DC Motor Control with PIC18F2420/2520/4420/4520

DC Motor Control with PWM

DC (Direct current) motors frequently use in motion control systems. These can be run your robots, give you relief in summer session as fan and etc. If you are going to motion control field and you did not learned about motors control, you cannot do anything.

In this chapter we will discuss about controlling a small DC motor with PWM(see my post on PWM for briefly detail). Hardware designing for motors is a pestilential task to selection the components, find accurate motor parameters value like as current, heating, torque, etc. We  need to test the circuit many of times.

Hardware Circuit

We are using L298 H-bridge driver IC to bidirectional DC motor control. L298 have duel bridge circuit and can be go up to 2 amperes current load each and accept TTL logic (Can connect directly with microcontroller) supply input in order to control the bridge circuit.

 

We will connect bridges parallel to get higher current output. See L298 datasheet “Figure-7” and read all of related information (Recommended) is given blow of figure (In datasheet) before make circuit.

In the schematic R1 resistance is current sensing resistance to sense the L298 output current. We can set output current limit by going on with practical and find the right value of resistance. R1 resistance watts would be calculated according to your motor load. You can change motor direction by S1 SPST switch.

CCP2 (PWM mode) module is using for controlling motor speed according to PORTA-0 pin analog input voltage. You can vary motor speed (0-100%) proportional to analog input (0-5v). 

Refer to my previous articles for detailed description:-

http://embeddedooo.blogspot.com/2017/02/pulse-width-modulation-pwm.html

http://embeddedooo.blogspot.in/2017/02/analog-to-digital-converter-adc-in.html

Codes

#include <p18f2520.h>

#define Rvrs_Input PORTBbits.RB0      // Forward/Reverse input

#define Forward PORTBbits.RB2          

#define Reverse PORTBbits.RB1

void ADC_result(void);

void config_timer2(void);

void config_PWM_ccp2(void);

float ADC_data;

void main()

{

            TRISA=0xFF;                        // PORTA as Input

            TRISB=0x01;                        // PORTB-0 as Input abd other pins as Output

            PORTB=0x00;         

            TRISC=0x00;                        // PORTC as Output

            PORTC=0x00;

           

            ADCON0 = 0x01;    // ADC on, Channel-0 select.

            ADCON1 = 0x0E;    // Volt reference VDD to Vss, AN-0 as analog input.

            ADCON2 = 0xAE;    // Right justified, 12 TAD, FOSC/64.

            config_PWM_ccp2();

            config_timer2();

           

            while(1)

            {

                        ADC_result();

                        if(Rvrs_Input==1)

                        {

                                    Reverse=1;

                                    Forward=0;

                        }

                        if(Rvrs_Input==0)

                        {

                                    Reverse=0;

                                    Forward=1;

                        }

                        CCPR2L = ADC_data * 45;      // Set ADC_data as per PR2 range.

            }          

}

void ADC_result()

{

            ADCON0bits.GO = 1;                   // Set ADC conversion in progress.

            while( ADCON0bits.GO == 1 );   // Wait until conversion is not complete.

            ADC_data = (ADRESL + (ADRESH * 256)) / 204.8;   // Convert AD value to                                                                                                            voltage.

}

void config_timer2()

{

            // Timer2 Registers:

            // Prescaler=1:1; TMR2 PostScaler=1:11; PR2=227 - Freq = 2,002.40288Hz -                   Period = 0.4994 ms

            T2CONbits.T2OUTPS3 = 1;          // Postscaler selection bits

            T2CONbits.T2OUTPS2 = 0;

            T2CONbits.T2OUTPS1 = 1;

            T2CONbits.T2OUTPS0 = 0;

            T2CONbits.TMR2ON  = 1;            // Timer2 on bit: 1=Timer2 is on;

            T2CONbits.T2CKPS1 = 0;             // bits 1-0  Prescaler Rate Select bits

            T2CONbits.T2CKPS0 = 0;

            PR2 = 227;                                      // PR2 (Timer2 Match value)

}

void config_PWM_ccp2()

{

            CCPR2L=0;                                  // Set duty cycle register value to 0.    

            CCP2CONbits.CCP2M3 = 1;       //Selecting PWM mode

            CCP2CONbits.CCP2M2 = 1;

            CCP2CONbits.CCP2M1 = 0;

            CCP2CONbits.CCP2M0 = 0;

}

Download Project file :- https://drive.google.com/file/d/0B886Kbl42IVuTDZqdGQtbFVnSEU/view?usp=sharing