Brushed Dc Motor Fundamentals

Microchip Technology Inc.

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appnote circuit ,Schematic
AN905
Brushed DC Motor Fundamentals
Author:
Reston Condit
Microchip Technology Inc.
Stator
The stator generates a stationary magnetic field that
surrounds the rotor. This field is generated by either
permanent magnets or electromagnetic windings. The
different types of BDC Motors are distinguished by the
construction of the stator or the way the electromag-
netic windings are connected to the power source.
(See
Types of Stepping Motors
for the different BDC
Motor types).
INTRODUCTION
Brushed DC Motors are widely used in applications
ranging from toys to push-button adjustable car seats.
Brushed DC (BDC) Motors are inexpensive, easy to
drive, and are readily available in all sizes and shapes.
This application note will discuss how a BDC Motor
works, how to drive a BDC Motor and how a drive
circuit can be interfaced to a PIC
®
Rotor
The rotor, also called the armature, is made up of one
or more windings. When these windings are energized
they produce a magnetic field. The magnetic poles of
this rotor field will be attracted to the opposite poles
generated by the stator, causing the rotor to turn. As the
Motor turns, the windings are constantly being
energized in a different sequence so that the magnetic
poles generated by the rotor do not overrun the poles
generated in the stator. This switching of the field in the
rotor windings is called commutation.
PRINCIPLES OF OPERATION
The construction of a simple BDC Motor is shown in
Figure 1. All BDC Motors are made of the same basic
components: a stator, rotor, brushes and a commutator.
The following paragraphs will explain each component
in greater detail.
FIGURE 1:
SIMPLE TWO-POLE BRUSHED DC Motor
N
NORTH
Axle
SOUTH
Brushes
Commutator
Field
Armature
Magnet
or Coil
2004 Microchip Technology Inc.
DS00905A-page 1