Abstract: A power tool includes a direct current (DC) unit, a motor, a driving circuit, a capacitor circuit, and a control unit. The capacitor circuit includes a switching element and a capacitor. The control unit drives the switching element to realize the control of charging or discharging of the capacitor. The capacitor circuit is connected between the DC unit and the driving circuit, and can buffer the impact on the power supply side of the power tool, making the power tool compact in structure.

Abstract: A method and system for correcting for the inertial error of a transducer as a function of frequency by applying a delay to a leading signal of the transducer to provide phase compensation.

Abstract: Computer system fans having fixed operating states corresponding to discreet operating speeds may be controlled by collecting temperature information upstream or downstream of the fans and commanding the fans to switch between the fixed operating states based on the temperature information at a frequency sufficient to controllably achieve speeds between the discreet operating speeds.

Abstract: The present invention discloses a controller and a method for improving motor driving efficiency. According to the present invention, multiple control parameters are inputted to the controller so that the controller can adjust timings of PWM driving signals for driving the motor to advance or delay the turned-ON or turned-OFF points, whereby the motor is driven efficiently.

Abstract: The invention concerns an electronic module for a motor vehicle, in particular a fan regulator (4?) with a control input (S) for a signal, in particular a pulse width modulated signal, transmitted via a signal line (3). The electronic module is designed for the generation of an essentially constant potential (Ubias, Ubias?UBE) at the control input (S), which preferably is designed as a current-controlled, low resistance control input. The invention also concerns an arrangement (1?) for the transmission of a preferably pulse width modulated signal with: a control device (2?) for the generation of the signal, a signal line for the transmission of the signal, and an electronic module as described above.

Abstract: An electric fan device includes a motor which drives an electric fan for a vehicle, a control switch which controls a motor current supplied to the motor, and a control unit which controls an on/off operation of the control switch with pulse-width modulation. The control unit outputs a PWM pulse having a main PWM pulse and a vibration reducing pulse within one cycle to the control switch.

Abstract: A motor system with reduced common-mode noise includes an AC power, a first transformer unit electrically connected to the AC power and providing a first DC power, and a second transformer unit electrically connected to the AC power and providing a second DC power. The first DC power is supplied to a motor driving section of the motor system, and the second DC power is supplied to a motor controlling section of the motor system. Therefore, a common-mode noise from the transformer winding for the motor driving section can be prevented from coupling to the transformer winding for the motor controlling section. Moreover, a safe stop signal is applied to turn down a PWM IC for power through a photo coupler or a relay. Therefore, the first transformer unit stops supplying current to the motor driving section of the motor system to enhance safe stop function for the motor system.

Abstract: A motor control circuit includes a pulse width modulation (PWM) signal generating circuit, a driving circuit and a waveform-shaping circuit connected between the PWM signal generating circuit and the driving circuit. The PWM signal generating circuit generates a square wave with a sequence of alternating on-time and off-time. The waveform-shaping circuit adjusts the rise-time and the fall-time of the square wave to be both within a range of 5% to 15% of the square wave period, and the driving circuit outputs a driving signal to a fan motor according to the adjusted square wave.

Abstract: The invention concerns an electronic module for a motor vehicle, in particular a fan regulator (4?) with a control input (S) for a signal, in particular a pulse width modulated signal, transmitted via a signal line (3). The electronic module is designed for the generation of an essentially constant potential (Ubias, Ubias?UBE) at the control input (S), which preferably is designed as a current-controlled, low resistance control input. The invention also concerns an arrangement (1?) for the transmission of a preferably pulse width modulated signal with: a control device (2?) for the generation of the signal, a signal line for the transmission of the signal, and an electronic module as described above.

Abstract: The disclosed embodiments relate to circuits that produce synchronized output signals. More specifically, there is provided a synchronization circuit adapted to receive an input signal, the synchronization circuit comprising a delay monitor adapted to produce a delayed input signal, a counter adapted to determine a difference between the input signal and the delayed input signal and produce a coarse timing signal in response thereto, a circuit adapted to produce a fine timing signal based on the input signal, and a circuit adapted to combine the coarse timing signal and the fine timing signal to produce an output signal.

