PIC Countdown Timer (0-99)

This project describes how to program PIC16F628A to function as a 00-99 min programmable timer. User can set any time between 00-99 minutes and can turn ON a device for that period. The device will be automatically turned OFF after the time expires. For demonstration, the ON/OFF condition of device is simulated by switching LED ON and OFF. With the use of three input switches (unit, ten, start/stop) the user can set ON time of the timer and can also control Start/Stop operation. The two time set switches are for selecting unit and tens digit of minute time interval (00-99). Once you set the value of minute interval, pressing the Start/Stop will turn the timer ON (LED will glow), and pressing the same button again at any point of time during timer operation will interrupt the process (LED will turn OFF) and the timer will be reset. LCD display will provide timer status and user interface for setting time.






Circuit

Code
Compiled using MikroC for PIC




/*
  ############################################

  MCU:16F628A
  Project: PIC Countdown Timer (0-99)
  Vishal K M
  Jan 10, 2012
  ############################################

 
*/

// LCD module connections
sbit LCD_RS at RA0_bit;
sbit LCD_EN at RA1_bit;
sbit LCD_D4 at RB4_bit;
sbit LCD_D5 at RB5_bit;
sbit LCD_D6 at RB6_bit;
sbit LCD_D7 at RB7_bit;
sbit LCD_RS_Direction at TRISA0_bit;
sbit LCD_EN_Direction at TRISA1_bit;
sbit LCD_D4_Direction at TRISB4_bit;
sbit LCD_D5_Direction at TRISB5_bit;
sbit LCD_D6_Direction at TRISB6_bit;
sbit LCD_D7_Direction at TRISB7_bit;
// End LCD module connections

// Tact switches and Relay ports
sbit Relay at RA3_bit;
sbit SS_Select at RB0_bit;    // Start Stop Timer Select
sbit Unit_Button at RB1_bit;  // Set unit min
sbit Ten_Button at RB2_bit;   // Set ten min


// Messages
char Message1[]="Timer by VISHAL";
char Message2[]="Device ON";
char Message3[]="Device OFF";
char Message4[]="Set Time:    min";
char Message5[]="Time Left:   min";
unsigned short i, j, unit=0, ten=0, ON_OFF=0, index=0, clear, time;
char *digit = "00";
// 300ms Delay
void Delay_300(){
 Delay_ms(300);
}

void Display_Digits(){
 digit[1]=unit+48;
 digit[0]=ten+48;
 Lcd_Out(2,11,digit);
}

void start_timer(unsigned short MinVal){
 unsigned short temp1, temp2;
 Relay = 1;
 ON_OFF = 1;
 Lcd_Cmd(_LCD_CLEAR);
 Lcd_Out(1,1,Message2);
 Lcd_Out(2,1,Message5);
 OPTION_REG = 0x80 ;
 INTCON = 0x90;
 for (i=0; i<MinVal; i++){
  temp1 = (MinVal-i)%10 ;
  temp2 = (MinVal-i)/10 ;
  Lcd_Chr(2, 12, temp2+48);
  Lcd_Chr(2, 13, temp1+48);
  j=1;
  do {
  Delay_ms(1000);
  j++;
  } while(((j<=60) && (Clear ==0)));
  if (Clear) {
   Relay = 0;
   Delay_ms(500);
   Lcd_Out(1,1,Message3);
   INTCON = 0x00;
   goto stop;
   }
 }
 stop:
 Relay = 0;
 ON_OFF = 0;
 unit = 0;
 ten = 0;
 clear = 1;
}

void interrupt(void){
  if (INTCON.INTF == 1)   // Check if INTF flag is set
   {
    Clear = 1;
    INTCON.INTF = 0;       // Clear interrupt flag before exiting ISR
   }
  }

void main() {
  CMCON  |= 7;                       // Disable Comparators
  TRISB = 0b00001111;
  TRISA = 0b11110000;
  Relay = 0;

