Nixie tube

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Applications and lifetime

The way the digits are stacked in a nixie tube is visible in this picture.

Nixies were used as numeric displays in early digital voltmeters, multimeters, frequency counters and many other types of technical equipment. They also appeared in costly digital time displays used in research and military establishments, and in many early electronic desktop calculators, including the first: the Sumlock-Comptometer ANITA Mk VII of 1961. Later alphanumeric versions in fourteen segment display format found use in airport arrival/departure signs and stock ticker displays. Some elevators also used nixies to display the floor numbers. food dehydrator

Pair of NL-5441 Nixie display tubes chopper and blender

Average longevity of nixie tubes varied from about 5,000 hours for the earliest types, to as high as 200,000 hours or more for some of the last types to be introduced. There is no formal definition as to what constitutes "end of life" for nixies, mechanical failure excepted. Some sources (Weston 1968, p. 340) suggest that 50% reduction in emitted light would not be acceptable; however cathode poisoning resulting in incomplete digit display, whilst generally not preventing the tube from being used, may also be considered unacceptable. Nixie tubes are susceptible to multiple failure modes, including food processor cuisinart

simple breakage,

cracks and hermetic seal leaks allowing the atmosphere to enter,

cathode poisoning preventing part or all of one or more characters from illuminating,

increased striking voltage causing flicker or failure to light,

sputtering of electrode metal onto the glass envelope blocking the cathodes from view,

internal open or short circuits which may be due to physical abuse or sputtering.

Driving nixies outside of their specified electrical parameters will accelerate their demise, especially excess current, which increases sputtering of the electrodes. A few extreme examples of sputtering have even resulted in complete disintegration of nixie tube cathodes.

As testament to their longevity, and that of the equipment which used them, in 2006 several suppliers still provide common nixie tube types as service replacement parts, new in original packaging.[citation needed] Equipment with nixie tube displays in excellent working condition is still plentiful, though much of it has been in frequent use for 3040 years or more. Such items can easily be found as surplus and obtained at very little expense. It is worth noting that in the former Soviet Union, nixies were still being manufactured in volume in the 1980s, so Russian and Eastern European nixies are still generally easily and cheaply available.

One significant advantage of the ordinary Nixie tube is that its cathodes are typographically designed, shaped for legibility. In most types, they are not placed in numerical sequence from back to front, but arranged so that cathodes in front of the one that is lit obscure it minimally. The digit sequence is rarely given; one arrangement is 6 7 5 8 4 3 9 2 0 1 from front (6) to back (1). However, the photo above that shows a digit-4 cathode lit seems to have a 5 frontmost.

History

Systron-Donner frequency counter from 1973 with Nixie-tube display

The Nixie display was developed by a small vacuum tube manufacturer called Haydu Brothers Laboratories, and introduced in 1951 by Burroughs Corporation, who purchased Haydu and owned the name Nixie as a trademark. The name Nixie was derived by Burroughs from "NIX I", an abbreviation of "Numeric Indicator eXperimental No. 1." Similar devices that functioned in the same way were patented in the 1930s, and the first mass-produced display tubes were introduced in the late 1940s by National Union Co. and Telefunken. However, their construction was cruder, and they failed to find many applications until digital electronics reached a suitable level of development in the 1950s.

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 specfied 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.

This tube displays symbols, such as % and C.

Glow-transfer counting tubes, similar in essential function to the Trochotrons, had a glow discharge on one of a number of main cathodes, visible through the top of the glass envelope. Most used a neon-based gas mixture and counted in base-10, but faster types were based on argon, hydrogen, or other gases, and for timekeeping and similar applications a few base-12 types were available. Sets of "guide" cathodes (usually two sets, but some types had one or three) between the indicating cathodes moved the glow in steps to the next main cathode. Types with two or three sets of guide cathodes could count in either direction. A well-known trade name for glow-transfer counter tube in the United Kingdom was Dekatron. Types with connections to each individual indicating cathode, which enabled presetting the tube's state to any value (in contrast to simpler types which could only be directly reset to zero or a small subset of their total number of states), were trade named Selectron tubes.

Some Nixie-like displays made by other firms were called by various trademarked names including Digitron, Inditron and Numicator. A proper generic term is "cold cathode neon readout tube", though the phrase "nixie tube" quickly entered the vernacular as a generic name. Hundreds of variations of this design were manufactured by many firms, from the 1950s until the 1990s.

