Fluorescent lamps have been around for a very long time, but CFL lamps designed to be used in small household fixtures are a fairly recent invention. Traditional fluorescents require a ballast that carefully controls the voltage running through the lamp.
The Fluorescent Lamp
- “You definitely cannot go against what the CFL has done because they’ve been around for a long, long time,” Frerotte said. “They don’t call it American football. Obviously, the rules are different, but it is still football, there is still hitting, tackling, forward pass — all the things that American football does.”.
- Think about it like this, the CFL was officially founded in 1958 and up until 1990, most salaries were unknown until it was reported that legendary CFL quarterback Doug Flutie signed a two-year contract with the B.C. Lions worth a whopping $350,000 CAD. That’s 175k (if my math is correct) a season.
- More than a few eyebrows have been raised around the CFL following a spate of signings by the Argos, who have suddenly turned into the talk of the small town that is three-down football.
The greatest development in lighting since the 1879 incandescent
History (1938 first commercially available - Today)
| Introduction & Statistics | Ballasts |
| Inventors and Developments | Timeline |
Fluorescents are a large family of light sources. There are three main types of fluorescent lamps: cold cathode, hot cathode, and electroluminescent. They all use phosphors excited by electrons to create light. On this page we will discuss the cold and hot cathode lamps. Electroluminescent lamps use 'fluorescence' but are so different they are covered on another page. From this point when we refer to 'fluorescent lamp' we will be talking about a lamp with a glass discharge tube and fluorescent coating on the inside, this is how the cold and hot cathode type of lamps are designed. Induction lamps are a form of fluorescent lamps but they don't have electrodes. We have a separate page for them here.
The standard fluorescent lamp was developed for commercial use during the 1930's. The idea of the fluorescent lamp had been around since the 1880's however it took steady work over the decades to finally create a working commercially viable model. This work was done by many, not one single inventor. See our inventors list to learn more.
Common uses:
lamps both outdoor and indoor, backlight for LCD displays, decorative lighting and signs, both high bay and small area general lighting. Not used for lighting from afar due to diffused nature of the light.
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Below: general video on the fluorescent lamp. 8 min.
1. How the Fluorescent Lamp Works
We discuss two types of fluorescent lamps: Hot Cathode, Cold Cathode
Simple Explanation Hot and Cold Cathode Lamps:
Fluorescent lamps work by ionizing mercury vapor in a glass tube. This causes electrons in the gas to emit photons at UV frequencies. The UV light is converted into standard visible light using a phosphor coating on the inside of the tube.
| 1A. Hot Cathode | 1B. Cold Cathode |
1A. How it works: Hot Cathode
The most common fluorescent lamp is the hot cathode:
Parts:
This lamp consists of a glass tube filled with an inert gas (usually argon) at low pressure. On each side of the tube you will find a tungsten electrode. The ballast regulates AC power to the electrodes. Older lamps used a starter to get the lamp going. Modern lamps use pulse start which is done by components within the ballast.
How it works:
Step by step explanation of a standard 4 foot long 40 watt straight tube lamps (this is the most popular size of fluorescent lamp in the world since the 1940s).
Note: There are two kinds of ballasts, the magnetic ballast which uses copper coils (transformers), and the electronic ballast. Electronic ballasts are favored today because they use a lot less material and are lower cost to produce.
1.) AC electric current passes through the ballast. The ballast will step up 120 AC volts (in the US) to 216 V, next the power passed through a 'choke' or 'reactor', this limits current and prevents the lamp from creating a type of short circuit which would destroy the lamp. All arc discharge lamps need a choke to limit current.
2.) The lamp's glass tube is called a discharge tube and it works by having electrons pass from one electrode to the other. This forms what is called an 'arc'. Getting this started is a real challenge.
To get the lamp started you need a spike of high voltage to get the arc started. The colder the lamp is, the higher voltage you need to get a start. The voltage 'forces' current through the argon gas. Gas has a resistance, the colder the gas, the higher the resistance, therefore you need a higher voltage with colder temperatures. Since creating a high voltage is a challenge and dangerous, engineers figured out ways to 'preheat' the lamp, that way less of a high voltage is required. There are different ways to start a lamp including: preheat, instant start, rapid start, quick start, semi-resonant start and programmed start. We will tell you about the main two ways to make it start.
