Soft start for power tool with momentary switch and mechanical direction selection switch

A soft start system for use with a universal motor, the system comprising:

• a momentary switch for switching an electrical power source, the momentary switch including a first state for actuation, the momentary switch providing a momentary switch actuation signal;
• a zero crossing detection provision for providing a zero crossing detection signal;
• a driver for switching and controlling the electrical power source, the driver having an input for receiving a driver control signal;
• a direction selection switch for switching the electrical power source, the direction selection switch providing a forward direction signal and a reverse direction signal;
• a microcontroller for performing a soft start algorithm, the microcontroller receiving the momentary switch actuation signal, the zero crossing detection signal, the forward direction signal, and the reverse direction signal, the microcontroller configured to generate a driver control signal using the soft start algorithm, the driver control signal provided to the input of the driver;
• wherein the direction selection switch and the momentary switch are configured such that if the momentary switch is in the first state for actuation, and the direction selection switch provides the forward direction signal, the universal motor operates in a forward direction.

An electrical power circuit for use with a universal motor, the power circuit comprising:

• a momentary switch;
• a direction selection switch;
• a soft start system;
• at least one direction feedback signal from the direction selection switch to the soft start system;
• wherein the direction selection switch includes a first state for a reverse direction of the universal motor, a second state for no rotation of the universal motor, and a third state for a forward direction of the universal motor;
• wherein the direction selection switch is configured to change the direction of rotation of the universal motor, the momentary switch includes a first state for actuation and a second state for de-actuation;
• and
• wherein the direction selection switch and the momentary switch are configured such that if the momentary switch is in the first state for actuation, and the direction selection switch is in the first state for the reverse direction of the universal motor, the universal motor operates in a reverse direction.