Nixie Clock Version 4

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This 6-digit nixie clock runs off a PIC 16F628 using a program written by Steve Rougier. The anode drivers consist of high voltage optocouplers, and the PIC provides sufficient signal voltage to activate the optocoupler LEDs via a 1K resistor to ground. The power supply consists of a small voltage doubler with two 10uF capacitors from 120V mains to get about 300 volts. An approximately 30K 2W resistor dropped the 300 volt source to 5 volts for the clock logics including the PIC. Otherwise, the circuitry is identical to the version provided by Steve Rogier. Steve used to host a website with information about the project, but it has gone defunct so the information provided here is the only copy of the information I have from his website.

A copy of the original schematic and source codes from Steve Rogier are provided here:
ASM source code
HEX source code - ready to program on a 16F628

Please note that the source code here was slightly modified to display the zero digit in the 10 hours during the single-digit hours like 09:00 instead of (blank) 9:00. I did not use all the features of this clock such as the alarm. Unfortunately, this clock has a very strange way with the switches for setting the time and changing modes from the default 24 hours to 12 hours. It took me a while playing around with the switches until I could find out what effects each switch had because the details were not quite clear on Steve's website. Below is a table that Steve provided on how to use the switches:

ModeButton 1Button 2Button 3Button 4Button 5Button 6
NormalNext modeAlarm on/offStop AlarmSnoozeStop AlarmStop Alarm
Set TimeNext modeHours +1Mins +1Reset secsReturn to Normal mode
Set AlarmNext modeAlarm hours +1Alarm mins +1Snooze +1Return to Normal mode
AdjustmentNext modeDownUp12/24 hourReturn to Normal mode
Alarm ToneNext modeDownUpFade Rate + 1
Display TestNext mode

Since I did not want to use all the features of the program, I only used 4 buttons for changing mode, hours, minutes, and to reset the seconds. According to my notes, the buttons did not seem to correlate to the suggested pinout ordering in the schematic. My notes indicate that I figured out Button 1 = RB3, Button 2 = RB1, Button 3 = RB4, and Button 5 = RB0.

I built a case using two layers of cedar wood glued together with the bottom piece cut out. The case was cut and sanded down to appear like a big wooden speedbump, then the six holes were cut out for the nixies. Since I did not have sockets for the nixies, I carefully soldered the wires directly on the pins of the nixies themselves. This is a very delicate job as the heat can crack the glass and render the nixie useless.

The case before drilling and staining.

The case after staining and the nixies glued in place.
The inner walls of the holes were painted black beforehand.

The completed innards of the clock.

The completed Version 4 Nixie Clock
This picture was taken at the instant the time rolled over to 4:00:00 so these digits began to fade in.

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