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Display and counting tubes

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Dekatrons   Electron-beam tubes Filament indicators Neon 7-segment tubes

Nixie Tubes

anim.gif (26707 bytes)These neon-filled numeric displays, also known as 'numicators', consist of an outer mesh anode, with ten cathodes (or 11/12 with decimal point/points) shaped to form numbers. They were popular in the 1960s and early 70s when the first logic ICs became available, the 7441 or 74141 TTL devices often being used as a driver, and can still sometimes be seen in old electronic test equipment. I can provide custom-built nixie displays for TV/Film use - please email if interested.

Nixie etc. Links      
Build a nixie clock Full construction info and PCB artwork. Nixie Sources, data and pinouts Tons of info on Nixies & dekatrons Here More info on nixies and other display devices Here.
Burroughs Nixie Catalogue Patents on nixies and similar devices Nixie Clock Gallery  
Ingenious use of neons in HP nixie instrument. Nixie tube power supply circuit For running nixoes from  low voltage DC supplies. Supertex make high voltage driver chips that can be used to drive nixies.

If counting glassware isn't clever enough for you, check out this amazing glass Analogue to Digital converter!

Javascript Nixie clock Neonixie discussion group at yahoogroups - all the latest nixie news and design hints etc. A nixie tube cable TV box Alphanumeric nixie four-letter word generator
History of the E1T counter tube      

Left to right : Standard tube (probably Mullard ZM1175), Mullard ZM1080, with orange coating on glass to improve colour, Unusual ITT tube with sine, spiral, minus and plus indicators, 'stretch NE-2' lamp used as first digit in 3 digit display, Valvo/Ultron ZM1042 1.3" high digit.
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Huge 6" nixie Type CD47/GR414 RODAN Indicator Tube by Okaya Japan,  plus East German 2" and 1.3" tubes (picture from Jorgen Lund-Nielsen), Burroughs B7971 2.5" alphanumeric tube, Okaya CD13 0.3" subminiature tube - as used in my nixie car clock.

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Three end-viewed nixies, 1" STC GN-4D, 1.3" Cintel 'Cathvisor' N.I.7, 1.5" STC GN-5 (sizes are bulb diameter).

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Giant National NL-8091 tube, digit height 1.5", tube dia. 2"

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A 'pixie' tube, which lights a neon glow on one of ten plates behind a numeric aperture mask. Unlike nixies, this one seems to  have a common cathode and ten anode connections - sounds odd but this is the only way I could get this tube to display properly. Markings worn off - probably made by Valvo. Info on Burroughs Pixie tube.
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Dekatron counter tubes

dekanim.gif (57613 bytes)These 1950's tubes function both as counters and displays. The one below left (Ericsson GC10B) has 30 cathodes arranged around a central anode disc. Each cathode is connected to one of three external pins, forming ten electrode groups. Applying three sequentially phased pulses to these pins makes the glow discharge jump from one electrode to the next. An external phase-shift network is used to provide the sequencing, resulting in a counter that advances the glow by three electrodes for every single input pulse. These tubes were often used in geiger and frequency counter applications, and as prescalers for a mechanical counter, count rates of 20-100Khz being possible. Other variations included divide-by 12 tubes, tubes with seperate connections to all ten cathode groups  (to enable divide-by-N operation - second photo), and display-only versions with ten electrodes, which were used to provide a consistent-looking display on instruments using a combination of high-speed valve dividers and dekatrons. Note that in the photo below, the exposure time makes more than one electrode appear lit. Got some dekatrons? Here are a couple of simple circuits to bring them to life.

Ericsson GC10B & GS10C, Hivac GS10H, 17 pin base, 1.5" high.

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Detailed description of dekatron operation from 1954 Ericsson data book, including datasheets. Info on an early dekatron based computer  Data sheets for Elesta (Swiss) EZ10/10B dekatrons  Original advertisment for dekatrons

Another related device was the Nomotron (G10/240E), which was a unidirectional counting tube, made by STC from 1951. It used only a single-phase input, as opposed to the three of the dekatron. The discharge was directed between the ten cathodes by means of special electrode shaping, and the tube was capable of counting at up to 25KHz. The count state is visible through small holes in the front electrode, but as th eglow is small and rather hard to see, this was really only useful as a diagniostic aid rather than a proper display. See this old advert  (Electronic Engineering, July 1951).

