Have you ever seen the trademark amber glow of the Nixie Tube?
Nixie tubes have made a bit of a comeback by Makers and tinkerers of today’s tech — an old-school look with old-school innards using pretty simple technology to create some pretty spectacular results. Nixie tube clocks, signs, and even Nixie tube wrist watches, as worn by Steve Wozniak:
For those of you nerds out there like me who HAVE TO KNOW MORE ABOUT WOZ’S NIXIE WATCH RIGHT NOW OMFG OCD LALALALAAAAAA, please check this video out! Here’s Woz talking about scaring the crap out of his seatmates on flights as he changes the time zone! The maker of this watch is Cathode Corner, and they are pretty freaking cool!
Ok, ok, enough about the watch. Now as I was saying… NIXIE TUBES! In short, a Nixie tube is a little illuminator/signal tube that looks a lot like a vacuum tube but is actually a cold cathode discharge device with either digits in it or symbols. If you’ve ever seen the very popular hacker device called a Nixie Clock (or Nixie Tube Clock), then you know what a Nixie tube looks like. They’re pretty unmistakeable – a lot of vintage Russian gear from the 1960’s and 1970’s are filled with Nixie tubes for some reason. They make such a beautiful display, it’s essentially a kind of neon discharge tube, but not really:
A side note – this entire article came from me wanting to know the origin of the term “Nixie” in reference to these tubes. Nixie comes from a name that the draftsman working on the tube signal wrote down on his drafting plate – “NIX1,” for Numeric Indicator eXperimental #1. As you can imagine, the nickname “Nixie” stuck, and the guy who owned the patent also patented the name “Nixie.” WHY do I love this kind of knowledge?!
Nixie tubes are pretty simple technology that relies on cold cathode glow discharge technology, which is actually pretty cool! I’m sure you’ve heard of cathodes (the place where electrons come from) and anodes (the place where electrons flow to) – this is extremely important in understanding how these Nixie tubes work. The difference between a “hot” cathode and a “cold” cathode is basically in how the electrons move from the cathode to the anode. Instead of using heat to release electrons from something in a vacuum (like in fluorescent tubes and HID lamps), in the case of cold cathode devices the electrons are released by manipulating the electrical field in a vacuum. Now before this gets really crazy into field emissions and the Zener Effect (not to mention the Aston Dark Space and Positive Columns and Faraday’s Space and whatnot), it’s probably a good idea to simplify this a bit for brevity’s sake.
So, are you familiar with the way that tungsten-halogen lamps work? Basically, the gas inside them is from the halogen group (I can still remember the mnemonic – ‘F, Cl, Br, I!!‘) at a high pressure vacuum, and the filaments are tungsten. Gasses from the halogen group loves them some tungsten vapor fo sho, actually, which is why we use them together. As the filament burns at incandescence, atoms of tungsten evaporate from the filament into gas (think of it as a metal gas because, well, it is) and they float around in this halogen family gas. As the atoms of tungsten get near the considerably yet minutely cooler glass envelope of the lamp, they also cool down and are re-deposited on the envelope. Consequently, this is why and how we are able to make T-H lamps last longer and put out higher amounts of light; the redepositing of the atoms back onto the filament helps lengthen its life by re-coating the filament with “fresh” atoms of tungsten. This is called the T-H life cycle.
I didn’t explain the tungsten-halogen lamp because the Nixie and the T-H lamp are similar; I wanted to put a picture in your head about how atoms (and smaller subatomics) travel inside of a vacuum environment. In a really simplified explanation of how the Nixie tubes work, look at this great image of a discombobulated Nixie lamp, courtesy of the awesome people at the Evil Mad Scientist Laboratories:
See the mesh? That’s the anode, or the positively charged part. The numbers themselves, each one in the stack there, is an individual cathode, or the negatively charged part. Electrons and ions travel from the cathode to the anode (remember ACID and CCD to remember current flow – Anode Current Into Device and Cathode Current Departs). Inside the Nixie tube, there is a gas – typically one of the Noble gasses group of elemental gasses – that exists in low pressure inside the tube. When the anode and cathode are given a potential difference in charge, the gas atoms get all angry and split up into negatively charged electrons and positively charged ions. The ions are attracted to the negative cathode, and the electrons are attracted of course to the positively charged anode. As these ions go slamming into the cathode, something really interesting takes place — atoms of metal from the cathode are basically knocked out of the cathode in a process called sputtering. This sputtering of the metal atoms is literally caused by these ions slamming into the cathode. Imagine breaking a rack of billiard balls with a cue ball — make sense now?