2a. Use a Starter (startswitch) - This method is the first and arguably the most reliable type of way to start a lamp according to some. Many facilities still have older fixtures with startingswitch preheat fluorescents.
Watch an animated schematic on our YouTube video below:
1.) In the early systems the starter contained a small neon or argon lamp. When the starter was cool at first, current ran through the starterswitch through the neon lamp. The 1 W lamp would warm a bimetallic strip in the starter, while in the main arc tube the current passed through the tungsten electrodes which would make them heat up and ionize some of the gas. This 'preheated' the lamp.
2.) Current passes through the tungsten electrodes on each end of the lamp. The electrodes are like a filament on an incandescent lamp, when current passes through they heat up and give off free electrons. This process of letting off free electrons is called thermionic emission. The free electrons ionize the argon gas in the tube. The first gas to be ionized is right around the filament, you can see it clearly in the photo above. An ionized gas is called a plasma.
3.) When the starter switch (with the little neon or argon lamp inside) gets warm enough, the bimetallic strip flips the other way, completes the circuit, bypassing the small lamp. The lamp goes out and the entire circuit shorts. During the short the voltage falls to zero. The bimetallic strip cools and pops back open, opening the circuit. In the ballast the transformer had a magnetic field, when the circuit is cut the magnetic field collapses and forms an 'inductive kick' from the ballast. Suddenly this kick of high voltage is sent through the lamp and this starts the arc. If it didn't work, if the lamp is still too cold, then the starter switch will light again and repeat the process.
2b. Rapid Start - This modern type of starting method constantly preheats the electrode (cathode) using low voltage AC power. The arc is started by passing through a grounded reflector or starting strip on the outside of the glass tube. The arc starts between the electrode and the starting strip first and rapidly propagates through the entire discharge tube. The schematic for this and other modern start methods is much more complex.
3.) So now your arc has started and current passes from your cathode to your anode (electrode to electrode) through the argon gas. Because your dealing with AC power, the cathode switches back and forth. AC power is good for the lamp because if the lamp was DC, the cathode side would be brighter and more intense since there are more free electrons spewing off of the tungsten electrode there. Also if the lamp was on DC power, the electrode which is acting as the cathode would become weaker as it lost tungsten atoms and the lamp would not last as long. Since we use AC the electrons or ions break off one side, reach the other, then on the next cycle are sent back. Also the lamp tube has a nice uniform brightness on both ends.
Powdered phosphors on the inside of the tube absorb the UV light. Here you can see the UV light as a purplish light. The quartz lamp used in this experiment is the same as a compact fluorescent lamp except that it has no phosphor.
4.) Vaporizing mercury and making light: The normal fluorescent lamp has a small amount of mercury in the tube. On a cold tube you would see it as a couple of pinhead sized dots if you were to break the tube so you can see inside. The arc which started in argon gas quickly warms up the mercury liquid stuck to the side of the tube. The mercury boils or vaporizes into the arc stream. The arc easily passes through vaporized mercury. This creates UV light. That light is emitted and strikes the phosphors on the inside of the glass tube. The phosphors convert the light into useful visible light.
Phosphors are chemically designed to give off a certain color. Here you see a warm white at 3000 Kelvin (color temperature) and cool white which is closer to daylight at 6000 Kelvin
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Ballasts
Watch the video above to learn the basics about different types of ballasts.
Ballasts are a fascinating part of the fluorescent lamp system due to the complex nature of resistance, inductance and reactance. There are two kinds of ballasts: the magnetic ballast, and the electronic ballast.
Magnetic Ballasts: magnetic ballasts use transformers to convert and control electricity. Understanding the ballast takes some background because it uses the complex property of induction The ballast raises voltage, but the most important thing is that is limits current.
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How it works: the Magnetic Ballast
The transformer which is called a 'choke' in a ballast is a coil of wire called an inductor. It creates a magnetic field. The more current you put through, the bigger the magnetic field, however the larger magnetic field opposes change in current flow. This slows the current growth. Since we are dealing with AC power, the current flows in one direction for only 1/60th or 1/50th of a second, then drops to zero before flowing in the opposite direction. Therefore the transformer only has to slow current flow for a moment.
