Robotics
NXT-G: variables, file
Rotation sensor
Lab: Use buttons to hit specific ball.
Homework: Postings. Start planning
mapping the room
Variable
• Store value under a name and then re-use
• NXT-G
– Need to set up variable: name and data type
• Logic (true or false)
• Number
• Text
– Then can read or write
– Use as input to data link
– Use as input to calculation
• Demonstrate
Button test
• Use variable to hold which NXT button
was pressed.
• Use Edit/Define Variables
– Need to give name (give meaningful name)
– Need to specify datatype (number, text, logic)
Warnings
• If the task is to determine left or right
button, you can’t wait for one button.
• Instead, loop checking first one then the
other button. Set variable (or use data
wires and an OR operation) to exit the
loop.
• Probably need to insert pause(s).
How to check?
• Use display screen
– Text
– Specify text
– NEED TO INSERT PAUSE SO I CAN SEE IT!
Lab assignment
• Do basic ball hitting exercise
– Hit only red ball and only blue ball.
• Enhance hitting ball exercise
– Use buttons to indicate which ball is to be hit
– Use variable
– NOTE: you probably can do this just with data
wires, but do it with a variable
• Why?
File
• Set of values
• Can be re-used by program or uploaded to
computer
• NXT-G
– Delete (might do this initially to make sure there isn’t
old file by the same name)
– Write (actually append to end)
– Close (need to do this before reading)
– Read
• Demonstrate
First part: records light readings
Second part: write out file
…and you can upload file: Other
under Memory
Rotation sensor
• Connect to particular motor.
• Reset to zero.
• Can measure in rotations or degrees.
Mapping
• Now have tools to record how far robot
has moved
– Rotation sensor: how many degrees a
particular motor has turned
– Variables and files to store data
• Need a plan/strategy to 'map room'
– Determine position of walls
– Note: you know how to move until bump or
move until ultrasonic indicates under a set
amount.
Challenges
• Robot to store (for later use) where it found walls
(or something else)
– Use rotation sensor to determine distance traveled
(will need to calibrate in terms of power)
– Create file
– Upload file
• LATER: Robot to send information to second
robot using Bluetooth.
Lab/Homework
• Use ultrasound than light to hit the red
ball. Change to hit the blue ball
• Use display, pause, buttons to specify
which ball to hit.
• Start planning room mapping task.
• Postings