Incandescent lamps are gradually becoming a thing of the past; their place is taken by modern energy-saving devices that require a minimum of electricity. Consumers are in demand for LED lamps, which are cheap, economical, and durable. When connecting them to the general power supply network, certain difficulties may arise.
When installing a backlit switch for LED lamps, you may notice that as a result the lighting fixture begins to blink or constantly shine with dim light.
How does an LED lamp work?
To understand the reason why LEDs do not work correctly, you need to understand how an LED lighting device works.
In appearance, a 220 V household energy-saving lamp does not differ from an ordinary incandescent light bulb. The difference lies in the internal design. The LED lamp has:
- base;
- a housing that also acts as a radiator for the device;
- control and power board;
- LED board;
- lamp cover.
In addition to the usual design elements, the LED lamp is equipped with a power supply and control unit, because LED devices cannot operate on alternating current. A lamp with a voltage of 220 V, powered from an alternating current network, where the current strength is 1 ampere, will simply burn out. A semiconductor circuit is built into the base of the device, rectifying the current and lowering the voltage.
Simple lighting devices use a power supply based on a non-polar capacitor, which cannot fully ensure compatibility of the electrical voltage with the lamp. Their resource is small.
Lamps in the mid-price range additionally use a combination of a resistor and a capacitor. In expensive LED devices, the manufacturer will install microcircuits in the housing that smooth out the voltage better.
Effect of an illuminated switch on an LED lamp
If the LED lamp flickers when turned off, check that the backlight switch has an indicator, which is represented by a small neon or LED light bulb. If there is one, that's the problem.
The indicator turns on if the lighting is turned off and the electrical circuit is broken. The circuit is designed so that the backlight is connected to the switch in parallel. When we turn off the lights, current flows to the indicator. Electricity moves in a circle, from the network to the switch light, then to the lamp and back to the network. This voltage allows you to charge the capacitor found in most LED lights. As a result, the capacitor tries to turn on the lamp, but there is too little charge, so flickering occurs in the lighting fixture or the LED may constantly burn dimly.
How to solve the problem of flickering LED lights
The simplest and most effective way to return the lamp to a stable state is to replace the switch with a new one, without an indicator. If desired, you can turn off the neon or LED lighting by cutting the power cord. If you don't understand which wire to disconnect, it's best not to do it.
Some craftsmen add an incandescent lamp to the lighting circuit, which will absorb the current that goes to charge the capacitor, excluding the start of the LED. However, there are two disadvantages: the electricity consumption of the device will increase, and it is not easy to install an additional lamp in a standard lamp. But overall the idea is good.
People knowledgeable about the topic advise connecting a small resistor to the lamp's power supply circuit, which absorbs voltage well. The resistor power should be 2 W. It is better to connect a resistor with a resistance of 50 kOhm in the area of the cartridge or junction box, connecting the contacts with a terminal block and insulating with heat-shrink tubing. Don't forget to turn off the power supply first. You should not use a resistor value higher than recommended to avoid unnecessary energy consumption.
There is another way to get rid of flickering lamps. You need to connect the switch indicator to the electrical network with a separate wire. The operation is simple, but requires additional wire connections, which not every premises owner can do on their own.
When choosing a way to solve the problem, we advise you to stop at disconnecting the backlight from the power supply or at the last option with installing a current-limiting resistor, which costs a few rubles and is easily hidden in the lamp. With a minimum of consumables and a little skill, your energy-saving light will work just fine.
Remember that a dim LED light does not mean it is faulty. Energy-saving lamps need to be purchased a little more than the nominal value required. When replacing a 60 W incandescent lamp, purchase an 8 W LED lamp.
Resistor resistance and power
The above resistor parameters correspond to a 220 V network voltage. It happens that the LED lamp is powered from a line of a different rating. Then you will have to calculate the resistance and power of the resistor yourself.
We calculate the resistance using the formula R=∆U/I, in which ∆U is the difference between the actual voltage in the device’s power supply line and the lamp voltage, I is the LED current.
The light bulb will work normally if the resistor value is in the range of 150 - 510 kOhm.
We calculate power using the formula P=∆U×I, where the letter values are similar to the above explanations.
Knowing these formulas, it is easy to make the necessary calculations of the resistor value.
Other causes of flickering
The above methods for eliminating the flickering of lamps with LED lamps are related to the switch. But there are exceptions when the light flickers and the switch is compliant.
- Low-quality energy-saving light bulb. It is more often observed in cheap Chinese-made products, when the lamp is defective from the factory. You'll have to spend money again and buy a good lamp.
- The service life of the diode lighting device has expired. The microcircuit element may have failed. As a result, the lamp glows, but blinks and crackles. There is no need to think that if the manufacturer provides an almost 10-year service life for the product, the lamp should work all the time. The service life of even a high-quality device is significantly reduced if voltage drops periodically appear in the network or the device operates at temperatures outside the standards determined by the designers.
In conclusion, it should be noted that if you postpone the search for a solution to the cause of the flickering light bulb, the energy-saving device will soon fail.
LED lamps are designed in such a way that each blink means the device is turned on. The service life of the lamps is tied to the number of switches on/off: the more often it flickers, the faster it will burn out. While repairing the lighting fixture, you can replace the LED with an incandescent lamp or temporarily install a regular switch.
220.guru
Flashing LED lamps how to get rid of the problem
I welcome all visitors to the “Electrician in the House” website. Today I want to look at the question of why the LED lamp blinks when it is turned off and how to get rid of the problem, which, as it turns out, worries many users. The question seems to be simple, but for some reason many people have difficulty solving it. This article will be an addition to one previously published on the same topic. If you remember, in the last article we looked at the reason for the blinking of energy-saving lamps. To solve the problem, a resistor was used. It was connected in parallel with the lamp, which in turn solved the problem with the blinking energy saving light.
On my YouTube video channel there is even a video on how to fix the problem. But there are a lot of comments. It is clear that people do not understand how to get rid of the problem. Some liked the solution using a resistor, others did not. Many people are looking for a solution in dismantling the backlight on the switch. Some people advise placing a regular incandescent lamp parallel to the LED lamp. This will certainly solve the blinking problem, but this option is not suitable for everyone.
Today, energy-saving lamps are being replaced by LED analogues. But the problem remains; when the switch is turned off, the effect of blinking LED lamps occurs; we will discuss how to get rid of this problem in this article.
I want to say right away that the effect flashing lamp when off observed regardless of whether the energy-saving lamp or LED. Therefore, this solution method can be applied to any types of lamps.