Abstract: Apparatus for reconstructing the phase currents of a multiphase load driven by a multiphase inverter fed by a DC link and controlled by a PWM controller, the apparatus including a sensor in the DC link, first and second sampling arrangements for sampling the current in the DC link by obtaining an output from said sensor, the first sampling arrangement obtaining a first sample of the current in the DC link during a first time period corresponding to a first switching pattern of said multiphase inverter and storing said first sample; the second sampling arrangement obtaining a second sample of the current in the DC link during a second time period after said first time period and corresponding to a second switching pattern of said multiphase inverter and storing said second sample; an A/D converter for converting said first sample to a digital signal during a time period after said first time period and for converting said second sample to a digital signal during a following third time period.

Abstract: An electric fan device includes a motor which drives an electric fan for a vehicle, a control switch which controls a motor current supplied to the motor, and a control unit which controls an on/off operation of the control switch with pulse-width modulation. The control unit outputs a PWM pulse having a main PWM pulse and a vibration reducing pulse within one cycle to the control switch.

Abstract: A motor controller is provided with: an estimated temperature calculating means that calculates an estimated temperature of a motor; and a control unit that can perform a driving control of the motor only when the estimated temperature is not larger than a predetermined value. A mode switching means switches the control unit and the estimated temperature calculating means between in a normal operation mode in which they can drive the motor and in a sleep mode in which electric power consumption thereof is smaller than in the normal operation mode in accordance with a predetermined condition while the motor is stationary. An activating means activates the estimated temperature calculating means in the sleep mode for a predetermined active time every time a predetermined sleep time is elapsed.

Abstract: A controller is operable in one of a plurality of operational modes, which include an estimated temperature computation performing mode for performing computing of an estimated temperature of the motor and an estimated temperature computation non-performing mode for stopping the computing of the estimated temperature of the motor. An operational mode of the controller is changed from the estimated temperature computation performing mode to the estimated temperature computation non-performing mode according to a predetermined condition in a stopped state of the motor.

Abstract: A control and motor arrangement in accordance with the present invention includes a motor configured to generate a locomotive force for propelling the model train. The control and motor arragement further includes a command control interface configured to receive commands from a command control unit wherein the commands correspond to a desired speed. The control and motor arrangement still further includes a plurality of detectors configured to detect speed information of the motor, and a process control arrangement configured to receive the speed information from the sensors. The process control arrangement is further configured and arranged to generate a plurality of motor control signals based on the speed information for controlling the speed of said motor. The control and motor arrangement yet still further includes a motor control arrangement configured to cause power to be applied to the motor at different times in response to the motor control signals.

Abstract: A motor control circuit includes a pulse width modulation (PWM) signal generating circuit, a driving circuit and a waveform-shaping circuit connected between the PWM signal generating circuit and the driving circuit. The PWM signal generating circuit generates a square wave with a sequence of alternating on-time and off-time. The waveform-shaping circuit adjusts the rise-time and the fall-time of the square wave to be both within a range of 5% to 15% of the square wave period, and the driving circuit outputs a driving signal to a fan motor according to the adjusted square wave.

Abstract: A system and method for reducing fan noise by controlling the drive current to the fan motor. In one embodiment the system approximates a linear drive using a number of transistors in parallel and sequentially deploying the transistors. In another embodiment, a scheme is used to activate and deactivate transistors in discrete steps thereby achieving the benefits of the linear controller topology.

Abstract: A fan speed control circuit includes a pulse width modulation (PWM) signal generating circuit, a driving circuit and a phase compensation unit. The PWM signal generating circuit generates a PWM control signal with a sequence of alternating on-time and off-time, and the driving circuit outputs a driving signal according to the PWM control signal to a fan motor. The phase compensation unit is connected to the fan motor for delaying or advancing the PWM control signal by a phase angle to synchronize the acting period of the back electromotive force formed by the magnetic flux variation with the off-time of the PWM control signal.

Abstract: A method for reducing line-conducted interference in a pulse width modulated triggering system of an electric motor, a triggering pulse width modulation signal having, in one clock cycle, one or more signal edges between a first signal level and a second signal level, the pulse width modulation signal being generated in such a way that at least one of the signal edges has a first segment having a first edge slope and a second segment having a second edge slope, the absolute value of the first edge slope being less than the absolute value of the second edge slope.