Alternatives and successors

Other numeric display technologies concurrently in use included backlit columnar transparencies, a.k.a. "thermometer displays", light pipe, rear-projection and edge-lit lightguide displays (all using individual incandescent or neon light bulbs for illumination); Numitron incandescent filament readouts; and vacuum fluorescent display tubes. Prior to nixie tubes' coming into prominence, most numeric displays were electromechanical in nature, using stepping switches either directly by use of cylinders bearing printed numerals attached to their rotors, or indirectly by wiring the switches' outputs to indicator bulbs. Later, a few vintage clocks even used a form of stepping switch to drive nixie tubes.

Nixie tubes were superseded in the 1970s by light-emitting diodes (LEDs) and Vacuum fluorescent displays (VFDs), often in the form of seven-segment displays. The VFD used a hot filament to emit electrons and phosphor-coated anodes, like a cathode ray tube, shaped to represent segments of a digit, pixels of a graphical display, or complete letters, symbols, or words. Whereas nixies typically require 180 volts to illuminate, VFDs only require relatively low voltages to operate making them easier and cheaper to use. VFDs have a simple internal structure, resulting in a bright, sharp and unobstructed image. Unlike nixies, the glass envelope of a VFD is evacuated rather than being filled with a specific mixture of gases at low-pressure.

Specialized high voltage driver chips such as the 7441/74141 were available to drive nixies. LEDs were better suited to the low voltages that integrated circuits used, which was an advantage for devices such as pocket calculators, digital watches and handheld digital measurement instruments. Also, LEDs were much smaller and sturdier, without a fragile glass envelope. LEDs had lower power consumption than both VFDs and Nixie tubes.

Revival

A Nixie clock.

Citing dissatisfaction with the aesthetics of modern digital displays and a nostalgic fondness for the styling of obsolete technology, significant numbers of electronics enthusiasts in recent years have shown interest in reviving nixies. Unsold tubes that have been sitting in warehouses for decades are being brought out and used, the most common application being in homemade digital clocks. This is somewhat ironic, since during their heyday, nixies were generally considered too expensive for use in mass-market consumer goods such as clocks. This recent surge in demand has caused prices to increase significantly, particularly for large tubes. The largest type known to be in the hands of collectors, the Rodan CD-47/GR-414 (220 mm [8.7 in.] tall), have been sold for hundreds of dollars apiece, but these are extremely rare and only found in a few areas of the world by persistent and fortunate seekers. Prices for other large types displaying digits over 25 mm (1 inch) tall have increased by double, triple or more between 1998 and 2005.

A Nixie watch on the wrist of Steve Wozniak, co-founder of Apple Inc.

In addition to the nixie tube itself, another important consideration is the circuitry to control the tube. One of the more popular ways to do this is to use the Texas Instruments' SN74141 BCD Decoder Driver IC (or its Russian equivalents, the K155ID1 and KM155ID1, with plastic and ceramic packages, respectively). These have long since been out of production, much like the nixie tubes they were designed for.

See also

Genericized trademark

Sixteen-segment display

References

^ (Weston 1968, p. 334), (Bylander 1979, p. 65)

^ a b (Bylander 1979, p. 60)

^ , KD7LMO Nixie Tube Clock -- There's an exploded diagram here.

^ 'Solid State Devices--Instruments' article by S. Runyon in Electronic Design magazine vol. 24, 23 November 1972, p. 102, via Electronic Inventions and Discoveries: Electronics from its Earliest Beginnings to the Present Day, 4th Ed., Geoffrey William Arnold Dummer, 1997, ISBN 0-7503-0376-X, p. 170

^ Scientific American magazine, June 1973, p.66

^ Numitron Readout

^ http://spectrum.ieee.org/consumer-electronics/gadgets/new-life-for-nixies Glen Zorpette, New Life for Nixies, IEEE Spectrum June 2002, retrieved 2010 Jan 31

^ Rodan CD-47 tube

Bylander, E.G. (1979), Electronic Displays, New York: McGraw Hill, ISBN 0-07-009510-8 , LCCN 78-31849.

Dance, J.B. (1967), Electronic Counting Circuits, London: ILIFFE Books Ltd , LCCN 67-13048.

Weston, G.F. (1968), Cold Cathode Glow Discharge Tubes, London: ILIFFE Books Ltd , LCCN 68-135075, Dewey 621.381/51, LCC TK7871.73.W44.

External links

Wikimedia Commons has media related to: Nixie tubes

Brief history of Haydu Brothers

Mike's Electric Stuff: Display and Counting Tubes

Nixie tube photos and datasheets (English) (German)

Nixie tube cross-reference tables

Giant Nixie Tube Collection (German)

Virtual nixie tube devices on-line: nixie display, clock, calculator

CD47 / GR-414 200mm Nixie Tube

YouTube video showing a Nixie Tube in action

Nixie Tube photographs and data

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