Abstract: A controller 20 for a stepper motor 10 comprises a plurality of outputs 26 for supplying drive signals to coils 16 of the stepper motor 10, pulse generating means for supplying full step signals each comprising a succession of digital pulses to each of the outputs 26, pulse width modulation means for supplying a pulse width modulated signal comprising a succession of width modulated digital pulses and mixing means 24 for mixing the full step signals and the pulse width modulated signal to produce digital stepper motor drive signals.

Abstract: The stator of an electric motor is provided by coils 22 disposed in an interrupted-annular array about a central space such that a path A through the array is provided whereby a selected one of a plurality of rotors 21 can be moved in the plane of and through the array into and out of said central space. In the preferred embodiment each rotor 21 is a gobo freely rotatable on a wheel which can be indexed to bring it into a light path, when it will be positioned to be rotated when the coils 22 are energised. The non-annular disposition of the coils 22 results in a motor of low torque but it is is adequate to rotate a gobo disc, which is simply a perforated sheet of metal. As applied to a disco lighting unit the motor of the invention provides a much cheaper and simpler drive arrangement for gobo discs.