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Above: electronic ballast in a CFL
Electronic Ballasts: The electronic ballasts use semiconductors to limit power to a fluorescent lamp. First the ballast rectifies the AC power, then it chops it to make a high frequency for improved efficiency. The ballast can more precisely control power than a magnetic ballast but does have a number of problems.
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Manufacturers use as little copper and other expensive materials as possible. Components have less ability to deal with heat and rigors of long life. Regular fluorescent lamps (discharge tube assemblies) have the ability to be highly efficient, but poorly made ballasts are the limiting factor. Electronic ballasts also have a way of failing prematurely due to overheating and this limits the great life of the lamp. The stated life of a lamp on the box usually is not to be believed.
1B. How it works: Cold Cathode Fluorescent Lamps
The Cold Cathode Lamp is different from a Hot Cathode in that it has an interior coating that more easily creates free electrons when used with higher voltages.
The Cold Cathode device was not born as a light source. It is an evacuated tube filled with gas with an electrode at each end. The earliest cold cathode tubes included the Geissler tube (1857) which was used for science and entertainment (provided an amusing glow depending on the gas within). Over the years cold cathode tubes were developed to perform a variety of functions including counting, voltage regulation, radio detection, phase angle control in AC, computer memory, radio frequency transmission, high voltage control switches, and more. Early devices were called: the Geissler Tube, Plucker Tube, Cathode Ray Tube, thyratron, krytron, and dekatron.
Cold Cathode Lamps
Neon Lamps and Cold Cathode Fluorescent Lamps (CCFLs) create light as their primary function. Neon Lamp is a term describing lamps with a tube smaller than 15 mm in diameter.
Applications of CCFLs:
-Back lighting for LCD screens
-Computer monitors (tube)
-Television Screens (LCD, CRT)
-Alcove lighting and background diffused indirect lighting
-Nixie Tubes - early form of numeric display, they are small glass tubes shaped as numbers, activated by a wire mesh anode and multiple cathodes, replaced by LEDs in the 1970s
Advantages
-CCFLs come on instantly at full brightness
-They are more reliable starting in cold weather
-They have a long life
-They are dimmable to some degree
-Light created is easier on the human eye
Disadvantages
-They use a complex ballast
-Not a full range in dimmability
-New devices in LCD screens are not as energy efficient as Cathode Ray Tubes of the past when used as a Television/Monitor
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3. Inventors and Developments:
The 80 year road to the modern fluorescent lamp.
Below: our YouTube video highlighting the inventors and their contributions:
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Myths about the fluorescent lamp and inventors:
The internet has permitted growth of myths about many technologies due to web authors using unsupported facts from dubious websites. As you can see from the list above Nikola Tesla and Agapito Flores did not invent the fluorescent lamp. Many poorly researched internet sources will claim they did. Most of these sources are 'content farms' which pump out online articles with less than one hours work on the part of the author. This means no proper research was done. Wikipedia can be edited by anyone and therefore is also prone to inaccuracies created by fanatics of Tesla and Flores. Read more about the Flores and Tesla issue here: 'Who Invented the Fluorescent Lamp?'
Development Timeline:
Early History: the invention was developed one part at time over many years.
1856 - The evacuated arc tube:
Heinrich Geissler was able to evacuate a glass tube, put two electrodes on the ends and make a lamp with a faint glow do to trace amounts of gas left over inside the tube (an accident). This work was the basis for Sodium, Mercury Vapor, Xenon arc, MH, and Fluorescent lamps. Bonn, Germany
1890s - Use of fluorescent coating, high frequencies:
Thomas Edison and Nikola Tesla separately pursued the idea of fluorescent lamps. Edison lamps used a calcium tungstate as a fluorescent coating. Tesla used a high frequency model that made a greenish light. All of these attempts failed to be commercially successful due to short lamp life, poor reliability, and poor light color.
1895 - Use of fluorescent coating, high frequencies:
Daniel McFarlan Moore developed the first commercial predecessor to the fluorescent lamp called a Moore Tube. The tubes were 2-3 meters long and were installed in offices and shops. Unlike the modern fluorescent lamp his device used an electric arc in CO2 or Nitrogen to make a white an pink light. It was much more efficient than the incandescent lamp. The problem was that the system was very expensive to install and used very high voltages (a danger to humans working on them).
