Robotics
NXT sensors
Back to Light sensor: red vs blue ball.
Lab: Maze. Add mallet. Hit red ball.
Homework: Postings. Develop task
involving multiple sensors.
Lego sensors
Include
• physical packaging: way to attach to other
Lego pieces
• electrical packaging: analog to digital
signal: bit pattern representing a number
• software for / in NXT-G: block(s) and help
text
Maze
• Ideas?
• Note: can simplify maze: say only right
angles.
• How can robot know it is done (outside of
maze)?
Maze: one approach
Loop
• Move forward a little (can set motors to
glide)
• Check bumper. If pressed, back up and
turn to the right (see next). May do this in
one or two steps.
• Check ultrasonic mounted on the left. If
>some amount, turn to left, move forward
a little.
THERE ARE OTHERS!
Preview: Compass sensor
• Calculates magnetic heading: 0 to 359
degrees
– Returns number
– Returns true/false if inside or outside specified
range
– Absolute or relative operation….
• Need to download software:
Tools/Block Import and Export Wizard
Cautions
• Note: The compass measures the very weak
earth's magnetic field. Ensure that is mounted at
least 4 inches or 10 centimeters away from the
NXT and motors.
Why????
Also ensure that it is mounted horizontally as the
heading will not be accurate if the compass isn't
level.
Why????
Tasks
•
•
•
•
Task using ultrasonic sensor?
Task using bumper (touch sensor)?
Task using light?
Task using compass sensor?
• Tasks using multiple sensors
Note: just 4 ports.
Red vs Blue ball
• Build mallet (my word)
– pp 50-61
• Build stand
– pp 62-67 OR
– Do your own design, perhaps use tire for stand (more
stabile but need to check height) and something
bigger to be detected by the ultrasound sensor.
• Use Mindstorms help for program.
– Need to pick value that distinguishes red and blue ball
Homework
• Postings
• Plan activity making use of multiple
sensors
• Note: next week: coordinate systems,
position[ing], NXT-G: variables, file system