PC BASED DC MOTOR SPEED AND DIRECTION CONTROL USING PWM AND BRIDGE A pulse width modulator (PWM) is a device that may be used as an efficient DC motor speed controller or light dimmer. This project is a versatile device that can control DC devices which draw up to a few amps of current. The circuit may be used in either 12 or 24 Volt systems with only a few minor wiring changes. This device has been used to control the speed of the DC motor and to control brightness of an automotive tail lamp. 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. In this manner, a variable amount of power is transferred to the load. The main advantage of a PWM circuit over a resistive power controller is the efficiency, at a 50% level, the PWM will use about 50% of full power, almost all of which is transferred to the load, a resistive controller at 50% load power would consume about 71% of full power, 50% of the power goes to the load and the other 21% is wasted heating the series resistor. Manasa.t (12671A0421) Roopa.p (12671A0433)
PC BASED DC MOTOR SPEED AND DIRECTION CONTROLUSING PWM AND
BRIDGEA pulse width modulator (PWM) is a device that may be used as
an efficient DC motorspeed controller or light dimmer. his pro!ect
is a versatile device that can control DC deviceswhich draw up to a
few amps of current. he circuit may be used in either "# or #$ %olt
systemswith only a few minor wiring changes. his device has been
used to control the speed of the DCmotor and to control brightness
of an automotive tail lamp. A PWMcircuit
wor&sbyma&ingas'uarewavewithavariableon(to(offratio)
theaverage on time may be varied from * to "** percent. +n this
manner) a variable amount of poweris transferred to the load. he
main advantage of a PWM circuit over a resistive power controller
is the efficiency)at a ,*- level) the PWM will use about ,*- of
full power) almost all of which is transferred tothe load) a
resistive controller at ,*- load power would consume about ."- of
full power) ,*-of the power goes to the load and the other #"- is
wasted heating the series resistor. /neadditional
advantageofpulsewidthmodulationisthat thepulsesreachthefullsupply
voltage and will produce more tor'ue in a motor by being able to
overcome the internalmotor resistances more easily. wo push(to(on
switches are provided for increasing 0 decreasingthe speed of the
motor. Manasa.t ("#1."A*$#")2oopa.p ("#1."A*$33)wo more push(to(on
switches are provided to rotate the motor in Cloc& wise 0
Countercloc& wise direction. "14# 5CD is connected to display
the speed level of the motor and thedirection. 56D indication is
also provided for visual indication.A bu77er is provided for audio
indication of DC motor speed variation and change indirection.
Wheneverthespeedisincreased0 decreased)
thesystemac&nowledgesbyashortbeep. his bu77er is driven by
transistor driver circuit.hispro!ectuses regulated,%).,*mA
8"#%),**mA power supply. .9*, and.9"#three terminal voltage
regulators are used for voltage regulation. :ridge type full wave
rectifieris used to rectify the ac out put of secondary of #3*0"#%
step down transformer.Manasa.t ("#1."A*$#")2oopa.p
("#1."A*$33)BLOCK DIAGRAM:Manasa.t ("#1."A*$#")2oopa.p
("#1."A*$33)Power ;upply"#% to DC motor>,% to all
sections2egulato2egulato?ilterCircuit:ridge2ectifier;tepdown;peedindicatorDirectionindicator9@;,#MC
