Published November 28, 2020 © GPL3+

DIY 6.5MHz Frequency Meter with MAX7219 7-Segment LED Module

A very simple but useful device for your lab.

BeginnerFull instructions provided10,268

DIY 6.5MHz Frequency Meter with MAX7219 7-Segment LED Module

Things used in this project

Hardware components

Arduino Nano R3

Max 7219 8 digit 7 Segmend Led module

General Purpose Transistor NPN

1N4148 – General Purpose Fast Switching

4 resistors

Capacitors

Software apps and online services

Arduino IDE

Hand tools and fabrication machines

Soldering iron (generic)

Story

A frequency meter is an instrument that displays the frequency of a periodic electrical signal. The video shows such an instrument where the value of the frequency is displayed on a 7-segment LED display in retro style, which is also very noticeable.

It can measure the frequency of signals with rectangular, sinusoidal and triangular shapes. Its measurement range is from a few hertz to 6.5 Megahertz. The code is simple thanks to "FreqCount" and "LedControl" libraries. The device consists of several components:

- Arduinio Nano microcontroller

- Shaping amplifier board

- 8 Digit 7 Seg Display

- and input jack

If we measure the frequency only on rectangular signals, then the input circuit (shaping amplifier) can be omitted, in which case we carry the signal directly to the D5 pin of the Arduino. The instrument is very precise in the whole range, and we can also calibrate the frequency meter with the simple procedure described below:

In the Arduino libraries folder find the FreqCount library,

in the FreqCount.cpp file find the lines:

#if defined (TIMER_USE_TIMER2) && F_CPU == 12000000L

float correct = count_output * 0.996155;

and replace them with:

#if defined (TIMER_USE_TIMER2) && F_CPU == 16000000L

float correct = count_output * 1.000000;

where 1.000000 is your correction factor, the

correction must be carried out by applying 1 MHz to the input of the frequency meter.

After changing the file, upload a new sketch to the Arduino board. Finally, the frequency meter is built into a suitable plastic box and is another useful instrument in the electronic laboratory.

Code

Arduino Code

#include <LedControl.h>//https://github.com/wayoda/LedControl/archive/master.zip
#include <FreqCount.h>//https://github.com/PaulStoffregen/FreqCount/archive/master.zip
LedControl lc = LedControl(12,11,10,1);// DIN(12), CLK(11), CS(10)

unsigned long f;
byte fq[7],pd=false;

void setup() {
  lc.shutdown(0, false);
  FreqCount.begin(1000);
  lc.clearDisplay(0); 
  lc.setIntensity(0,8); 
}

void loop() {
  if (FreqCount.available()) {f = FreqCount.read(); }
  lc.setRow(0,7,0x47);
  fq[6]= f/1000000%10;
  fq[5]= f/100000%10;
  fq[4]= f/10000%10;
  fq[3]= f/1000%10;
  fq[2]= f/100%10;
  fq[1]= f/10%10;
  fq[0]= f%10%10;
  for(int i = 0;i < 7;i++){
  lc.setDigit(0,i,fq[i],pd);
  }
}

Credits

Mirko Pavleski

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DIY 6.5MHz Frequency Meter with MAX7219 7-Segment LED Module

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

Schematics

Schematic

Code

Arduino Code

Credits

Mirko Pavleski

Comments

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DIY 6.5MHz Frequency Meter with MAX7219 7-Segment LED Module

DIY 6.5MHz Frequency Meter with MAX7219 7-Segment LED Module

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

Schematics

Schematic

Code

Arduino Code

Credits

Mirko Pavleski

Comments

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