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AN857

Brushless DC Motor Control Made Easy

Microchip Technology 

AN857

Brushless DC Motor Control Made Easy

Author: Ward Brown

Microchip Technology Inc.

INTRODUCTION

This application note discusses the steps of developing

several controllers for brushless motors. We cover sen-

sored, sensorless, open-loop, and closed-loop design.

There is even a controller with independent voltage and

speed controls so you can discover your motor’s char-

acteristics empirically.

The code in this application note was developed with

the Microchip PIC16F877 PIC® microcontroller, in con-

jucntion with the In-Circuit Debugger (ICD). This com-

bination was chosen because the ICD is inexpensive,

and code can be debugged in the prototype hardware

without need for an extra programmer or emulator. As

the design develops, we program the target device and

exercise the code directly from the MPLAB® environ-

ment. The final code can then be ported to one of the

smaller, less expensive, PIC microcontrollers. The

porting takes minimal effort because the instruction set

is identical for all PIC 14-bit core devices.

It should also be noted that the code was bench tested

and optimized for a Pittman N2311A011 brushless DC

motor. Other motors were also tested to assure that the

code was generally useful.

Anatomy of a BLDC

Figure 1 is a simplified illustration of BLDC motor con-

struction. A brushless motor is constructed with a per-

manent magnet rotor and wire wound stator poles.

Electrical energy is converted to mechanical energy by

the magnetic attractive forces between the permanent

magnet rotor and a rotating magnetic field induced in

the wound stator poles.

FIGURE 1:

SIMPLIFIED BLDC MOTOR DIAGRAMS

100

A

A

N

101

c

com

b

a

S

N

S

com

110

b

C

6

3

a

com

4

1

001

N

c

010

B

a

c

2

b

com

C

S

5

B

011

 2002-2011 Microchip Technology Inc.

DS00857B-page 1

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