Higher quality LED lamps do not blink, but such specimens are correspondingly more expensive. Not everyone can afford to buy a light bulb for $10. And if you consider that 5-6 such light bulbs are required per apartment, then the price generally turns out to be unaffordable for the family budget.
LED lamp blinks after turning off - problem solution
As you remember, the reason for the blinking of energy-saving and LED lamps when they are connected through a backlit switch lies in the electronic circuit of the lamp. Or rather, in a smoothing capacitor. When the lamp is connected via an illuminated switch, current flows through the backlight diode when the switch is off. This current is small, hundredths of an ampere, but it is enough to recharge the smoothing capacitor in the lamp circuit.
As soon as this capacitor gains enough charge, it tries to start the power circuit, but the charge is only enough for a short pulse, the lamp flashes and goes out. As the capacitor charges, the process repeats, resulting in a flashing lamp.
Here I will give the most common options that lead to blinking lamps and ways to solve them.
1) Single-key switch with backlight
The simplest connection diagram is one illuminated switch and one LED light bulb. There can be more light bulbs (for example, a three- or five-arm chandelier), the main thing is that they are all connected via a single-key switch.
So, blinking LED lamps, how to get rid of the problem with such a scheme? As I mentioned above, in the previous article, a 2 W resistor with a resistance of 50 kOhm was a way to solve the problem of flickering energy-saving lamps. Today we’ll look at another way to solve this problem using a capacitor.
I apply capacitors for voltage 630 V and capacity 0.1 µF. Many people advise using 220 Volt capacitors. I think this is not entirely correct, since such a capacitor may not withstand the mains voltage and will one day fail. It is not necessary that this will happen immediately after connection; it may take some time (it all depends on the quality).
Why do I think this? Everyone knows that the voltage in the network is 220 Volts.
what voltage is this? Correct action! What is the effective voltage? The maximum voltage value (amplitude) divided by the root of two. And the amplitude value of the voltage, in turn, is equal to: the root of two multiplied by 220 V. That is, during normal operation in a 220 Volt network, the amplitude value of the voltage is 311 Volts. And a capacitor that is designed for a voltage of 220 V can simply burst at this amplitude voltage value.
So, if you have one way to solve the problem, a 630 Volt, 0.1 µF ceramic capacitor may be.
We connect the capacitor in parallel with the lamp. For convenience, you can solder wires to the legs. The capacitor has no polarity, so it doesn’t matter how you connect it (phase - zero), the main thing is that it is connected in parallel with the lamp.
This can be done directly on the lampshade if it is a spotlight, if it is a chandelier then under the decorative plate of the chandelier, in the junction box, etc. That is, the main task is to hide it from view, but how you do it makes no difference.
For clarity, I decided to show how you can connect a capacitor in a junction box and directly in a lampshade (chandelier). The first option is to place the capacitor in the junction box.
When the switch is on, the lamp works without any problems, the capacitor does not heat up - everything is fine.
The second option is to connect the capacitor directly in the lampshade:
We check the functionality of the entire circuit, everything works:
2) Two-key switch with backlight
The next option is to consider a connection diagram when the lighting is divided into several groups. For example, when LED spotlights are divided into two groups and controlled via a two-key switch. Or simply a double switch controls the lighting in two different rooms.
Most users solve the problem connecting a capacitor to one lamp (group), forgetting that there are two lights. Then they wonder why the LED lamp blinks when it’s off, did I install a capacitor?
If, with this connection scheme, you screw an LED light bulb into each group, they will start blinking, regardless of each other. This happens because each light bulb (each group) is affected by its own backlight indicator in the switch.
The switch is two-key, so as you understand, there are also two light indications. Accordingly, you need to install not one capacitor, but two, each in its own group.
3) Incorrect connection diagram
Another reason Why does the LED lamp blink when turned off?, the connection diagram may be incorrect. Moreover, such a problem can arise even if the switch is without backlight. What do I mean by the expression incorrect scheme.
We all know that when connecting wires in a junction box, the circuit is assembled in such a way that the switch receives a phase. Zero is directly connected to the light bulb (chandelier). This is done for security reasons. If the connection is made the other way around, so that it is the phase wire that is connected directly to the luminaire, a flashing effect may occur when the switch is off.
Due to the fact that the lamp base is always at potential, the capacitor is constantly charged and when the switch is turned off, we observe the same effect as with a backlit switch.
It happens that a person deliberately places switches without backlighting so that get rid of blinking LED lamps, and after installation it gets the opposite effect. This confuses many people as to why this happens. This can often be observed especially in houses with old electrical wiring. Previously, when assembling distribution boxes, they were not very worried about this.
4) Induced voltage in electrical wiring
And one more option that can cause LED lamps to blink is induced voltage in the electrical wiring.
When several electrical wiring lines are laid in a groove, and even with a good load, induced voltage can occur in disconnected sections of the wiring. Its value may be quite enough for the lamp to start blinking. Moreover, this can happen even if the switch is not backlit and the connection diagram is correct.
Or, as it happens, some craftsmen, in order to save on cable costs, lay one four or five-core cable and connect two wires (phase and zero) to one consumer, and the remaining wires to another. It turns out that two consumers are powered by one cable. In this case, if one of the consumers is working and the other is disconnected, induced voltage may occur at its contacts.
And that’s all for today, I think I’ve considered all the options in which blinking LED lamps how to get rid of this problem, I also hope it’s clear. I am sure that this article will help you or has already helped you resolve this issue.
electricvdome.ru
neon indicator
Most switch models work with a neon type bulb. How does she look? The light bulb looks like a glass container containing neon. Electrodes are located at a distance. There is little pressure in the device. If you measure it, it will hardly reach a few tenths of a column. In such an environment, a glow discharge occurs between parts when electric current is applied. What does this phrase mean? Gas molecules are highlighted. If we take into account that the models differ from each other in the color of this filler, then the options can be very different: red, blue-green, and so on. ">
LED lights
Switches are often made with backlighting provided by LEDs. The shade appears immediately as electric current begins to flow into the device. The color directly depends on what the diode is made of, as well as on the voltage supplied to the switch.
What are LEDs? They are the result of combining two semiconductors. Moreover, they are necessarily of different types. This transition is called electron-hole transition. The tint appears immediately after the direct current begins to flow. The emission of light is the result of the recombination of charges in conductors.
