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Topic: PWM

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	PWM - ZikiWiki
		The simplest way to generate a PWM signal is the intersective method, which requires only a sawtooth or a triangle waveform (easily generated using a simple oscillator) and a comparator.
		PWM is also often used to control the supply of electrical power to another device such as in speed control of electric motors, volume control of Class D audio amplifiers or brightness control of light sources and many other power electronics applications.
		PWM is sometimes used in sound synthesis, in particular subtractive synthesis, as it gives a nice effect similar to chorus or slightly detuned oscillators played together.
	www.zikiwiki.com /wiki/PWM (1470 words)

	Introduction to Pulse Width Modulation - PWM, control systems, digital control
		PWM is employed in a wide variety of applications, ranging from measurement and communications to power control and conversion.
		The duty cycle is the ratio of the on-time to the period; the modulating frequency is the inverse of the period.
		One of the advantages of PWM is that the signal remains digital all the way from the processor to the controlled system; no digital-to-analog conversion is necessary.
	www.netrino.com /Publications/Glossary/PWM.html (1277 words)

	dontronics.com (pwm.htm)
		Pwm's output is not a high pulse of x duration followed by a low of y duration.
		To use Pwm, set the desired pin to output, put the port number (0 to 2 for RA through RC) into w, put the pin number into the variable pin, and the duty cycle into the variable duty.
		In those cases, the pwm output pin should be set up ; as an output when Pwm is called, then immediately switched to ; input when Pwm is done.
	www.dontronics.com /psbpix/pwm.html (1166 words)

	PWM Signal with PIC 16F84
		PWM signals can also be used to vary the voltage applied to a device by achieving an effective average voltage.
		A PWM signal is simply a pulse of varying length, in effect a rectangular wave.
		When the PWM otuput from the PIC is sent to the transistor, it will flip the transistor on and off and subsequently generate the same PWM signal to the motor, allowing you to control the motor with a PWM signal.
	www.pages.drexel.edu /~kws23/tutorials/PWM/PWM.html (1020 words)

	BASIC Stamp PWM Command
		The pin used by the PWM command is left in the input state upon completion of the command, so that the average level can be held on a holding capacitor.
		PWM is often used to drive motors for speed control.
		The PWM pulses in the Stamp version of PWM are 4.5 microseconds long, so the amplifier slew rates and transistor Ft parameters have to be fast, well less than one microsecond.
	www.emesystems.com /BS2PWM.htm (1078 words)

	PWM (Pulse Width Modulation) (Site not responding. Last check: 2007-11-01)
		When using PWM regulation, the current from the solar array tapers according to the battery's condition and recharging needs.
		PWM has recently surfaced as the first significant advance in solar battery charging.
		When the battery voltage reaches the regulation setpoint, the PWM algorithm slowly reduces the charging current to avoid heating and gassing of the battery, yet the charging continues to return the maximum amount of energy to the battery in the shortest time possible.
	members.optusnet.com.au /~doranje/PWM.html (489 words)

	PWM Motor Speed Controller / DC Light Dimmer (Site not responding. Last check: 2007-11-01)
		A pulse width modulator (PWM) is a device that may be used as an efficient light dimmer or DC motor speed controller.
		A PWM circuit works by making a square wave with a variable on-to-off ratio, the average on time may be varied from 0 to 100 percent.
		Finally, in a PWM circuit, common small potentiometers may be used to control a wide variety of loads whereas large and expensive high power variable resistors are needed for resistive controllers.
	www.solorb.com /elect/solarcirc/pwm1 (1377 words)

	PWM Generator (SimPowerSystems)
		In the second option, the PWM Generator needs one reference signal to generate the pulses for a single- or a two-arm bridge, or it needs a three-phase reference signal to generate the pulses for a three-phase bridge (single or double bridge).
		The amplitude (modulation), phase, and frequency of the reference signals are set to control the output voltage (on the AC terminals) of the bridge connected to the PWM Generator block.
		Pulse 2 is the complement of pulse1, pulse 4 the complement of pulse 3, and pulse 6 the complement of pulse 5.
	www.weizmann.ac.il /matlab/toolbox/powersys/pwmgenerator.html (793 words)

	Application of PWM Fan Control (Site not responding. Last check: 2007-11-01)
		Pulse Width Modulation (PWM) is the preferred method to regulate motor speed because no additional heat is generated, and it is energy efficient when compared to linear regulating (voltage control) the motor.
		The PWM duty cycle is defined as Ton/Toff (%) in one period and the range is 0% - 100%.
		The motor commutation circuit is still being switched on and off by the PWM signal and the tach signal is still likely to be invalid during the off cycle.
	www.coolingzone.com /Guest/News/NL_May_2003/JMC/JMC_May_2003.html (1032 words)

