Understand and program turns in NXT-G

1. MEASURED TURNS
NXT-G

2. NXT motors & Control Block
• The NXT servo motors have a built-in rotation
sensor block that continuously measure and
monitors the degrees covered by the motor.
• Motors can be manipulated using the move,
motor, and reset blocks.
• The move block synchronizes motor to enable the
robot to move straight.
• The move block can control all 3 motors
simultaneously. However the power is shared
among the 3 motors.
• The block has a built-in system for error
correction.

3. Move block – Configuration panel
Select ports corresponding to
the ports on the NXT
Amount of power used to
control the motor
Duration of the action, specified
in degrees, duration, time, or
unlimited
Direction
Steering: shares the power
among 2 motors, not reliable
at low power
Next Action: Brake causes the robot to come to an
immediate stop landing more accurately than coast. The
robot rolls to a coast occasionally overshooting the target.

4. Turn: Pivot, curve, and point
There are 3 ways to make a robot turn:
1. Move 1 motor, most accurate
2. Move both motors in the same direction, one faster than
the other
3. Move both motors in the opposite direction
Right
Brake
Forward
Forward
Forward
Backward
To make robot turn left,
Stop B motor, run C motor,
Right wheel will remain
stationary
To make robot turn left,
Use steering block to
power B motor
Motor block needs to be
used in parallel. Use for
tight turns

5. Turn: Spins or point
To make robot turn left, stop B motor, run C motor, right
wheel will remain stationary
Right
Brake
Both motors
stop
Port C

6. Turns: Pivot, both motors forward
Forward
Forward
To make robot turn left,
Use steering block to
power B motor
Steering

7. Motor Block
The motor block control motors with configurations different from the move block.
Ideal for controlling robot arms and performing turns, the motor block has the
following options.
Controls a single motor port
Increases power if
resistance is met
Action offers 3 options:
Constant: power remains constant
Ramp Up: Slowly increase speed till desired power
is reached
Ramp Down: Slowly decrease speed till it reaches
zero power
Wait: Program waits for
the completion of the
action of the motor block

8. Turns: Spin or point turn
Forward
Backward
Motor block needs to be
used in parallel. Use for
tight turns In order to add the parallel sequence
beam, hold the shift key and hover between
blocks till you see a spindle. Click on the
sequence and continue till you reach the
block, holding the shift key till the end.

9. Motors: Accumulated errors
As motors move, the built-in rotation sensor keeps track of the number of
degrees turned and makes correction to correct the “accumulated errors”.
While this is a great feature, the accumulated errors cause problems in
complex programs, requiring motors to be reset at critical points.
Block Specific duration Actual duration Accumulated error
Move Coast 200 degrees 220 degrees 20 degrees
Wait
Move Coast 200 degrees 230 degrees 50 degrees
Wait
Move Coast 200 degrees 210 degrees 60 degrees
Wait
Move Brake 200 degrees 140 degrees 0 degrees
Total 800 degrees 800 degrees

10. Programs on the PC
• Upon installation, the NXT-G software creates a sub-
directory “Lego Creations/MindStorms projects/profiles”
under the documents folder
• All programs are stored in the “default” folder
• All myblocks are stored in the Myblocks folder