Abstract: The present invention encompasses a high efficiency pulse width modulator comprising: a variable duty cycle oscillator for receiving an input signal and providing a low level switching signal; a source voltage differentiation dependant positive switching signal circuit for receiving the low level switching signal, a stable reference signal, a sample of a positive supply voltage signal, and an error signal and the providing a positive supply switching signal and a reference signal; a positive supply switching circuit for receiving the positive supply switching signal and providing an output signal to an inductive load; an output voltage dependant negative supply switching signal circuit for receiving the output signal and a negative supply voltage signal and providing a negative supply switching signal; a negative supply switching circuit for receiving the negative supply switching signal and providing clamping of the inductive load to the negative supply, an output sourced charge pump for receiving the output

Abstract: A motor driving system includes a power supply unit, a voltage-stabilizing unit, a signal-generating unit, a comparing unit, and a control unit. The power supply unit provides an input supply voltage to each other unit in the system. The voltage-stabilizing unit includes a voltage-stabilizing element and produces a constant voltage. The signal-generating unit generates an input signal, which varies with high and low levels of the input supply voltage. The comparing unit compares the constant voltage with the input signal to generate a comparison signal. The control unit controls a motor's rotating speed according to the comparison signal generated by the comparing unit. When the input supply voltage is low, a lowest rotating speed is set for the control unit to control the rotating of the motor.

Abstract: A method of operating a cooling fan in a cooling system for a vehicle includes determining a required speed of the cooling fan. First and second signals are provided to a motor controller operatively connected to a motor having a rotatable portion connected to the cooling fan. The first signal coarsely controls a rotational speed of the motor by adjusting a voltage level provided to the motor and the second signal finely controls the rotational speed of the motor by pulse width modulation so that the cooling fan rotates at the required speed.

Abstract: A speed control circuit for a brushless dc motor includes a motor drive circuit, a drive member and a PWM control circuit. The motor drive circuit includes at least one coil and at least one transistor serially connected to the coil. The drive member is provided with a plurality of output terminals adapted to output a driving signal to the transistor of the motor drive circuit. The PWM control circuit is in connection between the transistor of the motor drive circuit and the output terminal of the drive member, thereby turning the transistor on or off.

Abstract: A multi-mode motor controller architecture includes a motor, an integrated circuit controller, and an integrated circuit driver circuit. The integrated circuit controller includes a pulse generator, a DAC, an ADC, and a digital compensator circuit. The integrated circuit driver circuit is in communication with the controller and includes an error amplifier, first and second output amplifiers for driving the motor, and a sense amplifier. The motor controller architecture is configurable to operate in a linear mode, a pulsed mode, or a switchable linear/pulsed mode. The controller architecture can be implemented with external compensation circuitry, such as a resistor-capacitor circuit, or with the digital compensation circuitry located within the controller integrated circuit.

Abstract: A speed-control drive circuit for a D.C. brushless fan motor comprises a pulse width modulation input end for receiving a pulse width modulation signal and a motor winding drive circuit. The motor winding drive circuit and the pulse width modulation input end are connected to a set of motor winding. The pulse width modulation signal controls the motor winding drive circuit to cause excitation/unexcitation of the set of motor winding and to alternately change a direction of current such that the set of motor winding adjusts a speed of the fan motor in response to excitation of the set of motor winding responsive to the pulse width modulation signal. The speed of said fan motor increases when an operational period of the pulse width modulation signal increases, and the speed of the fan motor decreases when the operational period of the pulse width modulation signal decreases.

Abstract: A motor control circuit for use in a motor circuit includes a varying duty cycle pulse width modulation circuit and a switch. The varying duty cycle pulse width modulation circuit is operable to generate a PWM signal having a varying duty cycle, wherein an average of said varying duty cycle corresponds to a desired motor speed. The switch has a control input operably coupled to the pulse width modulation circuit to receive the PWM signal therefrom. The switch further includes first and second terminals, the first terminal adapted to be coupled to a coil of the motor circuit, the switch operable to selectively electrically connect and disconnect the first and second terminals based in part on the PWM signal received by the control input.

Abstract: A pulse width modulation circuit (10) for a motor controller is operated by generating an offset voltage and adding the offset voltage to a carrier timing signal to form an offset carrier timing signal. The operation of each of the phases of the motor is controlled as a function of the offset carrier signal.

Abstract: A speed control circuit of a direct current motor comprises a switching regulator IC 10. The switching regulator IC 10 is composed of a reference voltage generator 12 which generates a reference voltage of 5V, a first operational amplifier OP1, a second operational amplifier OP2, a third operational amplifier OP3, a triangular wave generator 14 which generates a triangular wave, and a transistor TR1. The speed control circuit is constructed using a general switching regulator IC; therefore, it is possible to cheaply and readily manufacture the speed control circuit of the direct current motor.

