A
neon lamp is a miniature gas discharge lamp that typically contains
neonNeon is the chemical element that has the symbol Ne and an atomic number of 10. Although a very common element in the universe, it is rare on Earth. A colorless, inert noble gas under standard conditions, neon gives a distinct reddish-orange glow when used in either low-voltage neon glow lamps or...
gas at a low
pressurePressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...
in a glass capsule. Only a thin region adjacent to the electrodes glows in these lamps, which distinguishes them from the much longer and brighter
neon tubesNeon signs are made using electrified, luminous tube lights that contain rarefied neon or other gases. They are the most common use for neon lighting, which was first demonstrated in a modern form in December, 1910 by Georges Claude at the Paris Motor Show. While they are used worldwide, neon signs...
used for signage. The term "neon lamp" is generally extended to lamps with similar design that operate with different gases. Neon glow lamps were very common in the displays of electronic instruments through the 1970s; the basic design of neon lamps is now incorporated in contemporary
plasma displayA plasma display panel is a type of flat panel display common to large TV displays or larger. They are called "plasma" displays because the technology utilizes small cells containing electrically charged ionized gases, or what are in essence chambers more commonly known as fluorescent...
s.
History
NeonNeon is the chemical element that has the symbol Ne and an atomic number of 10. Although a very common element in the universe, it is rare on Earth. A colorless, inert noble gas under standard conditions, neon gives a distinct reddish-orange glow when used in either low-voltage neon glow lamps or...
was discovered in 1898 by
William RamseyWilliam Ramsey may refer to:*William Marion Ramsey , American politician and judge in Oregon*William of Ramsey, 13th century English Benedictine monk of Croyland Abbey*William Ramsey , 14th century English architect...
and Morris W. Travers. The characteristic, brilliant red color that is emitted by gaseous neon when excited electrically was noted immediately; Travers later wrote, "the blaze of crimson light from the tube told its own story and was a sight to dwell upon and never forget."
Neon's scarcity precluded its prompt application for electrical lighting along the lines of Moore tubes, which used electric discharges in nitrogen and which were commercialized in the early 1900s. After 1902,
Georges ClaudeGeorges Claude was a French engineer and inventor. He is noted for his early work on the industrial liquefaction of air, for the invention and commercialization of neon lighting, and for a large experiment on generating energy by pumping cold seawater up from the depths...
's company,
Air LiquideL'Air Liquide S.A., or Air Liquide , is a major French company supplying industrial gases and services to various industries including medical, chemical and electronic manufacturers. Founded in 1902, it is first in the world market in its field, now operating in over 80 countries. It is...
, was producing industrial quantities of neon as a byproduct of his air liquefaction business, and in December 1910 Claude demonstrated modern neon lighting based on a sealed tube of neon. In 1915 a U.S. patent was issued to Claude covering the design of the electrodes for neon tube lights; this patent became the basis for the monopoly held in the U.S. by his company, Claude Neon Lights, through the early 1930s.
Around 1917,
Daniel McFarlan MooreDaniel McFarlan Moore was a U.S. electrical engineer and inventor. He developed a novel light source, the "Moore lamp", and a business that produced them in the early 1900s...
, then working at the General Electric Company, developed the neon lamp, which has a very different design than the much larger neon tubes used for
neon lightingNeon lighting is created by brightly glowing, electrified glass tubes or bulbs that contain rarefied neon or other gases. Georges Claude, a French engineer and inventor, presented neon tube lighting in essentially its modern form at the Paris Motor Show from December 3–18, 1910...
. The difference in design was sufficient that a U.S. patent was issued for the lamp in 1919. A Smithsonian Institution website notes, "These small, low power devices use a physical principle called coronal discharge. Moore mounted two electrodes close together in a bulb and added neon or argon gas. The electrodes would glow brightly in red or blue, depending on the gas, and the lamps lasted for years. Since the electrodes could take almost any shape imaginable, a popular application has been fanciful decorative lamps. Glow lamps found practical use as indicators in instrument panels and in many home appliances until the widespread commercialisation of Light-Emitting Diodes (LEDs) in the 1970s."
Description
A small
electric currentElectric current is a flow of electric charge through a medium.This charge is typically carried by moving electrons in a conductor such as wire...
, which may be
ACIn alternating current the movement of electric charge periodically reverses direction. In direct current , the flow of electric charge is only in one direction....
or
DCDirect current is the unidirectional flow of electric charge. Direct current is produced by such sources as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also flow through...
, is allowed through the tube, causing it to glow orange-red. The formulation of the gas is typically the classic
Penning mixtureA Penning mixture , named after Frans Michel Penning, is a mixture of gases used in electric lighting or displaying fixtures. Although the popular phrase for the most common of these is a neon lamp, it's more efficient to have the glass tube filled not with pure neon, but with a Penning mixture,...
