EXPERIMENT 5. Oven Temperature Control Using Open loop and Closed Loop Methods

Transcription

1 VDD VEE RS RW E D0 D1 D2 D3 D4 D5 D6 D7 68% EXPERIMENT 5 Oven Temperature Control Using Open loop and Closed Loop Methods Aim: To learn how to use the interrupt, ADC and PWM functions to control the temperature of an oven using buttons, potentiometer and feedback loop from the thermocouple of the oven. 1) Draw the following circuit diagram using the Proteus Simulator D C B B1 150V A R2 10k U1 RV1 1 RE3/MCLR/VPP RC0/T1OSO/T1CKI RC1/T1OSI/CCP2 2 RA0/AN0/ULPWU/C12IN0- RC2/P1A/CCP1 3 RA1/AN1/C12IN1- RC3/SCK/SCL 4 RA2/AN2/VREF-/CVREF/C2IN+ RC4/SDI/SDA 5 RA3/AN3/VREF+/C1IN+ RC5/SDO 6 RA4/T0CKI/C1OUT RC6/TX/CK 10k 7 RA5/AN4/SS/C2OUT RC7/RX/DT 14 RA6/OSC2/CLKOUT 13 RA7/OSC1/CLKIN RD0 RD1 33 RB0/AN12/INT RD2 34 RB1/AN10/C12IN3- RD3 35 RB2/AN8 RD4 36 RB3/AN9/PGM/C12IN2- RD5/P1B 37 RB4/AN11 RD6/P1C 38 RB5/AN13/T1G RD7/P1D 39 RB6/ICSPCLK 40 RB7/ICSPDAT RE0/AN5 RE1/AN6 RE2/AN7 D1 D2 LED-RED PIC16F887 LED-GREEN R4 R R1 100 Q1 BC Volts T Heater OV1 OVEN LCD1 LM016L Set the oven parameters as follows: Ambient Temperature 25 Thermal Resistance to Ambient 0,02 Oven Time Constant 60 Heater Time Constant 6 Temperature coefficient 0,005 Heating Power 0,2 k Battery Active DC Voltage Source 150 V DC Voltmeter can be selected from the INSTRUMENTS menu on the lefthand toolbar 2) Open a new project called OvenPotControl and write the following MikroC code using the MikroC pro for PIC IDE. unsigned int temp,adc_rd; char i, text[7]; unsigned short current_duty1; sbit LCD_RS at RD2_bit; sbit LCD_EN at RD3_bit; sbit LCD_D4 at RD4_bit;

2 sbit LCD_D5 at RD5_bit; sbit LCD_D6 at RD6_bit; sbit LCD_D7 at RD7_bit; sbit LCD_RS_Direction at TRISD2_bit; sbit LCD_EN_Direction at TRISD3_bit; sbit LCD_D4_Direction at TRISD4_bit; sbit LCD_D5_Direction at TRISD5_bit; sbit LCD_D6_Direction at TRISD6_bit; sbit LCD_D7_Direction at TRISD7_bit; void main(){ ANSEL=0x03; //A0 and A1 are assigned as analog inputs ANSELH=0; TRISA=0x03; TRISD=0x00; //All pins of Port D are assigned as outputs to drive the LCD TRISB=0x03; //RB0 and RB1 are assigned as inputs for the buttons PORTC = 0; // set PORTC to 0 TRISC = 0; // designate PORTC pins as output PWM1_Init(5000); // Initialize PWM1module at 5KHz current_duty1= 30; // initial value for current_duty1 OPTION_REG.F7 = 0; //Enable pull up resistors for PortB pins WPUB=0x02; // Enable pull up resistor for RB1 PWM1_Set_Duty(current_duty1); // Set current duty for PWM1 Lcd_Init(); Lcd_Cmd(_LCD_CURSOR_OFF); INTCON.GIE = 1; //Global interrupt is enabled INTCON.RBIE = 1; //Logical change on Port B pins is enabled IOCB.IOCB1 = 1; INTCON.RBIF = 0; // PORTB interrupt flag is reset INTCON.INTE = 1; // RB0 interrupt is enabled INTCON.INTF = 0; // RB0 interrupt flag is reset while(1){ temp = (long)adc_read(0)*500/1024; //convert analog voltage from thermocouple into temperature with max value of 300 Deggree C IntToStr(temp, text); //Convert integer value of the temperature into string to display on the LCD Lcd_Out(1,1,text); current_duty1 = (long)adc_read(1)*255/1024; //Current duty1 is set according to the pot value PWM1_Set_Duty(current_duty1); // Set current duty for PWM1 void interrupt(){ if (INTCON.INTF == 1){ //If interrupt comes from RB0 Start Button PWM1_Start(); //Start the PWM1 INTCON.INTF = 0; //Reset RB0 interrupt flag RB7_bit = 1; // Turn ON the green light if the Start button is pressed RB6_bit = 0; // Turn OFF the red light if the Start button is pressed if (INTCON.RBIF == 1){ //If interrupt comes from RB1 Stop Button PWM1_Stop(); //Stop the PWM1 INTCON.RBIF = 0; //Reset RB1 interrupt flag RB7_bit = 1; // Turn OFF the green light if the Stop button is pressed RB6_bit = 0; // Turn ON the red light if the Stop button is pressed

