3.4.1 Building the Second Beta Version
Stemie was built upon Kid Grígora’s foundations,
with a different design but simpler and faster to build.
After its construction, it was then, subjected to a
test in a heuristic evaluation by experts. This
evaluation had the objective of appraising both
usability and potential design problems and gathering
suggestions from the experts on how to solve the
problems they found and, possibly, add new features.
To test the prototype, we chose double experts
(Nielsen, 1993) experienced not only in usability but
also with specific expertise in robotics as they
potentially find 1.5 times more problems than simple
usability specialists (Nielsen, 1993). We used three
ICT and Robotics teachers from 3 different countries
(Italy, Lithuania and Croatia).
The evaluations were carried out according to
each expert’s agenda and started with an explanation
of the expected use of Stemie by end-users, as a
STEM tool. The evaluators had knowledge of the
previous version and had previously been given the
new robot’s parts and the updated assembly
instructions, and were asked to assemble it.
After the tests, each expert was asked to fill out a
heuristic evaluation questionnaire to report possible
problems, by using Nielsen’s severity rating scale
(Nielsen, 1993). In this scale, they used numbers from
0 to 4 in which 0 means "I don’t agree that this is a
usability problem at all" and 4 means a "Usability
catastrophe: imperative to fix this before the product
can be released".
About the strong points of the heuristic
evaluation, all the experts mentioned the evolution in
structure stability, using brass spacers instead of
screws and hex nuts and that the robot should be even
easier to build now. Although like in Kid Grígora’s
evaluation, all the experts said that it was a good idea
to use standard electronic components, easy to find
and replace, in case of malfunction. Also mentioned
was the large number of problem-solving tasks that it
is possible to solve using Stemie. Two of the experts
mentioned the fact that the instructions were very
detailed on both the electrical connections and the
GPIO pins, which would make it easier for children
to assemble the robot.
The weakest points in the heuristic evaluation
(ratings 3 and 4) are summarized in Table 8.
Table 8: Severe and catastrophic errors found, according to
Nielsen’s heuristics.
Nielsen’s heuristics
Interface (IN) Degree
IN1 Visibility of system status 3
IN5 Error prevention 4
Regarding IN1, one of the experts mentioned, that
although Stemie had an LED to visibly show the
system status, it would be more useful if it also had
audible status. Related to IN5, all of the experts stated
that there was an error in the connection of pin A6 to
the 3-channel infrared tracking module, as A6 and A7
on an Arduino Nano are pure analogue pins and
cannot be used as digital pins. Only A0-A5 can be
used as digital pins in that build of Arduino.
The results of the heuristics analysis led to some
changes in the final product. Regarding IN1, we
decided to add a Buzzer module to the parts list, add
a new chapter to the Assembly instructions and create
a mBlock extension (Figure 20) to allow the Buzzer
to be used as a musical instrument, allowing even
more activities to be done with Stemie.
Figure 20: Buzzer for Stemie extension.
Using the mBlock platform that allows users to write
custom extensions programmed in JavaScript, in a
way to add new functionalities to the programming
environment, we created two new blocks to be used
by students. The extension is made by two essential
parts: the definition of the block that shows in the
mBlock application and the translation to C++ code
which can be uploaded to the Arduino Nano for
execution. The following is an example of the code:
"extensionName": "Buzzer for
STEMIE",
"description": "An extension for
using a Buzzer with STEMIE",
"version": "1.5",
"author": "",
"homepage": "",
"sort":0,
"javascriptURL":"js/buzzer.js",
"firmware":"1.0",
"extensionPort":0,
"blockSpecs": [
[
"w",