People use rooms for various purposes, and these functions require different lighting conditions. It is convenient to adjust it with a dimmer - an electronic device that allows you to change the level of illumination from "almost dark" to full visibility by simply turning the knob or sliding the lever.
Why do we need dimmers?
The illumination of the rooms in the house is very important. The level in each room dictates what you can and cannot do, and this has a huge impact on your feelings. So, for example, you cannot read under one lit candle, but a romantic dinner for two does not seem so pleasant under a 1.5-kilowatt halogen lamp.
Modern dimmers, such as the Legrand dimmer, allow you to continuously adjust the illumination of lamps with lamps of various types.
Resistor dimmers
At first, a fairly simple solution was used to adjust the light level - a variable resistor, included as a dimmer. What did it give? An ordinary wire resistor is a thin conductor that creates a certain (in accordance with the nominal) resistance to the movement of electric charges. In addition to the resistive material and two fixed contacts, a movable contact with its output was added to the design of the variable resistor. Such an element is connected to the electric circuit by a movable and one of the fixed contacts.
In this design, the total resistance of the resistor is varied by adjusting the distance that the charge must pass through the resistive material, and simply put - the length of the wire from a fixed to a moving contact. If the movable contact is near the stationary (connected to the circuit), then the resistance of the resistor is minimal. If it is biased to the second fixed contact, the charge must pass through all the resistive material.
When a charge moves under the influence of electric forces through a resistor, its energy is lost in the form of heat. If you put a resistor in a series circuit, then the energy loss in it causes a corresponding voltage drop across the resistor, reducing the energy available for other loads (bulbs, for example). Reducing the voltage on the bulb lowers its light output.
The problem with this solution is that you end up spending a lot of energy heating a resistor that will not light your room, but will cost a pretty penny. In addition to energy inefficiency, resistor dimmers are usually bulky and potentially fire hazardous, as the variable resistor generates a significant amount of heat. Modern devices use a more efficient approach.
Principle of operation
So, actually a dimmer. What does this mean in terms of differences from a resistor? Instead of taking energy from a bulb in a variable resistance, modern dimmers in each period of current change briefly block the path for its passage to reduce the total amount of energy dissipated throughout the circuit. It turns out that the current in the light bulb turns off many times per second.
The switching cycle is built around the oscillation period of the household alternating current. They have different voltage polarity - in a hilly sinusoidal current wave, it ranges from a positive maximum to a negative one. In other words, a moving charge, which is an alternating current, constantly changes the direction of its movement. In Russia, it goes through one cycle of change (movement of charges in one direction, then in the other) 50 times per second.
The "gap" of the current sinusoid in each half-cycle is what the dimmer does. What does it mean? It automatically turns off the bulb circuit every time the current direction changes , that is, when the circuit is at zero voltage. This happens twice per cycle, or 100 times per second. The current supply to the luminaire circuit is switched on again when the voltage rises to a certain level.
This principle - “turn on the level” - sets the switch with a dimmer by the position of its handle. If it is installed in a bright environment, it turns on very quickly after a shutdown. The circuit is turned on for most of the cycle, so it delivers more energy per second to the light bulb. If the dimmer is set to lower illumination, it will wait longer after being turned off until it turns on again at the end of the cycle.
This is a basic concept, but how does a dimmer actually work? The wiring diagram presented in the next section will answer this question.
Electronic dimmer device
We already know that it quickly stops the light in the circuit in order to reduce the energy supplied to the lamp. And yet, specifically the dimmer itself - what is it? The central element of his circuit is an AC semiconductor switch, or triac.
A triac is a small semiconductor device, similar to a diode or transistor. Like them, the triac consists of different layers of semiconductor material. Among them are n-type materials, which have many free electrons, and p-type materials, which have many "holes" through which free electrons can pass.
The triac is capable of transmitting current at different polarity of the voltage applied to it, i.e., in both half-periods of the alternating voltage of the network, but only if a certain control voltage is applied to the third electrode - the gate. And so, in fact, the dimmer works. The diagram below shows how it turns on.
The voltage to the gate of the triac, which is necessary for its opening, is supplied from the storage capacitor, and the time of its charge from the beginning of the half-cycle of the supply voltage is controlled by a variable resistor. So what happens in this circuit? In a nutshell:
- The triac acts as a supply voltage switch.
- The voltage on the gate controls the moments of its inclusion.
- A variable resistor sets the voltage at the gate.
- The inductor is used to smooth the shape of the current in the lamp power supply circuit (see next section).
- The interference suppression capacitor prevents the generation of radio interference by a dimmer circuit.
Network connection
It should be noted that, structurally, all the electric radio elements shown in the diagram above are mounted in the dimmer body, which has only two terminals for connecting the device to a single-phase electric network. Therefore, from the point of view of the technology for making such a connection, the dimmer is completely similar to a conventional bipolar switch. By the way, some of their designs have such a built-in switch that is turned on at the input of the entire circuit, and its key is located next to the adjustment knob. Therefore, when connecting a dimmer, as in the case of connecting a conventional switch, follow these steps:
- Define a luminaire or group of luminaires to be controlled by a dimmer.
- Calculate the current consumed by lighting fixtures when powering them without a dimmer.
- Choose a dimmer with a maximum continuous operating current not less than that obtained in paragraph 2.
- Install the dimmer in a suitable place and connect to the network, as well as the usual two-pole switch. Remember at the same time that any switch should be installed in the gap of the phase wire, and not the "zero" wire, that is, it must be in the current path to the lamp (group), and not after it.
