Why do fluorescent lamps dim when they start lighting and only get brighter after a while?

I don't think it's a problem with the filament, because the filament reaches a stable temperature very quickly, which is the same as a white lamp. Part of the current of the fluorescent lamp is supplied to the filament to emit electrons, and the emitted electrons move under the electric field of the 2-pole filament to excite mercury vapor to emit ultraviolet light.

The working principle of fluorescent tubes is different from that of incandescent lamps, the gas between the two filaments mainly emits ultraviolet light when it conducts electricity, and the phosphor emits visible light only when it is irradiated by ultraviolet light. )

So I think it may be that although the temperature of the filament has stabilized when it is first opened, the temperature of the mercury vapor in the lamp is slowly rising, which makes the vapor impedance lower, and then more electrons pass through the mercury vapor, and the ultraviolet light strengthens to make the fluorescent lamp slowly brighter.

This can be confirmed by the fact that the tube is still as bright as before.

Because the residual temperature of the lamp is still there.

zhzhq 777 you don't know don't mess up, how can fluorescent lamps have thermistors, which filaments are shining, and where will the current gradually increase, please!

The fluorescent lamp is mainly composed of lamps, starters, and ballasts The working principle of the lamp: the mercury vapor in the lamp conducts electricity, emits ultraviolet rays, and makes the phosphor on the tube wall emit white light, and it needs a high voltage to excite the mercury vapor conduction, and the fluorescent lamp needs a much lower voltage than 220V when the starter suddenly interrupts the circuit When the fluorescent lamp is working normally, the alternating current constantly passes through the ballast and the lamp (without passing through the starter), due to the self-inductance phenomenon, the self-inductive electromotive force generated in the coil of the ballast hinders the current change, which plays a role in reducing voltage, and the voltage at both ends of the lamp is much lower than that of 220V, which meets the normal working requirements

The phenomenon you said should not appear in normal fluorescent lamps.

As the temperature of the filament increases, the thermistor inside changes, so that the current through the filament gradually increases, gradually brightens, and turns on immediately after turning off (the lamp is not on at this time) It takes a while for the lamp to start to gradually brighten,

Let's take a look at how fluorescent lamps work

Fluorescent lamps mainly consist of a tube, a ballast, and a starter. There is a filament at each end of the tube, which is filled with rare argon and trace amounts of mercury vapor, and the wall of the tube is coated with phosphor. The working principle of the lamp is different from that of an incandescent lamp, the gas between the two filaments mainly emits ultraviolet light when it conducts electricity, and the phosphor emits visible light only when it is irradiated by ultraviolet light.

Depending on the type of phosphor, the color of the glow is also different.

The conductivity of gas has a characteristic: the gas can only conduct electricity when the voltage at both ends of the lamp reaches a certain value; However, to maintain a certain amount of current in the lamp, the voltage required is much lower. Therefore, if you put 220V on both ends of the lamp, it will not ignite it.

With ballasts and starters, this problem can be solved.

The ballast is a coil wound around the iron core, and the self-inductance coefficient is very large; The starter consists of a static contact sealed in a glass bubble filled with neon gas. When a certain voltage is added between the two contacts, neon conducts electricity, emits light and heats up. The moving contact is made of a double layer of metal that is bonded together, and the two layers of metal expand differently after being heated, and the moving contact is slightly stretched out and in contact with the static contact.

The actuator no longer emits light, at which point the bimetal plate cools, the moving contact shape reverts, and the two contacts are separated again.

After the switch is closed, the voltage is added to both ends of the starter through the filament of the fluorescent lamp, and the starter heats up as described above, and the cooling contact is disconnected. At the moment when the contact is opened, the current in the ballast L decreases dramatically, resulting in a high induced electromotive force. The induced electromotive force and the mains voltage are superimposed on the filaments at both ends of the lamp to ignite the lamp.

In practice, there is often a capacitor in parallel at both ends of the neon bubble in the starter, which allows the two contacts to separate without sparking to avoid burning out the contacts, and at the same time to reduce interference to nearby radio equipment. The starter works even without capacitors.

The power source for lighting in the home is AC, which is constantly changing in size and direction. The self-induced electromotive force in the ballast L prevents the change of current so that the current flowing through the lamp is not excessive.

Now to explain your problem: when it starts to be dark, it is because the lamp is not working properly, the gas in the tube is not conductive, but the filament (electrode that emits electrons) at both ends is emitting, when the voltage at both ends of the lamp reaches a certain value after starting for a period of time, the gas can conduct electricity, the induced electromotive force and the power supply voltage are superimposed on the filament at both ends of the lamp, the lamp is ignited, and the gas in the lamp is discharged and emits rays (mainly ultraviolet rays that cannot be seen by the naked eye), The phosphors that excite the walls of the tubes emit white light or other colors of light that we can see with the naked eye.

When the fluorescent lamp is just turned off, it will continue to emit a faint light (pale green or off-white), which is a normal phosphor afterglow phenomenon that will disappear for about a minute. If the light glows faintly long after the light is turned off, check whether the switch is incorrectly connected in the neutral line.

First, the switch controls the neutral line. This is one of the more common reasons, the electrical line switch controls the neutral line, or the electrical box enters the neutral line to fire back. The switch controls the neutral line, which is still connected to the fixture and emits a shimmering light.

Solution: Adjust the wiring so that the switch controls the live wire.

Second, the double control switch has an incorrect connection. There are several ways to connect the dual control switch, and if the wrong connection is used, the light will turn off and turn on slightly.

Solution: Install the normal control live wire connection and rewire.

