DC Motor Controller

By Ashutosh Bhatt April 21, 2008

DC Motors are widely used for motion control in manufacturing industries. Motion of DC motor is controlled using DC Drive. DC drive changes the speed and direction of a motor. Many of the DC drives provides programmable facilities means to program the motion of motor. So here I am giving one such example where one can completely program the motion of motor. Using this DC Motor Controller one can:

Change the direction of motor
Change the speed of motor
Change the running mode of motor in continuous, reversible or jogging
Change the forward and reverse running time of motor

Some of the features of this controller are:

Programmable due to 89C51 controller
Push button control
Message display on LCD panel
LED indications
Can control DC motors from 12 V to up to 100V (up to 5 Amp)
Uses PWM (500 Hz) to change the speed of motor
Uses Darlington H-bridge for switching action

I have tested this controller with motor having following specifications

Motor type – DC series
Max operating voltage – 12 VDC
Max operating current – 2 Amp
Max RPM – 3000 @ 12 V

Complete circuit is combination of two sections

Control section
Driver section

DC Motor Control section includes 89C51 micro controller that actually controls the motion of motor depending upon given user commands. It receives user command through push buttons, generates all controlling signals, displays messages on LCD and give indications on LEDs

Driver section actually drives the DC motor. It provides sufficient voltage and current to run the DC motor in desire manner. It just receives signals from control section and rotates the motor

Control Section & Driver Section

Control section: –

Connections: – As shown in circuit tab 1 major components of the circuit are 89C51, LCD panel and hex inverter IC 7404. 8 push buttons are connected with P1. Data pins of LCD (D0-D7) are connected with P0. Control pins E, RS & RW are connected with P3.0, P3.1 and P3.2 respectively. Four LEDs are connected with P2.0 – P2.3 as shown. Other port P2 pins P2.4 – P2.6 are connected to the inputs of inverter IC 7404. The outputs of this chip are connected with driver section. One switch (RST) and capacitor C3 is connected in between Vcc and RST pin (pin no. 9) of 89C51 that will serve as power on reset circuit. EA pin (pin no 31) is connected with Vcc to enable internal excess. The circuit is energized by regulated 5 V supply.

Driver section: –

Connection: – Major components of this section as shown in circuit tab 2 are IC555, NPN Darlington pair TIP122 and PNP Darlington pair TIP127. This section will receive signals from control section A, B & C as shown. Signals B & C are used to switch ON / OFF relay RL1 and RL2 respectively through transistors Q1 & Q2. Signal A is connected to trigger input of IC 555 which is connected in monostable mode. Its output is connected with 2 inputs of Darlington H-bridge circuit through RL1 and RL2 connections. H-bridge circuit is made using 2 NPN and 2 PNP Darlington pairs. Collectors of TIP122 are shorted and tied to Vcc. The collector of TIP127 are shorted and tied to ground. A 220E resistor is connected with the base of each Darlington pair. As shown in figure bases of TIP122 and TIP127 of same side are shorted to take one common input. The DC motor is connected with output of h-bridge as shown.

Operation

Operation: – 8 push buttons connected are for eight different functions

Switch	Function
SW1	To start motor
SW2	To stop the motor
SW3	Change the direction
SW4	Change the mode
SW5	Increase speed
SW6	Decrease speed
SW7	Increase time
SW8	Decrease time

When SW1 is pressed micro controller will send low logic on P2.5 so signal B will be high (due to inheritor) that will switch on RL1. So output of IC555 is fed to Darlington pairs Q5 & Q6 through RL2 terminals 1 & 2. Darlington pairs Q3 & Q4 will be off due to their bases are connected to ground through 4 – 5 terminals of RL2. Now at the same time after switching RL1 micro controller will start generating PWM on P2.4 that is fed to trigger i/p of IC555 through inverter. The base frequency of generated PWM is 500 Hz that means time period is 2 ms = 2000 micro sec. The output pulse width varies from 500 micro sec to 1500 micro sec. The RC time constant of monostable mltivibrator is kept slightly less than 500 micro sec to generate exact inverted PWM that is generated by 89C51. PWM is fed to Q5 & Q6 that will start driving motor

Project Source Code

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#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();       // 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
    led1=0;     
    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
     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
     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=0;    // reset run flag
     PWM=1;    // send high on PWM pin
     RL1=0;    // switch on RL1
     time(20);   // wait for 1 sec
     RL1=1;    // switch off RL1
     PWM=0;    // send low on PWM pin
    }  
   }
 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
  else if(m==1) writestr("mode:reversible ");
  else if(m==2) writestr("mode:jogging    ");   
    }
  void incspeed()         // increase speed 
    {
      int z;     
   keydly();         // key debounce
   writecmd(0xC0);        // select second line on LCD
   if(y<15)          // 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==15) writestr("max speed: 10  "); // if max width display message      
  }
 void decspeed()           // increase speed 
    {
      int w;    
   writecmd(0xC0);         // key debounce        
   keydly();
   if(x<15)           // if not minimum width
       {
      x++;
    y--;          // decrease it      
    w=y-5+0x30;         // do same as above  
    writestr("speed: ");
    writedata(w);
    writestr("       ");
     }
   else if(x==15) writestr("min speed: 1   ");  // if min width display message      
  }
 void inctime()           // increase time 
   {
    int p;   
  keydly();           // key debounce delay
  writecmd(0xC0);          
  if(t<180)           // if not max time 
    {
   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)   // change 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, 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"); 
  time(50);      // wait for 2.5 sec
  writecmd(0x80); 
     writestr("mode:continuous "); // display current mode and speed
  writecmd(0xC0);
  writestr("speed: 5       "); 
  led3=1;       // stop LED on
  led2=1;       // clockwise direction
 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
    led2=0;     // stop LED 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
    led2=1;     // stop LED on
    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
   }
    
  
 
 
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