The incandescent lamp lasts longer. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Lighting

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Lighting lamps can burn out - everyone knows that. The reasons why this happens are known. It is also known how you can extend the "life" of the lamps. However, most of these solutions are rather complicated in their practical implementation: a large number of elements are required, which reduces the reliability of the device and makes it difficult to mount it in the box of a regular network switch; device adjustment is required.

It is easier to achieve what you want - you only need a two-pole (two-key) switch and a silicon diode.

On fig. 1 shows a schematic diagram of a luminaire, all parts of which (except for the EL1 lighting lamp) are mounted in the box of a regular mains switch or in a table lamp stand. They fix the parts with hinged mounting - and the whole structure turns out to be compact.

A feature of the switch is the presence of two keys - SA1, SA2. Therefore, if you have a single-gang switch installed, it must be replaced with a two-gang switch.

The device works as follows. In the initial state, the contacts of the switches SA1, SA2 are open. When the lamp EL1 is turned on, first press the SA1 switch key. The mains current passes through the circuit: diode VD1, closed contacts SA1, lamp EL1. Diode VD1 is needed as a half-wave rectifier. Therefore, a half-wave rectified voltage is supplied to the lamp, which reduces the value of the power dissipated by the lamp by half - the lamp burns half-heartedly. This protects the still cold filament from possible burnout, since the value of its resistance at this moment may not be sufficient to withstand the rated power.

After that, the contacts of the SA2 switch are closed and all the mains voltage is supplied to the lamp. Now the lamp will burn at full power.

In other words, thanks to the diode VD1 and the switches SA1, SA2, you can avoid the overload mode for the filament EL1 at the moment the lamp is turned on, which significantly prolongs its "life".

In order to make it easy to find the switch key SA1 in the dark, it is illuminated with a neon lamp HL1. At the same time, full lighting is often not required at night - a standby one is enough when the EL1 lamp is lit at half-light. Then only switch SA1 is used, which is visible in the dark.

The VD1 diode of the D226B series is used with incandescent lamp power up to 100 watts. If the lamps used for lighting are designed for a power of more than 100 W, it is necessary to install a diode of the KD202M series. A neon lamp can be of the TN-0,2 or MN-6 type. In the switch, it must be positioned so that it illuminates only the SA1 key.

Fig. 1

The disadvantage of the device is the need to comply with the order of pressing the keys of the switches SA1, SA2. To eliminate it, you will need another diode, which is mounted instead of a neon lamp (in Fig. 2 - this is VD1).

Diodes VD1, VD2 are turned on towards either their cathodes or anodes are connected to each other. Now the sequence of pressing the keys does not affect the operation of the lamp. In any case - whether the SA1 key or the SA2 key is pressed - the EL1 lamp lights up half-heartedly. And only when both keys are pressed, the lamp burns at full power.

The lamps are turned off (both in the first and second versions), while opening the contacts of the switches SA1, SA2.

Fig. 2

If several lamps are installed in the luminaire (chandelier) and they are switched on separately, a three-pole (three-gang) switch must be used. On fig. 3 and 4 show diagrams of such lamps. The principle of their operation is similar to the devices discussed above. First (depending on which lamp - EL1 or EL2 or both at the same time - you need to turn on, Fig. 3) close the contacts of the switches SA1 or SA2, or both at the same time. The lamps will burn brightly. Then the SA3 switch is closed - the lamps light up at full power.

For a device whose schematic diagram is shown in fig. 4, the sequence of switching on does not affect the operation of the lamps. And when the SA3 switch is closed, by combining the positions of the switches SA1, SA2, you can get additional modes of operation of the lamp. For example, if you close SA1, and SA2 remains open, then the lamp EL1 will burn at full power, and EL2 - at half light. Conversely, if you close SA2 and open SA1, then EL1 will burn at full power, and EL2 at full power.

To turn off the lamp, open the contacts of the switches SA1 - SA3 at the same time.

Diodes VD1 -VD3 are mounted directly in the three-gang switch box. Moreover, with a lamp power of more than 100 W, the diodes VD1, VD2 must be of the KD202M series or similar, designed for the current consumed by the lamp.

Fig. 3

Fig. 4

Despite the simplicity of the circuit design, the devices have the disadvantage that they do not protect the lamp filament from the destructive action of a short-term "surge" of the mains current at the moment the lamp is turned on, since the CVC of the diode is not similar to the characteristic of the barter. The "life" of the lamp will depend on the value of the power of the current pulse on the state of the filament. Because of this, with a combination of unfavorable factors - increased voltage in the network, severe erosion of the filament - the likelihood of a lamp burnout is no less than without this device. However, such a solution can be successfully used when it becomes necessary to transfer, for example, a table lamp to a standby (night) mode of operation. It should be said that the industry produces special switches for such purposes, in particular the PM-100, which are based on a half-wave diode rectifier.

Author: K. Kolomoytsev, Ivano-Frankivsk; Publication: cxem.net

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