The motor vehicle headlight auto-dimming controller

Published:2011/4/19 21:04:00 Author:Ecco | Keyword: motor vehicle, headlight , auto-dimming , controller | From:SeekIC

The working principle. The vehicle headlight auto-dimming controller circuit consists of photoresistor RG, potentiometer Rp, transistor V, diode VD and relay K, the circuit is shown as the figure 7-8. When driving at night, turning on the headlamp switch S, RG is in the high impedance state when no light exposure, V cuts off, K isin releasing state, the normally closed contact Kl is connected, the normally open contact K2 is off, the internal high beam ELl of headlamp is lit, low beam EL2 is off. When meeting other cars at night, the internal resistance of RC will decrease as the light exposure from the opposite traveling car, V will be saturated and conducted, K gets power and pulls in, the normally closed contact is disconnected, normally open contact is connected, the high beam ELl turns off, the low beam EHL2 turns on, that realizes the auto-dimming control. After meeting other cars, RG is in high impedance state, V cuts off, K releases, and the headlight automatically restores the upper light state. RG usesMG45 seriesphotosensitive resistor. RP uses small multi-turn potentiometers or variable resistor with carbon film synthesis. VD uses lN4007 silicon rectifier diode. V uses S8550 PNP transistors. K selects a l2V JRX-l3F or JQX-4 DC relay.



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