Neon Nostalgia

In smaller neon lamps, a different type of discharge is used. At a moderate voltage the neon gas will already light. This type of discharge is called glow discharge. The discharge area is a thin blanket in the area around the cathode (the negative electrode). The blanket will form holes if the current is lowered. If the current is too high, some ions will leave the cathode and the color of the light will change. Eventually this will damage the lamp.

Neon glow lamps can be used as indicator lights, displays and even as voltage stabilisers . This is because the working voltage is determined by the physical properties of the glow discharge, that can be determined by the designer of the tube. Some very intricate applications have been developed such as counter tubes where the ignited plasma is handed over from electrode to electrode like the stick in an estafette race.

Nixie tubes

From 1950 to 1970 Nixie-tubes were a common technique for displaying numerical data. Within a nixie tube, there are a number of cathodes (usually 10), shaped as numerals from thin metal wire. The stack of numerals is enclosed by a fine mesh of thin wire, which is the anode. Only one cathode is used at a time, the glow discharge around the cathode, will make the neon around that cathode light in the shape of a warm, velvety, red-orange digit.

The wire-numerals are placed in front of each other. When a nixie tube is displaying the contents of a running counter, you can see the digits jump to and fro. The dancing digits make the nixie tube a fascinating thing to look at.

On a separate page How To Drive Nixies, I'll discuss the principles for nixie driving circuits.

In December 1999, I caught the nixie fever. I found that a local electronics surplus shop in The Hague had some boards containing 12 nixies each, at a very nice price. I couldn't resist and bought two of them, one with multiplexing circuitry and the other just a bus board, handy to experiment with. After that, I started imagining what I could do with it.

• Make a nixie clock. Building nixie clocks has really started to be a rage in the late 1990-ies. Here are some nice examples. On nixieclocks.de you'll find beautiful photographs and you can also find kits to construct a clock yourself. But please, don't rip apart vintage equipment, only use new nixies from old stock! Mike's Electric Stuff tells you how to build a nixie clock using common CMOS ic's. Tom Jennings of World Power Systems builds elaborate nixie clocks and sells them at astronomical prices. His clocks seem to be based upon microcontrollers. Jason Rand Harper makes nixie clocks and a dekatron clock and sells them through Ebay.
  David Weiner of WestDave builds electronic clocks that are different. Some of them use nixie tubes. Be patient while his page loads, you'll get tons of pictures.
  Finally, Cosmodog has made a nice clock. Looks like he's found some quite large nixies!

• Make a digital voltmeter.
  There are some references on the web from people who have made plans to do this, but I never saw their results. I have tried this too. I built a breadboard prototype using an ICL7135 voltmeter chip, which did work for DC measurements, but I never finished it.

  In the meantime here is a description of a digital panel meter kit that I found in RB magazine.

  And in december 2001 I found a Heathkit IM1202 digital multimeter and found the circuit diagrams on the The Circuit Archive website, that has unfortunately disappeared since. A number of its pages can be found at The Heathkit Circuit Archive page on the UK Vintage Radio Repairs and Restoration" site.

• Build a frequency counter.
  I built a TTL counter with 4 nixies 20 years ago. Unfortunately, it got lost in a removal.
  If you want schematics, there are a few descriptions of Heathkit frequency counter kits on The Circuit Archive. There is also some Heathkit stuff on the BAMA boat anchors site.

Pandicon multi-digit nixies

Philips and some of their sub-brands fitted 8-14 nixie displays in a single tube. These so-called “Pandicon” displays were intended for multiplexed displays for calculators etc. They have a B17A base on both ends. One has all the anode connections, the other is connected to the cathodes. I have two different pandicons in my collection, an 8 digit ZM1200 and a 14-digit ZM1200.

Panaplex displays

There is another way to build numeric displays using neon glow discharge. One can arrange a number of metal strips in a 7-segment arrangement. This flat configuration can easier be read from an angle than Nixie tubes. Though the digits are not as well formed as nixie digits, these flat 7-segment displays have the same pretty orange glow as Nixies.

Sperry corporation produced multi-digit 7-segment flat planar displays under their “Panaplex” brand name. I particularly remember them from some advanced pinball machines in my youth.

I found a Berkel scale from a grocery shop that used these Panaplex displays. My Nordmende DiVo 3362 Digital voltmeter and my Feedback FM610 frequency meter also have them.

Vintage equipment

I have a few pieces of electronic equipment that use nixie tubes or other types of neon displays, such as calculators and weighing equipment:

• Casio model 122 desk calculator, late 1960's (traded).
• Japanese calculator using an 8-digit 7-segment neon display.
• Monroe 640 calculator, trying to look American but made by Canon (traded).
• Berkel 176SG scale (decommisioned)

measuring instruments:

• Advance DVM1 digital voltmeter from 1965.
• Philips PM2433 digital voltmeter from 1967.
• Systron-Donner 9000 digital Volt-Ohmmeter, made in US, 1968.
• Monsanto 101B frequency counter from 1969.
• Philips PM2420 digital multimeter
• Takeda Riken 3788B frequency counter made in Japan around 1970.
• An interesting Digavi nixie DC multimeter Made in Germany, 1970
• A Racal 9520 frequency period meter Made in Britain, 1970
• Philips PM2421 digital multimeter
• Philips PM6630 frequency counter
• Philips PM6630B frequency counter
• A Heathkit IM1202 digital multimeter from 1972.
• A Digistop 710 timer from Luctor Baarn from around 1972.
• Schneider DigiTest 500 digital voltmeter.
• Gay-Milano tracking voltmeter
• Nordmende DiVo 3362 Digital voltmeter using Panaplex displays, 1973.
• Feedback FM610 frequency meter with Panaplex display
• Philips PM2423 3.5 digit digital multimeter from 1974.
• Philips PM2424 4 digit autoranging digital multimeter from 1974.
• Philips PM2443 4.5 digit autoranging digital voltmeter from 1974.
• Homebuilt universal frequency counter using nixies and TTL circuits built by a German radio ham around 1974.
• Another homebuilt frequency counter marked SEV.

Nixie panel meters

Besides complete multimeters, I also have some of panel meters, actually half-products to be built into a switch panel or larger instrument.

• A Philips PM2494/01 3.5-digit digital panel meter from 1972.
• A Newport Laboratories Model 200A-3 3.5-digit digital panel meter from 1972.
• Description of a digital panel meter kit from RB magazine.

My nixie clocks

I also have some nixie clocks. Two I built and one I was given. In this 21^st century, they strongly remind me of the 20^th century and specifically the 1950's and 1960's, the “space age” with its optimistic expectations of the way high technology would shape the future of mankind.

• My ZM1040 Nixie clock in progress, built late 2007 after a design by Thomas and Claus from nixieclocks.de.
• A Karlsson Nixie Clock (design from 1997)
• And finally, a home-built clock, built 2002 after a kit by Frank Bemelman.