This entire process typically takes 30 seconds to 3 minutes to complete, which is why CFLs take longer than other lights to become fully lit. CFLs with decorative covers like globe or reflector shapes have a unique design challenge that results in the tradeoff of a slower warm up time, which is why these CFLs take longer than bare spirals to reach full brightness. Older CFLs used large and heavy magnetic ballasts that caused a buzzing noise in some bulbs. Most photocells, motion sensors and electric timers are not designed to work with CFLs.
Always check with the manufacturer of the control for compatibility. Using them in enclosed fixtures indoors can create a hot environment that reduces the lifetime of your bulbs. Note that covered reflectors are best used in recessed cans. Protect bulbs from the elements by placing them inside enclosed fixtures outdoors.
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 's. The idea of the fluorescent lamp had been around since the '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. Statistics -CRI -Color Temperature - comes in all variations, K for normal indoor applications - lumens per watt -Lamp life: 10, - 45, hours does not take into account ballast life.
Left: Early fluorescent tubes, available in various color temperatures. Below: general video on the fluorescent lamp. How the Fluorescent Lamp Works. We discuss two types of fluorescent lamps: Hot Cathode , Cold Cathode.
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. 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 s.
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.
AC electric current passes through the ballast. The ballast will step up AC volts in the US to 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. 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. 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:. 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.
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. 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. 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. 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. 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 Kelvin color temperature and cool white which is closer to daylight at Kelvin. Filament electrodes are preheated and glow red 2. The Cathode begins to ionize argon gas surrounding it 3. This lamp is powered by AC power, so the cathode switches to the other side and you see the left side begin to ionize, the other side now the anode stays warm and ionized 4.
The left side cathode warms to full and both sides are warmed up 5. The ballast provides a high voltage kick which instantly ionizes the entire tube to a high level of brightness 6. The lamp returns to normal voltage and its warmth has vaporized all the mercury, the lamp operates as normal.
More on the Science:. Why does electricity flow through the gas? In a solid metal wire electrons jump freely from atom to atom, while the atoms stand stationary. In a gas there are also free electrons "jumping" their way from the negative electrode to the positive at the other side.
What is different is that you also have ions moving as well. What is an ion? This photon has less energy than the original photon, because some energy was lost as heat. In a fluorescent lamp, the emitted light is in the visible spectrum -- the phosphor gives off white light we can see. Manufacturers can vary the color of the light by using different combinations of phosphors.
Conventional incandescent light bulbs also emit a good bit of ultraviolet light, but they do not convert any of it to visible light. Consequently, a lot of the energy used to power an incandescent lamp is wasted. A fluorescent lamp puts this invisible light to work, and so is more efficient.
Incandescent lamps also lose more energy through heat emission than do fluorescent lamps. Overall, a typical fluorescent lamp is four to six times more efficient than an incandescent lamp. People generally use incandescent lights in the home, however, since they emit a "warmer" light -- a light with more red and less blue.
As we've seen, the entire fluorescent lamp system depends on an electrical current flowing through the gas in the glass tube. In the next section, we'll see what a fluorescent lamp needs to do to establish this current.
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