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Pulse Width Modulators (PWM)
PWM Circuits:  # - G     H - O     P - S     T - Z


Last Updated: November 22, 2021 02:42 PM

Capacitance Proximity Switch
Draws very low power - Ideal for battery-powered applications
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Circuits Designed by Dave Johnson, P.E. :

PWM Circuit for Motor Speed Control - Sometimes you want to slow down a brush type DC motor.  The most efficient way to do this is with a pulse width modulation (PWM) technique.  The hobby circuit below can operate from about 3 volts to 15 volts.  The frequency is fixed at about 2KHz but the pulse . . . Hobby Circuit designed by David Johnson P.E.-December, 2007

PWM Motor Controller uses a 555 Timer - Using a CMOS version of the 555 timer, this circuit can be used to control the speed of a motor by adjusting the duty cycle of the pulses sent to the motor . . . Hobby Circuit designed by David Johnson P.E.-February, 2007


Links to electronic circuits, electronic schematics and designs for engineers, hobbyists, students & inventors:

PWM Motor Speed Controller/DC Light Dimmer-  This circuit will work as a DC lamp dimmer, small motor controller, and even as a small heater controller.  It would make a great speed control for a solar powered electric train.  The circuit has been tried with a 5 Amp electric motor using and IRFZ34N FET and worked ok, D1 may need to be replaced with a faster and higher current diode with some motors.  The circuit should work in applications such as a bicycle motor drive system, if you experiment with this, be sure to include an easily accessible emergency power disconnect switch in case the FET shorts out and leaves the circuit full-on. __ Designed by G. Forrest Cook

PWM Motor/Light Controller-  The diagrams are for 12V operation only and there are high side ( common ground) and low side ( common +12V) versions.  The low side version of the circuit uses an N Channel FET, the high side version of the circuit uses a P Channel FET.  N Channel devices tend to handle more current than P Channel devices, they are also less expensive.  The high side version of the circuit is useful when one side of the load has to be grounded __ Designed by G. Forrest Cook

PWM Power Amplifier-  Based on the ColdAmp BP4078 400W module, Class-D is here.  Definitely worth looking at! __ Designed by Rod Elliott  ESP

PWM ramp generator in switch-mode power supplies-  04/08/10 EDN Design Ideas:  Include this circuit in a switching-power-supply design. Design by Dwayne Reid, Edmonton, AB, Canada

PWM Speed Control-  includes theory and some example circuits __ Designed by Richard Torrens

PWM Subwoofer Amplifier-  Using a ColdAmp BP4078 module, this article has complete construction details __ Designed by Rod Elliott  ESP

PWM Timer with  555-  Schematic only, no circuits description. __ Designed by Tony van Roon  VA3AVR

PWM uses fuse to sense current-  EDN Design Ideas:  12/23/1999  High efficiency and, hence, low loss is a usual design goal for a PWM circuit.  Figure 1 shows one of several channels of low-loss PWM control for hydraulic valves used in heavy industrial machinery.  These valves usually have dc resistance of approximately 12W and substantial inductive reactance. Design by Eugene Kaplounovski

PWM uses one Op Amp-  07/06/00 EDN Design Ideas:  A previous Design Ideas is reminiscent of a similar but somewhat simpler circuit (see "Low-power PWM circuit is simple, inexpensive," EDN, Jan 6, 2000, pg 119).  This circuit delivers a rectangular signal with duty cycle varying between 0 and 100% in response to an input signal varying from 0 to 5V dc (Figure 1).  As with the above-mentioned circuit, the frequency is not constant (Figure 2) , but the circuit is so simple that it can be useful in certain applications. Design by Ferran Bayes, Electronica Digital, Barcelona, Spain

PWM using 555-  A simple oscilator with PWM that can be used to control speed of motors or light intensity. (4/29/2006) __ Designed by Jose Pino

PWM Watchdog Ensures Upper Bound-  11/07/96 EDN Design Ideas:  With PWM control of power factor, you need a continuous check on excess pulse width and dead periods to protect a variety of systems that may not incorporate such protection.  You also need regular pulsed power to ensure good averaged, reconstructed Design by Shyam Tiwari, IGCAR, Kalpakkam, India

PWM with 4 transistors-  I have not built it, but it looks like it should work.  It might be a good idea to put a resistor between the control pot's wiper and +VCC to limit the transistor base current. __ Designed by G. Forrest Cook

PWM with 555-  Some useful circuits using the LM555 IC.  Scroll to find the PWM with 555 circuit __ Designed by Jose Pino

PWMA High Current Pulse Width Control Excellent & Real Simple!-  Newly Revise Design NOW for Either N or P Channel Mos-Fet's __ Designed by G.L. Chemelec

PWM-Based Motor Speed Control Simulation using Ltspice-  Pulse-width modulation ( PWM) is one of the oldest and widely used techniques of controlling electrical motors.  To control the speed of the motor, the average value of the PWM pulse...__ Electronics Projects for You

PWM-Based Speed Control for DC Motors-  There are several methods for controlling the speed of DC motors.  One simple method is to add series resistance using a rheostat.  As considerable power is consumed in the rheostat, this...__ Electronics Projects for You

