
Nixie-clock using neon lamps as logic (2017) - Ivoah
http://www.pa3fwm.nl/projects/neonclock/
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Animats
The "integrated" form of that is the Dekatron.[1] That's essentially 10 neon
bulbs in one tube, with the electrodes arranged so they act as a counter.

Digital counting took too many parts before transistors. The Dekatron was one
attempt to get the parts count down.

[1]
[https://www.youtube.com/watch?v=o3HLZOJKEQU](https://www.youtube.com/watch?v=o3HLZOJKEQU)

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Symbiote
I see this clock on Copenhagen Main Station fairly often [1], made with giant
neon tubes.

It looks fairly old. Does anyone know how it originally worked, and if it
still works that way?

(My searching skills aren't good enough in Danish, but there are plenty of
Danish speakers on HN.)

[1]
[https://1684654000.rsc.cdn77.org/sites/default/files/public/...](https://1684654000.rsc.cdn77.org/sites/default/files/public/styles/fresco_1200/public/migrated/artikel/field_body_images/img_8836.jpg?itok=Ojf0mVti)
from [https://www.magasinetkbh.dk/indhold/neon-
bog](https://www.magasinetkbh.dk/indhold/neon-bog)

~~~
poizan42
There's surprisingly little information about it. All I can find is that it
was originally build in 1950 and was renovated in 2008, and it used to use
relays, which were broken for some time.

[http://www.aok.dk/byliv/vintertid-koebenhavn-i-en-
klokkestre...](http://www.aok.dk/byliv/vintertid-koebenhavn-i-en-klokkestreng)

[http://www.jernbaneklub.dk/jernbanen/2008/jernbanen_nr4-augu...](http://www.jernbaneklub.dk/jernbanen/2008/jernbanen_nr4-august2008.pdf)

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jackfrodo
This is cool as hell. Shame to hear it's no longer working.

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elvinyung
Woz is really well known for his interest in nixie clocks:
[https://www.youtube.com/watch?v=m4R3hODnTGo](https://www.youtube.com/watch?v=m4R3hODnTGo)

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jwcacces
Could you have used the individual Nixie digit tubes themselves as the
counting state tubes?

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loph
More good work by radio amateurs. PA3FWM is a ham.

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c12
Even given how unreliable this ended up being over time the very fact that it
was built in the first place is remarkably impressive.

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smaudet
So, looking at Wikipedia and comparing with his circuit PDF and what he said,
it sounds like there wasn't thought given to current stability. Apparently
these bulbs are very sensitive to too much current, so it sounds as if he was
literally breaking the bulbs to get it to work.

I wonder then if there might have been some way to control for this properly?

~~~
hazeii
Neon bulbs require a certain voltage to strike (for small ones, several 10's
of volts). Until they are struck they are very high resistance, once alight
they are low resistance until the voltage drops well below the striking
voltage.

This leads to an easy way to make a neon oscillator; put a capacitor across
the bulb, and a high value resistor in series to a 90v supply. The capacitor
charges to the strike voltage, then discharges until the neon extinguishes;
the oscillation rate and ratio characterises the particular bulb.

Don't know if it's still true, but they used to include radioactive tracers in
the neon to reduce the striking voltage (also I believe the striking voltage
varies with incident illumination).

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avian
> I believe the striking voltage varies with incident illumination

That is the principle behind this entry for the flashing light prize:

[https://www.youtube.com/watch?v=h8VJft5Xq5g](https://www.youtube.com/watch?v=h8VJft5Xq5g)

~~~
hazeii
Thanks for that! Great demo, and using strong UV shows the effect in spades
(I'd guess in this case you wouldn't want the radioactivity, so the
illumination effect from the photons is more pronounced).