3 3) Open a new project called OvenClosedLoopControl and write the following MikroC code using the MikroC pro for PIC IDE. unsigned int temp,adc_rd; char i, text[7]; unsigned short current_duty1; sbit LCD_RS at RD2_bit; sbit LCD_EN at RD3_bit; sbit LCD_D4 at RD4_bit; sbit LCD_D5 at RD5_bit; sbit LCD_D6 at RD6_bit; sbit LCD_D7 at RD7_bit; sbit LCD_RS_Direction at TRISD2_bit; sbit LCD_EN_Direction at TRISD3_bit; sbit LCD_D4_Direction at TRISD4_bit; sbit LCD_D5_Direction at TRISD5_bit; sbit LCD_D6_Direction at TRISD6_bit; sbit LCD_D7_Direction at TRISD7_bit; void main(){ ANSEL=0x01; ANSELH=0; TRISA=0x01; TRISD=0x00; //All pins of Port D are assigned as outputs to drive the LCD TRISB=0x03; //RB0 and RB1 are assigned as inputs for the buttons PORTC = 0; // set PORTC to 0 TRISC = 0; // designate PORTC pins as output PWM1_Init(5000); // Initialize PWM1module at 5KHz current_duty1= 30; // initial value for current_duty1 OPTION_REG.F7 = 0; //Enable pull up resistors for PortB pins WPUB=0x02; // Enable pull up resistor for RB1 PWM1_Set_Duty(current_duty1); // Set current duty for PWM1 Lcd_Init(); Lcd_Cmd(_LCD_CURSOR_OFF); INTCON.GIE = 1; //Global interrupt is enabled INTCON.RBIE = 1; //Logical change on Port B pins is enabled IOCB.IOCB1 = 1; INTCON.RBIF = 0; // PORTB interrupt flag is reset INTCON.INTE = 1; // RB0 interrupt is enabled INTCON.INTF = 0; // RB0 interrupt flag is reset while(1){ adc_rd = ADC_Read(0); // A/D conversion. Pin RA1 is an input. Read Potentiometer value temp = (long)adc_rd*500/1024; //convert analog voltage from thermocouple into temperature with max value of 300 Deggree C IntToStr(temp, text); Lcd_Out(1,1,text); if(temp>130){ //If the temperature is >130 deg C,

4 if(current_duty1>9){ current_duty1 = current_duty1-8; //decrease the duty ratio by 8 PWM1_Set_Duty(current_duty1); else ; if(temp<125){ //If the temperature is >130 deg C, if(current_duty1 < 250){ current_duty1 = current_duty1 + 5; //Increase the duty ratio by 5 PWM1_Set_Duty(current_duty1); else ; void interrupt(){ if (INTCON.INTF == 1){ PWM1_Start(); INTCON.INTF = 0; RB7_bit = 1; // Turn ON the green light if the Start button is pressed RB6_bit = 0; // Turn OFF the red light if the Start button is pressed if (INTCON.RBIF == 1){ PWM1_Stop(); INTCON.RBIF = 0; RB7_bit = 1; // Turn OFF the green light if the Stop button is pressed RB6_bit = 0; // Turn ON the red light if the Stop button is pressed 4) Open a new project called OvenClosed LoopControl and write the following MikroC code using the MikroC pro for PIC IDE. unsigned int temp,adc_rd; char i, text[7]; // Loop variable unsigned short current_duty1; sbit LCD_RS at RD2_bit; sbit LCD_EN at RD3_bit; sbit LCD_D4 at RD4_bit; sbit LCD_D5 at RD5_bit; sbit LCD_D6 at RD6_bit; sbit LCD_D7 at RD7_bit; sbit LCD_RS_Direction at TRISD2_bit; sbit LCD_EN_Direction at TRISD3_bit; sbit LCD_D4_Direction at TRISD4_bit; sbit LCD_D5_Direction at TRISD5_bit; sbit LCD_D6_Direction at TRISD6_bit; sbit LCD_D7_Direction at TRISD7_bit;

5 void main(){ ANSEL=0x01; ANSELH=0; TRISA=0x01; TRISD=0x00; TRISB=0x03; PORTC = 0; // set PORTC to 0 TRISC = 0; // designate PORTC pins as output PWM1_Init(5000); // Initialize PWM1module at 5KHz current_duty1= 30; // initial value for current_duty1 OPTION_REG.F7 = 0; //Enable pull up resistors for PortB pins WPUB=0x02; // Enable pull up rsistor for RB1 Lcd_Init(); Lcd_Cmd(_LCD_CURSOR_OFF); INTCON.GIE = 1; INTCON.RBIE = 1; //Logical change on Port B pins is enabled IOCB.IOCB1 = 1; //Logical change on RB1 is enabled INTCON.RBIF = 0; // PORTB interrupt flag is reset INTCON.INTE = 1; // RB0 interrupt is enabled OPTION_REG.INTEDG = 1; // RB0 interrupt is enabled on the rising edges of RB0 INTCON.INTF = 0; // RB0 interrupt flag is reset PWM1_Start(); while(1){ IntToStr(temp, text); Lcd_Out(1,1,text); void interrupt(){ if (INTCON.INTF == 1){ current_duty1 = current_duty1+10; INTCON.INTF = 0; RB7_bit = 1; // Turn ON the green light if the Start button is pressed RB6_bit = 0; // Turn OFF the red light if the Start button is pressed if (INTCON.RBIF == 1){ current_duty1 = current_duty1-10; INTCON.RBIF = 0; RB7_bit = 1; // Turn OFF the green light if the Stop button is pressed RB6_bit = 0; // Turn ON the red light if the Stop button is pressed PWM1_Set_Duty(current_duty1); // Set new current duty for PWM1 Conclusions: 1) Which instructions are used to configure the RB0 and RB1 interrupts? 2) How do you start and stop the PWM1 signal? 3) Why do you have to reset the interrupt flags in the interrupt routine? 4) How do you read analog values of the thermocouple and of the potentiometer?

6 5) How do you convert the value read from the analog inputs into a temperature and duty ratio? 6) Explain what you have learned from this experiment. 7) In which applications can you use the circuits and techniques that you have learned during this experiment? 8) What were the problems that you have faced with during this experimental work?