Every person knows that any device has negative and positive current charges. When an electric field is applied, the latter overcome the transition and connect with the former. After this, energy is supplied, part of which is necessary to obtain the color effect. If we talk about the design of the LED, it is metal. Often devices are made of copper. Semiconductors are fixed to the base - one anode, the second cathode. There is also a reflector made of aluminum. There is a lens on it. Manufacturers make sure that excess heat can be freely removed from the case. In this case, the “thermal corridor” should be small in size. The semiconductors working in it do not go beyond its boundaries, otherwise the LED lamp with a backlit switch will quickly break and be unusable. ">
Technical features
These parts decrease their resistance as the temperature increases when compared to metal components. Unfortunately, this has disadvantages - the current strength can increase to uncontrollable levels. The same thing happens with heating; accordingly, after a while after operating at such a peak, the diode fails. Also, such a part is very sensitive to an increase in voltage, so even the smallest impulse can break it. Accordingly, the manufacturer must select resistors as accurately as possible. Moreover, the diode may break if the voltage is reversed polarity. It should be noted that this component only copes with the passage of current in positive sequence.
Even with such disadvantages, switches with diodes are in demand. ">
Application of capacitor
The damping element is considered to be a capacitor. If you compare it with a resistor, then it has received reactance. Accordingly, when using such an element, excess heat will not be generated in the device. During the movement of electrons through the resistor, or rather, its front side, the molecules of the parts collide with each other. Because of this, kinetic energy is transferred. This is what causes the heating. The current receives strong resistance. If an LED lamp is connected to a backlit switch, it can quickly fail.
Other processes occur while the capacitor is in use. Its design differs significantly from the version described above. Capacitors have two metal plates that are separated by dielectrics. Thanks to this solution, the charge can be maintained for a long time. At the same time, it can be charged and discharged. After such manipulations, alternating current is present in the circuit.
Compatibility
For LED lamps, backlit switches are often installed. As was already clear, such devices are popular and convenient. Although it is used with the model described above, problems may still arise with most modern light sources. An LED lamp with a backlit switch often breaks.
Manifestation of incompatibility
How can incompatibility manifest itself? After a long period of operation, the lamp can flash on its own, glow evenly or chaotically. Moreover, this nuance applies to any LED-type lamps. Flickering can also be a cause of high power, especially if it is 100 W or more. Why are such lamps incompatible with switches? Often the problem arises from energy conservation. The lamps operate on constant voltage. Accordingly, any such device will have a rectifier and an alternating voltage network. Compatibility of LED lamps and backlit switches is a rather complex issue.
It must be said that the capacitor has a rectifier. It is necessary to smooth out pulsations. If the lamp is turned off, current will still flow, albeit in small quantities. Therefore, the lamp will flicker or glow even at night.
Is it worth connecting them together and how to do it correctly
The flicker discussed above is not entirely suitable for rooms such as a bedroom or children's room. In addition, if the operation is carried out incorrectly, a person may encounter the fact that the backlight stops working in a short time. This problem can be fixed. It will be enough to turn off the flickering. How to do it? It is necessary to install the switch so that the backlight is excluded. Buyers note that the method is not very convenient, since the highlighting is quite useful. It can help you easily turn on the lights in the room yourself. If the backlit switch and LED lamp are flashing, then you should pay attention - most likely the contact is damaged. ">
Nuances of use
If the installation is carried out incorrectly, the diode may stop working almost immediately. In addition, leaving it in this form is prohibited. It is not safe. If during operation the switch does not cut off the phases, then this should be done immediately. It is best to entrust the installation to a knowledgeable person if there is no experience in this field. If desired, you can put a regular incandescent lamp together with an energy-saving model. If the installation is done in this way, then the current passes through the indicator circuit. After this, you should continue to use the device. The current will flow through the channel thread. The disadvantage of this method of application is that this method has a bad effect on energy saving.
The same principle of operation is used when shunting a resistor. The connection is parallel. The device will not inject a person in any way. The desktop, lighting and so on are charged through a resistor. In this case, the latter should have a power of 2 W and a resistance of 50 kOhm.
Lamps that run on LEDs have also been created. Buyers like such devices due to the fact that there is a backlit remote control included. The device turns on for about 2 seconds. «>
Flaw
There is another disadvantage of backlit switches and LED lamps (they blink - this is not the only disadvantage), it lies in the price category. Their power and other indicators may be approximately the same, but the cost is not. When a person chooses a switch, it should be understood that not all lamps and lamps are capable of working with it. In addition, all models and their compatibility issues can be subject to small manipulations that allow you to troubleshoot. Accordingly, there is no need to abandon the indicator, switch or lamp itself. There are a large number of instructions on this matter.
Results
As is already clear, LED lamps with backlit switches are not the same. They may be the same or similar, but the designs and parts used are different. This is worth paying special attention to.
www.syl.ru
Having been stuck at work for two weeks without days off, I decided to devote part of my time to writing a series of posts about such seemingly insignificant details that often fall out of the buyer’s field of view when choosing lighting systems for an apartment or house. Unfortunately, sometimes the omission of a small detail can subsequently ruin the result of significant and often expensive efforts.
For example, such a simple thing as a switch, the key of which has a built-in backlight. Laying wires and selecting switches is usually carried out at an early stage of repair, long before it is time to select and install lighting. Therefore, when you come to the store to buy lamps, you no longer remember what switches you have installed, with or without backlight. And this turns out to be quite important.
The fact is that many modern light sources do not combine well with backlit switches. In particular, such switches are contraindicated for:
— compact fluorescent (energy-saving) lamps,
— fluorescent lamps with electronic ballasts (EPG),
— LED strips, powered by special units,
- LED lamps and luminaires powered both from low voltage sources (12, 24 V) and from current sources (drivers),
- even when using direct-on LED lamps (220 V), the presence of backlighting in the switch sometimes leads to strange, difficult-to-explain phenomena.
Incompatibility with energy-saving lamps can be expressed, for example, in the fact that after turning off the lamp continues to emit a weak pulsating glow, or periodically flashes brightly. As a rule, these phenomena gradually fade away as the lamp cools, but can continue for quite a long time.
Fluorescent lamps can periodically flash and then go out. The LED strip, as a rule, continues to glow with a weak, uniform light.
Essentially, backlit switches are only hassle-free when used with regular incandescent lamps and halogen lamps (which are also incandescent lamps). It has also been experimentally established that the effects described here cease to be felt when using LED strips with power supplies above 100 W. There are other exceptions.
The problem is easily solved - just remove the backlight element from the switch key. But, as practice shows, doing just this can be excruciatingly painful for the buyer. Another way to get rid of unpleasant phenomena is to connect an incandescent lamp in parallel, which will act as a shunt resistor and close the residual current of the switch backlight (but it will light up along with other lamps).
