Abstract: Determining the consistency of a mixture during a mixing process based on feedback from the mixer. The feedback may be indicative of the torque exerted on a motor shaft of the mixer. The consistency of the mixture may be determined based on the amount of torque, rate of change of torque, change in the rate of change of torque and/or a comparison of the torque information to a stored torque profile. The torque may be determined based on the current in the coils of a motor of the mixer (e.g., by measuring the voltage across a precision resistor in series with the coils). Alternatively, the feedback may be indicative of the angular velocity of the motor shaft, sound output by the mixer, vibration of the mixer, color of the mixture, or opacity of the mixture.

Abstract: A method of controlling a motor (106) used to drive a screwdriver bit (105) such that screws (107) are seated to the optimum point of grip between the screw (107) and the work piece material. An electronic control circuit controls the speed and output torque of the motor (106). The control system utilizes pulse width modulation (PWM) to control motor (106) speed and torque. The PWM signal controls the duty cycle of the transistors that supply current to the motor (106). The amount of current flowing through the motor (106) coils is proportional to the amount of torque the motor (106) is producing. Motor (106) current is measured as voltage produced across a precision resistor that is in series with the motor (106) coils. As the current in the motor (106) increases, the voltage across the resistor increases (V=IR).