Electronic speed control circuit for direct drive automatic washer

Claim 1

In a motor control circuit having a firing angle control circuit for operating a controlled conduction circuit to energize a motor with time-spaced energization pulses, a feedback loop between the motor and the firing angle control circuit for adjusting the spacing of the energizing pulses to control the speed of the motor comprising a tachometer connected to the motor and operable to generate a signal having a frequency corresponding to motor speed, a trigger circuit operated by said signal to generate a first pulse train of the same frequency, and means connected between said trigger circuit and the firing angle control circuit for controlling the operation of the firing angle control circuit in accordance with the frequency of said first pulse train, including means for producing a second pulse train in response to said first pulse train and at a frequency that is a multiple of the frequency of said first pulse train and means for converting said second pulse train into a control signal for controlling the operation of said firing angle control circuit, including a capacitor, means for charging said capacitor including a transistor connected in series with said capacitor and an electrical supply, and means connected between said transistor and said means for producing said second pulse train for controlling the rate of conduction of said transistor and the charging of said capacitor, comprising a sawtooth generator operable to generate sawtooth pulses in response to the pulses of said second pulse train.