This device is a must-have attribute of any room. When choosing it, you can prefer a regular one or one that has indicators. To make the right decision, you need to form an opinion about the pros and cons of each option. Having figured out what a backlit switch is, you can easily determine whether it is needed and how to choose it correctly.
Illuminated switch design Source sovet-ingenera.com
What are the features of such switches?
When choosing such products, many people pay attention to their practicality, reliability and functionality. Conventional devices have a simpler design and do not require additional effort during installation. However, in most cases, the connection for a switch with an LED does not involve any special difficulties.
Circuit diagram of the switch Source sovet-ingenera.com
Use brings additional convenience, allowing you to easily find the keys in low visibility conditions. The backlit switch has installed indicators. This is especially convenient when you need to turn on the light in a room with insufficient lighting. Having entered it, a person can immediately see where exactly the device is located and use it.
Illuminated switch Source sovet-ingenera.com
Why does a switched off energy-saving light bulb blink?
Many people have long replaced conventional incandescent lamps with energy-saving ones, and some of them have encountered the problem of the light bulb flickering when the lights are turned off.
What causes this unpleasant phenomenon and what electrical work to carry out in this regard, we will look into this in our article.
ENERGY-SAVING BULBS HAVE MANY ADVANTAGES, BUT FLINKING WHEN THEY TURN OFF IS THEIR “PREMISE” MINUS
Why does the energy-saving light bulb blink when the lights are off?
A similar phenomenon occurs in rooms where LED-backlit switches are installed. When the light is turned off, the LED lights up and indicates the path to the switch at night.
Advantages and disadvantages of such devices
The advantages of a backlit switch include the following features:
- The backlight allows you to immediately find it in the dark without having to feel the wall nearby.
- The presence of lighting allows you to keep the wall surface next to the switch clean. In this case, there will be no fingerprints on the wallpaper due to the inaccurate determination of its location.
It is also necessary to take into account the following disadvantages:
- When an illuminated switch is used, the circuit can be quite complex.
- Their installation is more complex than conventional devices due to the need to ensure that the indicators are connected correctly. The installation itself is not difficult, but in some types of products you can additionally set the signal operating mode.
- Connecting an illuminated switch creates additional electricity consumption. Although it is insignificant, it is nevertheless true.
- Some types of lamps sometimes turn on when using backlit switches. This is possible when using gas-discharge lamps (they occasionally flash) and when using energy-saving lamps (they may burn dimly). To cope with such problems, backlight control circuits are used.
You also need to take into account that the presence of dim lighting in a room with the electricity turned off may not be to everyone's liking. There are device options in which indicators are present on one, two or more keys. It is made in the form of a dot or a dash. Before you connect an illuminated switch, you need to make sure that it has the right design.
Illuminated switches controlled using a key card Source sovet-ingenera.com
Principle of operation
The operation of the backlight is based on the properties of electricity associated with Ohm's law. The lighting circuit contains an indicator connected in series with a resistor. It is located parallel to the room chandelier that provides connection. Current flows through the area whose resistance is lower.
When the backlit switch is open, the circuit is such that current continues to flow through the resistor and LED. However, due to its high resistance, it will be negligible. It is enough for an indicator, but not enough for full operation of the chandelier in the room.
If a person turns on the light in a room, the passage of current will determine the normal operation of the lighting fixtures. Moreover, if he connected backlit switches, the indicator will glow.
Interior of the switch with backlight Source sovet-ingenera.com
The resistor is selected depending on the type of lamp used. It is designed to limit the current to an acceptable value, which may differ for different types of lighting devices. Here we talk about the simplest scheme. However, such an installation of a backlit switch is associated with significant disadvantages:
- A resistance that is constantly connected to the network will become very hot.
- Reverse current may flow through it.
If you do not pay attention to this, a breakdown of the LED may occur. To avoid this, a diode must be added to the circuit. It must be installed parallel to the indicator. In this case, the risk of reverse current flow will be prevented.
This is what an LED lamp looks like Source sovet-ingenera.com
Calculation of circuit parameters
| Formulas for calculating electrical circuit parameters | ||||
| Voltage | Current strength | Resistance | Power | Capacitor reactance |
| U=I*R | I=U/R | R=U/I | P=Ur*I | Rc=2*π*£*C(f); Rc=314*C(f) |
Selecting a resistor for the LED. In this formula, the network voltage is taken as 320V, since it is necessary to take into account not the nominal parameter, but the effective peak voltage.
Selecting a resistor
Is it possible to get rid of blinking lamps?
Since even when turned off, current still flows through the backlight indicator, it will also flow to the lighting device. It will not work with halogen or incandescent filaments, since there is not enough energy for this. Economy lamps may flicker. If expensive models are used, then the backlit switch for LED lamps works fine.
Since, in the presence of illumination, a small current continuously passes through the lamp, it gradually charges the capacitor present in the circuit. When the charge on its plates increases to the required level, a discharge will occur, which will cause the lamp to glow for a short time.
