KS Project Manual
EFY june 2009
Microcontroller-based
DC Motor Controller
Fig. 1: Circuit of the microcontroller-based DC motor controller
M
otion control plays
a vital role in industrial automation. Manufacturing plants
in industries like chemical,
pharmaceutical, plastic and
textile, all require motion
control. And it may be a flatbelt application, flow-control
application or mixing of
substances. Different types
of motors—AC, DC, servo or
stepper—are used depending upon the application. Of
these, DC motors are widely
used because controlling
a DC motor is somewhat
easier than other kinds of
motors.
The motion of a DC motor is controlled using a DC
drive. DC drive changes the
speed and direction of motion of the motor. Some of
the DC drives are just a rectifier with a series resistor that
converts standard AC supply
into DC and gives it to the
motor through a switch and
a series resistor to change
the speed and direction of
rotation of the motor. But
many of the DC drives have
an inbuilt microcontroller
that provides programmable
facilities, message display
on LCD, precise control and
also protection for motors.
Using the DC drive you can
program the motion of the
motor, i.e., how it should
rotate.
Here are some of the
features of this DC motor
controller:
1. Controlled through
microcontroller AT89C51
2. Message displayed on
the LCD module
KS Project Manual
EFY june 2009
Fig. 2: Circuit of the power supply
read/write (R/
W) pins, respectively. Contrast
of the LCD is set
by preset VR1.
Port pins P1.0
through P1.7
are connected
to switches S1
through S8 for
performing the
Fig. 3: Proposed panel arrangement for the DC motor controller
various operations.
3. Start,
Power-on reset signal for the miFunctions of
stop and
crocontroller is generated by the comDifferent Switches change of bination of capacitor C1 and resistor
direction of
R1. Switch S9 provides manual reset to
Switch Function
the motor
the microcontroller. A 12MHz crystal
S1
To start motor
controlled
provides the basic clock frequency to
S2
To stop the motor
by pushbutthe microcontroller. Capacitors C2 and
S3
Change the mode
ton switchC3 provide stability to the oscillator.
S4
Change the direction es and inEA pin (pin 31) of the microcontroller
dicated by
S5
Increase speed
is connected to 5V to enable internal
LED
access. Port pins P2.0 through P2.3 of
S6
Decrease speed
4
.
the microcontroller are used for LED
S7
Increase time
Changes
indication of run, stop, clockwise and
S8
Decrease time
the running
anti-clockwise rotation. Port pins P2.4
mode of the motor to continuous, rethrough P2.6 are connected to the inputs
versible or jogging
of inverters N3, N2 and N1 of 74LS04
5. Changes the speed of the motor
(IC2). The output of inverter N3 is used
6. Time settings are possible for
to trigger pin 2 of NE555 timer.
forward and reverse running of the
Timer NE555 is configured as a
motor
monostable and its time period is decided by preset VR2 and capacitor C4.
Circuit description
When pin 2 of NE555 goes low, output
Fig. 1 shows the circuit of the micropin 3 becomes high for the predetercontroller-based DC motor controller.
mined period.
At the heart of the DC motor controller
The output of NE555 is connected
is microcontroller AT89C51. Port pins
to pole P of relay RL1. Normally-open
P0.0 through P0.7 of the microcontrol(N/O) contacts of relay RL1 are conler are interfaced with data pins D0
nected to N/O1 and N/C2 contacts of
through D7 of the LCD module, rerelay RL2. N/C1 and N/O2 contacts
spectively. Port pins P3.0, P3.1 and P3.2
of RL2 are connected to ground. The
control the LCD operation through
outputs of inverters N2 and N1 drive
enable (E), register-select (RS) and
relays RL1 and RL2 with the help of
transistors T1 and T2, respectively. D1
and D2 act as free-wheeling diodes.
Poles P1 and P2 of RL2 are connected
to IN1 and IN2 pins of motor driver
L293D. OUT1 and OUT2 of L293D
drive motor M.
Fig. 2 shows the power supply
circuit. The 230V AC mains is stepped
down by transformer X1 to deliver the
secondary output of 9V, 500 mA. The
transformer output is rectified by a
full-wave bridge rectifier comprising
diodes D3 through D6, filtered by capacitor C6 and then regulated by ICs
7805 (IC5) and 7806 (IC6). Capacitors
C7 and C8 bypass the ripples present
in the regulated 5V and 6V power supplies. LED5 acts as a power-‘on’ indicator and resistor R10 limits the current
through LED5.
