We’ll start by getting a broader understanding of the
light sensor and its functions.
• What exactly does a light sensor sense?
• What are some practical applications for a light
sensor in consumer electronics?
• How can we use the light sensor within the NXT
system to learn more about robotics?
After answering these questions, we’ll build two light
sensor attachments for our robot: one using just one light
sensor, and a second with two light sensors.
If you only have one light sensor, have no fear! We’ll
be focusing on the single light sensor attachment, offering
the double light sensor attachment as a challenge! Next
time, we’ll be covering multiple sensor programs, so you
may want to purchase an extra light sensor from LEGO
Education ( http://bit.ly/lightsensor).
What exactly does a light
A light sensor uses a photovoltaic cell to detect the
intensity of the light it is exposed to. It can sense either
reflected light (light originating from the sensor itself and
reflected off the nearest surface) or ambient light which is
light naturally existing in the robot’s environment. To put it
simply, a light sensor will sense the intensity of light that it
is exposed to, whether by itself or its environment.
What are some practical
applications for a light sensor
in consumer electronics?
Probably the most common use of photovoltaic (light
sensitive) cells in consumer electronics are street lamps that
turn on automatically at night. If you’ve ever been down a
road at dusk and watched different streetlamps turn on
and off at different times, it’s more than likely small
variations and imperfections in the photocells are causing
them to turn the lights on at a different threshold.
Beyond that, light sensors have many more interesting
applications. Lots of cellphones are now equipped with light
sensors to save battery life — screens need to be brighter
during the day to be visible, but at night it’s not necessary,
so screens dim automatically to save power.
How can we use the light sensor
within the NXT system to learn
more about robotics?
We could certainly make a LEGO street lamp or a LEGO
automatic dimmer switch, but that would be boring! We’ll
be taking a much more hands-on approach to learning
about the light sensor by creating several programs that
move and react based on the readings received.
Now, let’s get building!
First, find a long
Single Light Sensor Attachment
Slide a three-stud axle
Push two standard
joiners onto the open
edges of the three-stud axle.
Snap in long
friction pegs with
axle holes as
SERVO 10.2010 53