During Spring Break this year, members of the Family Trivium household have been working on robotics. One of us went to an introductory clinic while others of us worked on an independent project. One of the goals of the independent project was autonomous obstacle avoidance accomplished through the use of at least one sensor.

What is a Sensor?
Looking at the Merriam-Webster Dictionary, we find a sensor defined as

a device that responds to a physical stimulus (as heat, light, sound, pressure, magnetism, or a particular motion) and transmits a resulting impulse (as for measurement or operating a control)

We would argue that the sensor itself does not respond to physical stimulus. Rather, it simply takes, as input, the physical stimulus before transmitting an impulse. This is the case in our robotics projects where another component of the robot responds to the physical stimulus after the controller (brain) receives and processes the impulse provided by the sensor.

Wikipedia gives a more thorough, and practical, definition of sensor:

A sensor is a transducer whose purpose is to sense (that is, to detect) some characteristic of its environs. It detects events or changes in quantities and provides a corresponding output, generally as an electrical or optical signal; for example, a thermocouple converts temperature to an output voltage. But a mercury-in-glass thermometer is also a sensor; it converts the measured temperature into expansion and contraction of a liquid which can be read on a calibrated glass tube.

An Example
In the case of our independent robotics project, an ultrasonic distance sensor was used to help our robot determine when it was nearing an object. This sensor would continuously send a distance measurement from the front of the robot to the controller. When the controller receives a measurement under a certain threshold, it would send a command to the motors to stop, before completing some more actions and having more communications with the distance sensor to determine in which direction to move next. One member of the Family Trivium household likened the distance sensor to being the eyes of a robot, but upon an understanding of the input and output of the device revised the analogy to it being like a bat’s ears during echolocation.