Once the sputtered metal atoms are knocked loose and are flying around, there are also some electrons flying around, too. The electrons don’t have enough speed or energy to do much with the metal atoms floating close to the cathode (the number itself), so this weird little dark space called the Aston Dark Space (aka the Cathode Dark Space) takes place close to the cathode. It’s weird, but you can actually see it – look closely at this Crookes Dark Space Tube:
See the dark spaces right at the center? There is a small round cathode at the middle of that tube, and the dark space occurs right around it. The larger dark spaces on either side of the bright “ball” of light at the center of the Crookes tube is something else, called the Faraday Dark Space. Here’s another example, this one a diagram:
What’s cool about this glow outside of the Cathode Dark Space is what happens to make the glow happen — the electrons gain some speed and energy as they travel towards the positively charged anode (the mesh cage in the case of the Nixie Tube), and at a point outside of the Aston (or Cathode) dark space, they have enough energy and speed to cause a strong collision with the metal atoms sputtered away from the cathode. When this happens, *PRESTO* — we have the release of a photon which causes light!
I think these Nixie Tubes are quite awesome. Some history on the Nixie Tube’s patent and development:
The early Nixie displays were made by a small vacuum tube manufacturer called Haydu Brothers Laboratories, and introduced in 1955 by Burroughs Corporation, who purchased Haydu and owned the name Nixie as a trademark. [...] Similar devices that functioned in the same way were patented in the 1930s, and the first mass-produced display tubes were introduced in 1954 by National Union Co. under the brand name Inditron. However, their construction was cruder, their average lifetime was shorter, and they failed to find many applications due to their complex periphery.
Burroughs even had another Haydu tube that could operate as a digital counter and directly drive a Nixie tube for display. This was called a “Trochotron”, in later form known as the “Beam-X Switch” counter tube; another name was “magnetron beam-switching tube”, referring to their similarity to a cavity magnetron. Trochotrons were used in the UNIVAC 1101 computer, as well as in clocks and frequency counters.
The first trochotrons were surrounded by a hollow cylindrical magnet, with poles at the ends. The field inside the magnet had essentially-parallel lines of force, parallel to the axis of the tube. It was a thermionic vacuum tube; inside were a central cathode, ten anodes, and ten “spade” electrodes. The magnetic field and voltages applied to the electrodes made the electrons form a thick sheet (as in a cavity magnetron) that went to only one anode. Applying a pulse with specified width and voltages to the spades made the sheet advance to the next anode, where it stayed until the next advance pulse. Count direction was not reversible. A later form of trochotron called a Beam-X Switch replaced the large, heavy external cylindrical magnet with ten small internal metal-alloy rod magnets which also served as electrodes.
I found a lot of really amazing resources on the Nixie tube. I had to post some of it, this stuff is amazing, and there are a LOT of really big fans!
American Nixies from Sphere Research:
Russian Nixies from Sphere Research:
- One of the most complete and enormous collections of Nixie tubes on the internet. This site is quite intense.
- A scanned copy of the original Burroughs Corp. manual with Nixies and Pixie indicators
- A history on the Haydu Brothers corporation, the firm purchased by Burroughs
- A complete Nixie Tube disassembly from the awesome folks at Evil Mad Scientist Laboratories
- Build your own Nixie Tube Clock!
- a HUUUUUGE collection of purchasable Nixies from Sphere Research – this is a must-see website.
- Interactive DHTML Nixie tube clocks and counters for you Java nerds out there!
- Nixie Tubes on Wikipedia
- Display and counting tubes
- Nixie Tube Gallery from Tube Tester!
- Nixie Tubes from Explain That Stuff