3. The switch has an indicator light and uses an electronic switch. There is an indicator light inside the switch. When the light goes out, there will be a weak current flowing through. For example, lamps and lanterns use electronic switches, such as infrared, voice, remote control switches, etc. It will also light up when the lights are out.

Solution: Change the switch.

Energy-saving lamp is the use of the principle of gas discharge operation, its name is self-ballasted fluorescent lamp, the lamp is filled with rare gas, when the power is turned on in the lamp to produce high pressure, equivalent to a gas preheating process, just energized, the gas discharge is not significant enough, so it will be darker, when the gas preheating time is extended, the gas discharge becomes intense, the light will be brighter and brighter. Some energy-saving lamps are supplemented by special components that can instantly generate high voltage and start quickly, and there will be no such phenomenon.

When energy-saving lamps are first turned on, the temperature is generally low, so the brightness is low; As the energy-saving lamp is lit, the temperature will gradually increase, so it will become brighter and brighter; When the heat and heat dissipation of the energy-saving lamp are balanced, the temperature of the energy-saving lamp is stable, and the brightness is also stable, and it will not increase again.

First, there will be less and less nitrogen in energy-saving lamps.

Second, the filament of the energy-saving lamp will be shorter and thinner, and the resistance value will be smaller and smaller, according to w=p*t=u 2 r*t, the resistance decreases and the power becomes larger, so the energy-saving lamp will become brighter and brighter.

High-quality energy-saving lamps will not become very bright immediately after being lit, and the brightness will have a slow climbing process, and the maximum luminous effect can be reached in about 3 5 minutes, this is because the lamp belongs to gas discharge, and the luminescent material needs a certain amount of time to atomize, especially in winter (low temperature) It takes more time, and the luminous flux is the highest after full atomization.

Slow start-up response During the start-up process of the fluorescent lamp, the inductor ballast instantaneously generates a high voltage, and the starter emits electrons to hit the phosphor in the mercury vapor to produce light, and there is a certain process.

For the sake of the old one, it will be fine to replace it with a new one.

The fact that the energy-saving lamp is getting darker and darker may be caused by the poor quality of the phosphor coated on the inner wall of the energy-saving lamp, or the poor quality of the electrode wire.

Because the luminescence of energy-saving lamps relies on the positive and negative electrodes to excite the high-speed movement of electrons, the electrons collide with each other and then excite phosphors to emit visible light. The electrode wire has a lifespan, and the life will be reduced every time it is excited, that is, the strobe switch energy-saving lamp will greatly reduce the service life, and when the ability to excite is reduced, the energy-saving lamp will become darker and darker.

There is also a situation that when the electronic excitation ability is constant, if the phosphor quality of the energy-saving lamp is poor, then it will cause the light attenuation of the energy-saving lamp to decline rapidly, which will also make the energy-saving lamp darker and darker.

Because. Sodium filament in a street lamp.

It's filled with helium.

When the street lights are turned on.

The white light emitted by the first heating of the sodium metal, and the yellow light emitted when the sodium is vaporized.

Even the color of the sodium lamp.

The fluorescent lamp will dim after a long time because the lamp is aging, the fluorescent lamp (i.e. fluorescent lamp) is switched on and off too often, the starting current of the fluorescent lamp is very large, and the frequency of switching is too frequent will accelerate the aging of the lamp.

When the ignition time of the lamp is close to or beyond the specified service life, it is normal for the two ends of the lamp to turn black, indicating that the electric emission material coated by the filament is about to be exhausted. The blackened area is generally within about 50 to 60mm from both ends of the lamp. At this time, although the lamp can still emit light, the luminous intensity is lower than the normal brightness, and the lamp should be replaced.

If the two ends of the new lamp are seriously blackened soon after use, it is due to the fact that the electron emission material on the filament splashes too fast and is adsorbed on the tube wall, which may be due to the poor quality of the lamp, or it may be that the filament current is too large due to the problem of the ballast.

At the beginning, because the temperature of the filament is lower, the resistance is less, and the power of the lamp is small, and after a while, the temperature of the filament rises, the resistance becomes larger, and the power of the bulb becomes larger, so the bulb becomes brighter.

Generally, fluorescent lamps have a characteristic, that is, they are not very bright when they are just pointed, and they reach the maximum brightness after a while, this is because the fluorescent lamp is emitted by the mercury vapor in the lamp tube to hit the phosphor, and when it is just started, the mercury vapor has not been completely vaporized, and the brightness of the lamp can only reach normal after it is completely vaporized, which is more obvious in winter.

This is also the case with energy-saving lamps, which use inductive ballasts and flash a few times when they are turned on because they need to be turned on. Electronic ballasts fluorescent lamps do not have this problem. If it's not a fluorescent lamp, it's probably going to be damaged!

Because the pupils of the person have shrunk in strong light, the perception of stronger light will not be as strong as before. So this is a very normal phenomenon, but also a physiological reaction, we must treat it rationally, so when turning on the light, you must close your eyes, if you want to open your eyes, you must open them slowly. It's good for the eyes.

When the light is strong, our pupils will be smaller, so the scene we see will be particularly bright.

It's because when the light is on, turn on the light and the eyes don't have much contrast, so in this case, it won't feel very bright, and it's also because the surrounding light is brighter.

It may be that there is a problem with the light sensitivity of your eyes, and if the light is very bright, it will definitely be dazzling when the light is turned on.

The difference between the brightness of the phone and the brightness of the light when the light is on is less than the difference between the brightness of the phone and the darkness when the light is on.