	PWM electronic profitboards - electronic message centers - PWM Profitboard USA
		For almost a decade, PWM has produced Profitboards (LED message centers), providing merchants an attractive and modern advertising for products and service promotions that can be updated on an ongoing basis from outside locations or in the store.
		PWM products are located at over 22,500 service stations, numerous commercial premises, car dealers, workshops, restaurants and hotels.
		PWM was the first manufacturer to create and launch price signs for the petroleum industry in 1983; which enabled up-to-date price information to be entered electronically.
	www.pwm-profitboard.com (173 words)

	: Class PWM
		PWM is a virtual peripheral so it will continue to run in the background.
		The state that the pin should be set to whenever the PWM is stopped.
		The PWM will stop immediately and may leave the output pin in either a high or low state.
	www.parallax.com /javelin/doc/stamp/core/PWM.html (329 words)

	AVR-PWM-ADC-Test for STK500
		The PWM rectangle produced by TC1 is filtered by three RC combinations of 10k/100nF and fed into the analog comparator input AIN1, which is port bit PB3 of the AT90S8515.
		The accuracy of the PWM signal in the lower range from 0.00 to 0.10 V, but even more in the most upper range, is limited, because the MOS output drivers do not reach exactly the operating voltage bounds.
		By selecting the PWM cycle numbers as constants on the top of the program, the repeating frequency of the measurements and the delay before sensing the different bits can be adjusted.
	www.avr-asm-tutorial.net /avr_en/AVR_ADC500.html (2202 words)

	Pulse Width Modulated (PWM) Frequently Asked Questions - JMC Products - Manufacturer of Thermal Products
		On a PWM fan, the 4th wire consists of the PWM line and will be directly proportional to the speed of the fan.
		There is always a frequency associated with a PWM signal that is different from the PWM duty cycle and frequency will affect the acoustics of a fan.
		Electrically the PWM signal is TTL/CMOS compatible where the PWM input impedance is greater than or equal to 10 Kohm.
	www.jmcproducts.com /products/pwm_fans/pwm_faq.shtml (539 words)

	Pulse Width Modulation (PWM) with the MAXQ2000 Timer Type 2 - Maxim/Dallas
		PWM is often used to control fan speed and DC and servo motors.
		Using PWM with some external circuitry, it is even possible to implement a simple digital-to-analog converter (DAC) by charging an RC circuit of known time constant for a specific length of time.
		It is possible to gate the PWM signal on the secondary output pin by using the primary output pin as a gating input.
	www.maxim-ic.com /appnotes.cfm?an_pk=3666 (1025 words)

	PWM motor controller for DC motors and fans (via CobWeb/3.1 planetlab2.cs.unc.edu) (Site not responding. Last check: 2007-11-01)
		This 555 timer based PWM controller features almost 0..100% pulse width regulation using R1, while keeping the oscillator frequency relatively stable.
		Q output of 555 is used to drive the PWM cycle, so the discharge pin is used to drive output transistor instead.
		However, the tach signal is of no use, because besides a normal tach output it also disappears whenever the PWM cycle removes power from fan.
	www.nomad.ee.cob-web.org:8888 /micros/pwm555.html (455 words)

	Servo Pulse to PWM
		The PWM signals pass through analog switches U3B,C and are buffered by U1D,E. If there is a lack of incoming pulses, U1C as controlled by C7 and R4 will shut off the output.
		Attach the PWM outputs at J2 to your H-bridge.
		PWM frequency is approximately 3khz, which is very efficient through most H-bridges but is a little noisy.
	www.bobblick.com /techref/projects/sv2pwm/sv2pwm.html (1158 words)

	Pulse Width Modulation (PWM) Basics
		For a single low frequency sine wave as modulating signal modulating the width of a fixed frequency (fs) pulse train the spectra is as shown in Fig 2.
		The simplest analog form of generating fixed frequency PWM is by comparison with a linear slope waveform such as a sawtooth.
		Regular sampled PWM makes the width of the pulse proportional to the value of the modulating signal at the beginning of the carrier period.
	www.powerdesigners.com /InfoWeb/design_center/articles/PWM/pwm.shtm (636 words)

	STRONG PITCH TRIM PWM
		Through feedback systems, this PWm technique can precisely control the voltage allowed to generate the armature field of the motor, and thus the speed is controlled.
		PWM drives are most commonly used to control AC motors, but the system is also used in many newer, more precise, DC drives controlling DC motors.
		The gear box has a slip clutch designed to release at the end of of the stroke in both directions and reguires full speed to release, However since the PWM enables slower speed limit switches are needed.
	mysite.verizon.net /res80xp0/strongpitchtrimpwm (1164 words)

	bit-tech.net \| PWM Fan controller
		PWM or Pulse Width Modulation has generally been regarded as too complicated for PC fan speed control compared against using rheostats or linear voltage regulators such as the LM317.
		I present here a PWM circuit that is simple and cheap enough to be built by the casual electronics builder.
		In simple terms, PWM involves rapidly switching the supply to the fan on and off, in this case 30 times a second, (30Hz).
	www.bit-tech.net /modding/2001/12/03/pwm_fan_controller/1.html (815 words)