Abstract: A hand-off state determination section 73 estimates torque Th exerted on the steering handle by a driver. When the steering handle is in the hand-off state in which the torque is small, switching is effected to the side of compensator 75 having smaller gains set, so as to stabilize a steering control system.

Abstract: A control device for a DC motor driving a diaphragm pump including a pulse generating integral circuit and a variable voltage setting integral circuit. The variable voltage setting integral circuit sets a pulse-base voltage at a level such that the DC motor is not rotated when no pulse is applied, thereby a high voltage overshoot generated at the rising and the falling point of an electrical pulse is restricted. Discharge of the diaphragm pump is accurately regulated by means of modifying frequency, voltage, and duty ratio of the pulse.

Abstract: A method and apparatus for substantially reducing tonal noise and or vibration generated by a rotating machine. The power supplied to the rotating machine or motor drive signal is modulated as a function of time so that the shaft rate of the rotating machine is varied as a function of time. The motor drive signal or power signal can be modulated in an alternating current (AC) machine wherein the shaft rate is related to the power line frequency, as well as a direct current (DC) machine wherein the shaft rate is related to the DC level applied, to alter the shaft rate as a function of time. Such drive power modulation causes the drive signal energy to spread into new frequencies. As a result, the radiated tonal components are spread out such that the strength of the rotating machine's tonal radiation is substantially reduced. In addition, "beating" effects related to the operation of multiple machines can be reduced.

Abstract: An energy management system for optimizing low power and short term high power states of a power supply system. A significant feature of the present invention relates to a design of a power supply apparatus based on internal resistances of the power supply components. In an exemplary embodiment, the power supply supplies power for driving a load. The power supply includes a power source having a first internal resistance and includes a capacitor connected in parallel with the power supply and having a second internal resistance. The first internal resistance and the second internal resistance have a predetermined relationship.

Abstract: It is an object of the present invention to provide a steering control system which can be used with a plurality of control modes, thereby reducing the cost. A first control unit of an electric power-steering system detects a reference current i.sub.REF on the basis of a steering torque T detected by a steering torque detecting device S.sub.2 ; searches a gain K.sub.1 on the basis of a vehicle speed v detected by a vehicle speed detecting device, and carries out a feedback control, so that an actual current i of an electric motor detected by a current detecting device is equal to K.sub.1 .times.i.sub.REF. A second control unit added to the first control unit changes the characteristic of the electric power-steering system by changing the steering torque T and the vehicle speed v, to output the changed steering torque T and vehicle speed v to the first control unit.

Abstract: A method for controlling the operation of a brushless DC fan for cooling heat generating components of a system is provided. The method includes providing a system temperature signal indicative of a system temperature and providing an intelligent shutdown enable signal. The system temperature signal is compared with a shutdown temperature signal if the intelligent shutdown enable signal has a first value. The shutdown temperature signal is representative of a shutdown temperature value. The fan is operated at a generally temperature proportional speed after comparing the system temperature signal with the shutdown temperature signal if the system temperature as indicated by the system temperature signal is greater than the shutdown temperature value as indicated by the shutdown temperature signal.

Abstract: An arrangement is disclosed for controlling fan motors in fan-powered terminal units which permit the air flow of the terminal units to be factory preset and reset using a voltmeter. The fan motor is responsive to the pulse width of pulses of a pulse width modulated signal to provide an air flow which is proportional to the pulse width. By adjusting the pulse width, the air flow may be set as desired. A pulse width modulated signal having pulses with a set amplitude and frequency is generated. The dc voltage of the pulse width modulated signal is measured using a voltmeter. As the pulses have a set amplitude and frequency, the pulse width of the pulses may be adjusted by controlling the dc voltage of the pulse width modulated signal. The fan motor is programmed to deliver the set air flow over a range of static pressures.

Abstract: A method for reducing power supply current surges and power supply voltage noise in an electric motor control system. The method limits the rate of change of power to the motor. The rate of change of power is limited by microprocessor firmware. Use of firmware reduces the size and weight requirements of motor control hardware and power supply filtering hardware.