Quadrature (sine/cosine) voltage controlled oscillator-  Several schematics on this page, scroll to find this one.  The first circuit is a dual ramp generator where the positive and negative ramps are generated separately.  This circuit was used as a ramp generator for a transistor curve tracer: the positive going ramp was used for testing NPN transistors and the negative ramp for testing PNP transistors. __ Designed by Richard Torrens

Reduced Power Relay Driver-  Relays can handle a lot of power.  However, for certain power sensitive designs you would like to reduce the power needed to hold a relay closed.  The circuit below performs such a task.  It uses a single CD4093 quad NAND gate.  When the “on” logic input. . . Circuit by David Johnson P.E.-August, 2008

Relay Driver with Reduced Power-  Relays can handle a lot of power.  However, for certain power sensitive designs you would like to reduce the power needed to hold a relay closed.  The circuit below performs such a task.  It uses a single CD4093 quad NAND gate.  When the “on” logic input . . . Hobby Circuit designed by David A. Johnson P.E.-August, 2008

RF Wireless PWM DC Motor Speed control-  The wireless PWM DC motor transmitter circuit consists of WZ-X01 RF module, Holtek HT-640 encoder and 8-bit A/D converter.  U1 ADC0804 converts the analog voltage to digital data; U2 encodes that data ( D0~D6) along with D6, D7 and transmitting through the RF transmitter module.  The potentiometer VR1 varies the voltage to the A/D U1 pin6, __ Contact info @ wzmicro.com

Sequence Supplies for FPGAS-  01/23/03 EDN Design Ideas:  System designers must consider the timing and voltage differences between core and I/O power supplies (in other words, power-supply sequencing] during power-up and power-down.  The possibility of a latch-up failure or excessive current draw exists when power-supply sequencing does not occur properly.  The trigger for latch-up may occur if power supplies apply different potentials to the core and Design by David Daniels, Texas Instruments, Dallas, TX

Servo Pulse to PWM-  converter connects an H-Bridge to radio control receivers or robotic circuits __ Designed by Bob Blick

Simple Circuit ADC Is Surprisingly Accurate-  06/09/94 EDN Design Ideas:  The reference voltage in Fig 1a's simple rail-to-rail PWM ADC is the only critical component.  The input-voltage range extends from ground to the power rail which also acts as the reference.  The circuit is essentially a variation Design by Mike Walne, Farnell Instruments, Wetherby, West Yorkshire, UK

Simple Circuit allows long PWM soft starts-  02/01/07  EDN Design Ideas:  Enhance timing accuracy of a switching regulator's start-up ramp Design by Robert N Buono, Aeolian Audio LLC, Bloomfield, NJ

Simple Circuit DC Motor PWM speed control-  You need a power supply for a project, but only have a DC adapter available, so you can't use my AC power adapter trick ( Project 05).  This little project came about because a reader had just this problem, and didn't know what he could do.  This idea will work best with DC adapters having 12V DC or more - lower voltages will work, but the dynamic range will not be as good as it could be __ Contact IQ Technologies

Simple Circuit provides efficient PWM-  02/18/99 EDN Design Ideas:    NOTE:     Page includes several designs.  Scroll to find this one.  You often need to control the duty cycle of a square wave.  The circuit in Figure 1 works from a single 5V supply at a frequency of 100 kHz.  With minor component changes, you can configure it for a range of frequencies.  The circuit consists of a ramp   NOTE:  sawtooth]oscillator Design by Kenneth Levine, Eldec, Lynwood, WA

Simple Circuit Pulse Position Modulation-  In pulse position modulation, the amplitude and width of the pulses are kept constant, while the position of each pulse with reference to position of reference pulse, is changed according to the instantaneous sampled value of the modulating signal.  Below shown circuit diagram is the simplest pulse position modulation circuit __ Designed by Srihari Rao

Simple Circuit PWM ADC Is Surprisingly Accurate-  06/09/94 EDN Design Ideas:  The reference voltage in Fig 1a's simple rail-to-rail PWM ADC is the only critical component.  The input-voltage range extends from ground to the power rail which also acts as the reference.  The circuit is essentially a variation Design by Mike Walne, Farnell Instruments, Wetherby, West Yorkshire, UK

Simple Nanosecond-Width Pulse Generator Provides High Performance-  11/11/04  EDN Design Ideas:  If you need to produce extremely fast pulses in response to an input and trigger, such as for sampling applications, the predictably programmable short-time-interval generator has broad uses.  The circuit of Figure 1, built around a quad high-speed compara Design by Jim Williams, Linear Technology Corp

Square-wave Modulator has variable frequency & pulse width-  08/08/02 EDN Design Ideas:  A few years ago, I worked at a disk-drive company.  We had a plating facility that required square waves to drive the high-voltage plating operation.  The challenge was that the square wave's pulse width had to be variable, along with the duty cycle.  Also, the amplitude of the pulses had to be adjustable Design by Michael Fisch, Agere Systems, Longmont, CO

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