A NIXIE clock

For a long time I have wanted to build a NIXIE tube display type clock.

In fact, I started this project back in 2006 when I made a PCB at home to accommodate the 6 NIXIE tubes plus driver devices, 74HC595 and 74141.

The board sat unused in the project 'bin' until now, in late 2024 I decided to do some more work on it.. Too many other projects.

On another of my web pages, I built an NTP based clock using a a T FT display which works very nicely.

So, I decided to resurrect the NIXIE board and integrate it with the TFT display clock in link above.

This NIXIE clock is a little more complicated than the TFT display clock in that it needs a 12v and 5v supply plus a DC/DC converter to produce the high voltage required by the NIXIE tubes, of around 170v. Data for various NIXIE tubes is easily found on the WWW. It should be noted that the major source for NIXIE tubes is Russia and because of he current conflict, may not be available from that source. A search on the usual sites though, should find various NIXIE tubes as new old stock (NOS). In this project I used IN-17 devices.

The driver chips, 74141 are also sourced from Russia normally. These are a binary to decimal device but the output is rated to switch the high voltage of the NIXIE tubes.

For the 170v supply, I made my own PCB based on a design using the 64063 switch mode controller device. There are also complete, ready made supplies.

The Micro used must have a WiFi connection to access the NTP time data and the easiest device to use, I have found, is the ESP32 micro which is readily available.

I take no credit for the software ('sketch' in IDE speak) as the original NTP clock was heavily based on the project from Bruce Hall, W8BH. I came across this project on the SoftwareControlledHamRadio Groups.io group where Bruce posted links to his project. Thanks Bruce. (Bruce has a number of cool clock projects on his web pages. http://www.w8bh.net/clocks.pdf )

See http://www.w8bh.net/NTP_DualClock.pdf Full details of the original W8BH clock and how it works.

Bruce's Github software for this project.

In the conversion to a NIXIE display clock, I am indebted to John, WA2FZW for assistance with the NIXIE changes. A programmer I am not.

The original NTP clock, being based on a TFT display, had a number of advantages over the NIXIE clock in that much more data and text can be presented on a TFT based clock. Obviously a nostalgia NIXIE based version, doesn't have that capability and only offers Local or UTC time, selected by using a switch to ground on Port D4.

I have not done it, but things like alternaing DATE/TIME or switch to DATE could be made. etc.

Picture of the NIXIE display

< click for larger view >

Schematic of the NIXIE clock is here. It is not complete in that it does not show details of the 3v3 to 5v Logic level converter. The ESP32 is a 3v3 board, while the NIXIE board uses 5v logic levels. I used a small PCB available on the usual web sites for the logic voltage conversion. Packed BCD format is used to send each of the Hrs, Minutes or Seconds to the NIXIE tubes, 3 bytes are sent each update, one byte per 74HC595.

Software is here. (ZIP File, right click to SAVE) I used the Arduino IDE,configured for the ESP32 for the code writing. Please note that the Sketch (code) is unfinished at this stage (Jan 2025) and although functional, looks a bit messy as the original clock code for the TFT display has just been rem'd out, rather than totally removed. It will be tidied up later. I also plan to add alternate time information from a GPS receiver, to make it more standalone.

The ESP32 board I used in the pictures actually has a small 128x64 pixels OLED display on it, and was used in development to mirror the NIXIE time. It could be enhanced with other information if required, however, most any ESP32 board will work fine, without the OLED display. In that case, remove the OLED code.

< click for larger view >

This ESP32 board has a built in OLED display. Entirely optional. If not used, check where writes to the OLED are made and remove them from the code. The little PCB just visible on the right hand side, in the proto board, is a logic voltage converter. On eBay.com search for 4 channel logic level converter. Typically about US$1.20 + shipping. A 4 way board is required, even though only 3 are used.

Eventually, I may have a PCB made to take the ESP32 board and a logic converter board as the ESP32 is 3v3 while the NIXIE board uses 5v.

This is the DC/DC converter board which converts 12v to 170v of the NIXIES. It was home made based on the MC34063 data sheet. Actual output of mine was 158v from 12v input.

< click for larger view >

I used an old 19v output LAPTOP power supply to get 12v and 5v supplies from the AC mains supply (230v in Australia). This used another home made board using conventional circuits. ie LM7805 & LM7812 voltage regulator devices.

Another source for the 170v supply are various converter boards, ready made, available on the usual web pages. Search for NIXIE POWER SUPPLY. There are a number of them available, ranging from about US$6 to $20 or even more, don't buy those ! Some will run from 5v so you can eliminate the 12v supply for the 170v converter I used in my project.

This is NOT a full construction article on building a NIXIE clock, nor is it finished, but is presented as is, for experienced constructors. There are many NIXIE clock projects on the Web, have a look at them also.

No PCB's or any other material or parts are available from me.

Some mentions of companies on this page are for completeness only. I have no connection to any of them.

This project is based on the excellent work by W8BH.

The above is how I made a NIXIE tube version, your mileage may vary.

Page created by vk3pe (QRZ.COM) and last updated on January 10, 2025