Building Smart LEGO MINDSTORMS EV3 Robots
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Rotation

The tank also needs to be able to aim at the beacon. The entire turret assembly is mounted on a turntable, which allows it to rotate to the right and left. The turntable is powered by an EV3 medium motor, which is plugged into port D:

This motor is located in the back of the robot to the right side. It sends its power through a 90-degree gear connection, which is very similar to the one used with the cannons. However, there is another set of gears in this mechanism: a 24-tooth gear drives the gear on the turntable mechanism. The overall gear ratio between the motor and the turntable is 4.17:1, meaning the motor must make 4.17 rotations to get the turret to rotate a full 360 degrees. This is a much slower gear ratio than the one we saw on the cannon. Slowing down the rotation of the turret makes its motion more accurate and easier to control: