Abstract: An electrodynamic machine has a winding and a switching arrangement effectively dividing the winding into individually controllable portions. During a first operating condition, current flows through the entire winding in a manner controlled by the switching arrangement. In a second condition, the switching arrangement restricts current flow to only a portion of the winding. The second condition effectively reduces the inductive capacity of the winding.

Abstract: In an anti-crease operation incorporated after the program sections wash and spin to loosen laundry in the drum, the user should be offered the possibility of being able to actively influence this operation. For selecting the adjustable parameters for the duration and sequence of the anti-crease program the user is supported by a display and can depart upward or downward from predetermined values dependent on type or textile and loading after checking for compatibility. The detachment of the laundry ring at the inner wall of the drum can be monitored by measuring valid variables of state as a criterion for loosened and disentangled laundry at the beginning of the anti-crease operation in the reversing phases and comparing these with desired data which were determined in a short analysis section installed before the beginning of the actual wash program. As a result, errors in identifying a laundry ring can be largely avoided.

Abstract: A fan speed controlling circuit includes a temperature sensing circuit for transforming a temperature signal to a voltage signal, a reference voltage providing circuit for outputting a reference voltage, and a voltage amplifying and comparing circuit. The voltage amplifying and comparing circuit includes a negative terminal receiving the voltage signal from the temperature sensing circuit and a positive terminal receiving the reference voltage from the reference voltage providing circuit. A reactive circuit is connected to the voltage amplifying and comparing circuit. The reactive circuit produces a control signal according to a voltage signal output by the voltage amplifying and comparing circuit. The reactive circuit includes a driving component controlled by the control signal for providing a driving current to a fan.

Abstract: Disclosed herein are an apparatus and method for driving a compressor, which are capable of being suitably used for driving a refrigeration system such as a refrigerator with high efficiency and low noise. The compressor driving apparatus including a motor and a compressor driven by the motor includes an inverter which supplies power to the motor to drive the motor; a rotator position detector which detects the position of a rotator of the motor; and an inverter drive controller which includes at least one wave generator for generating an optimal driving wave according to an operation mode and a control mode of the motor, stores the generated optimal driving wave, and drives the inverter with the generated wave.

Abstract: A barrier movement operator includes an A.C. motor having a rotatable rotor connected to a barrier for movement thereof. A sensing apparatus generates motor signals representing an operational variable of the motor. The movement of the barrier is controlled by a controller, which responds to the motor signals by selectively stopping rotation of the rotor or reversing the rotation of the rotor. A power control arrangement provides energizing power to the motor by receiving AC power input substantially in the form of a sine wave and conducts portions of successive cycles of the sine wave of the received AC power to the motor to enhance the sensed operational variable to torque characteristic of the motor.

Abstract: A power hand tool includes a rotary adjustment knob for adjusting maximum output torque, which has a plurality of radial ribs, radial locating grooves alternatively arranged on the inner sidewall thereof, and a locating member for supporting the rotary adjustment knob in position, which has a mounting base coupled to a part inside the housing of the power hand tool and two locating portions located at two opposite sides of the mounting base. Each of the locating portions has a protrusion engaged with one of the radial locating grooves of the rotary adjustment knob.

Abstract: A method for controlling a driving tool having a power source, a driver, an actuator, a follower, and a control unit. The power source includes a motor and a flywheel that is driven by the motor. The actuator is configured to selectively move the follower to push the driver into frictional engagement with a surface of the flywheel. The control unit is configured to selectively activate the electric motor and the actuator. The control unit includes a speed sensor that is configured to sense a rotational speed of an element of the power source and produce a speed signal in response thereto. The method includes: directly determining a rotational speed of an element in the power source; controlling electrical power provided to the motor based on the rotational speed of the element in the power source to cause the flywheel to rotate at a predetermined speed; and actuating the actuator when a set of actuating criteria has been met, the set of actuating criteria not including a rotational speed of the element.

Abstract: A trailer jack system includes an electric linear actuator having an electric motor, a source of electric power, and a controller that supplies a first voltage to the electric motor when the electric linear actuator is loaded and a second voltage to the electric motor when the electric linear actuator is unloaded. The electric linear actuator also includes a cylindrically shaped housing, a leg coaxially extending and retracting from the housing, and a support foot at a free end of the leg. The controller supplies the first voltage to the electric motor when a motor current of the electric motor is below a predetermined threshold value and supplies the second voltage to the electric motor when the motor current is above the predetermined threshold value. Preferably, the first voltage is about 24 volts and the second voltage is about 12 volts.

Abstract: A system for reducing wheel sliding on a locomotive is provided for a locomotive including a plurality of axles. The system includes one or more speed inferring systems coupled to each axle to detect rotation of each axle and generate detection signals based upon detecting rotation of each axle. The detection signals include one of speed signals indicative of locomotive speed and non-rotating signals indicative of a non-rotating axle. More particularly, a main controller is coupled to each speed inferring system and is responsive to each detection signal. The main controller identifies non-rotating signals of the detection signals to initiate one or more alert signals of one or more respective non-rotating axles of the plurality of axles. Additionally, the main controller is coupled to an operator panel to alert a locomotive operator of an applied status of a locomotive parking brake in response to the alert signal.

Abstract: A motor speed control circuit which controls a rotational speed of a motor by controlling an amount of current flowing through a drive coil of the motor. The control circuit comprises a reference voltage circuit that generates a reference voltage corresponding to a speed-specifying signal inputted to specify the rotational speed of the motor; a clamp circuit that limits a level of the reference voltage generated by the reference voltage circuit; a comparator that has a speed voltage corresponding to an actual rotational speed of the motor and the reference voltage limited in level by the clamp circuit applied thereto and compares the two; and a control signal generator that generates and outputs a control signal for controlling the amount of current flowing through the drive coil based on the comparing result of the comparator.

Abstract: A system and method for controlling a rotational speed associated with a shaft or rotor of an electric motor comprises establishing a target rotational speed associated with a shaft or rotor of an electric motor. A sensor detects an actual rotational speed associated with the shaft or rotor of an electric motor. Speed error data is determined. The speed error defined as a difference between the target rotational speed and the actual rotational speed. A first duty cycle factor is determined based on the speed error data and a first gain constant. A second duty cycle factor is determined based on the speed error data and a second gain constant. Duty cycle input data is calculated for the electric motor based on a sum of the first duty cycle factor, the second duty cycle factor, and the target speed.

Abstract: A fan voltage regulation control device includes a voltage regulation control unit for providing the power to a heat-dispersing fan, wherein the voltage regulation control unit is connected to a temperature detecting element and a voltage detecting unit. The temperature detecting element may influence the output power from the control unit to the fan, and through the voltage detecting unit, an input current to the fan can be maintained for providing overload and overheated protections.

Abstract: A control circuit for a hard drive or sensorless DC spindle motor is provided. The control circuit includes a spindle driver generating a spindle motor control output. A spindle controller coupled to the spindle driver causes the spindle driver to vary the spindle motor control output during an inductive sense operation. An inductive sense system coupled to the spindle controller controls the operation of the inductive sense system, such as to turn the inductive sense system on when the spindle driver is off.

Abstract: An electric drive system includes a multi-phase electric machine, multiple electrical power output stages, and devices for controlling and/or regulating the electric machine, which are connected to the electrical power output stages. At least two control units are provided for control and/or regulation, at least one power output stage group being assigned to each control unit.

Abstract: A device for redundant speed monitoring of a synchronous motor, which is sine-commutated without the use of sensors and which has a permanently magnetically excited rotor, has a first control unit, a drive output stage, a plurality of drive phases, and a second control unit for monitoring an electrical value of at least one of the drive phases and connected to the drive output stage for turning off the drive output stage when an improper speed state is detected.

Abstract: Information indicative of the placement of spindle motor components may be obtained and used to provide a correction to one or more BEMF-derived attributes used to control the spindle speed. In some implementations, first and second signals indicative of BEMF of different stator windings may be used to determine a speed-related characteristic. The speed related characteristic may be used to determine an error amount, which may be used to determine a correction factor to control the speed of the spindle motor.

Abstract: A barrier operator comprises a first measuring apparatus for measuring a current used by a direct current (dc) motor to move a barrier and a second measuring apparatus for measuring a generated voltage of the dc motor. A controller is coupled to the first measuring apparatus and the second measuring apparatus. The controller is programmed to calculate a torque of the dc motor by using the current and to determine when an obstruction exists in the path of the barrier based upon the calculated torque.

Abstract: A system and method for controlling a rotational speed associated with a shaft or rotor of an electric motor comprises establishing a target rotational speed associated with a shaft or rotor of an electric motor. A sensor detects an actual rotational speed associated with the shaft or rotor of an electric motor. Speed error data is determined. The speed error defined as a difference between the target rotational speed and the actual rotational speed. A first duty cycle factor is determined based on the speed error data and a first gain constant. A second duty cycle factor is determined based on the speed error data and a second gain constant. Duty cycle input data is calculated for the electric motor based on a sum of the first duty cycle factor, the second duty cycle factor, and the target speed.

Abstract: A driving circuit has a driving circuit module, a rotation rate detecting module and a rotation status detecting module. The driving circuit module is used to drive an AC fan motor and has at least a driving IC having two controlling outputs and a rotation status detecting output. The rotation rate detecting module has a transistor and an photo coupler. The transistor is connected to one of the two controlling outputs of the driving IC. The photo coupler is connected to the transistor and outputs a rotation rate signal to compute the rotation rate of the AC fan motor. The rotation status detecting module has an photo coupler connected to the rotation status detecting output of the driving IC and outputting a rotation status signal to determine whether the AC fan motor operates normally.

Abstract: A fan voltage regulation control device includes a voltage regulation control unit for providing the power to a heat-dispersing fan, wherein the voltage regulation control unit is connected to a temperature detecting element and a voltage detecting unit. The temperature detecting element may influence the output power from the control unit to the fan, and through the voltage detecting unit, an input current to the fan can be maintained for providing overload and overheated protections.

Abstract: A method for controlling a fan is provided for adjusting the rotational speed of a fan. The method includes adjusting the rotational speed of the fan from a first mode value to a range of rotational speed variation, wherein the upper bound of the range of rotational speed variation is a second mode value plus a first variation value, and the lower bound of the range of rotational speed variation is the second mode value minus a second variation value; and adjusting the rotational speed of the fan in the range of rotational speed variation during a time period. Thus, a user will not consider the sound from the fan as a noise.

Abstract: A universal driving apparatus of a computer system, including a receptacle, a power switch, an integrator and a comparator, is provided to identify and drive a first fan and a second fan. The receptacle connects to the first fan or the second fan for electricity supply and system control. The integrator integrates speed signals of the first fan and the second fan to output an integrated-speed voltage. The comparator compares the integrated-speed voltage and a comparative voltage to output a comparative signal. Accordingly, the computer system uses the comparative signal to identify the fan type and actuate the first fan or the second fan correctly.

Abstract: A driving apparatus and a driving method for a single phase motor utilizes a driving transistor unit, and an auxiliary driving transistor unit to provide two driving currents with the same direction as the single phase coil. Next, a control unit is used to control the conducting and shutting down of the driving transistor unit and the auxiliary driving transistor unit according to the location of the rotating device of the single phase motor. Thereby, the driving current on the single phase coil recirculates to reduce the vibration and noise of the single phase motor, and prevent the problem of the single phase motor not turning on.

Abstract: A complex signal processing system for multiple fans is used to control the rotation of a first fan and a second fan. The speed signals of the first fan and the second fan are processed through an XOR operation to obtain a complex speed signal. In response to the complex speed signal, the speed and the operational status of the first fan and the second fan can be evaluated.

Abstract: A method of making an optical filter wheel of a device synchronizable with an internal, rotatable virtual reference wheel, created in a memory of a motor controller of the device, is disclosed. The method includes a single trigger event that initializes rotation of the virtual reference wheel. The controller determines the orientation of an optical filter wheel of the device and maintains an ongoing representation of said orientation over time. The controller controls the motor, which causes the filter wheel to become coincident with the virtual reference wheel after the trigger event. A self-contained light fixture is also disclosed, which includes an optical filter wheel driven by an electric motor that is synchronizable with an internal, rotatable virtual reference wheel of the fixture. The method and light fixture permits optical filter wheels of multiple light fixtures, which may be identical, to synchronize with one another.

Abstract: A vehicle which uses an internal combustion engine and a motor generator as drive sources is provided with a battery disposed under a seat and a fan for cooling the battery. Power is exchanged between the motor generator and battery via an inverter. An electronic control unit estimates the level of background noise which is noise other than the operating sound of the fan in the passenger compartment based on the vehicle speed and rotation speed, etc., of the internal combustion engine. Then, the electronic control unit calculates an operation command value for the fan based on the estimated background noise level and temperature level of the battery and controls the rotation speed of the fan through the operation command value. As a result, it is possible to effectively cool the battery while reducing sensible noise caused by the operating sound of the fan.

Abstract: An apparatus including a power source, a system board, coupled to the power source and disposed within the computer, on which an electrical component, which controls operations of the computer, is installed, a heat sink including heat transfer surfaces which are configured to contact the electrical component and to thereby remove heat therefrom, a fan reversing control card coupled to the system board and configured to generate normal and reverse cycle rotation signals in predetermined intervals, and a fan coupled to the fan reversing control card and configured to receive the rotation signals and to thereby operate in normal and reverse cycles in which the fan rotates in first and second directions, respectively. The fan is disposed proximate to the heat transfer surfaces such that the first and second directional rotations of the fan generate air flows in first and second directions with respect to the heat transfer surfaces, respectively.

Abstract: A device controller system incorporates an inexpensive Hall element to detect motion of a brushless DC motor. A magnet, which is part of a motor rotor, passes by the Hall element producing a Hall voltage each rotation. The Hall voltage is coupled through an interface port to a comparator within a process controller. A microprocessor within the process controller calculates a control response based on a comparator output signal. The interface port is rapidly configured to provide signals produced from the control response as output to device drivers on the same input-output pins that receive the Hall voltage. The device drivers produce a current through fan coils producing an update in the magnetic field of each motor phase which updates the speed of the fan according to programming within the process controller. Rapid configuring and reconfiguring of the interface port allows all necessary components of the controller system to be used with a single rotational commutation cycle.

Abstract: Disk drives such as hard (magnetic) disk drives take a certain amount of time to initialize and “spin up” to the operational rotational speed of the disk or disks, thereby creating a time lapse from power up to when data can first be read from or written to the disk drive. This time lapse can be reduced, whereby some tasks conventionally done sequentially instead are performed in parallel. For example, the motor controller that controls the spindle motor can perform its portion of the initialization beginning at the same time that the remaining electronic components, including the hard disk controller, begin their initialization process including downloading firmware. Additionally, other portions of the initialization process typically performed by firmware can be performed by dedicated circuitry or a bootstrap program in the motor controller and hard disk controller, thereby not requiring the relatively slow downloading of system firmware.

Abstract: A fan speed controlling system for a power supply comprises a fan having two pins and a voltage comparator connected to the fan. The voltage comparator comprises a first input terminal for receiving a first reference voltage controlled by an external temperature of the power supply and a second input terminal for receiving a second reference voltage controlled by an interior temperature of the power supply. The voltage comparator outputs a higher voltage of the first and second reference voltage to the fan via the two pins.

Abstract: A fan motor speed control circuit and a voltage-regulating module thereof are disclosed. The fan motor speed control circuit includes the voltage-regulating module and a driving module electrically connected to the voltage-regulating module. The driving module includes a pulse signal generating unit, a speed control unit, and a drive unit. The speed control unit compares a high frequency pulse signal generated by the pulse signal generating unit with a variable reference voltage signal output by the voltage-regulating module, and then outputs a control signal to the drive unit to proceed the speed control of the fan motor. In application, the voltage-regulating module and the driving module are electrically connected to a voltage source in parallel.

Abstract: A motor control method and device. The motor control device includes a programmable integrated circuit (IC) receiving a phase signal, the phase of which is consistent with the rotation phase of a coil of the motor. The programmable IC generates a duty-cycle signal in accordance with the period of the phase signal. The duty-cycle signal comprises a rising segment and a falling segment and when the phase signal changes phase, the duty cycle represented by the duty-cycle signal is a first duty cycle, allowing the input power of the motor remain at a minimum. The duty-cycle signal is input to the coil, controlling the coil on and off and, thereby rotating the motor.

Abstract: A direct current motor controlling method includes a mean for transforming a duty signal to computed value by a microprocessor unit. The microprocessor unit computes the computed value and then produces a target value by executing a dichotomy method, a rotation method and a transformed function, capable of reducing executing time and executing load of the microprocessor unit and saving memory space. The microprocessor unit sends a frequency signal to a driving circuit unit according to the target value. The driving circuit unit receives the frequency signal and then provides a driving voltage to a power switch. The power switch provides a voltage to a direct current motor or not according to the driving voltage for controlling output performance of the direct current motor.

Abstract: A motor control device includes a recording module and a controlling module. The recording module has a revolution speed table recording a plurality of predetermined revolution speed values. The controlling module receives a reference revolution speed control signal and measures the reference revolution speed control signal to correspondingly generate a reference measuring value. The recording module records the reference measuring value corresponding to one of the predetermined revolution speed values in the revolution speed table.

Abstract: A controlling apparatus of a BLDC motor and a controlling method thereof. A replacement of a motor with another motor having the different number of poles is automatically detected due to a variation of a load current of the BLDC motor, and rotation speed estimation information of the motor is automatically modified according to the number of poles of the replaced motor to accurately estimate an actual rotation speed of the motor.

Abstract: A motor control device that controls a permanent-magnet synchronous motor has: a magnetic flux controller that derives, as a specified excitation current value, a specified current value corresponding to a d-axis component of a current passing through an armature winding; and a current controller that controls, based on the specified excitation current value, the current passing through the armature winding. The magnetic flux controller makes the specified excitation current value vary periodically, based on an estimated or detected rotor position, in a current range in which the magnetic flux produced by the permanent magnet is weakened, and changes the specified excitation current value according to a rotation speed of the rotor.

Abstract: A rotor position detection circuit detects a position of a rotor in a motor from a detection signal of an induced voltage generated in a stator coil. The circuit includes: a first low pass filter having a first reference potential for filtering the detection signal; a comparator for comparing an output signal from the first low pass filter with a predetermined reference voltage and for outputting a rotation position signal; and a second low pass filter having a second reference potential for filtering a virtual neutral point potential of the motor. The first reference potential is the filtered virtual neutral point potential, and the second reference potential is a ground.

Abstract: A method and apparatus for managing power demand of a motor in a cyclic load system having a rotational mass is provided. Flat power draw is achieved through continuous manipulation of the motor torque as a function of feedback velocity while using the rotational mass of the cyclic load as a means to store/retrieve energy. Alternatively, reduced variation of power draw is accomplished through continuous manipulation of motor velocity as a function of feedback torque. The methods and apparatus are used in systems where zero or reduced power demand variation is either required or desired, such as in generator powered applications.

Abstract: Control over velocity of a model train may be determined based upon the speed of rotation of a control knob. A processor receives electronic pulses indicating rotation of the knob beyond a predetermined increment of angular distance. The processor calculates the amount of power ultimately conveyed to the model train based not only upon the number of pulses received, but also upon the elapsed time between these pulses. The shorter the elapsed time between pulses, the greater the change in power communicated to the train. Initially, a user can rapidly rotate the knob to attain coarse control over a wide range of velocities, and then rotate the knob more slowly to achieve fine-grained control over the coarse velocity. Utilizing the control scheme in accordance with embodiments of the present invention, in a compact and uninterrupted physical motion, a user can rapidly exercise both coarse and fine control over velocity of a model train.

Abstract: An apparatus for processing a signal output by an encoder, including a frequency multiplication unit to repeatedly multiply each of frequencies of two sinusoidal signals with a phase difference of approximately 90 degrees by a predetermined number a predetermined number of times; a converter to convert each pair of the two frequency-multiplied sinusoidal signals into square wave signals; and a processor to receive the square wave signals and count a number of rising and/or falling edges of the square wave signals in order to determine and control a position of an object to be controlled.

Abstract: An apparatus and method for controlling high speed operation of a motor for controlling high speed operation of a motor by estimating the position and the speed of the rotor of a synchronous motor without a PI regulator to eliminate the users' inconvenience and to secure the reliability of the control of a rotor's position and speed of a synchronous motor, which includes: a reference frame transformer that receives triangular coordinate voltages and currents and converts them to static coordinate voltages and currents, a flux observer that receives the converted static coordinate voltages and currents and observes and outputs the flux of the stator, a position estimator that receives the converted static coordinate currents and the observed flux of the stator and estimates and outputs the position of the rotor, and a speed estimator that receives the estimated position of the rotor and estimates and outputs the speed of the rotor.

Abstract: An air fan rotation speed control method and a structure thereof aim to provide an automatic control mode and a manual control mode at the same time to control rotation speed regulation of an air fan to achieve instant heat dissipation for an environment and reduce temperature rising of the environment efficiently. The present invention has a rotation speed determination mechanism that adopts the higher rotation speed request at a higher priority to regulate the rotation speed of the air fan in either control mode. Hence the temperature of the environment can be reduced at the higher rotation speed.

Abstract: This invention relates to a method of speed control selection for an electronically commutated motor comprising the following steps: (a) a motor controller receives an input signal T from a speed control selection circuit; (b) the motor controller retrieves a corresponding value for a motor running speed S from a comparison list correlating the input signal with the motor running speed, which list has been stored in the motor controller in advance, by searching the comparison list for the input signal T; and (c) the motor controller controlling a motor M to run at the motor running speed S, achieving the purpose of the speed selection. This method allows for from 2 to 256 speed choices with a single signal wire only. Such a circuit structure has the advantages of high integration, simple wiring, low cost, good performances, low failure rate, higher number of optional speeds, and simpler and more practical control.

Abstract: A hand-held power tool has an electric drive motor having a drive shaft and a tool connected to the drive shaft and rotatably driven by the drive shaft. The drive motor has a control device that has correlated therewith at least a first operating curve and a second operating curve. The control device operates the electric drive motor in idle according to the first operating curve and operates the electric drive motor under load according to the second operating curve. The first operating curve covers the low power range at low speed and the second operating curve covers a large power range at high speed.

Abstract: A system for controlling a roller shade having a roller tube windingly receiving a shade fabric varies roller tube rotational speed for constant linear shade speed. The desired linear shade speed, roller tube diameter and shade fabric thickness and length are stored in a memory for use by a microprocessor. Preferably, the roller tube rotational speed is varied by the microprocessor depending on shade position determined by signals from Hall effect sensors. The microprocessor maintains a counter number that is increased or decreased depending on direction of rotation. Based on the counter number, the microprocessor determines shade position and a corrected rotational speed for the desired linear shade speed. Preferably, the microprocessor controls roller tube rotational speed using a pulse width modulated signal. The system may be used to control first and second roller shades having roller tubes of differing diameters or shade fabrics of varying thicknesses.

Abstract: A multi-fan apparatus and method incorporates mutual active cancellation of fan noise and/or vibrations. The multi-fan apparatus includes two or more fans circuits, each comprising a fan, a fan speed controller and a separate tachometer, and a fan phase controller. The phase controller is connected to at least one fan speed controller and to each tachometer. Each fan's speed is independently and dynamically maintained at the same set speed by the fan speed controllers using an independent control loops. A noise and/or vibration cancellation phase difference between fans is determined in order to achieve destructive interference of pressure waves and, thus, noise and/or vibration reduction, in pre-determined region of a system incorporating the multi-fan apparatus. The phase controller establishes and maintains this cancellation phase difference between the fans based upon feedback from the tachometers.

Abstract: A control unit for driving a regulating transistor (2) of a fan arrangement, in which the regulating transistor (2) is connected in series with an electronically commutated fan (1), having control means (5, 6, R1, R2) for the analog driving of the regulating transistor (2) with a control signal (Ucontrol) in a manner dependent on a control input voltage (Uin). The control unit comprises compensation means (R3, R4) for influencing the control signal (Ucontrol) in a manner dependent on an AC voltage component (UAC) of an operating voltage (UB) of the fan arrangement, so that the AC voltage component (UAC) of the operating voltage (UB) is completely or partially compensated for in a voltage across the fan (1).

Abstract: A motor speed control system includes a pulse outputting device capable of outputting a pulse each time a motor rotates, a pulse interval determining device capable of determining a pulse interval between the pulses outputted, and a comparative value calculating device capable of obtaining a comparative value as the product of a first value and a second value. The first value can correspond to the pulse interval determined, and the second value can correspond to a set rotational speed of the motor. The system can further include a set value calculating device capable of obtaining a set value as the product of the second value and a third value and a controller capable of controlling a supply of power to the motor such that a difference between the set value and the comparative value decreases.

Abstract: A system and method for bi-directional communication between a system controller and a fan controller: The system operates in two modes and there are two communication paths between the system controller and the fan controller. The first communication path provides a PWM signal the frequency of which indicates the mode in which the system is operating. During the first mode, the duty cycle of the PWM signal on the first signal path indicates the desired fan speed. In the first mode, the second communication path carries a conventional tachometer signal. In the second mode the second communication path operates as a bi-directional communications signal path between said system controller and said fan controller.

Abstract: A method for attenuating switching noise from back electromotive force (EMF) observations in a motor is described. The motor is controlled by pulse width modulation (PWM) signals provided at a PWM frequency. The method comprises sampling back EMF observed in the motor at a sampling frequency at least two times greater than the PWM frequency to obtain over-sampled back EMF readings; and filtering the over-sampled back EMF readings to remove switching noise and obtain cleaned back EMF observations. A system implementing the method is also described.