Actually, all this is what I mean: please, when choosing lamps, lamps and power supplies, warn the seller that you definitely want to use a backlit switch!
avkost1955.livejournal.com
neon indicator
Many switches use a neon light bulb as an indicator; it is most often a glass container filled with neon, in which two electrodes are placed at some distance from each other.
The gas pressure is very low - a few tenths of a millimeter of mercury. In such an environment, a so-called glow discharge occurs between the electrodes when voltage is applied to them - ionized gas molecules glow. Depending on the type of gas, the color of the glow can be very different: from red for neon to blue-green for argon.
The figure shows a miniature neon light bulb; in electrical engineering they are most often used as indicators of the presence of current.
Neon light bulb illumination
The illuminated switch on the neon light bulb is very reliable, the service life of the light bulb is more than 5 thousand hours, the indicator is clearly visible in the dark. The connection diagram is simple.
The diagram shows the connection of a neon light to a switch. L1 is a neon lamp of type MH-6, current 0.8 mA, ignition voltage 90 V, this is data from the reference book. R1 – quenching resistor, S1 – light switch.
Calculation of the quenching resistor
The resistor resistance is calculated using the formula:
where R is the resistor resistance (Ohm);
∆U – difference (Uс – Uз) between the mains voltage and lamp ignition in volts;
I – lamp current (A).
R=(220-90)/0.0008=162500 OM.
The closest resistor value is 150 kOhm. In general, the resistor value can be selected in the range from 150 to 510 kOhm, while the light bulb works normally; with a higher value, durability increases and power dissipation decreases.
The resistor power is calculated using the following formula:
where P is the power (W) dissipated by the resistor;
P=220-90 × 0.0008 = 0.104 W.
The nearest higher resistor power rating is 0.125 W. This power is quite enough, the resistor heats up barely noticeably, no more than 40-50 degrees, which is quite acceptable. If possible, it is advisable to install a 0.25 W resistor.
Design
If you solder the resistor lead to any lamp lead, you can assemble a circuit.
All that remains is to connect the assembled circuit. To do this, with the switch housing removed, the resistor terminal is connected to one terminal, and the light bulbs to the other.
Now, when the key is in the off position, the current will flow through the circuit (bottom figure), and since the current is limited by resistance, its strength will be enough to light the backlight, but not at all sufficient to operate the lighting lamp. When turned on, the terminals of the backlight circuit are short-circuited, and current flows through the switch, bypassing the backlight, to the lighting lamp (top picture).
LED lights
Often you can find LED backlighting, which is a semiconductor device that emits light when electric current flows through it.
The color of a light-emitting diode depends on the material from which it is made and, to some extent, on the applied voltage. LEDs are a combination of two semiconductors of different conductivity types p And n. This connection is called an electron-hole junction; it is at this junction that light emission occurs when a direct current passes through it.
The occurrence of light radiation is explained by the recombination of charge carriers in semiconductors; the figure below shows an approximate picture of what is happening in an LED.
In the figure, a circle with a “–” sign indicates negative charges; they are located in the green area, which is how area n is conventionally designated. A circle with a “+” sign symbolizes positive current carriers; they are located in the brown zone p, the boundary between these areas is the p-n junction.
When, under the influence of an electric field, a positive charge overcomes a p-n junction, then right at the border it connects with a negative one. And since during the connection there is also an increase in energy from the collision of these charges, part of the energy goes to heating the material, and part is emitted in the form of a light quantum.
Structurally, an LED is a metal, most often copper, base on which two semiconductor crystals of different conductivity are fixed, one of them is the anode, the other is the cathode. An aluminum reflector with a lens attached to it is glued to the base.
As you can understand from the figure below, a lot of attention is paid to heat removal in the design; this is no coincidence, since semiconductors work well in a narrow thermal corridor, going beyond its boundaries disrupts the operation of the device until it fails.
LEDs are very sensitive to exceeding the threshold voltage; even a short-term pulse disables it. Therefore, current-limiting resistors must be selected very accurately. In addition, the LED is designed for current flow only in the forward direction, i.e. from the anode to the cathode, if a voltage of reverse polarity is applied, this can also damage it.
And yet, despite these limitations, LEDs are widely used for lighting in switches. Let's look at the circuits for switching on and protecting LEDs in switches.
LED backlight
The figure below shows the backlight diagram. It contains: quenching resistor R1, LED VD2 and protective diode VD1. The letter a is the anode of the LED, k is the cathode.
Since the operating voltage of the LED is much lower than the mains voltage, quenching resistors are used to reduce it; depending on the current consumed, its resistance will be different.
Resistor resistance calculation
The resistance of the resistor R is calculated by the formula:
where R is the resistance of the quenching resistor (Ohm);
Let's calculate the quenching resistor for the AL307A LED. Initial data: operating voltage 2 V, current from 10 to 20 mA.
Using the above formula, R max = (220 – 2)/0.01 = 218 00 ohms, R min = (220 – 2)/0.02 = 10900 ohms. We find that the resistor resistance should be in the range from 11 to 22 kOhm.
Power calculation
where P is the power dissipated by the resistor (W);
U c – network voltage (here 220 V);
U sd – operating voltage of the LED (V);
I LED – operating current of the LED (A);
We calculate the power: P min = (220-2)*0.01 = 2.18 W, P max = (220-2)*0.02 = 4.36 W. As follows from the calculation, the power dissipated by the resistor is quite significant.
Of the resistor power ratings, the closest larger one is 5 W, but such a resistor is quite large in size, and it will not be possible to hide it in the switch body, and it is irrational to waste electricity.
Since the calculation was carried out for the maximum permissible current of the LED, and in this mode its durability is greatly reduced, by reducing the current by half, you can kill two birds with one stone: reduce power dissipation and increase the service life of the LED. To do this, you just need to double the resistance of the resistor to 22-39 kOhm.
The figure above shows a diagram for connecting the backlight to the switch terminals. The phase wire of the network goes to one terminal, the wire from the light bulb goes to the second, the backlight is connected to these two terminals. When the switch is open, current flows through the backlight circuit and it lights up, but the light bulb does not light up. If the switch is closed, the voltage will flow through the circuit, bypassing the backlight, and the lighting will turn on.
Application of capacitor
A capacitor can be used as a damping element; unlike a resistor, it has reactance rather than active resistance, so no heat is generated when current passes through it.
The thing is that when electrons move along the conductive layer of the resistor, they collide with the nodes of the crystal lattice of the material and transfer part of their kinetic energy to them. Therefore, the material heats up, and the electric current experiences resistance to movement.