The proposed panel arrangement
for the microcontroller-based DC motor controller is shown in Fig. 3.
An actual-size, single-side PCB for
the microcontroller-based DC motor
controller is shown in Fig. 4 and its
component layout in Fig. 5.
Operation
The eight pushbutton switches are connected for eight different functions as
shown in the table.
When S1 is pressed, the microcontroller sends low logic to port pin
P2.5. The high output of inverter N2
drives transistor T1 into saturation
and relay RL1 energises. So the output
of NE555 is fed to inputs IN1 and IN2
of L293D through both the contacts of
relay RL2. Now at the same time, after
RL1 energises, the microcontroller
starts generating PWM signal on port
pin P2.4, which is fed to trigger pin
2 of NE555 through inverter N3. The
base frequency of the generated PWM
signal is 500 Hz, which means the time
period is 2 ms (2000µs). The output
pulse width varies from 500 µs to 1500
µs. The R-C time constant of the monostable multivibrator is kept slightly
less then 500 µs to generate exactly the
same inverted PWM as is generated by
the microcontroller.
When switch S2 is pressed, port-pin
P2.5 goes high and RL1 de-energises to
stop the motor.
When switch S3 is pressed, relay
KS Project Manual
EFY june 2009
RL2 energises. Pin IN1 of motor driver
L293D receives the PWM signal and
pin IN2 connects to ground. As a result, the motor rotates in one direction
(say, clockwise).
When switch S4 is pressed again,
relay RL2 de-energises. Pin IN2 of
motor driver L293D receives the PWM
signal and pin IN1 connects to ground.
The motor now rotates in opposite direction (anti-clockwise).
When switch S3 is pressed, different modes are selected in cyclic manner
as given below:
1. Continuous mode. The motor rotates continuously with the set speed
in either direction
2. Reversible mode. The motor reverses automatically after the set time
3. Jogging mode. The motor rotates
for the set time in either direction and
then stops for a few seconds and again
rotates for the set time. It is also called
‘pulse rotation’
Switches S5 and S6 are used to set
the speed of the motor, either in increasing order or decreasing order, in
continuous mode only.
Switches S7 and S8 are used to set
the time either in increasing order or
decreasing order.
Fig. 4: A single-side, actual-size PCB layout for the microcontroller-based DC motor controller
Software
The program is written in ‘C’ language
and compiled using Keil µVision3 compiler. It is well commented and easy
to understand. The program has three
major sections: initialisation and key
press, display and motor control.
Initialisation and key press. It consists of the main function that initialises
timers, ports, LCD module and LED indication and then waits for key press.
When any key is pressed, the program
calls that particular function.
In the main function, first the ports
are initialised as input/output, then the
LCD is initialised and cleared. At power-on reset or manual reset, message
“DC motor controller” is displayed on
the LCD and LED1 through LED4 turn
off. When start switch S1 is pressed,
message “Motor Start” is displayed for
a second, and then the mode and current speed are displayed. Run LED and
clockwise-direction LED are ‘on.’ Now
the program waits for key press. When
Fig. 5: Component layout for the PCB
any key is pressed, the program jumps
to one of the functions (start, direction,
mode, etc).
Display. It uses the following functions:
1. ‘writecmd’ function sends com-
KS Project Manual
EFY june 2009
Parts List
Semiconductors:
IC1
IC2
IC3
IC4
IC5
IC6
T1, T2
D1-D6
LED1-LED5 -
AT89C51 microcontroller
74LS04 hex inverter
NE555 timer
L293D motor driver
7805, 5V regulator
7806, 6V regulator
BC548 npn transistor
1N4007 rectifier diode
5mm LED
Resistors (all ¼-watt, ±5% carbon):
R1
- 10-kilo-ohm
R2-R5
- 2-kilo-ohm
R6-R10,
R12, R13
- 220-ohm
R11
- 1-kilo-ohm
VR1, VR2
- 10-kilo-ohm preset
Capacitors:
C1
C2, C3
C4, C7, C8
C5
C6
-
Miscellaneous:
X1
XTAL
RL1
RL2
M
S1-S9
LCD module 10µF, 16V electrolytic
33pF ceramic disk
0.1µF ceramic disk
0.01µF ceramic disk
1000µF, 25V electrolytic
230V AC primary to 9V,
500mA secondary
transformer
12MHz crystal
6V, 1C/O relay
6V, 2C/O relay
6V DC motor
Push-to-on switch
16×2 line
14-pin bergstik SIP
Connector (male & female)
mand byte to the LCD. It takes one
argument byte and sends it to P0.