Real circuits of dimmers are much more complicated. So, there may be a remote dimmer with a remote control, disconnected (automatically) by timer, connected to the Smart Home complex, as well as with an acoustic or voice control type. However, all this “smart filling” is hidden inside the device, and the process of connecting it to the network does not complicate at all.
Humming lamps with dimmers
According to reviews of some users, when a cheap dimmer is connected instead of a switch, a strange buzz is heard in the power circuit of the incandescent lamp. This is due to fluctuations in the filament of the lamp, caused by a change in the shape of the current coming from the triac.
As you know, the current flowing through the wires generates a significant magnetic field strength, and current fluctuations cause a pulsating magnetic field. The filament in the bulb is just a wire spiral, which, like a solenoid, is magnetized by the current passing through it, and its magnetic field oscillates with the frequency of the alternating current.
The normal sinusoidal alternating current oscillates gradually, as does its magnetic field. The current from the dimmer changes abruptly when the triac becomes conductive. This sudden change in current changes the magnetic field dramatically, which can cause the filament to vibrate. In addition to producing a soft, buzzing sound, a dramatically changing magnetic field will generate weak radio signals that can interfere with nearby TVs or radios!
The best dimmers contain additional components to eliminate the buzzing effect. Typically, the wiring diagram of the dimmer includes an inductive choke (see diagram above), which is a long wire wrapped around an iron core, and an additional noise suppressing capacitor. Both devices can temporarily store electricity (in the form of magnetic field energy, current and energy of electric charges) and spend it later. This energy smoothes out the sudden power surges caused by triac trips to reduce buzz and radio interference.
Dimmers and lamps
Dimmers create an atmosphere of comfort in the home and reduce energy costs. However, not all light bulbs are compatible with them, and this can create difficulties for homeowners. Many consumers publish negative reviews about dimmer light control, but the analysis of such responses leads to the conclusion that their authors are simply not familiar with the principles of compatibility of light bulbs and dimmers with each other.
Light bulbs are characterized by power and voltage. If the dimmer is improperly selected, some of their types get the wrong voltage for them and cause problems. Therefore, when choosing lamps for a dimmer, people should be aware of their various types and learn how to choose only compatible dimmers with their dimmers.
Consumers can choose incandescent, halogen, fluorescent and LED bulbs. The first two types of lamps are easy to control dimmers, while fluorescent and LED lamps with greater light output are more expensive and work worse with the devices in question.
Incandescent lamps
An incandescent lamp works because an electric current passes through its filament, which heats up and starts to glow. These bulbs, like their closest relatives - halogen bulbs (in fact, the same bulbs, but with the addition of halogen-containing compounds inside the flask to prevent evaporation of the filament material), are the most utilitarian kind of bulbs, because they work with any dimmer. They do not tolerate too high a voltage, but are good enough at its appropriate level. According to the reviews of those consumers who wanted to save electricity and increase the life of the bulbs through the use of dimmers, this works very well. Many users note that incandescent bulbs can work with inexpensive dimmers as well as with advanced models. They fade almost completely when the dimmer knob is in the position just above the off position.
Fluorescent lamps
These lamps have mercury vapor inside the bulb. The ultraviolet radiation generated by them during heating excites the phosphor, with which the walls of the bulb are coated from the inside to emit visible light. Some users in their reviews note that at the bottom of the dimmer control range their lamps simply turn off. The thing is that they use the so-called compact fluorescent lamps, not intended for use with dimmers: if the homeowner sets a low voltage through this device, the lamp will simply turn off and not fade. To be able to use a dimmer with such a lamp, it must have a dimming ballast, which should be indicated on the package. Some standard dimmers will be compatible with such a lamp, but not all of them. Consumers should always choose a 220V dimmer with an indication of the manufacturer about its compatibility with fluorescent lamps.
LED lamp
Their work is based on the ability of a light-emitting diode to induce electrons that interact with positively charged "holes" and emit photons that produce luminescence. They are less bright than fluorescent lamps, but the range of brightness adjustment is limited only by the circuit of its inclusion. According to consumer reviews, LEDs are also subject to shutdowns in the lower range of light intensity, and this can also occur with various types of dimmers. While the incandescent lamp will flicker with voltage fluctuations, the LED may turn off altogether or flicker excessively.
Choosing the right lamp
When buying, the consumer should remember that incandescent bulbs can dim from zero to 100 percent, and fluorescent and LED bulbs cannot be operated below 10-20% of the nominal value of their brightness, so that homeowners will not be able to achieve full comfort with them. In addition, fluorescent and LED lamps require a more expensive and sophisticated LED dimmer. However, in the long run, they provide significant energy savings.
Choosing the Right Dimmer
Modern dimmers, such as the Legrand dimmer (meaning the entire brand line), perform various functions, including various types of photocells, motion sensors and timers. When investing in these devices, people should keep in mind that advanced dimmer circuits are designed for high-performance light bulbs. While low-cost devices are adequate for incandescent and halogen lamps.
Summing up the reviews expressed by numerous users of dimmers, we can conclude that the greatest mass effect from their use can be obtained in homes illuminated by traditional incandescent lamps. After all, a dimmer makes it possible to reduce energy consumption without replacing cheap incandescent bulbs with expensive fluorescent or LED ones. If the dwelling is already illuminated with new types of lamps, the main effect, which is to increase the convenience of lighting control, can be achieved by "advanced" dimmer models, for example, a remote dimmer that allows you to control the lighting of rooms from the remote control without getting up.