Make it easy!: Nixie clock with Arduino

After long day working, finally i got successful making Nixie clock with Arduino and opto-isolation chip, no need Nixie driver which is difficult to purchase.

Watch the video for full instruction:

Part list to make project:

1. Arduino UNO https://amzn.to/2P58O7s

2. Nixie tube 6 pcs https://amzn.to/3aHyJvX

3. Opto coupler chip TLP627 https://amzn.to/2wiN0PG

4. DC step-up module from 12VDC to 390VDC https://amzn.to/30kpdK9

5. Breadboard https://amzn.to/2uCrnsW

6. Real time clock module DS3231 https://amzn.to/2SIyEzI

Step 1. Circuit design

The circuit uses opto-isolation chip to control Nixie tube (using 150VDC) by Arduino (using 5VDC). By matrix connection, so we need only 16 outputs from Arduino to control 60 lights of 6 nixie tube.
The real time clock module DS3231 is used to keep the time (even turn off power), it is communicated with Arduino by I2C network. Arduino will read real time, then turn on/off nixie lights by sequence in high frequency to make human eyes view 6 numbers as permanent

Step 2. Arduino code

//Youtube channel: engineer2you
#include <Wire.h>
#include "DS3231.h"

RTClib RTC;
DS3231 Clock;

int hour;
int minute;
int second;

const int nixie_0 = 2;
const int nixie_1 = 3;
const int nixie_2 = 4;
const int nixie_3 = 5;  
const int nixie_4 = 6;
const int nixie_5 = 7;
const int nixie_6 = 8;
const int nixie_7 = 9;
const int nixie_8 = 10;
const int nixie_9 = 11;

const int row_1 = 0;
const int row_2 = 1;
const int row_3 = 14;
const int row_4 = 15;
const int row_5 = 16;
const int row_6 = 17;

const int time_on = 2;

void setup() {
  pinMode(nixie_0, OUTPUT);
  pinMode(nixie_1, OUTPUT);
  pinMode(nixie_2, OUTPUT);
  pinMode(nixie_3, OUTPUT);
  pinMode(nixie_4, OUTPUT);
  pinMode(nixie_5, OUTPUT);
  pinMode(nixie_6, OUTPUT);
  pinMode(nixie_7, OUTPUT);
  pinMode(nixie_8, OUTPUT);
  pinMode(nixie_9, OUTPUT);
  pinMode(row_1, OUTPUT);
  pinMode(row_2, OUTPUT);
  pinMode(row_3, OUTPUT);
  pinMode(row_4, OUTPUT);
  pinMode(row_5, OUTPUT);
  pinMode(row_6, OUTPUT);
  //Serial.begin(9600); //should NOT use seiral println, it will effect to output pin D0 & D1
  Wire.begin();
}

void loop() {
    //-------------------get clock value---------------------------
    DateTime now = RTC.now();
    hour = now.hour();
    minute = now.minute();
    second = now.second();

    //-------------------show clock number ----------------------
    int j; //second number from right
    int k; //first number from right

      j = second/10;
      k = second%10;
      //-----------show first number of second
      off_all();
      on_number(0,k+2);
      delay(time_on);
      //-----------show second number of second
      off_all();
      on_number(1,j+2);
      delay(time_on);
      
      j = minute/10;
      k = minute%10;
      //-----------show first number of minute
      off_all();
      on_number(14,k+2); 
      delay(time_on);
      //-----------show second number of minute
      off_all();
      on_number(15,j+2);
      delay(time_on);

      j = hour/10;
      k = hour%10;
      //-----------show first number of hour
      off_all();
      on_number(16,k+2); 
      delay(time_on);
      //-----------show second number of hour
      off_all();
      on_number(17,j+2);
      delay(time_on);
}

void on_number(int row, int nixie){
  digitalWrite(row, HIGH);
  digitalWrite(nixie, HIGH);
}

void off_all(){
  digitalWrite(row_1, LOW);
  digitalWrite(row_2, LOW);
  digitalWrite(row_3, LOW);
  digitalWrite(row_4, LOW);
  digitalWrite(row_5, LOW);
  digitalWrite(row_6, LOW);
  digitalWrite(nixie_0, LOW);
  digitalWrite(nixie_1, LOW);
  digitalWrite(nixie_2, LOW);
  digitalWrite(nixie_3, LOW);
  digitalWrite(nixie_4, LOW);
  digitalWrite(nixie_5, LOW);
  digitalWrite(nixie_6, LOW);
  digitalWrite(nixie_7, LOW);
  digitalWrite(nixie_8, LOW);
  digitalWrite(nixie_9, LOW);

  delayMicroseconds(400);  //to prevent "ghost" effect to other tube
}