8 ms·

Nixie-clock using neon lamps as logic (2017)

119 points by Ivoah 9y ago

Animats 9y ago
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
jackfrodo 9y ago
This is cool as hell. Shame to hear it's no longer working.
jwcacces 9y ago
Could you have used the individual Nixie digit tubes themselves as the counting state tubes?
smaudet 9y ago
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?
- extrapickles 9y ago
  You have to match each bulb with a resistor as each bulb has slightly different requirements. Edit: The properties change over the lifetime of the bulb in a non-linear way to make things even harder.
  - ferongr 9y ago
    Why not use a constant current supply instead? Inline resistors are a very primitive way of limiting current.
    - extrapickles 9y ago
      You would need one for each bulb as the problem is that the bulbs characteristics are not tightly controlled like they are for vacuum tubes and vary widely even in bulbs from the same lot.
      - Kubuxu 9y ago
        Circuit for multiple output current mirror [0] is very simple but then you start using transistors to run the neons and I think not using transistors was point of the project [0]: https://electronics.stackexchange.com/questions/256530/current-mirror-with-multiple-outputs https://electronics.stackexchange.com/questions/256530/curre...
- hazeii 9y ago
  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).
  - avian 9y ago
    > 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 9y ago
      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).
Symbiote 9y ago
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/styles/fresco_1200/public/migrated/artikel/field_body_images/img_8836.jpg?itok=Ojf0mVti https://1684654000.rsc.cdn77.org/sites/default/files/public/... from https://www.magasinetkbh.dk/indhold/neon-bog https://www.magasinetkbh.dk/indhold/neon-bog
- poizan42 9y ago
  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-klokkestreng http://www.aok.dk/byliv/vintertid-koebenhavn-i-en-klokkestre... http://www.jernbaneklub.dk/jernbanen/2008/jernbanen_nr4-august2008.pdf http://www.jernbaneklub.dk/jernbanen/2008/jernbanen_nr4-augu...
c12 9y ago
Even given how unreliable this ended up being over time the very fact that it was built in the first place is remarkably impressive.
elvinyung 9y ago
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
loph 9y ago
More good work by radio amateurs. PA3FWM is a ham.

119 points by Ivoah 9y ago

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

jackfrodo 9y ago

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

jwcacces 9y ago

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

smaudet 9y ago

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?

extrapickles 9y ago
You have to match each bulb with a resistor as each bulb has slightly different requirements. Edit: The properties change over the lifetime of the bulb in a non-linear way to make things even harder.
- ferongr 9y ago
  Why not use a constant current supply instead? Inline resistors are a very primitive way of limiting current.
  - extrapickles 9y ago
    You would need one for each bulb as the problem is that the bulbs characteristics are not tightly controlled like they are for vacuum tubes and vary widely even in bulbs from the same lot.
    - Kubuxu 9y ago
      Circuit for multiple output current mirror [0] is very simple but then you start using transistors to run the neons and I think not using transistors was point of the project [0]: https://electronics.stackexchange.com/questions/256530/current-mirror-with-multiple-outputs https://electronics.stackexchange.com/questions/256530/curre...
hazeii 9y ago
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).
- avian 9y ago
  > 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 9y ago
    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).

Symbiote 9y ago

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

poizan42 9y ago
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-klokkestreng http://www.aok.dk/byliv/vintertid-koebenhavn-i-en-klokkestre... http://www.jernbaneklub.dk/jernbanen/2008/jernbanen_nr4-august2008.pdf http://www.jernbaneklub.dk/jernbanen/2008/jernbanen_nr4-augu...

c12 9y ago

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

elvinyung 9y ago

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

loph 9y ago

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