs. After this analysis, a new VISIR remote lab approach is presented. This extension of the VISIR project is based on LXI technologies with the aim of becoming it in a remote lab easily interchangeable with other instruments. The addition of new components and experiments is also easier and cheaper.

Full text

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LXI technologies for remote labs: an extension of
the VISIR project

J. García-Zubía1, U. Hernández-Jayo1
1 Faculty of Engineering, University of Deusto, Bilbao, Spain



Abstract—several remote labs to support analog circuits are
presented in this work. They are analyzed from the software
and the hardware point of view. VISIR remote lab is one of
these labs. After this analysis, a new VISIR remote lab
approach is presented. This extension of the VISIR project
is based on LXI technologies with the aim of becoming it in
a remote lab easily interchangeable with other instruments.
The addition of new components and experiments is also
easier and cheaper.
Index Terms— analog electronics circuits, IVI, LXI, VISIR
remote lab.
I.
INTRODUCTION
In the practices of a first course in analog electronics,
the students have their first contact with resistors and
capacitors, as well as laboratory instrumentation. They
learn to make the first resistance circuits to discuss their
different combinations (series, parallel) or to see how a
voltage divider works. They also make their first practical
exercises with diodes working as rectifier and analyze a
bit more complex circuits such as filters or voltage
limiters based on Zener diodes.
But for these practices is also necessary to use lab
equipment: oscilloscope, signal generator, multimeter and
power supply. The matter is complicated: not only they
must understand and run the circuit but also understanding
and see how it works. If the warnings by the teacher on
the use of equipment are added, work with tensions fear
and that it is the first time that students are in a lab, it is
normal to feel some trepidation before the laboratory
practice.
In general, students need time to become familiar with
equipment and overcome those fears to touch the buttons,
spinning the roulette wheels and connecting cables. But
unfortunately, time is missing, because every week there
are new practices and it is always necessary to have
assimilated the previous ones.
In addition, laboratories are often occupied by classes
and many students who need extra time after hours to end
the practices. In this scenario, a remote laboratory can
help manage and resolve these problems, from home and
using only an Internet connection.
For this reason, nowadays, several online remote labs
are focuses on the development of experiments related
with the analog electronics. The NetLab from the
University of South Australia, [1], the RwmLAB from the
Western Michigan University [2], the RemotElectLab
from the School of Engineering, Polytechnic Institute of
Porto [3], the ISILab from University of Genoa [4], the
iLab from the Massachusetts Institute of Technology [5]
and finally the VISIR developed by the Blekinge Institute
of Technology [6].
All these laboratories have in common that are targeted
for use in analog electronics subjects. Moreover, the users
are allowed to built or reconfigure a real circuit (not
virtual) using a web interface.
In the following sections, a brief analysis of each
laboratory is going to be made, with a short explanation
about how they work and the technologies used for their
development. Then, the solution proposed by the
University of Deusto is shown, stating the advantages of
this solution over previous. Finally, the conclusions and
future work are presented.
II.
NetLab (http://netlab.unisa.edu.au/) is an online remote
laboratory developed at the University of South Australia.
NetLab is currently used by students and staff at the
School of Electrical and Information Engineering for
practicals and demonstration purposes. Being online,
NetLab is available to students outside the scheduled
practical hours but may also be used by registered visitors.
NetLab provides remote access to real instruments and
circuits and therefore presents users with real
measurement data. NetLab is designed to give hands on
experience through its realistic graphical user interface
(GUI) which allows users to interact with instruments by
pressing buttons and turning knobs like they would on real
instruments. Using a circuit builder, the user has the
chance of creating real experiments through a web site
(Figure 1) [7].
NETLAB. UNIVERSITY OF SOUTH AUSTRALIA.

Figure 1. NetLab User interface


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A. Software technologies
NetLab is a Java based application, so it runs on any
operating system provided it has an installation of Java SE
runtime environment, version 6.0 or later. To run the
NetLab application, students only need to download and
setup an applet. Then, a shortcut is created in the desktop
[8].
The actual instrument I/O uses National Instrument‟s
VISA I/O library, through its C programming interface.
This is exposed to Java through a created library called
JVISA. It exposes most of the VISA API as object-
oriented Java interfaces. This requires a very thin wrapper
layer written in C which compiles the DLL.
The graphical interface is written in Java. All the
instrument user interfaces are done using photographs of
the instruments and done graphics using Java‟s 2D
drawing capabilities.