Completely different processes occur when current flows through a capacitor. A capacitor, in its simplest form, consists of two metal plates separated by a dielectric so that no direct electric current can flow through it. But a charge can be stored on these plates, and if it is periodically charged and discharged, then alternating current begins to flow in the circuit.
Calculation of the quenching capacitor
If a capacitor is connected to an alternating current circuit, it will flow through it, but depending on the capacitance and frequency of the current, its voltage will decrease by some amount. For calculation use the following formula:
where X c is the capacitance of the capacitor (OM);
f – frequency of current in the network (in our case 50 Hz);
C – capacitance of the capacitor in (μF);
For calculations, this formula is not entirely convenient, so in practice they most often resort to the following - empirical, which allows for the selection of a capacitor with sufficient accuracy.
C=(4.45*I)/(U-U d)
Initial data: U c –220 V; Usd –2 V; I sd –20 mA;
We find the capacitance of the capacitor C = (4.45 * 20)/(220-2) = 0.408 µF, from the range of nominal capacitances E24 we select the nearest smaller one 0.39 µF. But when choosing a capacitor, it is also necessary to take into account its operating voltage; it must be no less than U c * 1.41.
The fact is that in an alternating current circuit it is customary to distinguish between effective and effective voltage. If the current shape is sinusoidal, then the effective voltage is 1.41 times greater than the effective voltage. This means that the capacitor must have a minimum operating voltage of 220 * 1.41 = 310 V. And since there is no such rating, the nearest higher one will be 400 V.
For these purposes, you can use a film capacitor of the K73-17 type; its dimensions and weight allow it to be placed in the switch housing.
Having been stuck at work for two weeks without days off, I decided to devote part of my time to writing a series of posts about such seemingly insignificant details that often fall out of the buyer’s field of view when choosing lighting systems for an apartment or house. Unfortunately, sometimes the omission of a small detail can subsequently ruin the result of significant and often expensive efforts.
For example, such a simple thing as a switch, the key of which has a built-in backlight. Laying wires and selecting switches is usually carried out at an early stage of repair, long before it is time to select and install lighting. Therefore, when you come to the store to buy lamps, you no longer remember what switches you have installed, with or without backlight. And this turns out to be quite important.
The fact is that many modern light sources do not combine well with backlit switches. In particular, such switches are contraindicated for:
- compact fluorescent (energy saving) lamps,
- fluorescent lamps with electronic ballasts (EPG),
- LED strips, powered by special units,
- LED lamps and luminaires powered both from low voltage sources (12, 24 V) and from current sources (drivers),
- even when using direct-on LED lamps (220 V), the presence of backlighting in the switch sometimes leads to strange, difficult-to-explain phenomena.
Incompatibility with energy-saving lamps can be expressed, for example, in the fact that after turning off the lamp continues to emit a weak pulsating glow, or periodically flashes brightly. As a rule, these phenomena gradually fade away as the lamp cools, but can continue for quite a long time.
Fluorescent lamps can periodically flash and then go out. The LED strip, as a rule, continues to glow with a weak, uniform light.
Essentially, backlit switches are only hassle-free when used with regular incandescent lamps and halogen lamps (which are also incandescent lamps). It has also been experimentally established that the effects described here cease to be felt when using LED strips with power supplies above 100 W. There are other exceptions.
The problem can be easily solved - just remove the backlight element from the switch key. But, as practice shows, doing just this can be excruciatingly painful for the buyer. Another way to get rid of unpleasant phenomena is to connect an incandescent lamp in parallel, which will act as a shunt resistor and close the residual current of the switch backlight (but it will light up along with other lamps).
Actually, all this is what I mean: please, when choosing lamps, lamps and power supplies, warn the seller that you definitely want to use a backlit switch!
On store shelves you can see illuminated switches. But not everyone wants to replace a conventional installed switch. And I don’t want to look for it in the dark either.
Backlit switches are connected in the same way as regular ones. Any person who wants to stop searching for a switch at night can modify it even without knowing basic electrical knowledge. Read the article and you will understand that everything is simple. The switch can be supplemented with an LED using the simplest circuits. The difference between the schemes is not only in the configuration, but also in the characteristics. For example, an LED switch circuit may not work due to the fact that an LED lamp is installed in the lamps. Energy-saving lamps may flicker and glow dimly in dark environments. Let's look at the disadvantages and advantages of each scheme.
Switch illumination circuit based on LED and resistance
As a rule, to illuminate the switch, it is enough to install an LED according to the diagram below.
If the switch is “Off”, current flows through R1 (any type, from 100 to 150 kOhm), then through the LED VD2 (lit). VD2 is protected from voltage breakdown by diode VD1. For a good glow, R1 is suitable, the current of which is 3 mA. If the LED light is too weak, you need to reduce the resistance. VD1, VD2 – any type and color of glow. To independently calculate the parameters of the resistor used, you should remember the law of current strength. LED backlighting is used if a lamp with an incandescent lamp is installed. If there is an energy-saving lamp, you may notice flickering and blinking in the dark. If the lamp uses LEDs to illuminate the room, then such a circuit will not work because the resistance in the lamp is too high. And it is very difficult to create it in a switch. The scheme is simple, but it has a drawback - consumption of 1 kWh per month. Here's the diagram.
The ends facing downwards are connected to the terminals. This circuit is twisted and is suitable for those who do not have a soldering iron. But it’s better to solder the twists and insulate them and the resistor.
Switch illumination circuit using an LED and a capacitor
To increase the efficiency of the glow, you can include a capacitor in the circuit and reduce the current of resistor R1 to 100 Ohms.
The difference between this circuit and the previous one is that the capacitor serves as a replacement for resistor R1. R1 (100 - 500 Ohm; 0.25 W) in turn acts as a charge current limiter.
The disadvantages are large dimensions, the advantages are low energy consumption, 0.05 Wh per month.
Switch illumination circuit on a neon light bulb
This scheme is devoid of the disadvantages that are present in the above-described schemes. The big advantage is that it is suitable for lamps using both energy-saving and LED lamps, as well as incandescent lamps.
When the switch is open, the current flows through the gas-discharge lamp HG1, which lights up, and resistance R1 (any power, but not less than 0.25 W; 0.5-1 MΩ).
Gas-discharge neon lamps are presented in a wide range, you can choose any one. The photo shows a lamp and a resistor rated at 200 kOhm. It was removed from the extension switch of the Pilot computer. It can be built into any switch without additional modification. Such lamps can be found in electric kettles, a device with an indication.