Abstract: An impact wrench having a speed limiting control circuit to allow an operator of the wrench to controllably limit the maximum speed of the wrench to a predetermined value when a trigger thereof is fully engaged. The impact wrench includes a manually adjustable speed limiting control protruding from an outer surface of the impact wrench which is conveniently manually adjustable. The speed limiting control is coupled to the wiper arm of a speed limiting potentiometer which is electrically coupled to a speed control circuit within the impact wrench. The speed limiting potentiometer limits the maximum speed of the motor of the impact wrench (and thus the maximum torque which can be generated by the impact wrench 10) to an operator selected percentage of the maximum motor speed which would otherwise be produced when the trigger is fully engaged.

Abstract: A speed control circuit for a ventilation fan of an electronic device, such as a laser printer, adaptively varies a speed of the ventilation fan depending upon an internal temperature of the device. The speed control circuit has a temperature sensing circuit for generating a voltage depending upon the temperature, a triangular wave generator for generating a triangular wave signal having fixed period, a pulse width modulator for comparing the triangular wave signal with the voltage generated by the temperature sensing circuit and generating pulse-width modulated pulses, and a driving circuit for controlling the speed of the ventilation fan in response to the pulse-width modulated pulses so that the speed of the ventilation fan will be increased in response to an increasing temperature, for example.

Abstract: An electrical circuit and method for generating a continuous train of width modulated pulses. A square wave is generated and a delay circuit provides a delayed analog of the square wave. A controllable duration one-shot multivibrator generates a modulating pulse having a duration proportional to the sum of the absolute value of the modulating signal and a constant offset. The constant offset is chosen so that, in the absence of a modulating signal, the offset provides the largest control signal to the one-shot multivibrator which causes an output modulating pulse from the multivibrator equal in duration to the minimum duration which the multivibrator intrinsically is capable of obtaining. The polarity of the modulating signal is detected, a logical OR operation is performed upon the delayed square wave and the modulating pulse and an EXCLUSIVE OR operation is performed upon the combination of the result of the OR operation and the polarity detector output logic level.

Abstract: A motor-driven power steering apparatus and method for a vehicle are able to avoid frequent on-off operations of an electromagnetic clutch 14 as much as possible, which connects or disconnects a motor 13 with or from a steering system, thus improving the durability of the clutch 14 and suppressing the generation of undesirable noise and shocks upon connection and disconnection of the clutch 14. A clutch controller 191 controls a clutch current Ic supplied to the clutch 14 based on the vehicle speed V in such a manner that it sets the clutch current Ic to a first predetermined clutch current level I(V) so as to place the clutch into a substantially engaged state when the vehicle speed V is less than a first predetermined vehicle speed Vo, and to a second predetermined clutch current level Icr which is less than the first predetermined clutch current level I(V) so as to place the clutch into a partially engaged state when the vehicle speed V is equal to or greater than the first predetermined vehicle speed Vo.

Abstract: The present invention is a two unit electronic control system to reduce power demands imposed upon direct current power sources. The present invention comprises a contact/resistor network, a trigger generator, a pulse generator, a waveform stabilization circuit, a driver circuit, a voltage regulation circuit, a noise suppression circuit, a transient suppression circuit, a field effect transistor network and primary and secondary on/off control circuits. The input can be resistance, voltage, current or capacitance which is varied in response to an external stimulus. The chosen input is conditioned and applied to vary the duty cycle of a repeating pulse signal. That pulse signal is conditioned and applied to a switching device which controls the current from the DC power source to the load. The number of switching devices comprising the network will vary from one to many dependent upon the current carrying demand of the load and the current handling capability of the switching device utilized.

Abstract: A controller for slot cars on either or both domestic and/or commercial track. A programmable pulse width modulation circuit, using at least one integrated circuit to produce an output of variable duty cycle, is provided. This modulation circuit drives transistorized power switches to deliver a DC pulsation of same duty cycle as that of the modulator. The duty cycle is programmed with the use of a simple resistive network array mounted on a small board designed to plug into the rest of the device. Full power bypassing the modulator, transistorized power switches, and filter with another alternative, regenerative braking, are additional features. This controller is revolutionary in design replacing the old wire-wound power resistor technology with modern electronic technology offering the advantages of cool efficient operation and full programmability to match any slot car motor, track, or user.