, 99.5%
neonNeon is the chemical element that has the symbol Ne and an atomic number of 10. Although a very common element in the universe, it is rare on Earth. A colorless, inert noble gas under standard conditions, neon gives a distinct reddish-orange glow when used in either low-voltage neon glow lamps or...
and 0.5%
argonArgon is a chemical element represented by the symbol Ar. Argon has atomic number 18 and is the third element in group 18 of the periodic table . Argon is the third most common gas in the Earth's atmosphere, at 0.93%, making it more common than carbon dioxide...
, which has lower
striking voltageThe breakdown voltage of an insulator is the minimum voltage that causes a portion of an insulator to become electrically conductive.The breakdown voltage of a diode is the minimum reverse voltage to make the diode conduct in reverse...
than pure neon. The applied voltage must initially reach the striking voltage before the lamp is visible. At the striking voltage, the lamp enters a breakdown mode and exhibits a glow discharge. Once lit, the voltage required to sustain the discharge is significantly (~30%) lower than the striking voltage. This is due to the organization of positive ions near the cathode. When driven from a DC source, only the negatively charged electrode (
cathodeA cathode is an electrode through which electric current flows out of a polarized electrical device. Mnemonic: CCD .Cathode polarity is not always negative...
) will glow. When driven from an AC source, both electrodes will glow (each during alternate half cycles). These attributes make neon bulbs (with series resistors) a convenient low-cost voltage testers; they determine whether a given voltage source is AC or DC, and if DC, the polarity of the points being tested. Neon lamps operate using a low current glow discharge. Higher power devices, such as
mercury-vapor lampA mercury-vapor lamp is a gas discharge lamp that uses an electric arc through vaporized mercury to produce light. The arc discharge is generally confined to a small fused quartz arc tube mounted within a larger borosilicate glass bulb...
s or
metal halide lampMetal-halide lamps, a member of the high-intensity discharge family of lamps, produce high light output for their size, making them a compact, powerful, and efficient light source. By adding rare earth metal salts to the mercury vapor lamp, improved luminous efficacy and light color is obtained...
s use a higher current arc discharge.
Once the neon lamp has reached breakdown, it can support a large current flow. Because of this characteristic, electrical circuitry external to the neon lamp must limit the current through the circuit or else the current will rapidly increase until the lamp is destroyed. For indicator-sized lamps, a
resistorA linear resistor is a linear, passive two-terminal electrical component that implements electrical resistance as a circuit element.The current through a resistor is in direct proportion to the voltage across the resistor's terminals. Thus, the ratio of the voltage applied across a resistor's...
typically limits the current. Larger
neon signNeon signs are made using electrified, luminous tube lights that contain rarefied neon or other gases. They are the most common use for neon lighting, which was first demonstrated in a modern form in December, 1910 by Georges Claude at the Paris Motor Show. While they are used worldwide, neon signs...
sized lamps often use a specially constructed high voltage
transformerA transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field...
with high
leakage inductanceLeakage inductance is the property of an electrical transformer that causes a winding to appear to have some inductance in series with the mutually-coupled transformer windings...
or other
electrical ballastAn electrical ballast is a device intended to limit the amount of current in an electric circuit. A familiar and widely used example is the inductive ballast used in fluorescent lamps, to limit the current through the tube, which would otherwise rise to destructive levels due to the tube's...
to limit the available current.
When the current through the lamp is lower than the current for the highest-current discharge path, the glow discharge may become unstable and not cover the entire surface of the electrodes. This may be a sign of aging of the indicator bulb, and is exploited in the decorative "flicker flame" neon lamps. However, while too low a current causes flickering, too high a current increases the wear of the electrodes by stimulating
sputteringSputtering is a process whereby atoms are ejected from a solid target material due to bombardment of the target by energetic particles. It is commonly used for thin-film deposition, etching and analytical techniques .-Physics of sputtering:...
, which coats the internal surface of the lamp with metal and causes it to darken.
The potential needed to strike the discharge is higher than what is needed to sustain the discharge. When there is not enough current, the glow forms around only part of the electrode surface. Convective currents make the glowing areas flow upwards, not unlike the discharge in a Jacob's ladder. A photoionization effect can also be observed here, as the electrode area covered by the glow discharge can be increased by shining light at the lamp.
In comparison with incandescent light bulbs, neon lamps have much higher
luminous efficacyLuminous efficacy is a measure of how well a light source produces visible light. It is the ratio of luminous flux to power. Depending on context, the power can be either the radiant flux of the source's output, or it can be the total electric power consumed by the source.Which sense of the term is...
.
