Make a Frequency Meter with a PIC16F73

When you are working with electronics, especially power electronics you must have to measure line frequency. But in most cases, people do not have a frequency meter. If you knew how to make a frequency meter in a very easy way, you would make one for yourself. Here in this article, we’ll learn how to make Frequency Meter with a PIC16F73 general-purpose microcontroller and LCD display. Using a multi-meter is ok to measure frequency but many people do not have a multimeter with a frequency meter or sometimes, you need to attach a meter onboard not a multi-meter. Considering these issues, making a frequency meter yourself may become very helpful.

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What is frequency meter?

A frequency meter is an instrument that displays the frequency of a periodic electrical signal. There are different types of frequency meters available in the market. Here are 3 types of frequency meters.

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Making our own frequency meter:

In the market, there are types of frequency meters. Making our own frequency meter is not so complex at all. All we need to use a micro-controller to sense frequency and display on LCD. Micro-controllers have timers built-in. Using the timer as counter mode, we can easily measure the frequency. Then printing this information on LCD is not a critical job at all. In our circuit, we will use the PIC16F73 microcontroller and 16×2 LCD display.

Circuit diagram:

MikroC Coding

/*******************************************************************************
* Program for, "Frequency Meter"                                               *
* Program Written by_ Engr. Mithun K. Das                                      *
* MCU:PIC16F73; X-Tal: 8Mhz; mikroC pro for PIC v7.6.0                         *
* Date: 15-05-2020                                                             *
*******************************************************************************/

// LCD module connections
sbit LCD_RS at RB2_bit;
sbit LCD_EN at RB3_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 TRISB2_bit;
sbit LCD_EN_Direction at TRISB3_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


char *freq = "000";
void Display_Freq(unsigned int freq2write)
{
   freq[0] = (freq2write/100) + 48;    // Extract tens digit
   freq[1] = (freq2write/10)%10 + 48;    // Extract tens digit
   freq[2] =  (freq2write/1)%10 + 48;    // Extract ones digit
   Lcd_Out(2, 11, freq);
   Lcd_Out(2,14,"Hz");
}


void main()
{
 TRISA = 0xFF;//all input
 TRISC = 0x00;
 PORTC = 0x00;
 PORTA = 0x00;
 ADCON1=0x00;
 Delay_ms(1000);

 OPTION_REG = 0b00101000; //Timer settings; T0CKI as input
 // of Timer0

 Lcd_Init();
 Lcd_Cmd(_LCD_CLEAR);
 Lcd_Cmd(_LCD_CURSOR_OFF);
 Lcd_Out(1,1,"FREQUENCY METER");
 Lcd_Out(2,1,"WITH PIC16F73  ");
 Delay_ms(2000);
 Lcd_Cmd(_LCD_CLEAR);

  while(1)
  {

      TMR0=0;
      Delay_ms(985);  // Delay 1 Sec // you need to calibrate this delay for accurate result
      Lcd_Out(2,1,"FREQUENCY:");
      Display_Freq(TMR0);


  }// while
}// void main

Here we used Timer0 as counter mode.

Timer0 settings:

Timer0 has a physical input clock pin (RA4/T0CKI). Using this input we can measure the pulse number for a certain time.

Note that, as the timer is 8bit. So we can only measure up to 256Hz with this method. If you need to measure a higher frequency, then we have to use the INT0 hardware interrupt.

Test result:

Conclusion:

We have learned to make a frequency meter using the Timer counter mode of the micro-controller. This frequency meter can be used in panel meters or similar sectors. As this meter can measure upto 256Hz so we can call it a low-frequency meter. Making a higher frequency meter is not complex at all. I hope I’ll cover that in another article.

For Professional Designs or Help:

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