B. Hardware technologies
The NetLab‟s circuit builder is based on a switching
matrix with a 16x16 module available from Agilent
(E1465A). This relay matrix switch requires supporting
hardware that included: E8408A 4-slot VXI mainframe
and the E1406A command Module. These components
communicate with the NetLab server through the General
Purpose Interface Bus (GPIB), while the VXI standard
communication protocol is used for the internal
communication within the Command Module (Figure 2).
The matrix module consists of 256 nodes formed by 16
rows and 16 columns. Nodes are switched thanks to
double pole double throw (DPDT) latching relays. The
structure of these latching relays allows having two
separate layers, which each contain their own set of
components [9]. Now, the students can use up to 16 two
terminal components. This is limited by the number of
matrix terminal which is 32 max (16+16). Components
like 4 channels will occupy 5 terminals.
The available instruments are a oscilloscope, a signal
generator, a digital multimeter, four variable resistors, 2
variable capacitor, a variable inductor and one
transformer.


Figure 2. NetLab Switching matrix setup

III.
The RwmLab has been developed by the Electrical and
Computer Engineering Department of Western Michigan
University. The goal of this remote lab is to address real-
time remote wiring of electrical and electronic circuits,
and real data acquisition using a Web-based application
[10]. With this remote lab, students are able to wire up
electrical and electronics circuits at the host laboratory
using a Web Interface and by means of a conventional
circuit board. The students also can connect instruments to
the circuit and also change their settings. The data
acquisition interface allows students to connect the
instruments to all the nodes in the circuit and make
measurements (Figure 3)
RWMLAB. WESTERN MICHIGAN UNIVERSITY

Figure 3. RwmLab User interface

A. Software technologies
The web-based software used to develop the RwmLab
has been written in HTML and JavaScript. When the user
wires the circuit in the virtual breadboard, the software
sends a digital code that represents the node/connections
of the circuit. This code is sending using a common gate
interface protocol (CGI), that it is written in C language.
The instruments controls and displays are been
developed using National Instruments LabVIEW [11].
B. Hardware technologies
The Remote Wiring and Measurement Laboratory
consist of a matrix switching board (Xecom‟s AWC86A)
working as the controller of the platform with a Web-
based server and a CPLD. The back-end of the matrix is
an AMD 40-MHz AM186ES-based microcontroller with
SRAM and Flash Memory (Figure 4).

Figure 4. RwmLAB hardware platform

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The switching matrix is an 8 X 8 configurable array,
based on solid-state relays and controlled by the Web
microserver. The user can define the circuit using a
„virtual breadboard‟. One the circuit is designed, the
switching matrix wires physically the electrical circuit in
the laboratory. Components and wires placed around the
“virtual breadboard” may be dragged by the user. The
number of components is restricted by the number of
connections available in the 8x8matrix [11].
A set of instruments are available. All of them have a
GPIB interface and are fitted with a Webcam. The GPIB
is used to control each instruments and to read the desired
values in real-time. There are four instruments: digital
multimeter, oscilloscope, power supply and waveform
generator.
Once the user completes the circuit, it is analyzed by
the software to determine which hardware must be
connected together and to configure the relays.
IV.
REMOTEELECTLAB. POLYTECHNIC INSTITUTE OF
PORTO.

The remote lab for electronics teaching developed by
the School of Engineering, Polytechnic Institute of Porto
is currently being used as a complement in the course of
Electronic II, 2nd year, and 1st semester of the Bachelor
degree on Electrical & Computer Engineering. During this
course, the students study how the operational amplifier
works, in which this remote lab is presented as one more
learning tool. Using the user interface shows in the Figure
5, the students can modify part of the structure of the
experiment and perform measures over it, analyzing the
different values depending on the selected configuration.

