Wireless Sensor and Actuator Networks for Lighting Energy ...

controller higher liked the fact that they could conveniently control the lights whenever
they felt like it instead of having to go to the virtual controller even when not working
on the computer. These two conflicting opinions suggested that it might be a good
practice to have both virtual and physical overriding mechanisms when designing a
lighting system.
As mentioned in the previous section, there are three different ways to override
the research lighting system with the GUI: click on the stepwise control buttons, drag
the sliding bars and press the SET button, or type in a desired level and click on the SET
button. The step buttons, like those on the handheld remote controller of the commercial
system, allow the participants to adjust the lights gradually while the other two options
enable the subjects to quickly jump to a specific light level. An interesting observation
was that even though these three control options were equally and conveniently
available on the GUI, all the participants would settle for only one of them during the
entire test instead of a combination of all three. Nevertheless, the fact that the
participants didn’t choose the same control option on the GUI to set the light level
implied that it might be beneficial to offer more than one interaction method on
overriding interfaces.
The most common suggestion made by the subjects for improving user
satisfaction was to include certain feedback on the overriding mechanism, such as the
current light level. This confirmed the well-known interface design guidelines that
highlight the importance of providing user feedback [105-107]. The feature of status
feedback was originally available on the GUI of the research system, such as the
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