IMPROVEMENTS IN AND RELATING TO POWER TOOLS

摘要

A drill/driver (e.g. an electric drill) with a screwdriver attachment, and a method of controlling the drill/driver, are described. A control circuit (30 ) controls the speed of rotation of the motor (38, 39) through a time a time delay circuit (42) and a triac (41 ). The control circuit (30) uses the same time delay information and information inputted from a rotational speed sensor (43) to monitor the current in the motor or a parameter related at least in part to current in the motor. When a change corresponding to an increase in the rate of change of current in the motor is detected, the control circuit (30) stop s the motor to provide an automatic torque control feature for a screwdriving operation.