Figure 5. RemotElectLab User interface

A. Software technologies
All the
RemotElectLab is based on LabVIEW from National
Instruments. LabVIEW is a graphical language based on
software developed to deploy the
graphics. It is widely used in academia and industry
mainly to instruments control. Additionally, other
functions are defined, programmed and executed with
other programming languages [12].
The GUI provided to the user is also based on
LabVIEW (Figure 5), in which the student can change
different parameters in the circuit under test.
One of the advantages of this approach is its easy
integration in a Learning Manage System. In this case, all
the functions related with the access management,
information delivery, registering of results and evaluation
can be provided by the LMS [3].
B. Hardware technologies
Hardware platform (Figure 6) is based on the National
Instrument ELVIS (Educational Laboratory Virtual
Instrumentation Suite) [21]. This platform can be used in a
real lab and also to serve as a platform to build a remote
lab. Besides the ELVIS, RemotElectLab includes a
breadboard for the assemblage of the circuits, and a set of
twelve integrated instruments (power supply, digital
multimeter, oscilloscope and function generator), plus
some analog and digital I/Os.
To allow the user to perform measures in different
nodes on the circuit under test, switching modules
working as multiplexers/demultiplexers were developed,
based on electromechanical relays. With this solution, the
user can also exchange components in a prefixed circuit
and reconfigure it [3].


Figure 6. RemotElectLab hardware platform

V.
ISILAB. UNIVERSITY OF GENOA
The Internet shared Instrumentation Laboratory (ISILab)
has been developed by the University of Genoa, and
currently it is used to deliver remote access o experiments
on electronics for the benefit of some engineering courses
[13]. ISILab is a remote laboratory for practicing on
electronic instruments and measurement methods
executing real experiments of scalable complexity on
analog and digital circuits. The experiments deal with
basic electronic measurements, such as the delays in
digital circuits or the gain and the distortion of amplifiers,
and use a waveform generator and an oscilloscope. The
laboratory integrates experiences, lectures, exercises, and
hand-books that can be accessed through the user
interfaces shown at Figure 7. This remote lab can be
accessed at http://isilab.dibe.unige.it/.

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Figure 7. ISILab User interfaces

A. Software technologies
ISILab has been designed using a distributed
architecture in which the real laboratories can be spread
over a wide geographic area and are accessed seamless by
users. The web site portal shows the available experiments
and it is in charge of security policies and establishes the
communication between the client and the Real
Laboratory Server (RLS) in charge of the selected
experiment (Figure 8).

Figure 8. ISILab architecture

To interact with the experiments, the user doesn‟t need
any specific hardware or software except for a web
browser and the Java Virtual Machine. Through the
instrument virtual panels shown in web site, the user can
control the instruments and interact with real experiments
and instruments. These virtual panels are defined using a
specific XML schema [14]. These GUI can be set up
according to the objectives of each experiment and the
users‟ skills. That is, ISILab has a general purpose and
reconfigurable software modules that can be used to
control different instruments. These modules can change
their appearance and its behavior regarding with a
configuration file.
This approach is based on the product called
AppletVIEW shipped by Nacimiento [15]. This
development environment let the developer build applet
strongly integrated with programs written in LabVIEW.
AppletVIEW configuration files are written using a XML-
based language called VIML (Virtual Instrument Mark-up
Language). ISILab has improves these method and the
result is a Java applet that works on the base od these
XML configuration files.
B. Hardware technologies
ISIlab supports both stand-alone instruments and
computer-based ones (PCI, PXI, GPIB, etc.). It makes
transparent the hardware
Application Program Interface in the RLS engine. In this
way, if a new instrument wants to be added, it only must
be wrapped in an appropriate driver adapter to expose the
device functionalities. These drivers‟ adapters are based
on IVI (Interchangeable Virtual Instruments) technology
[16] and they are developed for oscilloscope, function
generator and digital multimeter.
If the students are offered to create circuit using discrete
components, the number of components and relays to
interconnect those increases exponentially with the
number of components. For this and other reasons [17],
ISIBoard has been created. It is a motherboard with
sixteen slots, where the experiments‟ cards can be placed
(Figure 9). Each card has eighteen lines for providing the
power supply, output/input signals and for connections
with the instruments. When the circuit is mounted on the
motherboard, the connections with the instruments are
dynamically created by a set of switches. That is, this
motherboard works as a switching matrix controlled by
the RLS, because each card has a unique identifier and a
configurable array enables each circuit to share the same
instrumentation. Depending on the experiment selected by
the user in the web portal, the corresponding card in
connected to the instruments and to the portal.

