Neon

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A neon sign with shaped glass tubes. The long, linear glow is entirely from the gas discharge

Neon is perhaps the most steampunk of electrical illumination. Its warm orange glow is easily recognised: it's both aesthetically pleasing and it's also in period for the Edwardian Age.

The drawback of neon is that it requires a high voltage, about 90V. This limits its use to mains electricity rather than batteries and it also makes it slightly hazardous to use for illuminated clothing. Neon is the province of the more advanced, or at least adventurous, contraptor. An expert contraptor can overcome these limitations and provide battery-powered neon, but that's slightly outside this page's remit.

An good emulation of the neon orange colour can be achieved, much more simply, with LEDs.

Contents

Fluorescent tubes

The mundane white fluorescent tube is not a neon tube, although the names are often confused. These tubes glow from a white phosphor powder on the inside of the tube, so the glow of the gas discharge inside the tube isn't visible.

Shaped neon tubes

The true 'neon sign' is a long glass tube, bent to shape. Its interior glow is visible. Different gas mixtures are used, not just neon, to give different colours. These signs are well-known from advertising, and from the recent contraptions of Tracey Emin.

Making these tubes is a problem of glass-blowing, more than electronics. They are still made though and the well-heeled steampunk can simply order tubes ready-made to their design.

Operation

Simple neon lamp, powered off (left), powered on with DC (note that only one electrode is glowing at a time)

Neon lamps contain two electrodes inside a glass envelope filled with neon gas. These electrodes don't touch and this often allows neons to be identified in a box of parts, as an obvious difference from incandescent lamps.

Neon lamps have been made in a vast range of shapes and sizes. A common form was a small glass tube with two bare wires. Others use screw-in lamp holders, as for most other incandescent lamps.

Mains operation

Neons work at around 90V. This is a voltage high enough to be hazardous, so contraptors should only approach it if they're already experienced with electrical work and feel confident to do so safely. Circuits must be appropriately constructed, reliable and well-insulated. Well-made mechanical and physical

Neons work with either direct current or alternating current. With direct current, only one electrode glows. With alternating current, both glow in turn although this is so fast that it is invisble to the eye.

Some neons were intended for use as mains indicators, connected directly across a mains supply. These are mounted into a small case, often with a plastic lens over the front, and they have a built-in series resistor to run directly from the mains. This series resistor is about 150 kΩ for 230V mains (UK & Europe) or 39 kΩ for 110V (US).


Glow lamps

'Vuk', a Czech cartoon fox, as a neon glow lamp

As the neon glow is most prominent around the electrodes, a type of 'glow lamp' with large shaped electrodes can be used to make glowing symbols and logos.

These glow lamps have long been used as religious and society symbols. Indian manufacturers to this day make a range of gods and goddesses for illuminating shrines. There is a tradition in the USA of making Masonic symbols as glow lamps, often used in a porch or lantern outside the home of a Mason.

Many specialist electronic devices also used neon glow lamps, such as 'Magic Eye' tuning indicators on radios. Neon lamps were often used as power indicators, which on valve radios meant operation form their 90V DC power rail. To give a good glow from these DC lamps (neons on DC only have one glowing electrode) this electrode was often a large disk or cup.

Coloured glow lamps

Surface coatings on the electrodes can give different coloured glows. These are often used for spectacular decorative flowers. The best-known maker of these is Aerolux in the USA, who are still manufacturing them.

Many of these glow lamps are designed for direct use on 240V (or 120V in the USA). It can be difficult to make the coloured surface electrodes work on 90V circuits.


Flicker lamps

Flicker lamp housed.jpg

As neon lamps can be used as oscillators (see Neon oscillators below) it is possible to make them with a built-in flickering effect. This is usually done with glow lamps, where the discharge 'dances' around the surface of the electrode. The most common is in the shape of a candle flame, with a realistic(sic [note 1]) flickering effect.

These flicker neons, in the shape of a flickering candle flame, are widely available today from UK electrical wholesalers.[note 2]

A number of hurricane lamps with flicker neons were used for set-dressing at Waltz on the Wye.


Nixie tubes

Nixie tube counting

Nixie tubes are a development of the neon glow lamp. If there are a number of electrodes in the same housing, each in the shape of a different numeral, ten turning them on one at a time gives one of the very first digital displays.

Nixie tubes are excellent devices for the steampunk contraptor. They're a route to digital electronics and computing, but they still have the warm aesthetics of neon. This is why we bother.

Nixie clocks

Nixie clock, in the style of Gustav Stickley

A favourite use for Nixie tubes is the manufacture of Nixie clocks.

A Nixie clock is a relatively complex device to design and to source parts for, however there are several suppliers out there (try eBay) selling kits. These kits usually include one of three levels of completeness:

  • Electronics only, supply your own tubes
  • Electronics and tubes
  • Electronics, tubes and case.

Most steampunks will want to make, or at least adapt, their own case designs.


Neon oscillators

NeonBulbRelaxationOscillator.svg

Neon lamps may also be used to make a very simple oscillator circuit or 'flashy thing'. They have very few, and very cheap, components. One resistor and one capacitor are all that's needed. The circuit will work at voltages from 90V to 240V mains, depending on the neons. The capacitor need to have a high voltage rating, but otherwise the values aren't critical. As the precise flashing depends on the neons used, tuning the flash rate is best done by experiment, once you have the actual neons to be used.

Note that (as for all neon circuits) this is a relatively complex circuit with hazardous voltages on it, construction standards should be competent for safety and insulation!

Multi-neon random oscillator

An interesting variation is the random oscillator. A number of neons are used and their capacitors are interconnected. This gives a pleasing random order to them all. Good for Blinkenlight computers, or just as a varying internal glow to a cabinet.


Notes

 

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