  Lcd_Init();                        // Initialize LCD
 start:
  clear = 0;
  Lcd_Cmd(_LCD_CLEAR);               // Clear display
  Lcd_Cmd(_LCD_CURSOR_OFF);          // Cursor off
  Lcd_Out(1,1,Message1);
  Lcd_Out(2,1,Message4);
  Display_Digits()  ;
 do {

     if(!Unit_Button){
     Delay_300();
     unit ++;
     if(unit==10) unit=0;
     Display_Digits();
    } // If !Unit_Button

    if(!Ten_Button){
     Delay_300();
     ten ++;
     if(ten==10) ten=0;
     Display_Digits();
    } // If !Ten_Button

    if(!SS_Select){
     Delay_300();
     time = ten*10+unit ;
     if(time > 0) start_timer(time);
    } // If !SS_Select

    if(clear){
     goto start;
    }
   } while(1);
}







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Digital Voltmeter using PIC Microcontroller

This is a simple voltmeter which measures 0-5V at a precision of 4.8 mV. This is a simple design using inbuilt ADC of PIC 16F877A. PIC 16F877A have 8 channel 10bit ADC.  Measured voltage is displayed on 16x2 LCD display.

Using one of the most popular 8 bit PIC 16f877A, for instance, reading the datasheet, we'll find that the ADC modules (10 bit) are controlled by four different registers. The first two, ADCON0 and ADCON1, are used to set and start the ADC module. When high level language is used, the programmer doesn't need to care a lot of the register connected to the results because they are normally stored in a variable by a routine of the language itself (adc_read, for instance, using mikroc).

The ADCON0
As we can see this registers are 8 bit registers where.
- bit6 and bit 7 are used to set the frequency of the conversions.
- bits 3, 4 and 5 are used to select the pins of the microcontroller enabled to theadc conversions.
- bit 2 represents the status of the conversion procedure.
- bit 0 starts the conversion.

Regarding the second register, ADCON1, it must be set for two reasons: to select the format of the result value (bit 7), to select (bit0...bit3) the reference voltage and to set the port configuration control bits according to the following table

This circuit uses AN0 channel of ADC. The voltage conversion is employed in a logic, 16F877A have 10 bit ADC. That is, it can have 1024 levels. Reference voltage is fixed at

0 – 5 V Analog I/P is mapped to one of the 1024 levels (0-1023 Digital Count)

Resolution = 5/(1024)   (as it is 10 bit ADC)
= 5/1024
= 4.8828 mV   It  means that for a change in 4.8828mV, the binary output changes by 1.

For More Details See
PC Based Digital Voltmeter Using PIC 16F877A

ADC module of PIC Microcontroller converts the Signals on its analog pin to 10 bit binary data and it has software selectable high and low voltage reference input to some combination of VDD, VSS, RA2 and RA3. The analog input to PIC is limited to 0 to 5.The converted value is in mV. It is then converted to volts and displayed on LCD.

 Circuit

Digital Voltmeter using PIC Microcontroller 

 Code

/**********************************************/

/*

  

 http://www.facebook.com/EmbeddedProjects

 http://microcontrollerprojects00.blogspot.in/

 Author: Vishal K M

 uC:16F877A

 Compiler: mikroC

 Crystal freq: 4MHz

                                              */

/**********************************************/

// LCD module connections

sbit LCD_RS at RC0_bit;

sbit LCD_EN at RC2_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 TRISC0_bit;

sbit LCD_EN_Direction at TRISC2_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;

// End LCD module connections

unsigned long temp;

unsigned int i;

char digit[]="0.000 VOLTS";

void main() {

TRISA=0xFF;

ADCON0=0x01;

ADCON1=0x0E;

 

     Lcd_Init();                        // Initialize LCD

  Lcd_Cmd(_LCD_CLEAR);               // Clear display

  Lcd_Cmd(_LCD_CURSOR_OFF);          // Cursor off

  LCD_Out(1,1,"EMBEDDED");

   LCD_Out(2,1,"PROJECTS BLOG");

   Delay_ms(1000);

  do {

    temp = ADC_Read(0);   // Get 10-bit results of AD conversion

    temp=temp*5000/1023;   //Convert ADC value to mV

   

