Published:2011/4/19 21:23:00 Author:Ecco | Keyword: motor vehicle, headlight , auto-dimming , controller | From:SeekIC
The motor vehicle headlight auto-dimming controller described in the example can automatically change the high beam into low beam at night, it does not need the driver to change the light by hand, and improve thesafety of driving at night.The working principle.The vehicle headlight auto-dimming controller circuit consists of power supply filter circuit and the light control circuit, the circuit is shown as the figure 7-7.
The power supply filter circuit is composed of isolation diode VD2, filter capacitor C2 and C3, inductor L, current limiting resistor R and light-emitting diode VL.
Light control circuit consists of photosensitive transistors Vl and V2, diodes VDl, potentiometer RP, capacitor Cl, transistors V3 and the relay K.
When driving at night, the power switch S1 is connected, +12 V voltage isprovided for control circuit afterfiltering. Light control switch S2 will be set to 1 (high beam) position, the high beam light ELl is lit,low beam EL2 is not lit.
R chooses 1/4W metal film resistor or carbon film resistors.
RP selects a small variable resistor or organic solid potentiometer.
Cl-C3 selects an electrolytic capacitor with thevoltagein 16V.
L selects a core fixed inductor with the current greater than 500mA.
K selects a l2V4098 DC relay.
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