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Sri Lanka Institute of Information Technology: Faculty of Engineering Department of Electrical and Computer Engineering

This document contains code to control a stepper motor and servo motor using a PIC microcontroller. The stepper motor code uses different bit patterns to turn the motor clockwise and counterclockwise. The servo motor code uses pulse-width modulation to rotate the servo through four positions: -90°, 0°, +90°, and back to 0° by varying the pulse width from 750μs to 2500μs. The period of the PWM signal is 20ms, giving a frequency of 50Hz.

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Madhushan Dassanayake
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65 views4 pages

Sri Lanka Institute of Information Technology: Faculty of Engineering Department of Electrical and Computer Engineering

This document contains code to control a stepper motor and servo motor using a PIC microcontroller. The stepper motor code uses different bit patterns to turn the motor clockwise and counterclockwise. The servo motor code uses pulse-width modulation to rotate the servo through four positions: -90°, 0°, +90°, and back to 0° by varying the pulse width from 750μs to 2500μs. The period of the PWM signal is 20ms, giving a frequency of 50Hz.

Uploaded by

Madhushan Dassanayake
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOCX, PDF, TXT or read online on Scribd
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Sri Lanka Institute of Information Technology

Faculty of Engineering

Department of Electrical and Computer


Engineering

EC248: Introduction to Controls and Robotics


Lab 04

Name : De Silva O.R.M.


Index Number : EN 14536458
Group : Group 03
Submission Date : 07th September 2015
INTRODUTCTION TO CONTROLS AND ROBOTICS EC248

SERVO AND STEPPER MOTOR CONTROL

Discussion

Part 1 Stepper Motor Control

Following code can be used to turn the stepper motor in clockwise direction.

void main() {
TRISC=0;

while(1){
PORTC = 0X01;
delay_us(900);
PORTC = 0X02;
delay_us(900);
PORTC = 0X04;
delay_us(900);
PORTC = 0X08;
delay_us(900);
}

In order to reverse the above stated direction of the stepper motor, the signal pattern of the bits
should be given in the opposite direction as below.

void main() {
TRISC=0;

while(1){
PORTC = 0X08;
delay_us(900);
PORTC = 0X04;
delay_us(900);
PORTC = 0X02;
delay_us(900);
PORTC = 0X01;
delay_us(900);
}

1
INTRODUTCTION TO CONTROLS AND ROBOTICS EC248

Part 2 Servo Motor Control

Servo motor is used to turn the motor in a desired angle using a PWM pulse.

90 0 +90 0 90
The above rotational pattern could be implemented to a servo motor using a PIC microcontroller
from the below code.
int i;

void main() {
TRISC=0;

while(1){
for(i=0; i<100; i++){
PORTC.RC0 = 1;
delay_us(750); //-90 Rotation
PORTC.RC0 = 0;
delay_us(19500);
}

for(i=0; i<100; i++){


PORTC.RC0 = 1;
delay_us(1500); //0 Rotaton
PORTC.RC0 = 0;
delay_us(18500);
}

for(i=0; i<100; i++){


PORTC.RC0 = 1;
delay_us(2500); //+90 Rotaton
PORTC.RC0 = 0;
delay_us(17500);
}

for(i=0; i<100; i++){


PORTC.RC0 = 1;
delay_us(1500); //0 Rotaton
PORTC.RC0 = 0;
delay_us(18500);
}

for(i=0; i<100; i++){


PORTC.RC0 = 1;
delay_us(750); //-90 Rotation
PORTC.RC0 = 0;
delay_us(19500);
}
}

2
INTRODUTCTION TO CONTROLS AND ROBOTICS EC248

The period of the pulse train is 20 ms.

= 20

1
=

1
=
20 103
= 50

As seen in the above code, the pulse width (time high) for the servo motor to turn at different
angles can be given as follows.

Angle Pulse Width (Time High)


-90o 750s
0o 1500s
+90o 2500s

`
+90o
2500s

-90o
750s

1500s

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