Abstract: A detection circuit senses whether a buttonhole type presser foot is attached to a sewing machine presser bar and through a control circuit enables or disables pattern selection switches for machine operation other than a buttonholing mode.

Abstract: A direct current obtained by rectifying an alternating current voltage by means of a diode bridge circuit is applied to a direct current motor connected to the diode bridge circuit. Use is made of the fact that the voltage developed across the diode bridge circuit varies, depending on the magnitude of the induced voltage across the motor. To that end, the interjunction of a capacitor series circuit coupled to the bridge circuit is connected through a voltage responsive bidirectional switching device, such as a diac, to a control electrode of a voltage controlled bidirectional switching device, such as a triac, for phase control of the alternating current voltage. One electrode of the voltage responsive bidirectional switching device is coupled to a variable resistor provided in a gang fashion with a controller, such as a foot controller pedal, so that the voltage obtainable from the variable resistor is superposed on the voltage in the switching device, such as a diac.

Abstract: A sewing machine driven by a motor which is adapted to be energized by an alternate current power supply and is phase controlled by means of thyristors. In a normal operating mode the conduction phase of the thyristors is made variable as a function of the extent of the depression of a foot controlled pedal, whereas in a low constant speed mode the thyristors are made conductive at a predetermined phase. The motor is coupled to a main shaft which is provided with a magnet located at a predetermined position, while a bracket arm is provided with a reed switch located at a predetermined position, such that if and when the foot controlled pedal is released, the reed switch is actuated to trigger the thyristors for reverse braking of the motor as a function of the counter electromotive force of the motor. Preferably, a timer is provided for interrupting the power supply after the lapse of a predetermined time period after the foot controlled pedal is released.