These lamps are everywhere. Are you surprised? All fluorescent lamps use a starter, this is a neon lamp built into a cylindrical housing. The number of starters in a luminaire equals the number of lamps. To remove it from there, turn the cylinder counterclockwise. There is also a capacitor in the case that suppresses interference. It is not needed when making illumination.
If the starter was removed from a broken lamp, check the functionality of the lamp. It is better to take neon glass from new type starters, since in old ones the glass darkens, which leads to a dull glow.
Attention! Before working on the switch, turn off the electrical power. If you have a problem with the dimensions of the resistor, that is, it turns out to be large and does not fit, replace it with several small ones connected in parallel.
When resistors are connected in parallel, the power that is dissipated by one resistor will be equal to the power that is divided by the number of resistors. Their value will become smaller and will be equal to the value divided by the quantity. For example, we need a 1 W, 100 kOhm resistor.
Let's convert kiloOhms to Ohms, we get 1 kOhm equal to 1000 Ohms. Therefore, this resistor can be replaced by two, connected in series in the circuit, each with a power of 0.5 W and a nominal value of 50 kOhm.
If the connection is parallel, the calculation is carried out in the same way. The difference is that the nominal voltage of the resistor is equal to the value that is multiplied by their number. For example, to replace a 100 kOhm resistor with three smaller ones, the resistance of each must be 300 kOhm. During installation, the capacitor or resistor should be connected to the phase wire. This is all because the currents that flow through the circuit parts are not higher than a couple of milliamps. Therefore, there are no special requirements for the quality of existing contacts. If the box in which the circuit will be mounted is made of metal, you need to take care of the insulation of the wires.
When installing the switch, it will not be possible to harm anything, because the lamp acts as a current limiter. The worst thing that can happen is the failure of the elements you will be installing. For example, if you take a resistor with a nominal value of 100 Ohms instead of 100 kOhms, or do not install it at all.
Step-by-step instructions for installing in a backlight switch
Nionki can either have a base or be without it. For the second, the leads come directly out of the flask. Therefore, the type of installation is different.
Installing a neon light bulb with flexible leads into a switch
Usually, the leads that stick out from the light bulb are not long enough to connect them with terminals to the switch, so you need to extend them with a piece of copper wiring. The wire used can have either one core or many. It is best to solder these wires to the terminals of the light bulb.
Before you start soldering, you need to strip the wires and tin these places with solder. Then connect the wires with an allowance of at least 5 mm and solder.
After soldering, do not forget to insulate the area by putting on an insulating tube or wrapping a couple of turns of insulating tape.
To make further installation convenient, a ring is created at the end of the wiring that has been soldered using pliers, to which the switch terminal will be secured.
As a rule, manufacturers make white switches. Against its background, the backlight is clearly visible even at night and there is no need to drill an additional hole for the LED.
Then, solder the resistor to the second terminal of the lamp. And then a piece of wire to it in the same way as the first one. We need it to connect the second output of the switch.
We perform a similar operation with the second output. We isolate the soldering area with a tube or insulating tape, twist the ring and attach it to the second terminal of the switch.
The backlight is mounted and connected to the electrical wiring. The work is almost complete, you just need to make a key to turn on the backlight.
Installing a neon light bulb with a socket into a switch
Using a socket for illumination is unnecessary. Since the life of a light bulb is much longer than the life of a switch. Therefore, instead of using a cartridge, we simply solder the base to the wires.
To do this, remove the insulation from the wires, tin them with a soldering iron and make small loops. After this, solder to the terminals on the lamp.
A wire extends from the central contact of the base; a resistor must be soldered to it at a distance of 2-3 cm from the base. The leads are made to the required length, and loops are twisted at their ends. We carry out the same operation with the second terminal of the resistor.
The threaded part of the base, as well as the resistor, must be insulated. This is done using insulation or heat-shrinkable tubing.
Or I offer my own method of isolation.
Many people are familiar with PVC tubes. EE is often used for wire insulation. In order to prevent a piece of tube (cambric) from coming off, its internal diameter must be smaller than the wire itself. The problem arises that such a cambric is difficult to find.
There is no tricky way. If you hold the cambric for about 15 minutes in acetone, it will soften and easily fit onto a part that is 1.5 times larger than the internal diameter. This is how I insulated the New Year's lamps onto the garland.
After the acetone has completely evaporated, the cambric will take its original form and will be tightly attached to the wire and lamp base. It will not be possible to remove it, unless you use acetone again to soak it. This method is similar to heat shrink tubing, with the difference that no heat is required.
After all the work has been done, the backlight is installed in the switch box and connected to the contacts.
Illuminated switches for electrical appliances
Illuminated switches can be seen on carriers, heating devices, and electrical appliances. Often, such lighting consists of a neon lamp and a resistor. Once I had the opportunity to carry out repair work on the Pilot extension cord. It had a cracked key that fell out and prevented it from being turned on.
After the switch was disassembled, I was surprised. There was no current-limiting resistor in it. Neon lamps are not connected to a 220 V current without a resistor, which serves as a current limiter. Such a device will fail in the first moments of operation. In the photo you can see the key from the neon lamp mounting side and the front one.
The resistance that I measured between the lamp terminal and the spring was 150 kOhm. This switch has an interesting design. Resistors, and there are two of them, are installed in the holes in the keys, pressed by a spring to the lamp terminals, which ensures good contact. These springs press the movable contacts located in the switch. When the switch is turned on, voltage is supplied to the neon lamp.
Using a backlight circuit for display
The backlight also serves so that you can track whether the switch is operational or not. If the backlight is on, but the light does not turn on, the switch is faulty. If the backlight does not work, the indication lamp has burned out.
The circuit option is suitable for indicating any devices and electrical circuits. Let's say that when you connect a lamp to a fuse, you can find out when it will burn out. If the electrical appliance does not have an indication, it can be built in. This way, it will be easy to monitor whether the device is working.
18.10.2014
Do backlit switches negatively affect LED bulbs?
Switches with built-in LED backlighting do not negatively affect the LED lamps themselves. At least in most cases.
Another thing is that using such switches can have an unpleasant effect for you - when turned off, the LED lamps begin to smolder, blink, flash, etc.
This happens because your illuminated switch does not completely disconnect the electrical network. The LED burning in it confirms this, because it lights up because the circuit is not open - otherwise where will it get the energy? In this case, the current flows through the lamps and the switch is very small. And if the lamps contain incandescent lamps, then they will never light up from such a current and will not react to it at all.