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The tube contains ten main cathodes (k0 to k9) brought out separately to base pins. The cathodes are equally spaced around a circle and between each is a transfer electrode (t). The transfer electrodes are joined and taken to a single base pin. Around the cathodes is a single anode cup and there is a shield to restrict the glow to discrete areas.
If a glow discharge be assumed between the anode and ko, the potential between them will be the normal maintaining voltage of a gas-filled valve ; the difference between this and the anode supply voltage is the voltage drop across anode and cathode load resistors. The asymmetric geometry of the cathode and transfer electrodes makes any shift of the glow discharge inherently unidirectional. When a negative pulse is applied to the transfer electrodes, the discharge is compelled to spread to the most strongly primed transfer electrode tt and the fall of anode voltage (due to increased current in the anode resistor) extinguishes the anode k;, gap. At the end of the negative pulse, tt will return to its positive bias potential and since k,~ is positively biased by the residual charge in a capacitor in the cathode circuit the discharge moves to the most strongly primed unbiased electrode, i.e. k1. At first, the discharge transfers to the cathode "tail" but quickly moves to the main part of the cathode to avoid the excessive maintaining voltage associated with high current concentration on the small tail area. Priming of tz is thus effected in readiness for the next transfer pulse.

Electron-beam counting tubes

burr.jpg (4603 bytes)e1t.jpg (7162 bytes)e1tanim.gif (38552 bytes)<Burroughs 'Beam-X switch' type BX-2004
Another type of counting device, a crossed-field decimal counting tube - more info on these devices Here.   This was purely a computing tube, and didn't display, but could drive a nixie tube. It originally had a metal magnetic shielding sleeve covering the tube, which has been removed on this example. The base has 26 pins. Mullard also produced a similar device, the ET51 Datasheet here Original press report on Burroughs tube  Datasheet for ETL VS10G Trochotron

> Valvo (Later Mullard) E1T,  an electron-beam count & display device, using a fluorescent screen to display the count. Datasheet here.


Neon 7-segment displays

These were the immediate ancestors of modern LED 7-segment displays, and are still used for some large-display applications.
Sperry SP-151 display from Heathkit car clock (half inch digits) Data, Tung-Sol Digivac S/G DT-1704B, modern Japanese (make unknown) NEO-8000M  flat-panel display (3.5"   digit)

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Filament displays

Before LEDs, filament lamps were also used for digital displays. To my knowledge there were three basic types of these:

00824001.JPG (306602 bytes)FilAlpd31.jpg (1868 bytes)1) Segment displays which used linear filaments as segments, the whole display being encapsulated in a sealed glass enclosure. These were made in in both rectangular Dual-In-Line and nixie-style 'bulb' packages , the former in 1 and 2 digit versions.  Sometimes known as 'minitrons', these can occasionally still be seen in old petrol pumps.
Images :  Japanese 7-segment DIL packaged display, 'Pinlites' 14-segment alphanumeric display,  RCA DR2000 'Numitron'

projdisp.jpg (3762 bytes)ruspro1.jpg (18538 bytes)2) Projection displays, using ten lamps with a digit mask in front of each, and optics to project the digit onto a translucent screen at the front. The only place I have ever seen these is in an old  digital voltmeter. Thanks to Richard Schipper for the picture (right) of a display made by Counting Instruments Ltd, Borehamwood, Herts UK. On the left is a russian projection display, picture from Alexander Bakerin.

99C08018.JPG (319785 bytes)project.gif (21820 bytes)Tiny projection displays "IN-LINE Digital Display Type 70" by Counting Instruments, UK. These plug into a mounting frame to allow easy access for lamp changing Digit height is 9mm, module size is 20 x 12 x 47mm. The digit masks are made from a piece of photographic film, and 3 sheets of moulded plastic lenses provide the required optics.

wpe15.jpg (76394 bytes)fruit.gif (42736 bytes)The Counting Instruments company appear to have also ventured into areas other than digital displays - These fairly large ones look like they were destined for fruit machines (Slot machines / one-armed bandits). Thanks to Pete Crunden for the following info : The fruit-machine display was probably used in a Spanish arcade
machine. I remember seeing something similar about 10 years ago while on holiday in Spain. I learnt later (while working for Barcrest) that the Spanish government (in a somewhat lame attempt to make things harder for fruit machine manufacturers/operators, without actually banning slot machines altogether) used to have a law whereby the reels of a fruit machine could not be greater than 1" in diameter. They got round this by using projection displays (like yours) or two small (legal)reels, between which was threaded a sort of conveyor belt on which were printed the fruit symbols. These 'flat' reels were rather clumsy devices (noisy and heavy on current), but are still used occasionally for aesthetic effects.

Another variant on the projector theme was the meter movement based display used in this old Venner frequency counter

00730013.JPG (334545 bytes)00730012.JPG (221784 bytes)filanim.gif (22316 bytes)3) Side-lit light-guide displays. These used sheets of thin glass, each having an engraved pattern of 'dimples' which lit up when light was shone into the edge of the glass sheet. I recently picked up a box of these (KGM Multi-Indicator Type M25), pictured right, and built a clock with 4 of them based on my Nixie Clock design. The body is an aluminium block, which houses the lamps and acts as a heatsink.


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