Dimmer: circuit, connection, reviews. Dimmer - what is it?

People use rooms for various purposes, and these functions require different lighting. Adjust it conveniently 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?

Illumination of premises in the house is very important. The level of it in each room dictates what you can and can not do, and it has a huge impact on your feelings. So, for example, you can not read under one lighted candle, but a romantic dinner for two seems not so pleasant under a 1.5-kilowatt halogen lamp.

Modern dimmers, for example dimmer Legrand, allow smoothly adjusting the illumination of lamps with lamps of various types.

Resistor dimmer switches

Initially, to adjust the light level, a fairly simple solution was used - a variable resistor, included as a dimmer. What did it give? A conventional wire resistor is a thin conductor that creates a certain (in accordance with the nominal) resistance to the movement of electrical charges. In the design of the variable resistor, in addition to the resistive material and two fixed contacts, a movable contact with its terminal was added. To the electric circuit such element is connected by a movable one and one of the fixed contacts.

In this design, the overall resistance of the resistor is varied by adjusting the distance that the charge must pass through the resistive material, and simply speaking, the length of the wire from the fixed to the movable contact. If the movable contact is near a fixed (connected to the circuit), the resistance of the resistor is minimal. If it is shifted to the second stationary contact, the charge must pass through the entire resistive material.

When a charge moves under the action of electrical forces through a resistor, its energy is lost as heat. If you put a resistor in a series circuit, the energy losses in it cause an appropriate 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 on heating a resistor that will not illuminate your room, but it will cost a pretty penny. In addition to energy inefficiency, resistor dimmers are generally bulky and potentially fire dangerous, since a variable resistor releases 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 the resistor? Instead of picking up energy from a bulb in alternating resistance, modern dimmers in each period of current change briefly overlap 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 period of oscillations of the household alternating current. They have a different polarity of voltage - in the hilly sinusoidal current wave it ranges from a positive maximum to a negative one. In other words, a moving charge, which constitutes an alternating current, constantly changes its direction of motion. In Russia, it passes through one cycle of change (movement of charges in one direction, then to another) 50 times per second.

The "rupture" of the current sinusoid in each of its half-periods is what a dimmer does. What does it mean? It automatically turns off the lamp circuit each time the current direction changes , that is, when the circuit has zero voltage. This happens twice per cycle, or 100 times per second. The supply of current to the circuit of the luminaire is switched on again when the voltage rises to a certain level.

This principle - "turn on the level" - sets the position of its handle switch with a dimmer. If it is set to light, it turns on very quickly after being turned off. The circuit is switched on for the most part of the cycle, so that it delivers more energy per second to the light bulb. If the dimmer is set to lower illumination, it will wait after the shutdown for a longer time until it turns on again at the end of the cycle.

This is the basic concept, but how does the dimmer actually work? The diagram of its connection, presented in the next section, will answer this question.

Electronic dimming device

We already know that he quickly stops the light in the chain in order to reduce the energy supplied to the lamp. And yet, it's the dimmer itself - what is it? The central element of its circuit is a semiconductor commutator of alternating current, or triac.

A triac is a small semiconductor device that looks like a diode or a transistor. Like them, the triac consists of different layers of semiconductor material. Among them, n-type materials that have many free electrons, and p-type materials that have many "holes" through which free electrons can pass.

The triac is capable of transmitting current at different polarities of the voltage applied to it, i.e. in both half-periods of the AC voltage of the network, but only if some control voltage is applied to the third electrode-the gate. That's it, actually, and working dimmer. The diagram below shows how it turns on.

The voltage for the triac shutter, which is necessary for opening it, is fed from the storage capacitor, and the time of its charging from the beginning of the half-period of the supply voltage regulates the variable resistor. So what happens in this scheme? In a nutshell:

• The triac acts as a voltage switch.
• The voltage on the gate controls the timing of its activation.
• A variable resistor sets the voltage at the gate.
• The throttle serves to smooth the shape of the current in the lamp supply circuit (see next section).
• The interference suppressor capacitor prevents the generation of a radio interference dimmer circuit.

Connecting to the network

It should be noted that structurally all the electro radio elements shown in the diagram above are mounted in the dimmer housing, which has only two terminals for switching the device into a single-phase electrical network. Therefore, from the point of view of the technology for making this connection, the dimmer is completely analogous to an ordinary two-pole switch. By the way, some of their designs have such an integrated switch, included at the input of the entire circuit, and its key is located next to the control knob. Therefore, by connecting the dimmer, as in the case of connecting a conventional switch, perform the following steps:

1. Identify the lamp or group of fixtures for control from the dimmer.
2. Calculate the current consumed by the lighting devices when feeding them without a dimmer.
3. Choose a dimmer with a maximum continuous operating current no less than the one obtained in point 2.
4. Set the dimmer to a suitable location and connect it to the mains, just like a normal two-pole switch. Remember at the same time that any switch should be installed in the break of the phase wire, and not "zero", i.e., it must stand in the current passing circuit up to the luminaire (group), and not after it.

