In this regard, it is recommended to limit the starting current using an additional resistor connected in series with the filaments of halogen lamps. After turning on the lamp, this resistance is short-circuited using a voltage relay installed in parallel with the lamp.
The disadvantage of such devices is the need to use one or two electromagnetic relays, parts that are not reliable enough, especially in a car that experiences vibration. In addition, at the moment of switching on, there is still an abrupt increase in current, although to a smaller value than with conventional lamp switching circuits.
Specialists have developed a non-contact device that does not require the use of a relay and provides a smooth increase in current in the lamp. The device consists of an additional resistor R1, two diodes VD1 and VD2 and an electrolytic capacitor C.
When the dipped beam filament is turned on, a positive potential is applied to clamp 1. In this case, the VD1 diode connects the capacitor C in parallel with the lamp filament, and the resistor R1 in series with it.
When the high beam thread is turned on, a positive potential is applied to terminal 2, and the capacitor C is connected in parallel to the high beam thread through the diode VD2.
With this connection scheme, the voltage on the lamps EL1 and EL2 increases smoothly.
The resistance of the cold filaments of ordinary automobile low and high beam lamps is approximately an order of magnitude lower than their resistance in a heated state. The heating time constant of the lamp filament is 0.0014–0.003 s.
To eliminate an unacceptably high current during the lamp on, it is necessary that the rate of increase in the resistance of the lamp filament be greater than the rate of voltage increase. This is achieved by installing electrolytic capacitors with a capacity of 4000-6000 microfarads, a nominal voltage of 25 V.
If you use these tips, then along with an increase in the life of the lamps, the life of the battery will also be extended due to a decrease in the starting current and an increase in the smoothness of its increase.