Abstract: A power tool such as an electric drill typically contains a gear train that couples the output spindle of the motor to the tool bit-receiving chuck and has associated therewith a degree of looseness which must be taken up before torque from the motor is applied to the tool bit. The control circuit for the power tool increases the effective torque output of the tool after a predetermined torque level is attained, by alternately turning the motor on and off, with the duration of the off-time sufficient to permit the gear train to relax, thus giving the motor a "running start" when power is reapplied. Various alternative schemes for transitioning to this ratcheting mode of operation are disclosed including the sensing of a predetermined threshold current, a predetermined increase in motor current, and a predetermined rate of deceleration in motor speed.

Abstract: The driving apparatus for a power antenna, e.g. an extensible-retractable automotive radio antenna, is provided with stability function which controls the operation of the motor driving the power antenna until the power antenna is varied into a state for performing normal operation, and provides hysteresis to prevent a state of the controlling signal from being varied too often by a voltage drop generated in rotation of the motor.

Abstract: A method of automatically controlling the operating speed of a vehicular windshield wiping system based on an average rate of change in the value of a sensor signal indicative of the moisture on the windshield. The wiping system includes a motor for driving at least one wiper blade at a high speed and a low speed, and a sensor mounted to the windshield for monitoring a portion of the windshield wiped by the at least one wiper blade. The method includes determining an average rate of change in the sensor signal value over a predetermined period of time and operating the wiper system with the motor at the high speed based on the average rate of change in the sensor signal value. In one embodiment, the method includes wiper system is operated with the motor at the high speed based on the frequency with which the average rate of change in the sensor signal value drops below a first predetermined threshold.

Abstract: A method of automatically controlling the operating speed of a vehicular windshield wiping system based on an average rate of change in the value of a sensor signal indicative of the moisture on the windshield. The wiping system includes a motor for driving at least one wiper blade at a high speed and a low speed, and a sensor mounted to the windshield for monitoring a portion of the windshield wiped by the at least one wiper blade. The method includes determining an average rate of change in the sensor signal value over a predetermined period of time and operating the wiper system with the motor at the high speed based on the average rate of change in the sensor signal value. In one embodiment, the method includes wiper system is operated with the motor at the high speed based on the frequency with which the average rate of change in the sensor signal value drops below a first predetermined threshold.

Abstract: A power tool such as an electric drill typically contains a gear train that couples the output spindle of the motor to the tool bit-receiving chuck and has associated therewith a degree of looseness which must be taken up before torque from the motor is applied to the tool bit. The control circuit for the power tool increases the effective torque output of the tool after a predetermined torque level is attained, by alternately turning the motor on and off, with the duration of the off-time sufficient to permit the gear train to relax, thus giving the motor a "running start" when power is reapplied. Various alternative schemes for transitioning to this ratcheting mode of operation are disclosed including the sensing of a predetermined threshold current, a predetermined increase in motor current, and a predetermined rate of deceleration in motor speed.

Abstract: The residential structure ventilating apparatus disclosed herein employs a variable speed exhaust fan. The speed is responsive to a sensor which detects air temperature at the exhaust port. The fan is energized when the sensed air temperature rises above a first preselectable temperature and the external environmental air is cooler that the air at the exhaust port. The fan speed is increased progressively from about one-half full speed at the preselected turn on temperature to full speed at a predetermined higher temperature. The fan is turned off when the exhaust port temperature falls below a second preselected temperature, lower than the first preselected temperature or when the external environmental temperature rises above the inside temperature, the fan speed being essentially constant between the first and second preselected temperatures.

Abstract: A method for controlling a vehicular windshield wiping system, the wiping system being controlled in response to recognition of a particular rain pattern, and being capable of distinguishing between the presence of moisture and dirt on the windshield. The wiping system is also controlled according to a plurality of operating thresholds established to ensure smooth operation of the wiping system during varying conditions, and is controlled according an amplification autoranging strategy to ensure the wiping system functions properly independent of certain conditions, such as the type of windshield on the vehicle. The wiping system includes at least one wiper blade, and a sensor mounted to the windshield for monitoring a portion of the windshield. The sensor generates a signal having a value which varies as both moisture and dirt collect on the monitored portion.

Abstract: An apparatus and method for controlling a windshield wiping system, based on a connection threshold defined for starting operation of the windshield wiping system, a disconnection threshold defined for ceasing operation of the windshield wiping system in an intermittent mode of operation, and a disconnection threshold defined for ceasing operation of the windshield wiping system in a continuous mode of operation. The apparatus includes a sensor apparatus and a circuit arrangement. The sensor apparatus which generates a signal the value of which varies based on the degree of liquid or dirt on the windshield. The sensor signal is then processed by a microprocessor. The thresholds are defined based on the sensor signal.

Abstract: The invention provides a speed controller which detects the period of an AC signal containing information of the rotational speed of a motor and controls the rotational speed based on the detected period value and a reference speed value. More particularly, the speed controller computes the amount of the deviation of the AC signal based on continuously detected period values and the reference speed value, and then stores the computed deviation amount in a memory as a correction value. Using the correction value stored in the memory, the speed controller corrects the deviation of the period, and thus, the speed of the rotation of the motor can be controlled with extremely high precision.

Abstract: A slow start motor control circuit for applications wherein extremely accurate speed control is required, such as, in a centrifugal blood separator application is disclosed. In a blood separator, the degree of separation of cellular components, such as red blood cells and platelets, from the blood plasma is a function of the rotational speed of the centrifuge and the spin time. The control circuit controls the spin time and the rotational speed of the drive motor by controlling the voltage applied to the motor. The control circuit allows the drive motor to start relatively slowly to avoid cell breakage which can contaminate the plasma. After the centrifuge attains its desired operational speed, the speed of the motor is regulated and is relatively uninfluenced by ambient temperature variations.