A system for determining the position of a moving part driven by an electric motor: a single position sensor, coupled to the electric motor, incrementally detects an amount of movement thereof; a direction switching arrangement controls a direction of movement of the electric motor; and a control unit, coupled to the single position sensor and the direction switching arrangement, at each incremental amount of movement detected by the single position sensor, determines a current position of the moving part based on a previous position thereof and the current direction of movement controlled by the direction switching arrangement.