Since my firmware now has the capability to display scrolling text messages on alphanumeric tubes using a Wifi module, I wanted to design a nixie clock to exploit that feature. The B7971 nixie tubes are rare, but it seems there are still some around, and may be a lot of them just waiting for the right design! These tubes are big and beautiful, and since they are rather rare and very large, I decided a four digit design would be economical and yet more than adequate for a scrolling text nixie clock. The clock can also be used without the wifi module, but will not have the scrolling text/date feature.
The text display can be selected from three choices of text message, date or just to keep time. Please click here to view the video on youtube with captions. The time zone can be selected and DST automatically updates in those time zones where it is employed. It can also be set for either standard twelve hour clock or for twenty four hour clock. It's also optional to select 12 hour format with leading zero or not, as well as 24 hour format with/without leading zero. The led under lighting color can be selected from several preset colors by pressing the "LED COLOR" button, and the display can be set to turn on/off at preset times and also the toggle button can turn the display on/off manually any time.
This video (above) demonstrates some of the available features, such as the four modes for 12/24 hour (with/without leading zero in each), the scrolling date, and the "sleep/wake" mode which presets "on" and "off" times for the display. Please click here to view it on youtube with captions.
The WIFI module is connected to the network using your device, and thereafter it updates time once per second. The date is also acquired from the network, and updated every second as well. To enter a text message to be displayed once every minute from seconds count 43 to 0, you press the reset button on the module until the small blue led lights, then connect to the module using your device and enter your message, then refresh the time on the clock.
Pressing the LED COLOR button rotates the led under lighting through the choices, and pressing the toggle button will turn the display on/off..
This nixie clock is available as a kit you can build yourself, or as a built clock complete except for tubes. There is only one complete assembled clock with tubes currently available, since I haven't been able to obtain any more of these tubes, however if I do I will add another! I still wanted to put this project up to let those of you who have some of these tubes (or hope to obtain some) the chance to try them in my design.
As always, the design is meant to be both aesthetically pleasing and sturdy. The circuitry is composed of standard size components that are easier to work with and much easier to replace than the small surface mount components. In many cases, the smaller parts like surface mount components are also not suitable for the nixie tube clocks, due to the wattage generated which may destroy these small parts over time. The design is deliberately simplified so only essential components are included, making it possible to place everything on one pc board. The circuitry is controlled using one microcontroller, the PIC18f46K20, which has enough digital I/O pins to control all the drivers and take input from the buttons as well as the WiFi module.
Risks and challenges
One challenge with this design was to adapt the scrolling text to four tubes instead of six, and also to a program for the firmware to drive the high voltage tubes using multiplexed outputs. In previous designs that used nixie tubes I used a high voltage decoder chip, however since the alphanumeric tubes have fourteen segments to drive, a different design had to be created. The microcontroller I chose was suited to the design because it has four ports with more than thirty I/O pins, making it possible to drive each tubes separately and each segment individually.Learn about accountability on Kickstarter
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