IncandescenceIncandescence is the emission of light from a hot body as a result of its temperature. The term derives from the Latin verb incandescere, to glow white....
is heat-driven light emission, so a large portion of the electric energy put into an incandescent bulb is converted into heat. Non-incandescent light sources such as neon light bulbs,
fluorescent light bulbsA fluorescent lamp or fluorescent tube is a gas-discharge lamp that uses electricity to excite mercury vapor. The excited mercury atoms produce short-wave ultraviolet light that then causes a phosphor to fluoresce, producing visible light. A fluorescent lamp converts electrical power into useful...
, and light emitting diodes are therefore much more energy efficient than normal incandescent light bulbs.
GreenGreen is a color, the perception of which is evoked by light having a spectrum dominated by energy with a wavelength of roughly 520–570 nanometres. In the subtractive color system, it is not a primary color, but is created out of a mixture of yellow and blue, or yellow and cyan; it is considered...
neon bulbs can produce up to 65 lumens per watt of power input, while white neon bulbs have an efficacy of around 50 lumens per watt. In contrast, a standard incandescent light bulb only produces around 13.5 lumens per watt.
Applications
Most small neon (indicator-sized) lamps, such as the common
NE-2, break down at between 90 and 110
voltThe volt is the SI derived unit for electric potential, electric potential difference, and electromotive force. The volt is named in honor of the Italian physicist Alessandro Volta , who invented the voltaic pile, possibly the first chemical battery.- Definition :A single volt is defined as the...
s. This feature enables their use as very simple
voltage regulatorA voltage regulator is an electrical regulator designed to automatically maintain a constant voltage level. A voltage regulator may be a simple "feed-forward" design or may include negative feedback control loops. It may use an electromechanical mechanism, or electronic components...
s or
overvoltageWhen the voltage in a circuit or part of it is raised above its upper design limit, this is known as overvoltage. The conditions may be hazardous...
protection devices.
In the 1960s
General ElectricGeneral Electric Company , or GE, is an American multinational conglomerate corporation incorporated in Schenectady, New York and headquartered in Fairfield, Connecticut, United States...
(
GEGê are the people who spoke Ge languages of the northern South American Caribbean coast and Brazil. In Brazil the Gê were found in Rio de Janeiro, Minas Gerais, Bahia, Piaui, Mato Grosso, Goias, Tocantins, Maranhão, and as far south as Paraguay....
), Signalite, and other firms made special extra-stable neon lamps for electronic uses. They even devised digital logic circuits,
binaryThe binary numeral system, or base-2 number system, represents numeric values using two symbols, 0 and 1. More specifically, the usual base-2 system is a positional notation with a radix of 2...
memoriesIn psychology, memory is an organism's ability to store, retain, and recall information and experiences. Traditional studies of memory began in the fields of philosophy, including techniques of artificially enhancing memory....
, and
frequencyFrequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
dividers using neon lamps. Such circuits appeared in
electronic organAn electronic organ is an electronic keyboard instrument which was derived from the harmonium, pipe organ and theatre organ. Originally, it was designed to imitate the sound of pipe organs, theatre organs, band sounds, or orchestral sounds....
s of the 1950s, as well as some instrumentation. At least some of these lamps had a glow concentrated into a small spot on the cathode, which made them unsuited to use as indicators. These were sometimes called "circuit-component" lamps, the other variety being indicators. A variant of the NE-2 type lamp, the NE-77, had three parallel wires (in a plane) instead of the usual two. It was also intended primarily to be a circuit component.
Small neon lamps are used as indicators in electronic equipment. Called "tuneons" in 1930s radio sets, they were fitted as tuning indicators, and would give a brighter glow as the station was tuned in correctly. Larger lamps are used in neon signage. Neon lamps, due to their low current consumption, are used as
nightlightA nightlight is a small light fixture, often electrical, placed for comfort or convenience in dark areas or areas that become dark at certain times, such as in an emergency...
s. Because of their comparatively fast response time, in the early development of
televisionTelevision is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...
neon lamps were used as the light source in many
mechanical-scan TVMechanical television was a broadcast television system that used mechanical or electromechanical devices to capture and display video images. However, the images themselves were usually transmitted electronically and via radio waves...
displays. They were also used for a variety of other purposes; since a neon lamp can act as a
relaxation oscillatorA relaxation oscillator is an oscillator based upon the behavior of a physical system's return to equilibrium after being disturbed. That is, a dynamical system within the oscillator continuously dissipates its internal energy...
with an added resistor and
capacitorA capacitor is a passive two-terminal electrical component used to store energy in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric ; for example, one common construction consists of metal foils separated...
, it can be used as a simple flashing lamp or
audioSound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.-Propagation of...
oscillator. (See
Pearson-Anson effectThe Pearson–Anson effect, discovered by Stephen Oswald Pearson and Horatio Saint George Anson, is the phenomenon of an intermittent electrical current through an electrical load exhibiting S-shaped negative resistance connected in parallel to an accumulating element...
