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In this article, I will describe each of these human senses and the VEX sensors that can be utilized in a similar manner to build equivalent anthropomorphic robotic platforms. To make things more interesting, I’ll include a
simple project that demonstrates using a particular sensor, the
VEX microcontroller, and some additional electronic
components. I will also describe how to interface this controller
to other sensors that are not yet part of Innovation First’s
inventory. I’ll start with an overview of the current sensors.
What Are Sensors?
Sensors play an ever-increasing important role in the
development of almost any new commercial, industrial,
transportation, medical, automation, aerospace, or robotic
application. Consumer appliances in particular need to be
energy efficient to obtain an Energy Star rating from the US
government. Washers, dryers, and dishwashers require very
efficient electric motors, sensors to measure tilt for balanced
loads, and humidity, temperature, and water sensors. The
sensors are required to detect if the washer or dryer door has
been opened during operation to avoid injury to the operator.
In transportation, sensors play a critical role in measuring
speed, altitude, and location (GPS) of an aircraft in flight. Rate
gyros and laser ring gyros are used for inertial navigation and
radar to detect the presence of other nearby aircraft in order
to avoid collisions. Trains depend on various sensors to detect
other trains on the track, cars at train crossings, and train
speed. Ships use radar and sonar to locate other ships and
land, as well as rocks and other obstacles found in the ocean.
Car manufacturers are under increasing pressure to
develop and produce higher mileage vehicles and at the same
time make them safer. New hybrid cars require constant
battery voltage monitoring, as well as measuring current and
power to new electric motors and generators. Car speed and
steering wheel angles are measured electronically using
encoders. Airbags use accelerometers to detect a collision and
deploy them in time to save car passenger’s lives. Weather
forecasting systems that we depend on for daily activities and
The year was 1969, strobe lights were beaming, and these were some of the haunting lyrics from the
song “Pinball Wizard” sung by Roger Daltrey from the original rock opera TOMMY, which was written by
lead guitarist Pete Townshend and performed by the legendary British super rock group, The Who. While
this song is not particularly about sensors, robotics, or VEX for that matter, its lyrics do in essence
summarize what an autonomous anthropomorphic robot is required to do in order to perform its daily
tasks. We humans cannot get around on our own without most of these senses available to us. One thing
missing from this list is the sense of smell which is very useful for detecting gas leaks, explosives, etc.
Using Advanced Sensors with VEX
“Hear Me, See Me, Feel Me, Touch Me ...”
By Daniel Ramirez
to get warnings of storms or hurricanes or even tornadoes put
sensors to use in combination with satellite imagery or weather
balloons to detect pressure, temperature, and humidity levels.
Although sensors by themselves seem passive when compared
to motors, servos, relays, and other kinds of actuators, they
play a crucial role in controlling motor speeds, HVAC
temperature, humidity, pressure, voltage, current, etc., using
closed-loop control, where sensors provide error feedback back
to the control loop.
VEX Sensor Subsystem
The VEX sensor subsystem describes the various kinds of
sensors, how they are used, and how these sensors are
interfaced to the VEX microcontroller, including: bumper
switches, limit switches, ultrasonic rangers, and IR ranger
sensors, potentiometers, joysticks, optical encoders, and xyz
accelerometers. The plug-and-play nature of the VEX sensors
makes it very easy to provide your robot applications with
sensory feedback necessary for various control tasks. Some of
the more common VEX sensors that are available are shown in
Figure 1.
Notice that they are all color-coded red to match the VEX
Inventor’s Guide sensor subsystem. You may recall the VEX
limit switches and optical encoders used previously (SERVO
April ‘ 11 issue on VEX stepper motor experiments), but we will
study these sensors more closely here. These sensors are
supported by three C compilers and include: the VEX bumper
switch, limit switch, optical encoder, quadrature optical
encoder, IR ranger, ultrasonic ranger, potentiometer, xyz
accelerometer, and a line following sensor. New sensors are
continuously being added by IFI Robotics as they are
developed for various contests, and support for them is
included in their C tools. Note that the VEX quadrature optical
encoder has two cables and the standard optical encoder only
has one cable. Although the list of available sensors is growing
every year, the five major sensor categories are very similar to
our biological senses, and each measure physical properties.
Let’s go over the descriptions of the VEX sensors that are