Real schemes of dimmers are much more complicated. So, there can be a remote dimmer with a remote control, disconnected (automatically) by a timer, connected to the complex "Smart House", as well as with an acoustic or voice control. However, all this "smart stuffing" is hidden inside the device, and the process of connecting it to the network does not complicate it at all.

Loud buzz in the presence of dimmers

According to a number of users, when connecting instead of a cheap dimmer switch, a strange buzz is heard in the filament lamp supply circuit . This is due to oscillations in the lamp filament 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 oscillations cause a pulsating magnetic field. The filament in the bulb is simply a wire spiral, which, like a solenoid, is magnetized by the current passing through it, and its magnetic field oscillates at an alternating current frequency.

A normal sinusoidal alternating current oscillates gradually, like its magnetic field. The current from the dimmer changes abruptly when the triac becomes conductive. This sudden change in current changes the magnetic field sharply, which can cause the filament to vibrate. In addition to producing a soft buzzing sound, a sharply changing magnetic field will generate weak radio signals that can interfere with neighboring TVs or radios!

The best dimmers contain additional components to destroy the buzzing effect. Typically, the dimmer connection circuit includes an inductive choke (see diagram above), which is a long wire wrapped around an iron core, and an additional noise suppression capacitor. Both devices can temporarily store electricity (in the form of the energy of the magnetic field, current and energy of electric charges) and expend it later. This energy alleviates the sharp voltage jumps caused by triac switching to reduce hum and radio interference.

Dimmers and lamps

The dimmers create an atmosphere of comfort in the home and reduce the cost of electricity. However, not all light bulbs are compatible with them, and this can create difficulties for homeowners. Many consumers publish negative feedback on dimmer light regulation, but an 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.

Lamps are characterized by power and voltage. If the dimmer is incorrectly selected, some of the types receive an unsuitable voltage and create problems. Therefore, when choosing lamps for a dimmer, people should be aware of their various types and learn how to choose only those compatible with the dimmers they have.

Consumers can choose incandescent lamps, halogen, fluorescent and LED lamps. The first two types of lamps are easy to control dimmers, while fluorescent and LED lamps that have a high luminous efficiency are more expensive and work less with the devices in question.

Incandescent lamps

The incandescent lamp works because the electric current passes through its filament, which is heated and begins to glow. These bulbs, like their closest relatives - halogen lamps (in fact, the same incandescent bulbs, but with halogen containing compounds inside the bulb to prevent evaporation of the filament material), are the most utilitarian kind of light bulb, because they work with any dimmer. They do not tolerate too much tension, but they are good enough at the appropriate level. According to reviews of those consumers who wanted to save electricity and increase the life of light bulbs due to the use of dimmers, this works out very well. Many users note that incandescent bulbs can with inexpensive dimmers work just as well as with advanced models. They fade almost completely when the dimmer knob is in a position just above the off.

Fluorescent lamps

These lamps contain mercury vapor inside the bulb. Generated by them during heating, ultraviolet radiation excites the phosphor, which from inside are covered with the walls of the bulb in order to radiate visible light. Some users in their reviews note that in the lower part of the dimmer control range, their lamps are simply turned off. The thing is that they use so-called compact fluorescent lamps that are not intended for use with dimmers: if the homeowner sets 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 dimmer 220V with the manufacturer's indication of 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 producing luminescence. They are less bright than fluorescent lamps, but the brightness adjustment range is limited only by the circuit of its inclusion. According to consumer reviews, LEDs are also subject to shutdowns in the lower range of luminous intensity, and this can also manifest themselves with different types of dimmers. While the incandescent lamp will flicker with voltage fluctuations, the LED can generally turn off or flicker excessively.

Choosing the right lamp

When buying a consumer should remember that incandescent lamps can dim from zero to 100 percent, and fluorescent and LEDs can not be operated below 10-20% of the nominal value of their brightness, so that homeowners will not be able to reach them with a level of total comfort. In addition, fluorescent and LED lamps require a more expensive and sophisticated LED dimmer. However, in the long term, they provide significant energy savings.

Choosing the right dimmer

Modern dimmers, such as the Legrand dimmer (meaning the entire brand line) perform different functions, including different 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 inexpensive devices are adequate for incandescent and halogen lamps.

Summing up the opinions expressed by numerous users of dimmers, it can be concluded that the greatest mass effect from their application can be obtained in dwellings illuminated by traditional incandescent lamps. After all, the dimmer allows you to reduce power consumption without replacing cheap incandescent bulbs with expensive fluorescent or LED lights. 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 given by "advanced" dimmer dimmer models, for example, a remote dimmer that allows you to control the illumination of rooms from the remote control without getting up.