A first switching element is connected to one end of a brake and switches from the off state to the on state when a switch command is input to cause a brake drive current to flow through the brake. The system includes a console, which contains all motors, pumps, sensors, valves and control circuitry, and a unique disposable set that includes a cassette supporting a centrifuge with an improved design, pump interfaces with an improved design, component and solution bags, and tubing. The electrostatic protective part is formed by applying solder on a conductive foil. The closed end of each piston chamber is connected by a passageway to one of the tires. An effective way of taming the motion is to assume that behind every array is an underlying array of regular cells.