   

    digit[0]=(temp/1000)+48;

    digit[2]=((temp%1000)/100)+48;

    digit[3]=(((temp%1000)%100)/10)+48;

    digit[4]=(((temp%1000)%100)%10)+48;

   

    LCD_Cmd(_LCD_CLEAR);

    LCD_Out(1,1,digit);

      //Carriage Return

    Delay_ms(500);

  } while(1);

}

Download Project Files

PC Based Digital Voltmeter Using PIC 16F877A

Voltmeter C# .Net PIC, Arduino, AVR

This is a simple voltmeter which measures 0-5V at a precision of 4.8 mV. This is a simple design using inbuilt ADC of PIC 16F877A. PIC 16F877A have 8 channel 10bit ADC.  This is a computer interfaced project. Measured voltage is output in serial interface software in computer. There is a serial interface circuit (MAX232) is necessary for interfacing with computer, which is not included in the circuit. Please check     PIC Serial Communication Tutorial (UART)  for the circuit and more details.

Using one of the most popular 8 bit PIC 16f877A, for instance, reading the datasheet, we'll find that the ADC modules (10 bit) are controlled by four different registers. The first two, ADCON0 and ADCON1, are used to set and start the ADC module. When high level language is used, the programmer doesn't need to care a lot of the register connected to the results because they are normally stored in a variable by a routine of the language itself (adc_read, for instance, using mikroc).

The ADCON0
As we can see this registers are 8 bit registers where.
- bit6 and bit 7 are used to set the frequency of the conversions.
- bits 3, 4 and 5 are used to select the pins of the microcontroller enabled to the adc conversions.
- bit 2 represents the status of the conversion procedure.
- bit 0 starts the conversion.

ADCON1

Regarding the second register, ADCON1, it must be set for two reasons: to select the format of the result value (bit 7), to select (bit0...bit3) the reference voltage and to set the port configuration control bits according to the following table

ADCON1

This circuit uses AN0 channel of ADC. The voltage conversion is employed in a logic, 16F877A have 10 bit ADC. That is, it can have 1024 levels. Reference voltage is fixed at

0 – 5 V Analog I/P is mapped to one of the 1024 levels (0-1023 Digital Count)

Resolution = 5/(1024)   (as it is 10 bit ADC)
= 5/1024
= 4.8828 mV   It  means that for a change in 4.8828mV, the binary output changes by 1.

ADC module of PIC Microcontroller converts the Signals on its analog pin to 10 bit binary data and it has software selectable high and low voltage reference input to some combination of VDD, VSS, RA2 and RA3. The analog input to PIC is limited to 0 to 5.


The converted value is in mV. It is then converted to volts and characters to send to serial port.
Normal hiperterminal application can be used for reception. Comments are given in program to easy understanding.

Click here for the PC program

PIC 16F877A Voltmeter

Code

/**********************************************/

/*

  

 http://www.facebook.com/EmbeddedProjects

 http://microcontrollerprojects00.blogspot.in/

 Author: Vishal K M

 uC:16F877A

 Compiler: mikroC

 Crystal freq: 4MHz

                                              */

/**********************************************/

unsigned long temp;

unsigned int i;

char digit[]="0.000-VOLTS ";

void main() {

TRISA=0xFF;

ADCON0=0x01;

ADCON1=0x0E;

UART1_Init(9600);               // Initialize UART module at 9600 bps

  Delay_ms(100);                  // Wait for UART module to stabilize

 

   UART1_Write_Text("Embedded Projects");

   UART1_Write(0x0D);

  do {

    temp = ADC_Read(0);   // Get 10-bit results of AD conversion

    temp=temp*5000/1023;   //Convert ADC value to mV

   

   

    digit[0]=(temp/1000)+48;

    digit[2]=((temp%1000)/100)+48;

    digit[3]=(((temp%1000)%100)/10)+48;

    digit[4]=(((temp%1000)%100)%10)+48;

   

    UART1_Write_Text(digit);

    UART1_Write(0x0D);   //Carriage Return

    Delay_ms(500);

  } while(1);

}