ADLS - Fig 2

Adaptive Lighting System for Automobiles

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.

ADLS - Fig 1

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 Effect

A 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!

Functional Block Diagram

ADLS - Fig 2

Proposed electrical wiring diagram for existing connection

ADLS - Fig 3

Proposed electrical wiring diagram for new connection

ADLS - Fig 4

Schematic Circuit Diagram

ADLS - Fig 5

Parts list

  • IC: NE555 – 1
  • 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


Join the conversation!

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  • amenjas

    Thnks a alot sir… I will try and let u know… my previous auto dipper was equiped with 4-5 components only I.e. two bc109 transistors only and 3 resistors. I hope that this should work on road test also as this circuit seems better than previous circuit. Rest god knows.. thnks for ur nice and quick comments. In india, hardly any doctor knows electronic stuff.

  • amenjas

    Thnkew krokkennoster for ur quick reply. I will do test ur method. I do have that fittment i.e. shielded tube. I dont think that will help bcoz I tested in room also by switching of the the room lights and using high beam torch. It works perfect but when ever I take torch closer to sensor, at a certain point , at threshold it chatters. Somebody recommended capacitors in their own circuits to remove chatter. But where to place capacitor in this circuit as this circuit is bit differnt from circuits. It has got auto signaling mode which I like the most. Actually , I am doctor by proffessional, its my hobby to do electric things. Thnkew sir…


      I left out where to connect the plus it is on the cathode of diode two the one that is direct over that diode and relay coil effectively. I added this comment for those that are starting to play with electronics and all connections and mods there must be no doubt left with them


      Dear Dr.Amenjas hi If you want to stop the chattering of the relay is to fit a cap as you stated You can start at 470 microfarad 25 volt cap with the negative on the ground or negative. Do you try to imitate the road conditions?The light of a passing vehicle will only go to certain illumination and not as I do understand your tests directly at a near distance direct onto the photocell
      Here in South Africa if you ask any male in medical field then about 70% plus are into super hi fi or electronics.

  • amenjas

    hello sir your circuit is too good. Atlast, i am successful in constructing the circuit and its working. I am facing one problem that is chattering of relay during transition of light so much so that i m not able to use this in car. kindly tell me the solution. I dont want to spoil the car wiring system if something goes wrong due to chattering. Previously, my car was fitted with hyundai original auto dipper but that was crap and i removed that. i want to use ur circuit for my car. Please help. Thankew.


      Amenjas hi! The only solution that I can think of is to put a short piece of pipe around you photocell so the “stray” lights cannot illuminate the photocell I think this is the solution A similar circuit was in one of the “Summer circuits” from “Elektor” and “Electronics International” in their “Short circuits” NO it is not an electrical “Short” that blow fuses (pun intended)
      I remember that they recommended the fitting of a black painted shield around the photocell and this had to point at the correct angle for this application Maybe if you still have your Hyundai’s eye use the shield fitted to it

  • Rkphadke

    Dear Sir

    I am happy to receive the project it will really help to avoide accident I shall try and let you know
    Thanks and regards

  • Jim Keith

    Correction: The transistor was invented in 1948. I obtained my first hobby transistors in 1958 –the classic 2N107 germanium PNP and 2N170 NPN. Transistors did not get into automotive applications until about 1958 when they were used in the audio power output stage of car radios –other electronic functions were accomplished in those radios via hybrid vacuum tubes that functioned with a 12V plate supply.


      Jim did those Yankee radio’s messed a lot with my workmates with their HT of 12 volts! I sort of liked them as the old vibrator was not as reliable as could be! I serviced one with a dynamotor motor and H T genny on same shaft. These were scarce and only the super sets sported them

  • Jim Keith

    Thank you Mr. Hareendran for the very interesting article. My earliest recollection regarding the implementation of this gadget (and gadget it was) was in the mid 1950’s. My dad had a ’54 Cadillac Fleetwood with an automatic headlight dimmer. It worked on the same principle with a photocell. However, the control box measured approx 150mm on each side. It contained a number of vacuum tubes –this was before the discovery of the transistor. Operation tended to be a bit fickle and the brights came on immediately after the oncoming car passed. It was not reliable and the dealer had to service it a number of times.

    Regarding the Troxler Effect, years ago I had a problem with headlight glare recovery and treated it myself with vitamin A –amazing and almost instant relief, and it has not returned. Note that vitamin A plays a major role in the human imaging phenomena. Also note that this miracle of vision absolutely did not happen by itself –so complex that we barely understand how it functions. Evolution NOT!

    • fred

      Dear Jim
      Just calling you out on your lack of education on evolution.
      Making such ignorant comments is not in tune with the rest of this really good web site.

    • T.K.Hareendran

      Thank you dear Mr.Jim Keith for the thoughtful & wonderful comment you left here.Have a great time!

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