2. ‘writedata’ function sends data
byte to be displayed on the LCD. It also
takes one argument byte and sends it
to P0.
3. ‘writestr’ function writes the
whole string (message) on the LCD. It
takes pointer as an argument that points
address of the first character of the
string, then through the pointer it sends
all the characters one by one to P0.
4. ‘busy’ function checks the status
of the busy flag of the LCD. If the flag
is set, the LCD is not ready and the program remains within the loop. When
the flag is reset, the LCD is ready and
the program comes out of the loop.
Motor control. It uses the following
functions:
1. ‘start’ function starts motor rotation in one of the modes (continuous,
reversible or jogging). The mode is
selected by mode-selection flag ‘m.’ As
explained earlier, in continuous mode
the motor keeps rotating with the set
speed. In reversible mode, the motor
changes direction automatically after
the set time. In jogging mode, the motor rotates for the set time, stops for a
few seconds and then rotates.
2. ‘stop’ function stops rotating the
motor and displays the message on
the LCD module. This is indicated by
glowing of the stop LED.
3. ‘direction’ function increments
the counter by ‘1’ every time and
checks whether the count is even or
odd. If the count is even, it selects
clock-wise direction, and if the count is
odd, it selects anticlockwise direction.
This is also indicated on direction CLK
and ACLK LEDs.
4. ‘mode’ function changes modes
in cyclic manner. It increases modeselection flag ‘m’ every time. If m=0
it selects continuous mode, if m=1 it
selects reversible mode and if m=2 it
selects jogging mode. If m=3 it is reset
to ‘0’ again and selects continuous
mode and likewise.
5. ‘incspeed’ function increases the
width of the pulse by 100 µs. The generated PWM is of 500 Hz. That means total
time is 2 ms=2000 µs. The width of the
pulse is varied from 500 µs to 1500 µs in
steps of 100 µs. To display the speed, the
variable is first converted into speed factor ‘1’ to ‘9’ and then into ASCII.
6. ‘decspeed’ function is the same
as ‘incspeed’ but here the width of the
pulse is decreased by 100 µs.
7. ‘inctime’ function increases the
reversible time of the motor by one
second. It increases the variable in multiples of 20. To display it on the LCD
module, it is first divided by 20 and
then converted into ASCII.
8. ‘dectime’ function is the same as
‘inctime’ but it decreases reversible
time by one second.
Delay. It uses the following functions:
1. ‘keydly’ function generates a
fix delay of around 50 ms for key debouncing.
2. ‘delay’ function generates a variable delay by timer 0. The basic delay is
of 100 µs. It is rotated in loop from five
to 15 times to generate minimum 500µs
and maximum 1500µs delay.
3. ‘time’ function again generates a
variable delay by timer 1. The basic delay
is of 50 ms. It is rotated in multiples of 20
from 20 to 180 to generate minimum 1second and maximum 9-second delay.
