A vibrating armature motor, which includes a voltage source, an armature, an electromagnet having at least one exciter coil disposed adjacent the armature, a spring for rotationally biasing the armature, a sensor element for sensing the rotational velocity of the armature and for generating a signal proportional to the sensed velocity, a variable duty cycle pulse generator for generating a stream of triggering pulses, the duty cycle of the triggering pulses being dependent upon the sensor signal, and an electronic switch for controlling the current flow from the voltage source through the exciter coil in response to the triggering pulses.

A control for regulating the AC voltage provide to a vibratory feeder, which includes electronic circuitry for generating a "desired" voltage signal, feedback circuitry for generating an "actual" voltage signal, a logic circuit for comparing the "desired" and "actual" voltage signals and generating a difference signal, and a controller which uses the difference signal to generate a control signal for regulating the AC voltage provided to the feeder. An initialization circuit enables the control a predetermined time after AC power is applied and an automatic relay couples a DC power source to the control for selective adjustment of the control output. A fault circuit automatically shuts down the control if the feedback signal is lost when the "desired" voltage signal is at or turned down to a predetermined level. A maximum AC output indicator identifies the optimum setting for a maximum output adjustment, regardless of load, and a ramp function determines the build-up and decay of the AC output voltage. Logic circuits are utilized in conjunction with the control for independently setting "on" and "off" delay periods and for controlling the on/off operation of the control in response to high and low sensor signals relating to backlogs of parts.

A blocking oscillator for a reciprocating electromagnetic actuator having a solenoid coil, a detection coil for generating a control signal in response to a charge in the magnetic field generated by the solenoid coil, a silicon Darlington amplifier responsive to the control signal to control the current through said solenoid coil, and a diode connected in series with the collector of the Darlington amplifier rendering the Darlington amplifier immune to reverse voltage and transient signals.

A vibrator motor is coupled to the frame of a body support structure to vibrate the latter. The motor is energized by a train of triangular pulses modulated by a triangular pulse signal having a lower frequency than that of the triangular pulse train.

A control unit for controlling a vibratory bowl feeder which is effective to maintain, for varying feeder loads, a constant preselected amplitude of bowl feeder vibration at a vibratory frequency which coincides with the changing mechanical resonant frequency of the feeder system. The control unit includes a sensor which detects the amplitude and frequency of feeder bowl vibration, a frequency control loop and an amplitude control loop. The frequency control loop is responsive to the detected frequency of vibration and provides an oscillating signal which coincides with the resonant frequency of the system. The amplitude control loop is responsive to the detected amplitude of vibration and includes a variable gain amplifier which amplifies the oscillating signal to provide a feeder driving signal which causes the feeder to vibrate at the system resonant frequency at a preselected amplitude. The sensor for detecting amplitude and frequency of the bowl vibration is preferably a device for sensing the third harmonic of the drive current in the electromagnetic drive of the system. A variable capacitive reactance coupling circuit between the power drive amplifier as the electromagnetic drive of the system is set to match the inductive reactance of the electromagnetic drive.