Another thing is LED lamps. Something like this happens. This small current passes through the snubber capacitor at the input of the lamp power supply and gradually charges it. At some point, the capacitor discharges and the lamp flashes.
Of course, the use of backlit switches does not always lead to such effects - it all depends on the electrical parameters of the lamp and the backlight LED.
If your question needs to be understood like this: LED lamps do not blink when using a backlit switch, but is this harmful to them?, then the answer is this. As a rule, no, but it all depends on the internal structure of the lamp. This will not harm most LED lamps; it certainly will not harm our lamps. However, the market is now filled with cheap “crafts” about which we cannot say the same.
There are backlit switches on sale, but rarely does anyone get around to replacing one that is already installed without backlighting and is still in good working order.
After spending half an hour, anyone who wants to improve the comfort of night life will be able to add lighting to the switches in their apartment on their own, even without the skills of an electrician.
You can install the backlight switch according to one of the proposed schemes. The circuits differ not only in configuration, but also in technical characteristics. For example, an LED circuit may not work if the luminaire contains LED lamps. And energy-saving lamps may flicker or glow faintly in the dark. Let us consider in detail the advantages and disadvantages of each of the schemes.
Switch illumination circuit based on LED and resistance
Currently, switches for lighting are usually equipped with LEDs, which are included in the switch according to the electrical diagram below.
When the switch is in the “Off” position, the current passes through resistance R1, then through the LED VD2, which lights up. Diode VD1 protects VD2 from reverse voltage breakdown. R1 of any type with a power of more than 1 W, rated from 100 to 150 kOhm. With the R1 rating indicated on the diagram, the current flows about 3 mA, which is quite enough for a clearly visible glow in the dark. If the LED glow is insufficient, then the resistance value must be reduced. VD1 of any type, VD2 of any type and color of light. In order to understand the theory and independently calculate the size and power of the resistor, you need to read the article “The Law of Current Strength”.
An LED switch illumination circuit can be installed if the lamp uses incandescent light bulbs. If there are compact fluorescent (energy-saving) ones, then it is possible that in the dark you may notice their faint glow or blinking. If the lamp is equipped with LED bulbs, then the backlight made according to this scheme may not even work, since the resistance of the LED bulb is very high and a current of sufficient strength for the LED to glow may not be created. In the dark, the LED light may glow faintly. The scheme is very simple, but has a big drawback: it consumes a lot of electricity, about 1 kW×hour per month. This is what the assembled circuit looks like.
All that remains is to connect the ends that point down to the switch terminals. If you did not make any mistakes during installation, the circuit will work immediately. I specifically posted a photo of the twists for those who do not have the opportunity to solder the connections with a soldering iron. For reliability and safety, you still need to solder the twists and cover the bare wires and resistor with electrical tape.
Switch illumination circuit using an LED and a capacitor
To increase the efficiency of the backlight in the switch, you can install an additional capacitor in the electrical circuit, while reducing the value of resistor R1 to 100 Ohms.
This circuit differs from the above by using capacitor C1 as a current-limiting element instead of a resistor. R1 here performs the function of limiting the capacitor charge current. Resistance R1 can be used from 100 to 500 Ohms with a power of 0.25 W. Instead of a simple diode VD1, you can install an LED, the same as VD2. The efficiency of the circuit will not change, and both LEDs will shine at once with the same brightness.
The advantage of a circuit with a capacitor is low energy consumption, about 0.05 kW×hour per month. The disadvantages of the scheme are the same as those presented above and, in addition, large overall dimensions.
Switch illumination circuit for a neon light bulb (neon)
The backlighting circuit for a switch on a neon light bulb (neon) is devoid of the disadvantages inherent in the LED backlighting circuits presented above. This switch illumination scheme is suitable for chandelier switches and any other types of lamps, with both incandescent light bulbs and energy-saving fluorescent and LED lamps installed in them.
When the switch is open, current flows through resistance R1, the discharge lamp HG1 and it lights up. R1 of any type with a power of more than 0.25 W, rated from 0.5 to 1.0 MOhm.
In the photo you see the assembled switch illumination circuit, which couldn’t be simpler. It is enough to connect a resistor in series with a neon light bulb of any type and the circuit is ready.
Where to get a neon light bulb
Neon gas-discharge bulbs (neons) are presented in a wide range and you can use any of them available. Please note that on the left in the photo there is a gas-discharge light bulb with a 200 kOhm resistor, removed from a failed computer extension cord switch, which is also called the Pilot. It can be successfully installed in any switch without the additional hassle of finding components. The same light bulbs with a resistor are installed in electric kettles and other electrical appliances to indicate the on state. In the center of the photograph, a Small-sized Thyratron (triode) with a Cold Cathode MTX-90 unexpectedly appeared. To be fair, I’ll say that the MTX-90 thyratron has been shining in my sconce for decades.
Neon bulbs (neons) surround us almost everywhere. Are you surprised? All older fluorescent light fixtures use a starter, which is a real neon light bulb housed in a cylindrical housing. In order to remove it from the lamp body, you need to turn the cylinder slightly counterclockwise. There are as many starters as there are fluorescent lamps in a luminaire. In the starter, a capacitor is also connected in parallel to the neon lamp; it serves to suppress interference and is not needed in the manufacture of the indicator.
If the starter is taken from an old lamp, before using a neon bulb, do not be lazy to check it. Before installation, you must connect the light bulb according to the above diagram. It is better to take a neon from a new starter, since in old ones the glass of the bulb bulb from the inside is usually covered with a dark coating and the glow will be less visible. A light bulb from a starter can be successfully used to make your own phase indicator.
A ready-made lighting kit for installation in a wall switch can be taken from a faulty modern electric kettle. As a rule, most models have a water heating indicator. The indicator is a neon light bulb with a current-limiting resistor connected in series and this circuit is connected in parallel to the heating element. If you have a faulty electric kettle lying around in your household, then a neon light bulb with a resistor can be removed from it and mounted in the switch.
The photo shows three neon lights from electric kettles. As you can see, they shine quite brightly, so in the dark they will be visible in the switch from a great distance.
If you look closely at the insulating tubes placed at the junction of the terminals of the neon light bulb with the wires, you will notice a thickening on one of the tubes. A current-limiting resistor is located at this location. If you cut the tube lengthwise, a picture will open, as in this photo.
Step-by-step instructions for installing in a backlight switch
When working on the switch, you must turn off the power supply!
Neon light bulbs come with a base and without a base, in which the leads come directly from the glass bulb. Therefore, the method of their installation is somewhat different.
