D.c. motor speed controller

Abstract From the Canadian patent

A direct current variable duty cycle control circuit for the manual control of the supply of power from a direct current source to a motor is disclosed including a transistor arrangement operable when enabled to couple the direct current source to the motor along with means for enabling that transistor arrangement during an operator determinable portion of each of a series of time intervals and a sensing circuit receptive to an overload condition of the transistor arrangement for disabling that transistor arrangement. The disclosed system includes an operator control member effective in a first position to prevent the energization of the motor by preventing the supply of electrical power to …