By watching this video you can learn how to stop the lamp from flickering when using a backlit switch:
Video description
Eliminating flickering of LED and energy-saving light bulbs if the switch is backlit.
It must be remembered that manufacturers of LED lamps warn that their products cannot be used in conjunction with displays, motion sensors and other similar devices. However, sometimes taking additional measures can help improve the situation. In this case, the backlit switch wiring diagram must be modified accordingly.
Single-key switch with backlight Source 220.guru
Examples of calculations
Since our task is only to illuminate the switch and achieve maximum viability, we take the LED current 30% of the nominal - 6mA
Resistor current limiter
Usd=3.5V, Isd=20mA (0.02A) - We do the calculation at 6mA (0.006A);
R1= (330-3.5) /0.006=55000 Ohm (55 kOhm). In order to reduce heating, the resistor value can be doubled to 100 kOhm.
Resistor power P=Ur1I=3270.006=2W.
It is better to mirror a 1000V diode in parallel with the LED.
Capacitive current limiter
Instead of a resistor, you can use a high-voltage capacitor; R1 is necessary for the self-discharge of capacitor C1. The capacitive circuit does not heat up.
The diode is the same as in the previous design.
If the switch is intended for an energy-saving lamp, it is better to replace the LED with a neon lamp, the donor of which will be the starter of the fluorescent lamp. Classical circuits, due to half-wave damping, can cause flickering of “energy-saving” devices. The connection principle remains the same, but due to the higher rated current, about 100 mA, the resistor or capacitance (on a neon light bulb) should be increased to 500-600 kOhm.
Video description
How to connect an illuminated switch.
It should be borne in mind that a backlit switch may work well, but the LED lamp will continue to flicker. This is possible, for example, if it is faulty or the service life of the lighting device has expired. If a double backlit switch is connected, the problems may be similar.
Illuminated switch disassembled Source 220.guru
Application of illuminated switches
Their use can add additional features to the design of the room. There may be situations in which the use of backlighting is convenient. Examples include the following cases:
- If the room is such that in the dark it is difficult to guess where exactly it was done, for example, connecting a single-key switch with backlight.
- In a room where wallpaper is used, which can quickly wear out from a large number of touches, inevitable in cases where you have to grope for the device key with your hands. In such a situation, there are reasons to connect an illuminated switch.
- In some rooms, if there is no lighting, it can be dark for 24 hours. After installing the double illuminated switch, the indicator will help you easily find how to illuminate the room.
- Where you need to be in the dark. This may, for example, apply to some production or storage areas. A night light switch will help solve the problem.
Indicators are used in designs that have several buttons. In this case, you can easily avoid the risk of pressing the wrong key. The design of the backlit switch must correspond to the tasks of its use.
Disconnecting the indicator circuit from the switch Source 220.guru
Eliminate blinking LED lamp using a capacitor
If you don’t have a resistor, then instead you can use a capacitor with a capacity of 0.01 to 1 µF and a voltage with a double surge noise margin of 2*220=440V. But it is most reliable to take at least 630V.
When there is no capacitor for 630V, but there is one for 400V, then using a soldering iron you can assemble a circuit like this.
Here, one resistor serves to protect the capacitor from impulse noise, and the second to discharge the capacitor.
In an alternating current circuit, a capacitor is essentially a reactance, which is not taken into account by the electric meter and, unlike a resistor, the capacitor does not heat up.
Therefore, installing a capacitor is more preferable and safer. Install it in the same places as described above using resistance (distribution box, chandelier terminal block).
Where can I find such a capacitor? In order not to run around radio stores, you can simply disassemble the already burnt-out energy-saving lamp and pull it out or take it from a regular starter for fluorescent lamps.
True, there is one BUT. It is better to use paper or ceramic, because... Electrolytic may explode unsafely during power surges. So if you take it as a shunt, be sure to take it with a large voltage margin.
How to choose an LED switch
When choosing, the price of the device, although it is an important circumstance, nevertheless should not be the only argument when purchasing. Connecting a Chinese backlit switch will help save money, but will not always allow you to get a high-quality device. You should pay attention to the following features:
- It is important to consider the reliability of the device’s contact group.
- The design of the device must match the one in the room. You need to pay attention to the material from which the body is made.
- There are backlit switches available in a variety of applications. They can be keyboard, rotary, corded or touch.
- The security class must meet the operating conditions. IP20 is considered the minimum acceptable. If you plan to use the device in an unfavorable environment, choose the appropriate ones: IP45 (in the presence of high humidity), IP65 or higher is suitable for switches that are intended for outdoor use.
Depending on the type used, the location of the indicators may differ. Before connecting a single-key backlit switch or another type, the owner must make sure that such models will not create discomfort during use
Operating principle of the switch indicator light Source profazu.ru
