This document describes a simple circuit that can automatically switch a vehicle's headlights between high beam and low beam depending on whether oncoming traffic is detected. The circuit uses a phototransistor to sense incoming light and triggers a relay to change the headlight setting. When no other vehicles are detected, the headlights remain on high beam, but switch to low beam when oncoming headlights are sensed to avoid blinding other drivers. This automatic switching allows for safer night driving with high beams on highways.

4. INTRODUCTION
 Driving the highway with your high-beam headlights
can really increase your visibility, but can be a blinding
hazard for other drivers. This simple circuit can be
wired into your headlight switch to provide automatic
switching between high and low beam headlights
when there is oncoming traffic. It does this by sensing
the lights of that traffic. In this way, you can drive
safely with your high-beams on without blinding other
drivers.

5. CIRCUIT DIAGRAM

7. COMPONENTS
 5K 1/4W Resistor
 5K Pot
 NPN Phototransistor
 2N3906 PNP Transistor
 Low Current 12V SPST Relay
 High Current 12V SPDT Relay
 SPST Switch
 Car Battery
 Case, wire, board, knobs for pots

8. WORKING
 Automatic headlight brightness switch switches the
headlight from high beam to low beam when light
from oncoming vehicle strikes the phototransistor of
the vehicle. It holds the lights on the upper beam until
the vehicle approaches from the other direction. Also
the moment the car passes by,it shifts automatically
the headlight back to upper beam.

9. High current 12vSPDT relay
 Single pole, double throw relay that provides the
switching of the headlight beam.

10. SPST(single pole single throw)switch
 One-way switch.
 A simple on-off switch: The two terminals are either
connected together or disconnected from each other.
An example is a light switch

11. ADVANTAGES
MAINLY USEFUL IN THE HIGHWAYS
PREVENTS ACCIDENTS

12. DISADVANTAGES
When we drive the vehicle fitted with automatic dippers
on a road in which different types of vehicles and hence
varying light intensities cause frequent flickering of
Headlight
This is only useful on highways and straight width roads

13. CONCLUSION
The Auto dipper can perform a great deal in reducing
the manual efforts and fatigue of drivers in dipping the
headlamp frequently while driving through highway
full of moving vehicles.
Newer and better technologies always come with time
and it will help in reducing the manual labour and
difficulties in the sector where it is made use. In short
it is a device with bright future