Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc. Introduction to Sensors

Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.

Introduction to Sensors


What are sensors?

• Your answers here!


What are sensors?

• A sensor tells a robot one simple thing about it’s environment– Temperature– Distance– Light intensity

• Allow robots to see and feel the physical world through which they travel

• Two main types of sensors: digital and analog


Analog Sensors

• Can provide a range of feedback• The robot will interpret feedback from the sensor

as a number from 0 to a pre-defined maximum (1024 for most Vex sensors)

• A light sensor has many states:– If it is very bright, the sensor will return a number

close to 30– If it is very dark, the sensor will return a number close

to 1000


Digital Sensors

• Can distinguish between two different “states”• The meaning of the states depends on the

sensor• A bumper sensor has two “states”

– If it is pressed, it is a 0– If it is not pressed, it is a 1


Variables

• A value-holding “container” with a label

• You can retrieve the value in this “container” when it is needed

» There are different types of values you can store in variables.

» You will use the “int” type, which allows you to store any whole number from 0 to a large number (positive or negative)

» You can assign a starting value to your variable which will store that value at the start of the program


Bump Sensor Introduction

• Open the project “BUMPERTEST.ECP” • Download it to your robot and open the terminal

window


Understanding bump sensor code

• Comments - allows you to leave notes to yourself and others about your code

• The compiler ignores comments



• While Loop – block of code that repeats itself as long as the condition inside the parenthesis is true– The == operator returns true if both sides are equal,

and false if they are not equal– In our code loop will always equal 1, so this loop will

run forever



• Bumper sensor – stores the value of the digital input 6 to the variable “bumper”– Now the robot knows if the bump sensor is being

pressed in (0) or not (1)



• Print to screen – displays information in the terminal window– This particular code displays the value of the bump

sensor

For now, make sure your settings are as follows:

* Variable: the variable you want to display

* Message: the message with the variable

* Directive: %d

* Type-cast: int


Writing your own code

• We are going to write a program that runs one motor until a bump sensor is pressed in

• Begin by opening easyC

Documents

Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc. Introduction to Sensors