dcmd.c
#include<reg51.h>
#include <string.h>
sbit rs = P3^1;
// rs pin of LCD
sbit en = P3^0;
// en pin of LCD
sbit rw = P3^2;
// rw pin of LCD
sbit b = P0^7;
// busy flag
sbit led1=P2^0;
// run indicator
sbit led2=P2^1;
// stop indicator
sbit led3=P2^2;
// clockwise direction indicator
sbit led4=P2^3;
// anticlockwise direction indicator
sbit PWM=P2^4;
// PWM output
sbit RL1=P2^5;
// relay 1 pin
sbit RL2=P2^6;
// relay 2 pin
unsigned int x=10;
//
ontime
unsigned int y=10;
//
offtime
unsigned int m=0;
// mode
unsigned int d=0;
// direction
unsigned int t=100;
// time
unsigned int r=0;
// run flag
void start(void);
// function initilization
void mode(void);
void direction(void);
void incspeed(void);
void decspeed(void);
void inctime(void);
void dectime(void);
void time(unsigned int);
void delay(unsigned int);
void keydly(void);
void busy(void);
void writecmd(unsigned char a)
// send command to LCD
{
busy();
// check busy flag
rs = 0;
// select command register
rw = 0;
// write enable
P0 = a;
// send byte to LCD
en = 1;
// apply strobe pulse
en = 0;
}
void writedata(unsigned char b)
// send data to LCD
{
busy();
KS Project Manual
EFY june 2009
// check busy flag
rs = 1;
// select data register
rw = 0;
// write enable
P0 = b;
// write enable
en = 1;
// send byte to LCD
en = 0;
// apply strobe pulse
}
void busy()
// check busy flag of
LCD
{
en = 0;
// disable display
P0 = 0xFF;
// P0 as input
rs = 0;
// select command register
rw = 1;
// read enable
while(b==1)
// if busy bit is 1
{
en=0;
// remain withine loop
en=1;
}
en=0;
}
void writestr(unsigned char *s)
// send string message to LCD
{
unsigned char l,i;
l = strlen(s);
// get length of string
for(i=0;i<l;i++)
{
writedata(*s);
// till the length of string
s++;
// send characters one
by one
}
}
void start()
// start rotating motor
{
if(m==0)
// for m=0 start continuous
mode
{
RL1=0;
// switch on RL1
r=1;
// set run flag
P1=0xFF;
// send all 1’s to P1
while(P1==0xFF)
// till no key is pressed
{
led1=1;
// indication on run LED
PWM=1;
// send high logic to PWM pin
delay(x);
// on time delay
PWM=0;
// now send low logic to PWM
delay(y);
// off time delay
}
}
else if(m==1)
// for m=1 start reversible mode
{
r=1;
// set run flag
P1=0xFF;
// send all 1’s to P1
while(P1==0xFF)
// till no key is
pressed
{
led1=1; // run LED=1
led3=1;
led4=0;
PWM=1;
// send high on PWM pin
RL2=1;
// select one direction
RL1=0;
// switch on RL1
time(t); // wait for desired time
RL1=1;
// switch off RL1
led1=0; // run LED=0;
time(20); // wait for 1 sec
led1=1; // again run LED=1
led3=0;
led4=1;
RL2=0;
// select other direction
RL1=0;
// switch on RL1
time(t); // wait for desire time
RL1=1;
// switch off RL1
led1=0; // run LED=0
time(20); // wait for 1 sec
}
PWM=0;
}
else if(m==2)
// for m=2 start jogging mode
{
r=1;
// reset run flag
P1=0xFF; // send all 1’s to P1
while(P1==0xFF)
// till no key is
pressed
{
led1=1;
PWM=1;
// send high on PWM pin
RL1=0;
// switch on RL1
time(t); // wait for 1 sec
RL1=1;
// switch off RL1
PWM=0;
// send low on PWM pin
led1=0;
time(20);
}
}
}
void direction()
// alter the direction
{
keydly();
// key debounce delay
d++;
// increment count
if((d%2)==0)
// check for even or odd
{
led3=1;
// indicate on LEDs
led4=0;
RL2=1;
// switch ON / OFF RL2
}
else
{
led3=0;
led4=1;
RL2=0;
}
}
void mode()
// change mode of rotation
{
keydly();
// key debounce delay
writecmd(0x80);
// display message on first line
first column
m++;
// increment count
if(m==3) m=0;
// if it is 3 reset it
if(m==0)
{ writestr(“mode:continuous
“);
// otherwise display mode
time(15);
}
else if(m==1)
{writestr(“mode:reversible “);
time(15);
}
else if(m==2)
{writestr(“mode:jogging
“);
time(15);
}
}
void decspeed()
// increase speed
{
int z;
keydly();
//
key debounce
writecmd(0xC0);
//
select second line on LCD
if(y<14) //
if not max pulse width
{
x--;
y++;
//
increase it convert it in to
z=y-5+0x30;
//
