Movit represents my personal favorite "simple" robot base for movement and sensor testing.

The robot is perhaps the simplest mobile robot base I've found, making it a perfect start for more complex projects. Basic programming is simple, but by adding one or more sensors, the programs can quickly be enhanced to create much more complex robot behavior.

The basic form preseneted here uses a very simple movement loop - move forward 3 seconds at 50% power, then turn right for 1 second at 50% power, play a sound, then test the loop termination condition. If met, the loop terminates. If not met, the loop repeats, thus repeating the two basic movements. If left alone, it will move in this modified "star" pattern until the batteries run down. The loop terminating condition for this specific robot is based on the ultrasonic sensor. If something is detected withing 10 units of the sensor, the loop will terminate.

This is a very simple robot to build. The pictures below show the parts and the steps. It is important to note the NXT ports used for the motors and sensor. They must agree with the ports you use when programming the robot.

This is a very simple robot to program. The pictures below show the finished program and the parameters for each block. Note the sensor is linked to the loop as the loop's termination condition. Please note the motor and sensor ports used in the build must agree with the ports you use when programming the robot or it won't work as expected.

The following link presents a quick movie on YouTube that I recorded showing the program being compiled and downloaded to the robot, followed by a test run.

LEGO robot run Video