IN-8 single nixie tube clock using PIC16F84
After receiving one IN-8 tube from a friend (thanks), I decided to build myself a clock. This clock is more an ornament than a useful machine because it consists of just one digit (tube) so it displays current time every minute for three times. It is built inside of an old wooden box and it’s powered from a 7V DC wall adapter. Under a nixie tube there is a very bright green LED which makes everything look more beautiful. When time is not displayed, this LED blinks with 1 second period (seconds counter).
To power-up a nixie, some 170V DC is required, which means that there is a step-up converter on board with MC34063A IC.
You can download the project files at the bottom of this page by clicking on red “download” button.
Setting up the time
To set the time press the button and power-up the clock. This will enter the programming mode. Now 00, 00, 00,… will be displayed. Press and hold the button until hours are set. Release the button to switch to minutes. Now do the same thing with the minutes and that’s it! After programming, the current time will be displayed.
Timekeeping and measuring
Inside of this box there is a 3V Lithium battery (CR2032) that keeps the PIC microcontroller running even when the clock is turned off (the wall adapter). This is very convenient because after powering it up again, we don’t need to set the time – again. If a button is pressed during a power-down, nothing will happen. With PIC microcontroller I used a “watch” crystal at 32,768kHz. It’s value is pretty cool and now we will see why. PIC16F84 has internal TMR0 counter that increments itself no matter what the PIC is doing at the moment.
For more detail: IN-8 single nixie tube clock using PIC16F84