Brightness control: circuit and device. Dimmable switches

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Brightness control: circuit and device. Dimmable switches
Brightness control: circuit and device. Dimmable switches

To adjust the brightness of incandescent lamps, special regulators are used. These devices are also called dimmers. They exist in various modifications, and if necessary, you can always choose the necessary model in the store. Basically, they replace the switch in the incandescent lamp. The simplest modification includes one rotary controller with a handle. When adjusting the brightness, the power consumption indicator also changes.

If you remember the old days, then the controls for adjusting the brightness were not used. Instead, special rheostats were installed. With their help, it was also possible to regulate fluorescent lamps. In general, they coped well with their duties, but they had one drawback. It has to do with power consumption. As mentioned earlier, modern regulators consume less electricity if they are not used at full capacity. In the case of rheostats, this rule does not apply. At minimum power, electricity is consumed in the same way as at maximum. The excess in this case is converted into heat.

lighting dimmer

Scheme of a conventional regulator

A simple dimmer circuit uses a linear potentiometer and a pair of low power transistors. Capacitors are used to suppress high frequencies in the system. Cores in devices of this type are needed only of the ferrite type. A dinistor with a thyristor is installed directly in front of the terminals.

dimmable switches

How to install the rotary control in the lamp?

In order for a table lamp with a dimmer to work properly, you should check the voltage on the semiconductor. This can be done using a regular tester. Next, you should inspect the incandescent lamp board. If it is installed single-channel type, then everything is quite simple to do. It is important to connect output semiconductors to output holes that have a negative polarity. In this case, the maximum resistance should be 3 ohms. To check the device, you need to turn the controller and at the same time monitor the brightness of the incandescent lamp.

Installing the pushbutton control into the lamp

In order for the incandescent lamp dimmer to work properly, it is important to carefully familiarize yourself with the control board of the device. Next, you need to connect all the contacts. If the circuit is used multi-channel, then the voltage on it is checked by a tester. Directly connecting the contacts is carried out by soldering. It is important not to touch the resistors during operation. Additionally, care must be takenwiring insulation. Before turning on the regulator, check the reliability of all connections. After power is supplied, you must try to change the brightness by pressing the button.

dimmer circuit

High voltage dimmers

High voltage dimmer switch typically found in theaters. There, incandescent lamps are used quite powerful, and the devices must be able to withstand heavy loads. Triacs for this purpose are used high-voltage (marked KU202). Transistors used are bipolar, but their usual modifications are also installed.

Diode bridges are soldered near the thyristors and are necessary for fast signal transmission. Zener diodes can most often be found with the marking D814. They are quite expensive in the store, and this should be taken into account. Variable resistors in the system can withstand the maximum voltage at the level of 60 ohms. At this time, conventional analogues are fused only with 5 ohms.

Models with precision resistors

The dimmer with resistors of this type is designed for medium power incandescent lamps. Zener diodes in this case are used at 12 V. Variable resistors in regulators are quite rare. Low frequency modifications can be used. In this case, it is possible to increase the conductivity coefficient by increasing the number of capacitors. Behind the triac, they must be located in pairs. In this case, heat losses will be minimal. Negative resistance in the network sometimes represents a seriousproblem. Ultimately, overload leads to a breakdown of the zener diode. Electrolytic capacitors with low-frequency interference cope quite well. The main thing at the same time is not to give a sharply high voltage to the lamp.

incandescent lamp dimmer

Regulator circuit with high-megaohm resistors

This type of dimmer can be used to control various types of lamps. Its circuit includes high-megaohm AC resistors, as well as a conventional zener diode. The thyristor in this case is installed next to the capacitor. To reduce the limiting frequency, specialists often use fuses of the fuse type. They are able to withstand a load of 4 A. In this case, the limiting frequency at the output will be a maximum of 50 Hz. Triacs for general purpose input voltage can withstand 15 V.

Switches with FET regulators

Field-effect transistor dimmer switches are well protected. Short circuits in the system are quite rare, and this is undoubtedly an advantage. Additionally, it should be borne in mind that zener diodes for regulators can only be used with the KU202 marking. In this case, they are able to work with low-frequency resistors and cope well with interference. Triacs in the circuits are located behind the resistors. The limiting resistance in the system must be maintained at 4 ohms. The resistors hold the input voltage at about 18 V. The limiting frequency, in turn, should not exceed 14Hz.

Regulator with trimmer capacitors

A dimmer with trimmer capacitors can be successfully used to adjust the power of fluorescent lamps. The switches in this case should be located behind the diode bridge. Zener diodes in the circuit are needed to suppress interference. Variable type resistors, as a rule, withstand the limit resistance at the level of 6 ohms.

In this case, thyristors are used solely to maintain the voltage at the proper level. Triacs are capable of passing a current through themselves at a level of approximately 4 A. Fusible type fuses in regulators are quite rare. The problem with electrical conductivity in such devices is solved by using a variable resistor at the output.

table lamp with dimmer

Model with simple thyristor

Dimmer with simple thyristors is best suited for push-button models. The system of protection, as a rule, is absent in it. All contacts in the regulator are made of copper. The maximum resistance at the input of a conventional thyristor is able to withstand 10 V. They are poorly suited for rotary controllers. Precision resistors with such regulators are not able to work. This is due to the large level of negative resistance in the circuit.

High-frequency resistors are also installed quite rarely. In this case, the level of interference will be significant and will lead to an overload of the zener diode. If we talk about ordinary table lamps, then it is best to use an ordinary thyristor paired with wire resistors.Their current conductivity is at a fairly high level. They rarely overheat, the power dissipation averages around 2 watts.

light dimmer

Using variable capacitors in a circuit

Thanks to the use of variable capacitors, it was possible to achieve a smooth change in the brightness of incandescent lamps. However, electrolytic models work in a completely different way. Transistors for such capacitors are most suitable for 12 watts. The input voltage must be maintained at 19 V. Fuses must also be provided. Thyristors are usually used with the KU202 marking. For rotary modifications, they fit well. To increase the conductivity coefficient, potentiometers are used with network switches.

brightness control

Single junction regulator device

The one-way dimmer is famous for its simplicity. Resistors in it, as a rule, are used at 4 watts. At the same time, it is able to keep the maximum voltage at a level of 14 V. When using it, it is important to consider that the light bulb may flicker during operation. Fuses are rarely used in devices.

At the input, the rated current can leave a maximum of 4 A. Thyristors of the KU202 type are capable of operating in such a system only on a pair with a diode bridge. The triac in the device must be connected behind the resistor. To connect the dimmer to the lamp, you need to clean all the contacts. It is important to use a dielectric housing for the device. In suchcase, work safety will be guaranteed.

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