Arte De Guerra

Nixie clock using neon lamps as logic elements
(c) 2007, Pieter−Tjerk de Boer, pa3fwm@amsat.org − version 20070127 http://wwwhome.cs.utwente.nl/~ptdeboer/ham/neonclock/
+151V
100k

+151V

100k+151V

100k

+151V

100k

0 1 2 3 4 5 6 7 8 9

0 1 2 3 4 5 6 7 8 9

0 1 2 3 4 5 6 7 8 9

0 1 2 3 4 5 6 7 8 9

ten hours
820k

hours

ten minutes
820k 10k

minutes

LDRpulls Nixie cathode towards −90V when lit by neon lamp; otherwise 820k pulls it towards +8V, thus enhancing contrast. Two reasons for pulling to +8V and not +157V: − mechanical convenience − save somecurrent (but +8V now varies slightly with ambient light)

15n

15n

6k8

820k 6k8

15n

820k 10k

15n

68k 68k

220k

68k

68k

−90V

−90V

−90V

82n

82n

330n

82n−90V

+8V

+8V

+8V

+8V

82n

150k 100k 150k

15n 1M

150k 220k 150k

15n 330k 1M

150k 100k 220k

15n 1M 330k

100k 100k 220k

15n 1M

+8V

+8V

+8V

+151V+151V

+151V

Two blue LEDs illuminate the clock, which is needed for it to operate reliably when there is no ambient light.

When hours indicate 24...29, this capacitor discharges, changingDC−bias for buffer lamp such that it will oscillate to skip these hours. +157V

When a magnet closes the reed switch, the DC−bias for the buffer lamp changes such that it will oscillate, thus allowing theuser to set the clock.

+151V
180k 10uF 680n 100n 100n

230V
180k 10uF

47k 47k 100k 680n

+8V 0V
10k 47k 47k 47k

There’s nothing magic about the +8V: one shunt regulator couldn’tsupply enough current, so a second one was added whose output voltage happened to be less. Similarly, there’s nothing magic about +157V vs. +151V. A standard 5−stage ring counter. −90V

15n

8k2+151V

1/60 Hz

10k

10k

180k resistors serve both to evenly distribute the voltage over the electrolytic caps, and as "bleeder" to discharge them when 230 V is disconnected.

15n 15n 6k8...