.)
Neon lamps with several shaped electrodes were used as alphanumerical displays known as
Nixie tubeA nixie tube is an electronic device for displaying numerals or other information. The glass tube contains a wire-mesh anode and multiple cathodes. In most tubes, the cathodes are shaped like numerals. Applying power to one cathode surrounds it with an orange glow discharge...
s. These have since been replaced by other display devices such as light emitting diodes,
vacuum fluorescent displayA vacuum fluorescent display is a display device used commonly on consumer-electronics equipment such as video cassette recorders, car radios, and microwave ovens. Invented in Japan in 1967, the displays became common on calculators and other consumer electronics devices...
s, and
liquid crystal displayA liquid crystal display is a flat panel display, electronic visual display, or video display that uses the light modulating properties of liquid crystals . LCs do not emit light directly....
s.
Novelty glow lampsAerolux Light Corporation was a manufacturer of artful gas-discharge light bulbs from the 1930s through the 1970s. Aerolux made these bulbs in a factory in New York City. US Patents dating back to the 1930s describe the design and construction of these bulbs....
with shaped electrodes (such as flowers and leaves), often coated with phosphors, have been made for artistic purposes. In some of these, the glow that surrounds an electrode is part of the design.
In AC-excited lamps, both electrodes produce light, but in a DC-excited lamp, only the negative electrode glows. Thus a neon lamp can be used to distinguish between AC and DC sources and to ascertain the polarity of DC sources.
Colour
Neon indicator lamps are normally orange, and are frequently used with a coloured filter over them to improve contrast and change their colour to red or a redder orange, or less often green.
They can also be filled with
argonArgon is a chemical element represented by the symbol Ar. Argon has atomic number 18 and is the third element in group 18 of the periodic table . Argon is the third most common gas in the Earth's atmosphere, at 0.93%, making it more common than carbon dioxide...
,
kryptonKrypton is a chemical element with the symbol Kr and atomic number 36. It is a member of Group 18 and Period 4 elements. A colorless, odorless, tasteless noble gas, krypton occurs in trace amounts in the atmosphere, is isolated by fractionally distilling liquified air, and is often used with other...
, or
xenonXenon is a chemical element with the symbol Xe and atomic number 54. The element name is pronounced or . A colorless, heavy, odorless noble gas, xenon occurs in the Earth's atmosphere in trace amounts...
rather than neon, or mixed with it. While the electrical operating characteristics remain similar, the lamps light with a bluish glow (including some
ultravioletUltraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
) rather than neon's characteristic reddish-orange glow. Ultraviolet radiation then can be used to excite a
phosphorA phosphor, most generally, is a substance that exhibits the phenomenon of luminescence. Somewhat confusingly, this includes both phosphorescent materials, which show a slow decay in brightness , and fluorescent materials, where the emission decay takes place over tens of nanoseconds...
coating inside of the bulb and provide a wide range of various colors, including white. A mixture of neon and
kryptonKrypton is a chemical element with the symbol Kr and atomic number 36. It is a member of Group 18 and Period 4 elements. A colorless, odorless, tasteless noble gas, krypton occurs in trace amounts in the atmosphere, is isolated by fractionally distilling liquified air, and is often used with other...
can be used for green glow, but nevertheless "green neon" lamps are more commonly phosphor-based.
See also
- Timeline of lighting technology
Timeline of lighting technology- Antiquity :* 70,000 BCE A hollow rock, shell, or other natural found object was filled with moss or a similar material that was soaked in animal fat and then ignited.* c. 4500 BCE oil lamps...
- 1910 in science
The year 1910 in science and technology involved some significant events, listed below.-Chemistry:* Albert Einstein and Marian Smoluchowski find the Einstein-Smoluchowski formula for the attenuation coefficient due to density fluctuations in a gas...
- List of light sources
- Neon lighting
Neon lighting is created by brightly glowing, electrified glass tubes or bulbs that contain rarefied neon or other gases. Georges Claude, a French engineer and inventor, presented neon tube lighting in essentially its modern form at the Paris Motor Show from December 3–18, 1910...
- Neon sign
Neon signs are made using electrified, luminous tube lights that contain rarefied neon or other gases. They are the most common use for neon lighting, which was first demonstrated in a modern form in December, 1910 by Georges Claude at the Paris Motor Show. While they are used worldwide, neon signs...
- Nixie tube
A nixie tube is an electronic device for displaying numerals or other information. The glass tube contains a wire-mesh anode and multiple cathodes. In most tubes, the cathodes are shaped like numerals. Applying power to one cathode surrounds it with an orange glow discharge...
External links