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Company Logo TE Connectivity

  • Automatic Headlight Control

  • Created: Sep 16, 2015

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During night, cars with headlights on high beam tend to blind the drivers due to the glare of approaching vehicles, which may cause accidents. To avoid this from happening, the drivers have to switch from high beam to low beam lights. A driver usually switches the automobile headlights from high to low beam with a manual control. Controlling this task manually can sometimes be awkward and troublesome for some drivers especially during fast travels.

This project is an automatic headlight control that automatically controls the headlight from switching between high beam and low beam lights. It is mainly comprised of a 20 mm light dependent resistor (LDR), a 555-timer and a relay. The 555-timer in the design is configured as a modified gated-astable multivibrator with both threshold and trigger pins connected to ground. When the LDR detects no light from approaching vehicles, it provides a high resistance on the circuit. With this Q1 is saturated providing a low state to the reset pin of the timer. This condition provides a low output from the timer, which does not activate the relay, and the headlights maintain a high beam position. When the LDR detects a light, it ideally cuts off the transistor Q1 making the input at the reset pin “high”. This enables the timer to function providing a high state output. The relay is then energized switching from high beam lights to low beam lights. The design uses the 1461069-5 ORWH relay from TE Connectivity. It is an SPDT non-latching relay that has a 12VDC coil voltage and 10A contact current rating.

The circuit can be supplied directly from the automobiles’ battery. The switching contact of the relay can directly be connected in parallel with the existing dim/bright selector switch of the car. The LDR should be fitted at the front side of the vehicle in an appropriate position. The variations can be done to the project to provide more features and functionality depending on the users’ convenience.



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