When a vehicle is driven on the highway at night, it is required that light beam should be of high density and should illuminate the road at a distance sufficiently ahead. However, when a vehicle coming in the opposite direction approaches the vehicle with a high-beam headlight, driver of that vehicle will experience a glare, which may blind him. This dazzle effect is one of the major problems faced by a driver in night driving. To avoid this impermanent blindness, a separate filament is usually fitted in the “dual-filament” headlight bulb in a position such that light beam from this second filament is deflected both down and sideways so that the driver of the oncoming car is not blinded. In practice, one mechanical dimmer switch is used by the driver to manually select high (bright) or low (dim) headlight beam. However, this is an awkward task for the driver especially during peak traffics.



Our project “Adaptive Lighting System for Automobiles” is a smart solution for safe and convenient night driving without the intense dazzling effect and aftermaths. Adaptive Lighting System for Automobiles needs no manual

operation for switching ON and OFF headlight/downlight (Bright/Dim) when there is a vehicle coming from front at night. It detects itself whether there is light from the front coming vehicle or not. When there is light from front coming vehicle, it automatically switches to the downlight and when the vehicle passes it automatically switch back to headlight. The user can adjust the light detection sensitivity of this Adaptive Lighting System.

Prominent Features

  • 12V automobile battery powered automatic switching circuit with negligible current consumption in standby mode
  • Reliable and weatherproof light sensor module (Cds photocell)
  • Independent variable control to set the “light detection sensitivity to avoid false triggering caused by the influence of other light sources like streetlights
  • Optional selector switch for “Automatic Signaling Mode” (ASM). In this mode, dim/bright control of headlight is in pulsed, i.e. headlight automatically changes to dim level from bright level and vice versa in a rhythmic style (like a signal to the other motorists) when light from the front coming vehicle is detected by the light sensor module
  • “Energy Saving Mode” – If the circuit is in active state, by default, headlights automatically goes off when the vehicle enters in a well-lighted area.
Troxler EffectA study by Dr. Alan Lewis, who runs the College of Optometry at Ferris State University in Big Rapids, Michigan, found that during nighttime driving, headlight glare from the vehicles traveling with you could be blinding. Even after the source of the glare is removed, an after-image remains on the eye’s retina that creates a blind spot. Known as the Troxler Effect, this phenomenon increases driver reaction time by up to 1.4 seconds. That means that if driving at 60 mph, a motorist would travel 123 feet before reacting to a hazard. Normal reaction time to a change in driving conditions is .5 seconds and the distance travelled before applying the brakes is 41 feet when traveling at the same speed!



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Parts list

  • IC: NE555 – 1   555 datasheet
  • IC Socket 8 Pin – 1
  • Transistor: BC547 – 1
  • Diode: 1N4007 – 2
  • Resistors: 100K Trimpot – 1, 47K 1/4W – 1 ,22K 1/4W – 1 ,10K 1/4W – 1 , 1K 1/4W – 2
  • Capacitors: 10uF/25V – 1, 100uF/25V – 1
  • LEDs: 5mm Red /Green – 2
  • LDR: 20mm Encapsulated Type – 1
  • Relay: 12VDC SPDT – 1
  • Switch: SPST Rocker Switch – 2

Working of the circuit

This circuit is built around the popular timer chip NE555 (IC1). Here IC1 is configured as a gated-astable multivibrator running at a frequency of about 1.5 Hertz ( duty cycle 75%),determined by the values of components R1, R3 and C1. The whole circuit can be directly powered from the 12V automobile battery.

When power switch S1 is turned to “on” position, 12VDC supply from the battery is fed to the whole circuit through polarity guard diode 1N4007 (D1). Capacitor C3 (100uF/25V) is a traditional buffer capacitor to improve the circuit stability. Initially, astable built around IC1 is disabled by the light sensor circuit realized using the 20mm – Light Dependent Resistor (LDR),100K trimpot (P1) and BC547 (T1) transistor. As a result output (pin 3) of IC1 is at a “low” level, and the 12V electro-magnetic relay (RL1) connected at the output of IC1 is in “off “state. The first LED (LED1) indicates this condition. As per the wiring (+ve supply is routed to headlights through the N/C contacts of RL1), headlights are in now in “on” condition.

However, when a strong light falls on the LDR, IC1 is enabled immediately and as a result its output goes “high” to energize the relay. Now the downlights are powered by the N/O contacts of the relay and stays in this condition until the light level on LDR is reversed. The second LED (LED2) indicates this condition. Note that, switch for the ASM mode (S2), directly grounds pin 6 and 2 of IC1, when it is in “on” mode and hence the astable function of IC1 is in disabled state. If S2 is in “off” mode, the “ASM” function turns to “on” and this flashes headlights and downlights rapidly, as long as strong light level (from another headlight) is detected by the LDR.


  • Switching contact of the relay (RL1) can directly be connected in parallel with the existing dim/bright selector switch. It is also possible to route + 12V through the relay contacts to Headlights (Bright) and Downlights (Dim)
  • One 20 mm encapsulated LDR is recommended for this circuit. The LDR should be fitted at the front side of the vehicle in an appropriate position



  1. Good one Shriram. Can you make one for my car?!

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