Control of a network lamp on two wires. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Control of a network lamp on two wires. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Lighting

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If there are several lighting lamps in a network lamp, for example, a chandelier, it is advisable to turn them on and off individually or in groups. If the power supply of such a lamp is three-wire, it will not be difficult to organize independent control of two groups of lamps, it is enough to use a double switch. With two-wire power, this is not possible. At the same time, the method of controlling two groups of lamps in a lamp via two wires has been known for decades. It is suitable for the case when it is not possible to replace two-wire wiring with three-wire. It uses rectifier diodes, and the circuit is shown in Fig. 1.

Such a simple circuit allows, depending on the position of the switches, to turn on one, two or three lamps (groups of lamps). However, earlier this method was not widely used due to the fact that incandescent lamps were the main source of light. When powered by a half-wave rectified voltage, their brightness is significantly reduced and noticeable pulsations of the light flux appear.

Control of a network lamp on two wires
Fig. 1

But if compact fluorescent lamps (CFLs), which are now becoming more widespread, are used in the luminaire, these shortcomings will be eliminated. This is due to the fact that the CFL uses the so-called electronic ballast (more correct name - electronic ballast - electronic ballast) - a specialized switching power supply that is powered by a 220 V network through a built-in rectifier with a smoothing capacitor. This makes it possible to feed low-power CFLs with a half-wave voltage, and in most cases the brightness of the glow decreases slightly. Therefore, to control a chandelier with CFLs, you can apply the circuit shown in Fig. 1.

True, rarely, but low-power CFLs come across, in which manufacturers, in order to save money, use in electronic ballasts not a full-wave bridge rectifier, but a half-wave, on one diode. This should be taken into account when using CFLs in a luminaire. In addition, in the rectifier of electronic ballasts (especially low-power CFLs), as a rule, smoothing capacitors of small capacity (2,2 ... 3 μF) are used, which can lead to a noticeable increase in the pulsation of the light flux with a frequency of 50 Hz. To eliminate this drawback, the CFL should be powered from additional half-wave rectifiers.

Control of a network lamp on two wires
Fig. 2

The control scheme for two groups of lighting CFLs over two wires is shown in fig. 2 (the part of the diagram to the left of connectors XT1, XT2 is the same as in Fig. 1). Here, each of the switches SA1, SA2 supplies voltage to "its" group of lamps. Resistors R1, R3 limit the inrush of the charging current of capacitors C1, C2 when turned on, R2, R4 ensure their discharge after the lamp is turned off. An additional convenience of such a solution is the possibility of using CFLs with different light temperatures, which are more convenient to use in one or another case or together.

Most of the elements for assembling the device can be removed from failed CFLs, be sure to check each part for serviceability before installation. Oxide capacitors must be with a rated voltage of at least 400 V, and their capacitance must be at least 8.10 microfarads, and the more lamps in the group, the larger the capacitance should be (several capacitors can be used by connecting them in parallel). Connectors XT1-XT5 - any screw terminals designed for operation in a 220 V network.

Diodes VD1, VD2 are mounted in the switch, the rest of the parts are in the lamp. There is no need to make a printed circuit board, all elements can be placed on a 1.1,5 mm thick plastic sheet plate, having previously determined its dimensions according to the free space available in the chandelier. Capacitors are attached to it with hot glue, terminal blocks - with screws, the rest of the elements are mounted on their terminals. The appearance of one of the board options is shown in Fig. 3.

Control of a network lamp on two wires
Fig. 3

After installing the mounted board inside the lamp and checking its performance, it is closed with a plastic cover.

In a chandelier with the described control scheme, LED lamps can also be used, but only those that have a built-in switching power supply, and not a rectifier with a ballast capacitor.

It should be remembered that in accordance with GOST R 51317.3.2-2006, methods of one-half-wave rectification of the current consumed from the network can be used "if the controlled active power of the technical facility does not exceed 100 W".

Author: I. Nechaev

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