A stepper motor is used to drive the carriage. The motion of the stepper motor is transmitted to the linear carriage with the help of a belt and pulley mechanism. The belt is attached to the acrylic mounts (see Figure 2), which are in turn attached to the carriage with the help of screws. The acrylic mounts have two circular holes. Steel guide bars pass through these holes, and help in keeping the carriage in an upright position.
Figure 1. The Belt-Pulley Mechanism
Figure 2. Acrylic mounts and linear bearings
We have inserted linear bearings (see Figure 2) in between the mounts and the guide bars. This reduces the friction by a large amount, and hence increases the speed of the carriage, ensuring that a move is completed well within 20 seconds. The steel guide bars are lubricated to further reduce the friction.
The stepper is calibrated to ensure that the the carriage stops at the desired column while the game is being played.