using a homogeneous

Figure 9. ISILab motherboard an experiments' cards

VI.
ILAB. MASSACHUSETTS INSTITUTE OF
TECHNOLOGY
The iLab project (http://ilab.mit.edu) was started at MIT
in 1998 by J. A. del Alamo [18][17], due to the frustration
of not being able to teach practical subjects of
semiconductor devices at MIT. Traditionally, students in
these courses were exposed only to theoretical device
models presented in lectures and course texts. An initial
grant from Microsoft allowed Del Alamo explores the
potential of remote access device. A first version was
developed, called Microelectronics WebLab, based on a
Java applet that allowed sending alerts to a server
connected directly to the device using Microsoft ASP. In
autumn 1998 the lab could be used by students, and by the
spring of 1999 it had been used by nearly 100 students for
practice.
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In 2001, an architecture based on Web services began
to develop. It provides a common infrastructure to all
types of experiments, with development led by the Center
for Educational Computing Initiatives at MIT. Moreover,
this architecture stand for the first time-sharing
experiments between different universities. In 2004, on
this architecture called iLab Shared Architecture (ISA), a
new version of the Microelectronics WebLab was
developed as an experiment within the already called
iLab.

Figure 10. iLAB WebLab java Client

A. Software technologies
The iLab project is not domain specific. It attempts to
provide a unifying context and middleware to support
online laboratories from a wide variety of fields. Its main
features are: a) It allows developing experiments on
different platform and operating systems; b) Allows
development of both interactive and batch experiments; c)
Enables the sharing of experiments between different
universities; d) Provide efficient management tools for
laboratory providers; e) It has a scalable design.

Figure 11. iLABs architecture

iLab provides three categories of experiments: 1)
Bached experiments, are those in which the entire course
of the experiment can be specified before the experiment
begins; 2) Interactive experiments are those in which the
user monitors and controls one or more aspects of the
experiment during its execution. 3) Sensor experiments
are those in which users monitor or analyze real-time data
streams [19].
Depending on the remote lab, iLab is developed using
technologies that only works on Microsoft Windows.
Although eventually you can develop an experiment over
another platform by implementing the required interface,
all servers are obligatory deployed under Microsoft
Windows using privative technologies Microsoft IIS,
Microsoft SQL Server and Microsoft Visual Studio for the
development. Client is developed with multi-platform
technologies like Java, so users of the system can use
other platforms [20].
B. Hardware technologies
To control the semiconductor analyzer and the
switching matrix used in the iLabs the server contain an
Agilent GPIB interface board. Web services should also
make it easier to incorporate vendor supplied modules in
the overall architecture. The switching matrix allowed the
system to host multiple semiconductor devices for
characterization.
Recently, the iLab Project has focused on building
remote laboratories around the National Instruments
Educational Laboratory Virtual Instrumentation Suite
(ELVIS) platform, an all-in-one electronics workbench.
Different iLab based on ELVIS have been developed at
MIT, using the hardware instruments available on ELVIS:
the Function Generator, the Oscilloscope, DMM, Digital
I/O, Bode Anaylzer, etc [21]. These instruments enable
students to perform basic time domain measurements on
electronic circuits and test and debug analog and digital
circuits [22]. Using the combination of ELVIS and a
switching matrix (Figure 12), the user can change the
configuration of the system under test [23].

Figure 12. Architecture of iLab based on ELVIS platform
VII. VISIR. BLEKINGE INSTITUTE OF TECHNOLOGY
The Signal Processing Department (ASB) at Blekinge
Institute of Technology (BTH) has created an online lab
workbench known as VISIR (Virtual Instrument Systems
in Reality), for electrical experiments, mimicking and
supplementing workbenches in local laboratories [24].
Using the VISIR interface, the students can create their
own electrical circuit and test those using real components
and real devices as oscilloscope, function generator,
digital multimeter, and a power supply. The user interface
(Figure 13) has been designed using the same front panels
as the students use in the hands-on sessions, so they can
reproduce the same actions and procedures as in the real
laboratory.
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Figure 13. Virtual breadboard using in VISIR remote lab.

A. Software technologies
The software architecture used to develop the VISIR
lab is shown in Figure 14. This architecture is divided in
different servers, each one plays a role in the laboratory
set up and experimentation. VISIR is an OpenSource
project, so all the software and related information can be
download from http://svn.openlabs.bth.se [25][26].


Figure 14. VISIR architecture

-
Web Server: The web server is in charge of being the
join between the student at home and the experiment
at the university. The user interface the student uses
to create the circuit and test it has been developed in
Adobe Flash, so the user only needs to install a Flash
player to run the VISIR at his computer. However,
the VISIR developer needs to run other applications
to install the server located in the university. These
other technologies are: a HTTP server, PHP 5 or
later, Smarty, Text_Wiki and MySQL.
Measurement Server: The main responsibility of the
measurement server is to serve measurement
requests, sent by the experiment clients. These
requests are encoded using the experiment protocol,
which contains the settings and functions of the
equipment used in the experiment. The requests are
then validated and transformed to a format that the
equipment servers or directly connected instruments
can understand. Authentication and queuing are also
-
handled. The measurement server is written for
Microsoft Windows, in C++ using Microsoft Visual
C++, so it depends on their runtime libraries.
Equipment Server: this server is in charge of
receiving the measurement server requests and
configures the instruments and the switching matrix,
according with these requests. The interface between
the measurement server and the equipment server is
TCP/IP, so they can be running in separate machines.
Equipment server is written in National Instruments
LabVIEW and the instrument drivers are IVI [16]
compliant, but there are not IVI drivers.
-

B. Hardware technologies
VISIR remote lab uses a National Instruments PXI
chassis or a PCI solution to gather all the instruments
needed to configure and perform measures over the real
circuit built by the remote students. The available
instruments are: oscilloscope, function generator, digital
multimeter and power supply. All these instruments
should be from National Instruments, because the
LabVIEW Equipment Server is written using the drivers
provided by National Instruments.
manufacturer would be used, the code should be adapted.
To built the real circuit designed by the user using the
web interface, VISIR uses a proprietary switching matrix
(Figure 15) also controlled by the Equipment server. The
relays are arranged in a three dimensional matrix pattern
together with instrument connectors and component
sockets. That is, there are two different card designs: one
for instruments and one for components. In this way, the
relay switches are embedded into the circuit created
limiting the length of the wires in order to gain bandwidth.
The nodes of the switching matrix are propagated from
board to board creating a node bus. The notation “node”
refers to the fact that every conductor created by these
stacked connectors can be a node in a desired circuit [27].

If different

Figure 15. VISIR Switching Matrix
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VIII. THE VISIR-LXI CONCEPT. UNIVERSITY OF
DEUSTO
Since 2008, the University of Deusto is enrolled in the
VISIR consortium, which aim is to spread the VISIR
project in those interested universities around the world.
Carinthia University of Applied Sciences and FH Campus
Wien University of Applied Sciences both in Austria are
already involved in the VISIR project.
The University of Deusto started to work in 2001 in the
development of remote labs, and the result of these works
is the WebLab-Deusto [28]. One the main characteristic of
the WebLab-Deusto (accessible at www.weblab.deusto.es)
is its software architecture that has been developed
completely independent of the experiment, hardware or
instruments used in the remote lab [29] .
Gathering the VISIR Project and the experience in the
development of an unique software architecture in the
WebLab-Deusto, the idea of creating a remote lab based
on the potentials of the VISIR (its graphical interface and
logic to control the experiment) and the advantages of
WebLab-Deusto was born in 2009.
At the end of 2009, the version 3.9 of WebLab-Deusto
has been released and now it is available at
www.weblab.deusto.es. During that year, the hardware
architecture of this VISIR-LXI started to be developed,
based on the previous experience of the WebLab-GPIB
[30] and a first experiment based on LXI instruments [31].
In this first work, the possibilities of LXI were analyzed
and a simple laboratory based on this technology was
presented.
A. VISIR-LXI Objetives
This remote lab is based on the VISIR concept and on
the architecture shown at Figure 14, but some
modifications have been applied, to achieve the following
objectives:
-
Create a remote lab independent of the instruments
manufacturer.
-
Use standards devices, not proprietary solutions.
-
The instruments‟ configuration and control must be
using standards and easily setup.
-
Build a remote lab
reconfigurable.
-
It should be accessible by several students at the
same time.
-
Use a switching matrix configuration able to reduce
the components needed to create complex circuits.
-
This switch matrix should be able to be used with
discrete components and/or prefixed circuits.
-
Reduce the time a complexity of adding new
experiments to the matrix
-
The remote lab obtained should be able to be easily
integrated into a Learning manage System.
-
The obtained systems should be able to be wrapped
into WebLab-Deusto platform.
-
The cost of deploying this remote lab for electronics
must be reduced.

