A method of reworking a photoresist layer. The control circuit is connected to an input end of the motor. The outer body surface is an oxidized surface to resist corrosion, and a clear coating may be provided over the surface. Magnetic field or eddy current based inductive and giant magnetoresistive sensors may be used on magnetizable andor conducting materials, while capacitive sensors can be used for dielectric materials. A lid covers selected ones of the electrical components except for at least the power amplifier. In a preferred embodiment of the invention, the valve actuation mechanism is designed to control the opening and closing of engine valves by the use of an uncomplicated structure with minimum solenoid valves and hydraulic lines.