yet another NixieClock.

about the project

It's my second Nixie Clock project (here is the first one). This time it's gonna be the birthday gift for my Father


Tubes controlling

Nixie tubes work that way, that each character (eg. each digit) has its own output (unlike LED displays, there are no common segments here). There is one common Anode, where the high voltage is provided. To turn on a specific digit, we need to provide ground (-) to the appropriate cathode. For this we use transistors as keys. In the case of IN-16 tube, it's 12 pins, so 12 transistors for each tube (characters 0-9 and 2 dots); 48 transistors in total. Of course the microcontroller doesn't have so many GPIOs, so we need to use some extra chips. That chip is called a shift register. Without going into detail shift register receives data in serial and send it out to its outputs in parallel (after receiving all data). So in order to show a specific digit on the tube we need to send a certain combination of bits from the microcontroller to the shift registers. Let's consider such an example for the current hour 15:32 (CET). We need to send bit combination for digits 1 & 5 & 3 & 2

in case of hour 23:59 register values would be:

In the heyday of Nixie tubes, a special Nixie-drivers were produced (74141 or its soviet replacement K155ID1) that simplified controlling the tubes. However in this project, I chose transistors on purpose, as the availability of these chips is decreasing.

clock synchronization

At the beginning I wanted to synchronize the internal clock by radio signal through a special antenna on a ferrite core (photo below on the right) and the DCF77 protocol. However the DCF signal quality in Poland (aspecialy inside the buildings) is rather poor, and the protocol itself is quite slow and problematic. I guess, also the interference coming from the high-voltage converter could have cause the problem with DCF77. Anyway, with regret, I decided to synchronize time with GPS, which is absolutely perfect and easy to use . GPS module with antenna in the photo below on the left.

making of

adapting the Voltmeter (1 resistor has been replaced and the new scale has been installed)

yeaah ; there was a lot of soldering (each of the tube requires 12 transistor and 2 8-bit shift registers)

painting the box & preparing new scale

cutting the hole and preparing the box (it was a wine box)

At the video below you can see as the „Cuckoo” starts playing every full hour
There's 6 different melodies (stored on the SD card) ; which are played randomly.

Gliwice, 09/2020