easily scalable and
B. Software Technologies
As it was described at section VII, the VISIR remote
lab is divided into three different servers. These servers
have been modified in the next way to be compliant with
the cited objectives:
-
Web Server: basically, this server has not modified,
because the user interface developed in the VISIR
project is really good and not easily improved.
Nevertheless in following steps, the web server
develop will be wrapped in the WebLab-Deusto code.
The objective of this work is to be able to obtain more
information about the actions that the user perform
over the laboratory, because at present, the teacher
only can know if a student has connected and when to
the system, but there in not any else feedback about
the performed experiment.
-
Measurement Server: a new module called lxicom has
been developed. The function of this module is to
check the circuit created by the user in the breadboard
and translate this circuit to a code that can be
understood by the new circuit builder developed in
the Equipment Server. This code contains the
description of the wired circuit and the instruments
connections on the circuit.
-
Equipment Server: the instruments used in this lab are
LXI compliant (only LXI-c is required) [32]. One of
the characteristics of this standard is that the
instruments must be IVI compliant to. In this way, the
instruments controls have been rewritten completely
using IVI drivers IVI. The main characteristic of
these drivers is that they are completely independent
of the manufacturer. That is, e.g. a scope IVI driver
can be used to control a scope from any manufacturer
that implements IVI drivers over their devices [16].
The circuit builder has also been rewritten completely
due to in this lab, the switching matrix is a
commercial solution, and it is not proprietary as at
VISIR. Moreover, as the instruments are LXI
compliant, the connection between the server and the
instruments is through
connection, and IP addresses are used to identify each
instrument.
To configure the instruments, first, the instrument IVI
driver must be installed and the IVISharedComponent
must be setup. They can download from [16]. When this
package is setup, the file IVIConfigurationStore.xml is
saved. This file contents all the updates and registers about
the IVI drivers that are setup in the system. This XML file
configures the relationship between the IVI driver of each
instrument and its I/O reference. It also saves information
regarding with the instruments‟ models and drivers so that
just modifying the reference to the model, the instrument
can be controlled without updating the code. The
structure of the IVIConfigStore is shown at Figure 16

a standard Ethernet

Figure 16. IVIConfig Store configuration

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C. Hardware Technologies
As it has been described before, the instruments are
independent of the manufacturer. In our case, instruments
from Agilent have been chosen N5746A (Power supply),
DSO5012A (oscilloscope), 33220A (signal generator),
34410A (digital multimeter), 34980A (switching matrix),
2 x 34982A (matrix). (Figure 17).

Figure 17. Instruments used at VISIR-LXI

As all of them are LXI instruments, they are connected
with the PC in which the equipment server runs, with a
common Ethernet connection trough a Hub. In this case,
the instruments form a subnet that can is acceded through
the server (Figure 18). The server has a public IP but the
instruments don‟t need it.
POWER SUPPLY
WAVE GEN.
SCOPE
DMMMATRIX
IP1 IP2 IP3IP4 IP5
IPX

Figure 18. VISIR-LXI connections architecture

In this system, the proprietary switching matrix of the
VISIR has been replaced by a commercial one. The
selected switch is the 34480A equipped with two dual
4x16 matrixes 34932A. These matrixes have been
connected as is shown in Figure 19. The objective is to be
able of creating the same circuits as in the VISIR
platform, using less components and obtaining the same
results.
Matrix 1
Matrix 1
Matrix 2
Matrix 2
Slot 1
Slot 5
R1 R2R3R4R5R6 R7R8
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
C11
C12
C13
C14
C15
C16
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
C11
C12
C13
C14
C15
C16

Figure 19. Switching matrix configuration

In this moment we only are using the Slot 1 and Slot 5.
The switch has 8 slots, so it can host 8 dual 4x16 matrixes,
because in each slot two matrixes 4x16 are setup. In each
slot, the matrixes columns are interconnected (blue lines),
and the matrix of different slots are joined by the rows
(red lines). In example, if a new slot is occupied, its two
matrixes will be interconnected (blue lines) and connected
with matrix in Slot 1 and 5 through the rows (red lines).
To create these interconnections, the boards shown in
Figure 20 have been created.