Installing a neon light bulb with flexible leads into a switch
As a rule, the length of the leads of a neon light bulb (neon) or LED is not enough for direct connection to the switch terminals and therefore they must be extended with a piece of copper wire. For these purposes, both single-core and stranded wire of any cross-section are suitable. The best way to connect the wire to the terminal is by soldering.
Before soldering, the terminals of the neon light bulb and the ends of the conductor must be cleaned of oxides and tinned with solder using a soldering iron. Then join to a length of at least 5 mm and solder.
Then the soldering point and the terminal of the neon light bulb need to be insulated by putting an insulating tube on them. You can simply wrap a couple of turns of insulating tape.
For ease of soldering, the end of the soldered conductor is formed into a ring using pliers and secured to the switch terminal.
The keys or covers of wall switches are usually made of white plastic and the light from a neon bulb (neon) or LED passes through them well. It is enough to make the switch key visible in the dark. Therefore, there is no need to drill a hole in the switch opposite the backlight installation location.
An insulating tube is also placed on the soldered resistor or it is insulated with insulating tape. The end of the output is formed into a ring and secured to the second terminal of the switch.
The switch illumination circuit is installed, the switch is connected to the electrical wiring, all that remains is to install the key and the work can be considered complete.
Installing a neon light bulb with a socket into a switch
It is not advisable to use a socket for illumination, since the service life of a neon light bulb (neon) is longer than the service life of the switch, and there is not enough space in the box. Therefore, it is more advisable to connect the base to the circuit using soldering.
To do this, you need to remove the insulation from the wires, tin the bare ends and make small loops. Then solder the light bulb terminals on the base to the soldering points.
A resistor is soldered to the wire extending from the central contact of the base at a distance of 2-3 cm. The resistor leads need to be shortened and wire loops made at the ends. A wire is also soldered to the second terminal of the resistor.
The threaded part of the base and the resistor must be insulated. This can be done using heat-shrinkable tubing, insulating tape, or the method I suggest.
Many good polyvinyl chloride (PVC) tubing is often used to insulate wires. To prevent the tube section (cambric) from slipping, the internal diameters should be slightly smaller than the insulated solder. There are always difficulties in finding a cambric of suitable diameter.
But if you hold the cambric for about 15 minutes in acetone, it becomes elastic and can be easily put on a part that is one and a half times larger than its internal diameter. This is how I insulated light bulbs in a homemade New Year's garland in the distant past.
After the acetone evaporates, the cambric again returns to its original size and tightly fits the lamp base. It is no longer possible to remove the cambric unless it is re-soaked with acetone. This insulation method is similar to heat-shrinkable tubing, but no heating is required.
After the preparatory work, the backlight is placed in the switch box and connected to its contacts.
If there is not enough space to place a resistor or you do not have the required power at hand, then the resistor can be replaced with several of lower power, connecting them in series or in parallel.
When resistors of the same resistance are connected in series, the power dissipated on one resistor will be equal to the calculated power divided by the number of resistors, and their value will decrease and will be equal to the calculated value divided by the number of resistors. For example, according to calculations, a resistor with a power of 1 watt and a nominal value of 100 kOhm is required. 1 kOhm=1000 Ohm. This resistor can be replaced with two 0.5-watt, 50-kOhm resistors connected in series.
When connecting resistors of the same resistance in parallel, the power is calculated as with a series connection, and the value of each resistor must be equal to the calculated value multiplied by the number of resistors connected in parallel. For example, to replace one 100 kOhm resistor with three, the resistance of each must be 300 kOhm.
When installing the circuit, connect the resistor (capacitor) only to the phase wire of the switch. Since the currents flowing through the circuit elements do not exceed several milliamps, there are no special requirements for the quality of the contacts. If the box with the switch in which the backlight will be mounted is metal, then it is necessary to exclude the possibility of the current-carrying conductors touching its walls.
It is impossible to spoil anything when installing the backlight in a wall switch, since the lamp itself is a current limiter. The worst thing that can happen is the failure of the mounted elements if serious mistakes are made. For example, turn on the LED without a current-limiting resistor, or the resistor value is mistakenly taken to be 100 ohms instead of 100 kOhm.
Calculator for calculation
current limiting resistor parameters
When installing it yourself in a backlight switch on an LED or neon light bulb, it is necessary to determine the size and power of the current-limiting resistance. The calculation can be done using formulas, but it is much more convenient to calculate the resistor parameters using a special calculator. Just enter the parameters and get the finished result. The calculator can also be useful for selecting a resistor in a factory-made backlit switch in case the resistor fails.
Reference. On an LED the voltage drop is in the range of 1.5-2 V, on a neon bulb it drops 40-80 V. The required minimum current at which the LED is guaranteed to glow is 2 mA, for a neon bulb - 0.1 mA. This data can be used for calculations on a calculator if the parameters of an LED or neon bulb are unknown.
When choosing a resistance, it becomes necessary to determine its value by color marking. An online calculator will help solve this issue.
Illuminated switches for electrical appliances
Illuminated switches are often installed in switches on carriers and extension cords, heaters and other electrical appliances. They usually have a neon light bulb with resistors built into them. I once had to repair a Pilot type extension cord in which the switch control key fell out and cracked.
When I disassembled the switch, I did not find a current-limiting resistor, which I was very surprised by. Neon bulbs must not be connected to a 220 V electrical network without current limitation. It will fail immediately. On the left photo is a view of the key from the side where the neon light bulb is installed, and on the right, the reverse side of the same switch key.
I measured the resistance between the spring and the terminal of the neon light bulb, it was 150 kOhm. This switch used an interesting design solution: two 150 kOhm resistors were installed in the key holes and a spring pressed them to the terminals of the neon light bulb, ensuring reliable contact. The springs themselves exert pressure on the movable contacts in the switch, from which, when the switch is in the On position, power is supplied to the neon light bulb.
Using a backlight circuit for display
The backlight of the switch performs another additional useful function - it indicates the functionality of the switch and the serviceability of the light bulb. If the backlight works, but the light does not turn on, then the switch is faulty. If the backlight does not work, then the light bulb has burned out.
Any of the above presented circuit options can be used to indicate the health of devices or electrical circuits. For example, if you connect it in parallel with a fuse, then if it blows, the indicator will light up. If an electrical appliance does not have a standard on indicator, then by connecting the indicator immediately after the switch, you can always see whether the appliance is on. When installed in a socket (connected parallel to the current-carrying wires), you will know whether the socket is energized or not.
