Digital Voltage Temperature And Frequency Meter Using PIC 16F877

Digital Voltage Temperature And Frequency Meter Using PIC 16F877

Voltage meter

Volt meter can measure dc voltages up to 50v. 5V is the maximum voltage can handle PIC microcontroller, as it is voltage divider (10K,1.1K) use for convert 50V to 5V . 5v zener diode use for safety of PIC microcontroller analog input pin.

Temperature meter 

Temperature meter can use between 0⁰C to 150⁰C. But LM35 sensor can use between -55⁰C to 150⁰C. Sensor’s resistant is changing opposite to temperature, as it is maximum temperature gives maximum voltage output(5v)  and minimum temperature gives minimum voltage output(0v).

                                                      Frequency meter

Theoretically, frequency meter can use up to 65KHz, that is because this circuit made by using Timer 1(16bit) of PIC microcontroller.

// LCD module connections
sbit LCD_RS at RB4_bit;
sbit LCD_EN at RB5_bit;
sbit LCD_D4 at RB0_bit;
sbit LCD_D5 at RB1_bit;
sbit LCD_D6 at RB2_bit;
sbit LCD_D7 at RB3_bit;

sbit LCD_RS_Direction at TRISB4_bit;
sbit LCD_EN_Direction at TRISB5_bit;
sbit LCD_D4_Direction at TRISB0_bit;
sbit LCD_D5_Direction at TRISB1_bit;
sbit LCD_D6_Direction at TRISB2_bit;
sbit LCD_D7_Direction at TRISB3_bit;
// End LCD module connections

unsigned short cnt;
unsigned int freq_result;
int x, y, t;

// Define Messages
char message1[] = "      Hz  /65KHz";
char message2[] = "FERQUANCY METER";
char Message4[] = "VOLTAGE METER";
char Message5[] = "/MAX:50V";
char Message8[] = "TEMPERATURE ";
unsigned int ADC_Value, DisplayVolt;
unsigned int tempinF, tempinC;
unsigned long temp_value;
char *volt = "00.0";
char *freq = " 0000";
char *tempC = "000.0";
char *tempF = "000.0";

void Display_Freq(unsigned int freq2write) {

  freq[0] = (freq2write/10000)%10 + 48;
  freq[1] = (freq2write/1000)%10 + 48;
  freq[2] = (freq2write/100)%10 + 48;
  freq[3] = (freq2write/10)%10 + 48;    // Extract tens digit
  freq[4] =  freq2write%10     + 48;    // Extract ones digit

 Lcd_Out(2, 2, freq);                   // Display Frequency on LCD
}

void Display_Volt(unsigned int volts2write) {

  volt[0] =  volts2write/1000 + 48;
  volt[1] = (volts2write/100)%10 + 48;
  volt[3] = (volts2write/10)%10 + 48;

 Lcd_Out(2, 2, volt);                   // Display Voltage on LCD
}

void Display_Temperature() {
 if (tempinC/10000)
 tempC[0] = tempinC/10000 + 48;
 else
 tempC[0] = ' ';
 tempC[1] = (tempinC/1000)%10 + 48;
 tempC[2] = (tempinC/100)%10 + 48;
 tempC[4] = (tempinC/10)%10 + 48;
 Lcd_Out(2, 1, tempC);
 if (tempinF/10000)
 tempF[0] = tempinF/10000 + 48;
 else
 tempF[0] = ' ';
 tempF[1] = (tempinF/1000)%10 + 48;
 tempF[2] = (tempinF/100)%10 + 48;
 tempF[4] = (tempinF/10)%10 + 48;
 Lcd_Out(2, 10, tempF);
}

void main() {
  PORTB = 0;                            // Initialise PORTB
  TRISB = 0b01000000;                   // PORTB is output
  TRISA = 0b00001101;                   // PORTA All Outputs, Except RA0,RA3 and RA2
  TRISD = 0x0F;
  TRISC = 0x01;
  T1CON = 3;                            // Timer1 on, external input RC0
  TMR1IF_bit = 0;                       // clear TMR1IF
  TMR1H = 0x00;                         // Initialize Timer1 register
  TMR1L = 0x00;                         // Initialize Timer1 register
  cnt =   0;                            // initialize cnt
  Lcd_Init();                           // Initialize LCD
  ADCON0 = 0b00010000;                  // Analog channel select
  ADCON1 = 0x00;                        // Reference voltage is Vdd
  CMCON = 0x07 ;                        // Disable comparators
  Lcd_Cmd(_LCD_CURSOR_OFF);             // Cursor off
  x=1, y=0, t=1;
  do
  {
    temp_value = ADC_Read(0);
    temp_value = temp_value*56.238;
    tempinC = temp_value;
    tempinF = 9*tempinC/5 + 3200;
    ADC_Value = ADC_Read(2);
    TMR1H = 0;                             // reset high byte of timer 1 (takes effect when low byte written)
    TMR1L = 0;                             // reset low byte of timer 1 (also loads in high byte now)
    Delay_ms(500);  // Delay 1 Sec
    freq_result = TMR1L;                   // get low byte of timer 1 count (and read high byte to buffer)
    freq_result += TMR1H*256;              // add in the high byte from buffer
    freq_result *= 2.033;

     if(PORTD.B0==0 || x==0 )
      {
      x=0, y=1, t=1;
      PORTC.B1=1;
      PORTC.B2=0;
      PORTC.B3=0;
      PORTC.B4=0;
      Lcd_Cmd(_LCD_CLEAR);                  // CLEAR display
      Lcd_Cmd(_LCD_CURSOR_OFF);             // Cursor off
      Lcd_Out(2,1,message1);                // Write message1 in 1st row
      Lcd_Out(1,2,message2);
      Display_Freq(freq_result);            // show the Frequancy on LCD
      }
      if(PORTD.B1==0)
      {
      PORTC.B4=1;
      Lcd_Out(1,1,"p");
      x=1, y=1, t=1;
      }
      else{}
      if(PORTD.B2==0 || y==0 )
      {
      PORTC.B1=0;
      PORTC.B2=1;
      PORTC.B3=0;
      PORTC.B4=0;
      y=0, x=1, t=1;
      Lcd_Cmd(_LCD_CLEAR);                      // CLEAR display
      Lcd_Cmd(_LCD_CURSOR_OFF);                 // Cursor off
      Lcd_Out(1,3,Message4);
      Lcd_Out(2,9,Message5);
      Lcd_Chr(2,6,'V');
      DisplayVolt = ADC_Value * 4.94471;
      Display_Volt(DisplayVolt);                // show the Voltage on LCD
      }
      else{}
      if(PORTD.B3==0 || t==0)
      {
      PORTC.B1=0;
      PORTC.B2=0;
      PORTC.B3=1;
      PORTC.B4=0;
      y=1, x=1, t=0;
      Lcd_Cmd(_LCD_CLEAR);                     // CLEAR display
      Lcd_Cmd(_LCD_CURSOR_OFF);                // Cursor off
      Lcd_Out(1,4,message8);
      Lcd_Chr(2,6,223);
      Lcd_Chr(2,15,223);
      Lcd_Chr(2,7,'C');
      Lcd_Chr(2,16,'F');
      Display_Temperature();                  // show the Temp on LCD
      }
      else{}
  }
  while(1);                                   // Infinite loop
}

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