	Why PWM?
		Pulse Width Modulation (PWM) is the most effective means to achieve constant voltage battery charging by switching the solar system controller’s power devices.
		When in PWM regulation, the current from the solar array tapers according to the battery’s condition and recharging needs.
		When a battery voltage reaches the regulation setpoint, the PWM algorithm slowly reduces the charging current to avoid heating and gassing of the battery, yet the charging continues to return the maximum amount of energy to the battery in the shortest time.
	www.morningstarcorp.com /support/Why-PWM/why-pwm-1.shtml (538 words)

	Using PWM to Generate an Analog Voltage
		To convert the PWM signal to an analog voltage, a low-pass filter is used.
		PWM signals contain strong noise components at the PWM frequency and at odd harmonics of that frequency.
		PWM modules in all ADR products can operate at 9.76 Khz thus the strong noise components are at 9.76Khz and higher.
	www.ontrak.net /pwm.htm (262 words)

	FreshPorts -- x11-wm/pwm
		PWM is a rather lightweight window manager for X11.
		PWM does not provide pixmapped themes or other bloated eye candies but has a clean and simple look inspired by BeOS and Motif.
		PWM does not even have titlebar buttons and may not be the easiest window manager to get into, most Good Things are not.
	www.freshports.org /x11-wm/pwm (326 words)

	The 68HC912B32 PWM Module
		The purpose of the PWM module is to allow for time critical waveform operations to be handled by the hardware, instead of trying to accomplish everything in software.
		The B32 PWM module allows you to specify width of the Duty and the width of the Period.
		There are many different uses for PWM, such as controlling the position of servo motors, dimming the brightness of a lamp, or controlling the speed of a DC motor.
	www.seattlerobotics.org /encoder/apr98/68hc12pwm.html (3796 words)

	pwm converter, pwm controller, PWM proportional solenoid driver, pwm valve drivers, pwm speed controllers, pulse width ...
		For proportional solenoid control with a PWM signal input, a PWM Controller is available in a DIN rail mount housing, IP67 rated rugged metal box or as a stand alone PCB board.
		PWM output can be measured using a multi-meter with a PWM measurement feature.
		PWM to current (0-20 mA, 4-20 mA) or voltage (0-5VDC, 0-10VDC) with 3 sec.
	www.axiomatic.com /pwm-converter.html (963 words)

	Pulse Width Modulation
		By adjusting the duty cycle of the signal (modulating the width of the pulse, hence the 'PWM') ie, the time fraction it is "on", the average power can be varied, and hence the motor speed.
		A different approach is adopted in a PWM controller from Nomad using little more than a 555 and a PNP switching transistor.
		I don't see the problem with low-power fans as a detriment, PWM control is most appropriate for more powerful fans that produce a lot of waste heat with linear control.
	www.cpemma.co.uk /pwm.html (2006 words)

	PWM Motor/Light Controller
		An additional advantage of pulse width modulation is that the pulses are at the full supply voltage and will produce more torque in a motor by being able to overcome the internal motor resistances more easily.
		If additional filtering is needed, a car radio line choke may be placed in series with the DC power input, be sure not to exceed the current rating of the choke.
		PWM Frequency: 400 Hz Current Capacity: 3 Amps with IRF521 FET, more with IRFZ34N FET PWM circuit current: 1.5 ma @ 12V with no LED and no load Operating Voltage: 12V or 24V depending on the configuration.
	www.electronics-lab.com /projects/motor_light/003 (1270 words)

	PWM
		In this un-optimized example, we start the PWM output in the high state and initialize the falling edge counter with the desired duty cycle (or actually MAX_COUNT - duty_cycle, since the algorithm increments the counters).
		When the counters reach their maximum count, they're cleared back to zero and the PWM output is updated.
		For example, all of the PWM outputs could be synchronized so that their rising edges all occur at the same time.
	www.dattalo.com /technical/theory/pwm.html (542 words)

	PWM (Site not responding. Last check: 2007-11-01)
		PWM was the first window manager to implement "tabbed frames" or the back then unique feature allowing multiple client windows to be attached to the same frame.
		While the original PWM, or PWM1, is no longer maintained, Ion, versions 2 and 3, can to some degree emulate this behaviour, and indeed provide nominal PWM2 and PWM3, although the bindings are different, employing prefix keys.
		This version of PWM has not for a long time (since circa year 2000) been actively maintained by me, but high-quality patches to found problems are still accepted.
	www.modeemi.fi /~tuomov/pwm (307 words)

	Pico Systems Universal PWM Servo Controller
		Complete PWM drive systems Pico Systems is currently evaluating the price point at which we could make complete drive boxes available.
		The Universal PWM Servo Controller is a small board with everything needed to control a 2-, 3- or 4 axis machine tool with PWM-driven servo amplifiers.
		It contains 4 PWM generators with variable PWM drive frequency, 4 digital encoder counters to follow the machine position, 16 channels of opto-isolated digital inputs, and 8 positions for Solid State Relays of your choice to be mounted.
	pico-systems.com /univpwm.html (868 words)

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