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Implementing Pulse Width Modulation using the PIC18F4520
Bryan Thomas
A35345102
October 28
th
, 2007
Keywords: Pulse Width Modulation, Voltage Levels, Duty Cycle, Analog Control
Table of Contents:
Abstract…………………Page 1
Introduction……………..Page 1
PWM Implementation……Page1
PWM Application…………Page 2
Summary………………….Page 3
Useful Figures…………….Page 3
References………………….Page 6
Abstract
The technique of pulse width modulation
(PWM) is used to regulate the output
voltage in a circuit. By changing the
duty cycle, the average output power can
be adjusted even though the output pulse
remains the same throughout the
different duty cycles. The uses of PWM
are many. For our project, PWM will be
implemented to create variable
frequencies to operate our speaker at.
One of the requirements of the sponsor
is that the frequency of the sound
coming from the base be different than
the frequency of the sound coming from
the ball. Keeping this in mind, we have
decided to make the frequency of the
base be under 1 kHz.
Introduction
Pulse width modulation is a technique
used to manipulate the average power
seen at a load. By using the formula*:
The average value of a waveform can be
calculated. By changing the length of
time in which the signal is considered
“high”, also known as the duty cycle, the
area under the signal can be
manipulated. Without changing the
period, changing the area under the
signal will thereby change the average
value of the signal during one period.
The microcontroller that we are using,
the PIC18F4520, comes with an onboard
PWM module. Using this module and
the appropriate registers, we will be able
to manipulate our signal going to the
speaker using PWM.
PWM Implementation
To properly implement PWM into our
design, a reference of the PIC18F4520
datasheet had to be made**. Upon