1 to 10 scale and ASCII
writestr(“speed: “); // diaplay speed on LCD
writedata(z);
writestr(“
“);
}
else if(y==14)
writestr(“min speed: 9 “);//
if max speed display message
}
void incspeed()
//
increase speed
{
int w;
keydly();
writecmd(0xC0); // key debounce
if(y>6) //
if not minimum width
{
x++;
y-- ;
// decrease
it
w=y-5+0x30;
// do same
as above
writestr(“speed: “);
writedata(w);
writestr(“
“);
}
else if(y==6)
writestr(“max speed: 1 “); //
if min speed display message
}
void inctime()
//
increase time
{
int p;
keydly();
//
key debounce delay
writecmd(0xC0);
if(t<180)
if not max time
{
//
KS Project Manual
EFY june 2009
t+=20;
//
increase it by 1 sec
p=t/20;
p=p+0x30;
//
convert it in to ASCII
writestr(“time: “); //
display it
writedata(p);
writestr(“
sec
“);
}
else if(t==180)
writestr(“max time: 9 sec”);
// if max time display message
}
void dectime()
//
decrease time
{
int q; keydly();
//
key debounce delay
writecmd(0xC0);
if(t>20) //
if not min time
{
t-=20;
//
decrease it
q=t/20;
q=q+0x30;
//
do same as above
writestr(“time: “);
writedata(q);
writestr(“
sec
“);
}
else if(t==20)
writestr(“min time: 1 sec”);
// if min time display message
}
void keydly()
//
key debounce delay
{
int a,b;
for(a=0;a<50;a++)
for(b=0;b<1000;b++);
}
void time(unsigned int c)
// change
time in seconds
{
int k;
TL1 = 0xAF;
// use timer 1
TH1 = 0x3C;
// to generate 50 ms delay
TR1 = 1;
//
start timer
for(k=0;k<=c;k++)
//
rotate loop in multiples of 20
{
while(TF1==0);
//
wait till timer overflow
TF1 = 0;
//
reset the flag
TL1 = 0xAF;
// reload it
TH1 = 0x3C;
}
TR1 = 0;
//
stop timer
}
void delay(unsigned int c1) / / c h a n g e
time in micro seconds
{
int a;
TH0=0x9B;
//
select timer 0
TL0=0x9B;
//
to generate 100 micro second delay
TR0=1;
//
start timer
for(a=0;a<c1;a++)
//
rotate loop between 5 to 15
{
while(TF0==0);
//
wait until timer overflow
TF0=0;
//
reset the flag
}
TR0=0;
//
stop timer
}
void main()
{
TMOD=0x12; // timer1 in 16
bit,timer 0 in 8 bit auto reload mode
P2=0xE0;
//
LEDs off, relays OFF
P0=0x00;
//
P0, P3 output ports
P3=0x00;
writecmd(0x3C);
//
initilize LCD
writecmd(0x0E);
writecmd(0x01);
writecmd(0x84);
//
display message
writestr(“DC Motor”);
// DC motor
controller in
writecmd(0xC3);
//
center of LCD
writestr(“Controller”);
agin:P1=0xFF;
//
P1 as input port
while(P1==0xFF);
//
wait until any key press
loop:switch(P1)
{
case 0xFE:
// for first key
keydly();
// key debounce
writecmd(0x01);
writestr(“motor start”);
time(50);
// wait for 2.5 sec
writecmd(0x80);
writestr(“mode:continuous
“);// display current mode and speed
writecmd(0xC0);
writestr(“speed: 5
“);
led1=1;
//
Run LED ON
led2=0;
//
stop LED OFF
led3=1;
//
clockwise direction ON
led4=0;
//
anticlockwise direction OFF
start();
//
sart rotating motor
break;
case 0xFD:
// for second key
keydly();
// key debounce
r=0;
// run flag reset
writecmd(0x01);
writestr(“motor stop”);// display message
led1=0;
//
Run OFF
led2=1;
//
stop LED ON
led3=0;
//
clockwise direction OFF
led4=0;
//
anticlockwise direction OFF
PWM=0;
//
low logic to PWM pin
RL1=1;
//
relay1 off
break;
case 0xFB:
// for third key
mode();
//
select mode
if(r==1) start();
//
jump to start if run flag is set
break;
case 0xF7:
// for fourth key
direction();
//
change direction
if(r==1) start(); // jump to
start if run flag is set
break;
case 0xEF:
// for fifth key
incspeed();
//
increase speed
if(r==1) start(); // jump to
start if run flag is set
break;
case 0xDF:
// for sixth key
decspeed();
//
decrease speed
if(r==1) start(); // jump to
start if run flag is set
break;
case 0xBF:
// for seventh key
inctime();
// increase time
if(r==1) start(); // jump to
start if run flag is set
break;
case 0x7F:
// for eigth key
dectime();
// decrease time
if(r==1) start(); // jump to
start if run flag is set
break;
}
if(r==1) goto loop;
//
if run flag is set jump of key detect
else goto agin;
//
if not jump to again
}