Abstract: A controller for a vehicle fuel pump electric motor is connected to one or more vehicle sensors for sensing fuel flow demand and pulse width modulating the motor to control the speed. A fuel demand sensor and a triangle generator are connected to a summing controller for generating a pulse width modulated control signal to a driver. The driver has a pair of outputs for generating a pair of complementary pulse width modulated switch signals to a pair of switches whereby the switches are switched on and off alternately. One of the switches is connected in series between a power supply and the motor armature and the other switch is connected across the armature. A crash sensor, such as an inertia switch, is connected to the summing controller for terminating pulse width modulation in the event of a crash. The switch connected across the armature can be turned on to short circuit the armature and quickly stop the motor in the event of a crash.

Abstract: A drive arrangement comprises an a.c. induction motor (M1) having a rotary output shaft, and a drive control (FIG. 2), by which the speed of rotation of the shaft is controlled. The drive control comprises a signalling arrangement (e.g. a transducer (T) supplying an analogue signal converted by an analogue-to-digital converter (ADC) or a direct digital signalling arrangement) for supplying a digital signal having a value corresponding to the desired speed of rotation of the motor shaft, together with a processor (CPU) which receives the digital signal and at least one other input and processes the digital signal in accordance therewith. The processor supplies a corresponding, but modified, digital output signal to a digital-to-analogue converter (DAC) which converts the digital output signal to an analogue control signal and supplies it to an inverter which, in response thereto, drives the a.c. induction motor.

Abstract: The present invention is directed to an electric-car controller comprising a chopper for controlling the speed of a DC motor, a by-pass contactor for applying a DC source voltage directly to the DC motor, means for detecting that an acceleration command has reached a certain specified value or above, means for detecting that the acceleration of the car has dropped to a certain specified value or below, and means for turning on the by-pass contactor when the acceleration command has reached the certain specified value or above and the acceleration of the car has dropped to the certain specified value or below.

Abstract: A control motor comprising an integrated direct current motor and speed control circuit, the speed control circuit controlling a rotational speed of the direct current motor by means of changing a voltage applied to an armature by a chopping of a switching element, the speed control circuit being composed upon a printed circuit board, the printed circuit board being supported in the direct current motor by a case member formed of a heat-conducting material, and a radiation portion of the switching element which is closely contracted with a projection formed integrally with the case member and is installed in the projection.

Abstract: The present invention provides solid state power controller governance circuitry which includes a power level select circuit, an power level transition circuit, a controlled power limiting circuit, and a power level transition reset circuit. The circuits together provides an analog voltage or resistance signal for input to a standard power controller device that allows not only for the efficient control of the power level in the powered device, but additionally provides for controlled power limiting to the powered device when changes in the function of the powered device are initiated, or when other conditions warrant rapid power limiting to the device. The circuits also provide means whereby the powered device may be appropriately re-powered from a zero power state after controlled power limiting has occurred. Together the circuits of the present invention provide a means whereby powered devices may be efficiently, smoothly, and safely operated by standard power motor controller circuits.

Abstract: A motorized power steering apparatus for a vehicle has a torque sensor which generates an output voltage proportional to a steering torque exerted by the driver of the vehicle. A motor controller controls the output torque of a motor which generates an auxiliary steering force corresponding to the output voltage of the torque sensor. A current limiter limits the motor current to a value which decreases as the engine rotational speed or the vehicle speed increases.

Abstract: A motorized power steering apparatus for a vehicle has a torque sensor which generates an output voltage corresponding to a steering torque exerted by the driver of the vehicle. A motor controller controls the output torque of a drive motor which generates an auxiliary steering force corresponding to the output voltage of the torque sensor. The motor controller is a self-excited pulse width modulation circuit with feedback from the motor which supplies the motor with drive pulses having a pulse width modulated by the output voltage of the torque sensor.

Abstract: An arrangement is disclosed for controlling fan motors in fan-powered terminal units which permit the air flow of the terminal units to be factory preset and reset using a voltmeter. The fan motor is responsive to the pulse width of pulses of a pulse width modulated signal to provide an air flow which is proportional to the pulse width. By adjusting the pulse width, the air flow may be set as desired. A pulse width modulated signal having pulses with a set amplitude and frequency is generated. The dc voltage of the pulse width modulated signal is measured using a voltmeter. As the pulses have a set amplitude and frequency, the pulse width of the pulses may be adjusted by controlling the dc voltage of the pulse width modulated signal. The fan motor is programmed to deliver the set air flow over a range of static pressures.