On this enterprise, I will design and present a straightforward Frequency Counter Circuit, which might be utilized to measure the frequency of an indication. This enterprise depends on 8051 Microcontroller, although you probably can design a non-microcontroller mannequin.


A frequency counter is an instrument that is used to measure the frequency of an indication. In scientific phrases, frequency is the number of cycles per second of an indication. In layman phrases, frequency of an indication denotes the pace of incidence of the register certain time. Frequency Counters are primarily straightforward counter applications with a restricted time interval for counting.

Proper right here we design a straightforward frequency counter system using two timers and two counters. Whereas certainly one of many Timer IC is used to produce clock indicators, the other is used to produce the time restricted signal of 1 second.

Moreover Study the Submit – Two Digit Up-Down Counter Circuit

Frequency Counter Circuit Working Principle

This circuit depends on the simple definition of frequency, which is the number of cycles per second. Principally, a Sq. Wave Generator circuit is used to produce a straightforward pulse wave. These pulses are given as enter to the Timer / Counter of the 8051 Microcontroller and rely the number of pulses.

After performing some straightforward calculations, the following frequency is displayed on a 16X2 LCD Present in Hertz.

An important stage to note is that I’ve used Arduino UNO as a result of the provision for Sq. Wave. It is advisable to use each Arduino or a really assemble your particular person Sq. Wave Generator using 555 Timer IC by configuring it as an Astable Multivibrator.

Frequency Counter Circuit Diagram

Frequency Counter Circuit Circuit Diagram

Frequency Counter Circuit Design

As I’ve used Arduino to generate the Sq. Wave, all I would like is only a few strains of code and entry to a single Digital I/O Pin. Nonetheless in case you might be planning to assemble a Sq. Wave Generator circuit using 555 Timer IC, the understand the subsequent rationalization.

The primary requirement inside the 555 Timer circuit is to generate an oscillating signal with an obligation cycle of about 99% such that the time low value is decrease than the time extreme value of the output signal.  Since duty cycle depends upon solely on the price of the sting and discharge resistors, it might be adjusted by choosing the right values of resistors.

Schematic of IC 555 as Astable Multivibrator

The duty cycle is given by D = (R1+R2)/(R1+2R2)

Substituting the price of D to be 0.99, we get the price of R1 to be 98 events the price of R2. Thus, deciding on a value of 100Ω for R2 and 9.8KΩ for R1. Just about the price of 10KΩ is chosen for R1.

Subsequent step inside the designing of the circuit is the design of the counter circuit. Proper right here our requirement is the measurement of frequency of the order of few Kilo Hertz. As talked about inside the circuit principle, I’ll in all probability be using the Timer / Counter of 8051. Truly, I’ll in all probability be using every Timer Zero and Timer 1 of the 8051 Microcontroller.

I’ll in all probability be using Timer Zero to generate Time Delay and Timer 1 to rely the Pulses coming from the center beat generator. Timer Zero is configured as Timer in Mode 1 whereas Timer 1 is configured as Counter in Mode 1. 

Do you in regards to the concept – Bi Directional Buyer Counter using 8051 Microcontroller


Following is the code for Frequency Counter Circuit using 8051 Microcontroller.

Frequency Counter Circuit Operation

Make the connections as per the circuit diagram and apply the Pulse generated by Arduino at Port three Pin P3.5, which is the Timer 1 Pin. As I’ve configured the Timer 1 as counter, using the TCON Bit TR1, I’ll in all probability be counting the pulses for a interval of roughly 100 milliseconds by making TR1 HIGH and LOW. The rely of the pulses is saved in Timer 1 i.e. in TH1 and TL1 Registers.

To get the price of the frequency, you could use the subsequent parts.


With a goal to transform the Frequency Value to Hertz i.e. Cycles per Second, it’s advisable to multiply the resultant value by 10. After this, the resultant value is formatted by performing some straightforward arithmetic so that will in all probability be easy to indicate the tip end result on the 16X2 LCD Present.

Frequency Counter Circuit Image 2

Functions of this Circuit

  1. The Frequency Counter Circuit using 8051 Microcontroller might be utilized to exactly measure the frequency of an indication.
  2. Since we’re counting pulses, we are going to measure the frequency of solely sq. waves and its derivatives (with completely totally different duty cycles.)



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