Nixie Clock with Arduino | Simplest Design

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

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

Buy electronic component on utsource.net

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
}

Basically, the code will get real-time from module DS3231 and show to 6 nixie tube via opto-isolation chip.

Step 3. Build the circuit

This is just experiment, so I made everything in breadboard. Fortunately, it works at first time, no any problem

In next step,  I will try to make nixie clock in MDF case with good decoration, so I can put it in my room.