Overview
In this project i built a six digit nixie clock based on Z5660M tubes with 30mm digits. The concept of the electronics is based on a main circuit board and an additional tube board. The Case is made out of single wooden block.
This project is fully open source and open hardware so you can do your own modifications!
Electronic Design
The idea of this project was, to design a main board with a microcontroller, power supply and control logic. This board can be used for a lot of different builds and tubes. I also developed a tube board for B13B base tubes with colon separators.
For the controlling the nixie cathodes i used two HV5122 IC's from Microchip, they contain a 32bit shift register and can sink up to 250 Volts per Channel. This leaves 2 Outputs per IC for colon speparators or something like this.
For keeping the time i used a battery-backed DS3231 RTC which comes with built in very accurate crystal. A DS3232 which has additional eeprom space could also be used. Four buttons and one potentiometer are used for various settings
The microcontroller is a Atmega238 with Arduino Bootloader. This makes it very easy to change the code or make custom versions.Serial and ISP connection is available. There are enough pins left for additional devices/inputs on X1. Its possible to connect a DCF77 or GPS time receiver and a enable signal (PIR etc.), im currently working on the code for this.
For the power supply i used a MAX1771 along with suitable parts. Choice of parts is really important for stability and efficiency. This circuit can deliver up to 50mA at 190V. Voltage is adjustable from 150V to 250V. The coil i used makes very low audible noise compared to alot of other coils. If the coil is glued to the pcb, the noise will even be more quiet.
Here you can see the assembled circuit board:
Colon separators
The two colon separators are selfmade, i used IN-3 Neon Bulbs and 12mm chemical test tubes. The tubes were cutted to the right lenght (70mm) with a Dremel Tool and a diamond blade. This had to be done, because the Z5660M Tubes have that little stem on top, if i had used 75mm standart test tubes it would look very odd. For ZM1042/1040 tubes, 75mm tubes fit very well.
Case
The case is made out of a 50mm thick walnut plank. 30mm holes for the tubes and 13mm holes for the separators were drilled by a box column drill. The space for the pcb was milled out by a hand router. After finishing all milling and drilling i used oil and wax to give the wood a nice, but still natural look. It took very long to make the case, but the cost for the material was about 0$, because got some free wood from a carpenter.
Schematic
Here you can find the schematic of the main board.Schematic of the tube board is available in the .zip file below.
Resources
Here are the design-resources like Eagle files and arduino code.
Eagle, Mainboard.zip Eagle, Tubeboard.zip Drawing, Case-Top Drawing, Case-Top 2