Clock 1: A discrete nixie clock

STATUS: Developing

This is not a DTL clock but it still using only discretes. I found the idea here:
http://www.dos4ever.com/ring/ring.html#amazing

I have four TAF1093A nixies refurbished from scrap boards and I wanted to build a clock with it. Four digits meaning a minut resolution and not much visual effects. I decided to build a decimal time clock to get more visual effects:
https://en.wikipedia.org/wiki/Decimal_time

The TAF1093A has a point segment which can be used as running light 1/4 digit. A neon bulb acts as seconds marker.

The clock has also an alam function.

Some calculations

Mains frequency is 50Hz: 24x60x60x50 = 4320000 pulses/day
Clock range is: 0..9999
Running light range is: 0..3
Divisor is: 4320000/10000/4 = 108

I’m using synchronised astable multivibrators for the dividers. Maximum divisor ratio for such dividers is approx. 1/10, thus we need two of them: 9x12 = 108

The 3 and 4 digit outputs is used for the alarm. This gives a resolution of: 24*60/100 = 14.4 minuts (± 7.2 minuts )

Schematics

Figure 1. Schematic diagram clock 2 (1/2)

Figure 2. Schematic diagram clock 2 (2/2)

Table 1. Board list
#	Name	Status	PCB-files	PCBA-files	View
clk20a	discrete nixie clock	Development	brds/CLK20A/release/CLK20A-pcb.zip	brds/CLK20A/release/CLK21A-pcba.zip