okay my machine's operation is basically divided into a few stages,
1. push a button (START)
2. the vehicle travels along an L-shape track while launching 'seeds' left and right into pre-determined patches on the track.
3. because the machine can't roll off the track after its operation(pts deducted), power must be cut from the main motor
4. brakes are applied to completely bring the vehicle to a stand still(END)
some extra info, my machine must weigh less than 15 kgs and not be more than 40 cm cube in volume. so basically i have to design a circuit to switch from one stage to the other. we do not want to do this mechanically since its pretty unreliable at our current level of skill. once again thx for your time. hope my explanation is clear enough