Figure 20. Connection board

The instruments are connected as follow:
Function generator: Matrix 1 Slot 1 C16
Oscilloscope channel2: Matrix 1 Slot 1 C15
Oscilloscope channel1: Matrix 1 Slot 1 C14
DMM HI: Matrix 1 Slot 1 C13
DMM LO: Matrix 1 Slot 1 C12
DMM I: Matrix 1 Slot 1 C11
Power supply +DC: Matrix 1 Slot 1 C10
Power supply Ground: Matrix 1 Slot 1 C9
-
-
-
-
-
-
-
-
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TABLE I.

COMPARISON BETWEEN PREVIOUS LABS

NetLab RwmLAB RemotElectLab ISILab iLab(1) VISIR VISIR-LXI
Circuits
Discrete Discrete
Fixed and
modifiable
Fixed Fixed
Fixed,
modifiable
and discrete
Fixed,
modifiable and
discrete
Instruments
control
GPIB-VXI GPIB NI-ELVIS
PXI, PCI, GPIB
under IVI
drivers
GPIB, NI-
ELVIS, etc
PXI
LXI and IVI
drivers
Control
Software
JAVA LabVIEW LabVIEW LabVIEW LabVIEW LabVIEW LabVIEW
Matrix
Agilent E1465A
Xecom
AWC86A +
owner matrix
NI-ELVIS +
Owner switching
modules
Owner
motherboard
matrix
NI-ELVIS
Owner
switching
matrix
Agilent 34980A
and 34982A
Availability
Yes No Guest Yes Yes Guest
Guest (Under
test)
Concurrency
Three users at
the same time
Without
information
No
Several users
can be watching
the experiment
at same time
No
Max 16,
depending on
the
experiment
Yes (Under
test)
User
Interface
Virtual
Workbench in
Java
Virtual
Breadboard
in Java
LabView front
panel.
AppletView and
AJAX
Java Applet
Virtual
breadboard
in Flash
Virtual
breadboard in
Flash
Singular
features
It includes a
collaborative
platform for
students and
teachers.
The matrix is
controlled by
a CPLD
Easily deployable
using LabView
remote panels
XML is used to
describe the
whole
experiment
Integrated
into ISA
architecture.
Powerful
user interface
Independent
from the
manufacturer
using LXI.
(1)Experiment based on analog electronics with NI-ELVIS

The other columns are occupied by the discrete
components. Each component is connected between two
columns, so in each matrix 8 duel-terminal components
can be connected.
The Equipment Server‟s Circuit Builder code is in
charge of determinate which relays must be closed to wire
the described circuit in the breadboard. Each node is
determinate by two strings, one for the column and one for
the row. In example, if a 10KΩ resistor is between C1 and
C2 on Slot1 and is wanted to be connected in serial with a
1KΩ placed between C16 and C15 on Slot5, and then
measure the equivalent resistance, the following strings
must be sent to the switch matrix:
-
10KΩ: s1m1r1 – s1m1c1 & s1m1r2 – s1m1c2
-
1KΩ: s5m1r2 – s5m1c16 & s1m1r3 – s1m1c15
-
DMM: s1m1r1 – s1m1c13 & s1m1r3 – s1m1c12
The nodes of the components are represented at with
red dots, and the nodes to connect the DMM with blue
dots. The Circuit Builder uses a Circuit.list file to obtain
the information about where are placed the components.
This file is written by the developer or the instructor of the
course. This file is easier to describe than the VISIR,
because in this solution, a resistor can be connected in
multiple nodes (R1 to R8). However, in VISIR a resistor
only can be placed between two nodes.

D. Advantages and disavantages over the privious
solutions
The principal advantages and disadvantages of this beta
system, respect the previously analyzed are:
Advantages:
-
Using LXI-IVI compliant instruments, the developer
can choose the solution best fits with his
requirements.
-
Using IVI drivers, the used instruments are
transparent for the developer.
-
The connection with the instruments is over a
common Ethernet connection. Not special hardware
(GPIB, PXI, VXI or others) is required.
-
The price of the needed instruments is lower than the
used in the VISIR. Cheaper solutions can be found in
the market.
-
Once the VISIR-LXI will be wrapped in WebLab-
Deusto, it should be easily integrated into a LMS.
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-
A component can be placed in multiple nodes. The
number of components needed to created different
circuits is reduced.
The file that describes where are placed the
components and the file that describes how the
components can be wired by the user, are easier to
write than in VISIR.
The created boards to place the components and to
interconnect the matrixes are very simple, so they are
not expensive.

