Or night duty (with reduced brightness) lighting, allowing at the same time significantly increase the lamp life, can be implemented in different ways. Among the simple and reliable method using a quenching capacitor in power supply circuit (Fig. 1). The capacitance C1 is calculated as reactance to obtain the desired lamp voltage ЕL1. Resistor R1 is necessary for capacitor discharge after disconnecting the circuitry from the network. Its value is in the range of 100-500 ohms.

Due to the nonlinearity of resistance of the filaments and the real scatter of the static parameters of the lamps themselves, the exact calculation of the capacitance of the capacitor C1 is quite difficult even for experienced professionals. However, the calculations can be significantly simplified, if we use the approximate formulas. In particular, for an electric circuit with low-voltage and low-power incandescent lamps (switch, lights, indicator and other 10-42 voltage V and current up to 0.5 A) is acceptable practice, the calibrated value:

where: C — capacity plus (damping) capacitor UF; I n — rated current of the lamps, And; Il — the voltage that you want to get the lamp; IP — mains voltage AC V.

When using standard lighting bulbs, on the cap or bulb which shall include the nominal operating voltage (usually 220-240V) and power (10-200 W), the coefficient in the numerator should be reduced to 1150, and I find using are known to everyone from school by Ohm’s law.

As practice shows, the damping capacity of the capacitor in any case it is better to count with the lamp on the half of its nominal voltage. For example, if h is In 24, the Sludge is recommended to take equal to 12 V. Found roughly the value of C1 is subsequently specified — depending on the desired brightness of the lamp. You do not need to forget about the nonlinearity of the resistance of the filament, leading to the fact that a slight increase in the capacity of the quenching capacitor can sometimes cause a sharp rise of lamp voltage, and reduction threatens almost abrupt decrease of the Il.

In order to even more simplify the procedure of calculation and selection of the quenching capacitance is recommended to use the ready data (table 1), aligned by practice for some types of lamps when connected to the mains (220 V, 50 Hz) in accordance with the above scheme.

**Table 1. Recommended values of damping (extension) tanks for conversion of common types of lamps in an ultra-reliable operating in the 220-volt mains power at a conservative tension of the filament**

It is useful, I think, to emphasize that the blanking voltage using capacitors really can significantly increase the lifespan of the lamps at a fairly minor decrease in the brightness. In addition, this technical solution (unlike the classical circuits for power semiconductor diodes) leads to irritating 50-or 100-Hertz flicker of the lighting…

**Fig. 1. A circuit diagram of a nln night duty (with reduced brightness) illumination, allowing at the same time significantly increase the lamp life by introducing an additional (capacitive) resistance**

**Fig. 2. Conventional table lamp can serve as a nightlight, thanks to a bit of tweaking with the use of the quenching capacitor**

Additional benefits and amenities you can get if you build damping (extension) a capacitor corresponding to capacitance in a conventional table lamp, a few modifying the schema inclusion (Fig. 2). However, it will have to replace the stock two-pole toggle switch re-lucatelli button ЅА1 on three fixed positions.

Decide on a revision of his lamp — you will not regret!

M. PRANCING, Moscow region