East Orange, New Jersey
1901 - Use of mercury vapor arc to create UV light (critical to lighting up the modern fluorescent) and use of a ballast with the lamp:
Peter Cooper Hewitt developed the first commercial mercury vapor lamp. While some had experimented with using mercury vapor in Germany and England, Hewitt's design was able to produce a bright high quality light with a wide enough spectrum of emitted light to be usable. This lamp produced UV rays which would turn out to be useful later on. A ballast was located above the lamp to create a reliable, controlled power source. New York, New York
1911 - Invention of ductile tungsten used in the electrodes:
William D. Coolidge develops ductile tungsten for use in incandescent bulbs at General Electric in Schenectady. This miracle material finds use in many other lamps such as halogen, sodium, mercury vapor, fluorescent, and more. It is a wire which is wrapped into a filament or electrode. Schenectady, New York
1915 - Development and commercial success of Neon lamps.
Georges Claude developed this cold cathode lamp which lead the way to the fluorescent lamp. Paris, France
1926 - First fluorescent lamp to use UV:
Edmund Germer built a low voltage fluorescent lamp similar to the modern fluorescent. It used UV rays to excite phosphors. The color of the lamp was an unpleasant greenish color and the product was never fully developed. His lamp is considered the first fluorescent lamp, however a lot of work still needed to be done to make the lamp have a decent lifespan.
Berlin, Germany
1927 - Electrode design in the fluorescent lamp:
Albert W. Hull develops a tungsten electrode which would not disintegrate and created a stronger UV light. Some of this work had been based on the work of Leroy J. Buttolph at GE in 1919. Albert Hull was also the developer of many electron tubes, improved xray, and numerous other developments.General Electric bought Germer's patents in order to continue work on the lamp. Schenectady, NY
1934 - The first modern fluorescent lamp!
1.) Arthur H. Compton (inventor of the sodium vapor lamp at Westinghouse, 1920) visits Oxford, England. He meets with local lamp inventors who are working with a 2 ft long tube with yellow-green colored phosphors. He writes to William L. Enfield at General Electric.
2.) William Enfield leads a group to develop a fluorescent lamp which would be a white color, and have reliability sufficient for commercial sale. Nela Park, Ohio.
3.) By November George Inman, Richard Thayer, Eugene Lemmers, and Willard A. Roberts develop the first modern fluorescent lamp.
It is 10 inches long 3/4 diameter and used zinc silicate phosphor (phosphor is the work of Willard A. Roberts).
Nela Park, Ohio.
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1970s -In the 1970's it was found that a diameter of 38 mm gave the greatest efficiency. The 40 W 1200 mm x 38 mm lamp became the most used lamp in commercial/industrial buildings.
1980s- John Anderson advances the fluorescent lamp by improving the electrodes, inventing a dimmable fluorescent lamp
The Bright Stik:
The Bright Stik is a type of fluorescent that was developed by John H. Harnden at General Electric. It uses a F20 T12 tube and the ballast as a resistance, it does not use a transformer.
For a comprehensive early history on the invention and development of the fluorescent lamp see the link below:
READ MORE DETAIL: Fluorescent Lamp Development - a comprehensive history by Rick DeLair (historic lighting collector)
An original 1939 daylight fluorescent tube at the Edison Tech Center, visit us.
Lamps are presented in the order of chronological development
Next: Halogen Lamps 1953 |
Arc - Incandescent - Nernst - Neon - Mercury Vapor - Sodium Lamp - Fluorescent - Halogen - EL - LED - MH - Induction |
More Technologies:
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Article by M. Whelan with assistance from Rick DeLair
Photos, video stills and video by M. Whelan
Sources:
John D. Harnden Jr.
Rick Delair - lighting collector
The General Electric Story by the Hall of History
Workshop of Engineers. John Miller. 1953
Wikipedia
US Patent Office
Smithsonian Institute
How Long Has Nfl Been Around
Photos:
Edison Tech Center
Schenectady Museum
Smithsonian Institute
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