Disadvantages
-
Although the solution will be open source when it
will be finished, a LabVIEW distribution will be
required to run the equipment server. Other solutions
should be analyzed to over this inconvenient.
-
By the moment, only circuits with single polarization
can be used, because the chosen power supply has not
implemented negative tension.
-
The number of components is limited by the number
of slots available in the switch. With the
configuration shown here, 52 components (2-
terminals) can be placed.
-
The maximum signal frequency tested has been
30MHz. Over this frequency, the signal can be
distorted.
-
It has not tested yet with students accessing at the
same time to the platform. The relays time response
could be a problem, and the number of user working
at the same time could be reduced.

-
-
IX. COMPARISON BETWEEN REMOTE LABS FOCUS ON
ANALOG ELECTRONICS CIRCUITS
TABLE I. shows the comparison between the remote
labs analyzed previously. All of them are based on analog
electronics circuits, although some of them are prepared to
deploy digital circuits, as in ISILab. iLAB is an special
case, because iLABS hosts several diverse thematic
remote labs. To perform this comparison, the iLAB based
on NI-ELVIS and analog circuits has been analyzed.
The comparison has been performed analyzing the
following characteristics:
-
Circuits: the user can build the complete circuit using
discrete components: discrete. Fixed: the user only
can change the inputs of the circuits and analyze the
outputs. Modifiable: part of the circuit is fixed and the
user can change some parts of it.
-
Instruments control: the communication interface
used to control the instruments.
-
Control Software: the software technology used to
control the instruments
-
Matrix: the used matrix that gathers the different
circuits available in the lab or the discrete
components to build the circuits.
-
Availability: is the remote lab open for all users? Do
you need an account? Can you access as a guest?
-
Concurrence: could the lab be used by several
students at the same time?
-
User interface: the technologies used to develop the
user interface.
X.
CONCLUSIONS AND FUTURE WORK
Some solutions to create remote labs to support
practical lessons in analog electronics subject have been
presented in this paper. All of them have been developed
using proprietary solutions from the software and
hardware point of view. These approaches make difficult
to replace the instruments for other ones, or to create new
experiments in an easy and fast way, because in all remote
labs, the used technologies during the development,
determinate the characteristics of the WebLab.
The VISIR-LXI solution presented here is the first step
to develop a remote lab completely independent from the
instruments and that enables the addition of new
components and experiments easily.
This remote lab must to be tested with students in a
current year to obtain results about its performance and
compare it with the VISIR solution from the students and
utilization point of view. It has been compared from the
instructor side, and it has been proved that the addition of
new components and the creation of wiring rules are
easier than in VISIR. I has also tested, that to create
different circuits using the same components (i.e. resistors
configurations), less components are required than in
VISIR.
In future steps, expected LXI oscilloscope will be
added to the lab and then the remote VISIR-LXI will be
completed. The software will be wrapped into the
WebLab-Deusto software and the functions related with
the administration and management will be supported by
it. Applications to obtain information about the users‟
actions on the lab will be developed.
This remote lab is wanted to be included into a
Learning Management System to analyze if it is possible
to generate random questions for the students to be
implemented over the remote lab and correct their results
automatically using the LMS.
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AUTHORS
J. García-Zubia is with University of Deusto,
Electronics and Automation Department, Avenida de las
Universidades 24, 48007 Bilbao (Spain), is with the
University of Deusto, he is Head of Dpt. Of Industrial
Electronics, Control Engineering,
Architecture of the Faculty of Engineering. He is the
responsible of the remote lab at the University of Deusto
(WebLab-DEUSTO: weblab.deusto.es). The WebLab-
Deusto has been implemented using web 2.0 techniques
(AJAX, SOAP, etc.), this approach is a novelty in Europe.
Different works have been published explaining the
results and the technology of this weblab and the
evolution of WebLab-DEUSTO has been supported by
different projects. (e-mail: zubia@eside.deusto.es).
U. Hernández is with the University of Deusto in the
Telecommunications Department at the Faculty of
Engineering. He is developer of the research group on
web-based laboratories and he is in charge of the remote
labs based on instruments control. He is involved too in
the deployment in University of Deusto of the VISIR
project leaded by the Blekinge Institute of Technology
(Ronneby, Sweeden). (e-mail:
deusto.es).
and Computers
unai.hernandez@
REV 2010 29 June - 2 July, Stockholm
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