Our targets were to move left and right inside C-channel rails, and we wanted them to be able to change directions autonomously. We created a full H-bridge with a L293B push-pull driver to allow our motors to turn in both directions. In order to provide the proper direction control on the L293B chip, a HC14 Schmidtt trigger inverter is used to invert the signal from a slide switch mounted on our motors. The relation between inverter input and output signals are used by the push-pull driver to determine motor rotation direction. If the inverter input state changes due to the slide switch position, the polarity of the current across the motor also changes, which causes the motor rotation direction to change.

The end result is that when the slide switch is pushed in one direction, the motor shaft turns in a certain direction, and when the switch slides in the other direction, the motor shaft will change rotation direction. One of these setups is used for each rail of moving targets.